Redis Functions - Move code to make review process easier.

This commit is only move code around without changing it.
The reason behind this is to make review process easier
by allowing the reviewer to simply ignore all code movements.

changes:
1. rename scripting.c to eval.c
2. introduce and new file, script_lua.c, and move parts of Lua
   functionality to this new file. script_lua.c will eventually
   contains the shared code between legacy lua and lua engine.

This commit does not compiled on purpose. Its only purpose is to move
code and rename files.

1 files changed, 1693 insertions, 0 deletions

diff --git a/src/eval.c b/src/eval.c
new file mode 100644
index 000000000..6e6aeac7c
--- /dev/null
+++ b/src/eval.c
@@ -0,0 +1,1693 @@
+/*
+ * Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   * Redistributions of source code must retain the above copyright notice,
+ *     this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *   * Neither the name of Redis nor the names of its contributors may be used
+ *     to endorse or promote products derived from this software without
+ *     specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "server.h"
+#include "sha1.h"
+#include "rand.h"
+#include "cluster.h"
+#include "monotonic.h"
+#include "resp_parser.h"
+#include "script_lua.h"
+
+#include <lua.h>
+#include <lauxlib.h>
+#include <lualib.h>
+#include <ctype.h>
+#include <math.h>
+
+void ldbInit(void);
+void ldbDisable(client *c);
+void ldbEnable(client *c);
+void evalGenericCommandWithDebugging(client *c, int evalsha);
+void luaLdbLineHook(lua_State *lua, lua_Debug *ar);
+void ldbLog(sds entry);
+void ldbLogRedisReply(char *reply);
+sds ldbCatStackValue(sds s, lua_State *lua, int idx);
+
+/* Debugger shared state is stored inside this global structure. */
+#define LDB_BREAKPOINTS_MAX 64  /* Max number of breakpoints. */
+#define LDB_MAX_LEN_DEFAULT 256 /* Default len limit for replies / var dumps. */
+struct ldbState {
+    connection *conn; /* Connection of the debugging client. */
+    int active; /* Are we debugging EVAL right now? */
+    int forked; /* Is this a fork()ed debugging session? */
+    list *logs; /* List of messages to send to the client. */
+    list *traces; /* Messages about Redis commands executed since last stop.*/
+    list *children; /* All forked debugging sessions pids. */
+    int bp[LDB_BREAKPOINTS_MAX]; /* An array of breakpoints line numbers. */
+    int bpcount; /* Number of valid entries inside bp. */
+    int step;   /* Stop at next line regardless of breakpoints. */
+    int luabp;  /* Stop at next line because redis.breakpoint() was called. */
+    sds *src;   /* Lua script source code split by line. */
+    int lines;  /* Number of lines in 'src'. */
+    int currentline;    /* Current line number. */
+    sds cbuf;   /* Debugger client command buffer. */
+    size_t maxlen;  /* Max var dump / reply length. */
+    int maxlen_hint_sent; /* Did we already hint about "set maxlen"? */
+} ldb;
+
+/* ---------------------------------------------------------------------------
+ * Utility functions.
+ * ------------------------------------------------------------------------- */
+
+/* Perform the SHA1 of the input string. We use this both for hashing script
+ * bodies in order to obtain the Lua function name, and in the implementation
+ * of redis.sha1().
+ *
+ * 'digest' should point to a 41 bytes buffer: 40 for SHA1 converted into an
+ * hexadecimal number, plus 1 byte for null term. */
+void sha1hex(char *digest, char *script, size_t len) {
+    SHA1_CTX ctx;
+    unsigned char hash[20];
+    char *cset = "0123456789abcdef";
+    int j;
+
+    SHA1Init(&ctx);
+    SHA1Update(&ctx,(unsigned char*)script,len);
+    SHA1Final(hash,&ctx);
+
+    for (j = 0; j < 20; j++) {
+        digest[j*2] = cset[((hash[j]&0xF0)>>4)];
+        digest[j*2+1] = cset[(hash[j]&0xF)];
+    }
+    digest[40] = '\0';
+}
+
+/* redis.breakpoint()
+ *
+ * Allows to stop execution during a debugging session from within
+ * the Lua code implementation, like if a breakpoint was set in the code
+ * immediately after the function. */
+int luaRedisBreakpointCommand(lua_State *lua) {
+    if (ldb.active) {
+        ldb.luabp = 1;
+        lua_pushboolean(lua,1);
+    } else {
+        lua_pushboolean(lua,0);
+    }
+    return 1;
+}
+
+/* redis.debug()
+ *
+ * Log a string message into the output console.
+ * Can take multiple arguments that will be separated by commas.
+ * Nothing is returned to the caller. */
+int luaRedisDebugCommand(lua_State *lua) {
+    if (!ldb.active) return 0;
+    int argc = lua_gettop(lua);
+    sds log = sdscatprintf(sdsempty(),"<debug> line %d: ", ldb.currentline);
+    while(argc--) {
+        log = ldbCatStackValue(log,lua,-1 - argc);
+        if (argc != 0) log = sdscatlen(log,", ",2);
+    }
+    ldbLog(log);
+    return 0;
+}
+
+/* redis.replicate_commands()
+ *
+ * Turn on single commands replication if the script never called
+ * a write command so far, and returns true. Otherwise if the script
+ * already started to write, returns false and stick to whole scripts
+ * replication, which is our default. */
+int luaRedisReplicateCommandsCommand(lua_State *lua) {
+    if (server.lua_write_dirty) {
+        lua_pushboolean(lua,0);
+    } else {
+        server.lua_replicate_commands = 1;
+        /* When we switch to single commands replication, we can provide
+         * different math.random() sequences at every call, which is what
+         * the user normally expects. */
+        redisSrand48(rand());
+        lua_pushboolean(lua,1);
+    }
+    return 1;
+}
+
+/* Initialize the scripting environment.
+ *
+ * This function is called the first time at server startup with
+ * the 'setup' argument set to 1.
+ *
+ * It can be called again multiple times during the lifetime of the Redis
+ * process, with 'setup' set to 0, and following a scriptingRelease() call,
+ * in order to reset the Lua scripting environment.
+ *
+ * However it is simpler to just call scriptingReset() that does just that. */
+void scriptingInit(int setup) {
+    lua_State *lua = lua_open();
+
+    if (setup) {
+        server.lua_client = NULL;
+        server.lua_caller = NULL;
+        server.lua_cur_script = NULL;
+        server.lua_timedout = 0;
+        server.lua_disable_deny_script = 0;
+        ldbInit();
+    }
+
+    /* Initialize a dictionary we use to map SHAs to scripts.
+     * This is useful for replication, as we need to replicate EVALSHA
+     * as EVAL, so we need to remember the associated script. */
+    server.lua_scripts = dictCreate(&shaScriptObjectDictType);
+    server.lua_scripts_mem = 0;
+
+    luaEngineRegisterRedisAPI(lua);
+
+    /* register debug commands */
+    lua_getglobal(lua,"redis");
+
+    /* redis.breakpoint */
+    lua_pushstring(lua,"breakpoint");
+    lua_pushcfunction(lua,luaRedisBreakpointCommand);
+    lua_settable(lua,-3);
+
+    /* redis.debug */
+    lua_pushstring(lua,"debug");
+    lua_pushcfunction(lua,luaRedisDebugCommand);
+    lua_settable(lua,-3);
+
+    /* redis.replicate_commands */
+    lua_pushstring(lua, "replicate_commands");
+    lua_pushcfunction(lua, luaRedisReplicateCommandsCommand);
+    lua_settable(lua, -3);
+
+    lua_setglobal(lua,"redis");
+
+    /* Add a helper function that we use to sort the multi bulk output of non
+     * deterministic commands, when containing 'false' elements. */
+    {
+        char *compare_func =    "function __redis__compare_helper(a,b)\n"
+                                "  if a == false then a = '' end\n"
+                                "  if b == false then b = '' end\n"
+                                "  return a<b\n"
+                                "end\n";
+        luaL_loadbuffer(lua,compare_func,strlen(compare_func),"@cmp_func_def");
+        lua_pcall(lua,0,0,0);
+    }
+
+    /* Add a helper function we use for pcall error reporting.
+     * Note that when the error is in the C function we want to report the
+     * information about the caller, that's what makes sense from the point
+     * of view of the user debugging a script. */
+    {
+        char *errh_func =       "local dbg = debug\n"
+                                "function __redis__err__handler(err)\n"
+                                "  local i = dbg.getinfo(2,'nSl')\n"
+                                "  if i and i.what == 'C' then\n"
+                                "    i = dbg.getinfo(3,'nSl')\n"
+                                "  end\n"
+                                "  if i then\n"
+                                "    return i.source .. ':' .. i.currentline .. ': ' .. err\n"
+                                "  else\n"
+                                "    return err\n"
+                                "  end\n"
+                                "end\n";
+        luaL_loadbuffer(lua,errh_func,strlen(errh_func),"@err_handler_def");
+        lua_pcall(lua,0,0,0);
+    }
+
+    /* Create the (non connected) client that we use to execute Redis commands
+     * inside the Lua interpreter.
+     * Note: there is no need to create it again when this function is called
+     * by scriptingReset(). */
+    if (server.lua_client == NULL) {
+        server.lua_client = createClient(NULL);
+        server.lua_client->flags |= CLIENT_LUA;
+
+        /* We do not want to allow blocking commands inside Lua */
+        server.lua_client->flags |= CLIENT_DENY_BLOCKING;
+    }
+
+    /* Lua beginners often don't use "local", this is likely to introduce
+     * subtle bugs in their code. To prevent problems we protect accesses
+     * to global variables. */
+    scriptingEnableGlobalsProtection(lua);
+
+    server.lua = lua;
+}
+
+/* Release resources related to Lua scripting.
+ * This function is used in order to reset the scripting environment. */
+void scriptingRelease(int async) {
+    if (async)
+        freeLuaScriptsAsync(server.lua_scripts);
+    else
+        dictRelease(server.lua_scripts);
+    server.lua_scripts_mem = 0;
+    lua_close(server.lua);
+}
+
+void scriptingReset(int async) {
+    scriptingRelease(async);
+    scriptingInit(0);
+}
+
+/* ---------------------------------------------------------------------------
+ * EVAL and SCRIPT commands implementation
+ * ------------------------------------------------------------------------- */
+
+/* Define a Lua function with the specified body.
+ * The function name will be generated in the following form:
+ *
+ *   f_<hex sha1 sum>
+ *
+ * The function increments the reference count of the 'body' object as a
+ * side effect of a successful call.
+ *
+ * On success a pointer to an SDS string representing the function SHA1 of the
+ * just added function is returned (and will be valid until the next call
+ * to scriptingReset() function), otherwise NULL is returned.
+ *
+ * The function handles the fact of being called with a script that already
+ * exists, and in such a case, it behaves like in the success case.
+ *
+ * If 'c' is not NULL, on error the client is informed with an appropriate
+ * error describing the nature of the problem and the Lua interpreter error. */
+sds luaCreateFunction(client *c, lua_State *lua, robj *body) {
+    char funcname[43];
+    dictEntry *de;
+
+    funcname[0] = 'f';
+    funcname[1] = '_';
+    sha1hex(funcname+2,body->ptr,sdslen(body->ptr));
+
+    sds sha = sdsnewlen(funcname+2,40);
+    if ((de = dictFind(server.lua_scripts,sha)) != NULL) {
+        sdsfree(sha);
+        return dictGetKey(de);
+    }
+
+    sds funcdef = sdsempty();
+    funcdef = sdscat(funcdef,"function ");
+    funcdef = sdscatlen(funcdef,funcname,42);
+    funcdef = sdscatlen(funcdef,"() ",3);
+    funcdef = sdscatlen(funcdef,body->ptr,sdslen(body->ptr));
+    funcdef = sdscatlen(funcdef,"\nend",4);
+
+    if (luaL_loadbuffer(lua,funcdef,sdslen(funcdef),"@user_script")) {
+        if (c != NULL) {
+            addReplyErrorFormat(c,
+                "Error compiling script (new function): %s\n",
+                lua_tostring(lua,-1));
+        }
+        lua_pop(lua,1);
+        sdsfree(sha);
+        sdsfree(funcdef);
+        return NULL;
+    }
+    sdsfree(funcdef);
+
+    if (lua_pcall(lua,0,0,0)) {
+        if (c != NULL) {
+            addReplyErrorFormat(c,"Error running script (new function): %s\n",
+                lua_tostring(lua,-1));
+        }
+        lua_pop(lua,1);
+        sdsfree(sha);
+        return NULL;
+    }
+
+    /* We also save a SHA1 -> Original script map in a dictionary
+     * so that we can replicate / write in the AOF all the
+     * EVALSHA commands as EVAL using the original script. */
+    int retval = dictAdd(server.lua_scripts,sha,body);
+    serverAssertWithInfo(c ? c : server.lua_client,NULL,retval == DICT_OK);
+    server.lua_scripts_mem += sdsZmallocSize(sha) + getStringObjectSdsUsedMemory(body);
+    incrRefCount(body);
+    return sha;
+}
+
+void prepareLuaClient(void) {
+    /* Select the right DB in the context of the Lua client */
+    selectDb(server.lua_client,server.lua_caller->db->id);
+    server.lua_client->resp = 2; /* Default is RESP2, scripts can change it. */
+
+    /* If we are in MULTI context, flag Lua client as CLIENT_MULTI. */
+    if (server.lua_caller->flags & CLIENT_MULTI) {
+        server.lua_client->flags |= CLIENT_MULTI;
+    }
+}
+
+void resetLuaClient(void) {
+    /* After the script done, remove the MULTI state. */
+    server.lua_client->flags &= ~CLIENT_MULTI;
+}
+
+void evalGenericCommand(client *c, int evalsha) {
+    lua_State *lua = server.lua;
+    char funcname[43];
+    long long numkeys;
+    long long initial_server_dirty = server.dirty;
+    int delhook = 0, err;
+
+    /* When we replicate whole scripts, we want the same PRNG sequence at
+     * every call so that our PRNG is not affected by external state. */
+    redisSrand48(0);
+
+    /* We set this flag to zero to remember that so far no random command
+     * was called. This way we can allow the user to call commands like
+     * SRANDMEMBER or RANDOMKEY from Lua scripts as far as no write command
+     * is called (otherwise the replication and AOF would end with non
+     * deterministic sequences).
+     *
+     * Thanks to this flag we'll raise an error every time a write command
+     * is called after a random command was used. */
+    server.lua_random_dirty = 0;
+    server.lua_write_dirty = 0;
+    server.lua_replicate_commands = server.lua_always_replicate_commands;
+    server.lua_multi_emitted = 0;
+    server.lua_repl = PROPAGATE_AOF|PROPAGATE_REPL;
+
+    /* Get the number of arguments that are keys */
+    if (getLongLongFromObjectOrReply(c,c->argv[2],&numkeys,NULL) != C_OK)
+        return;
+    if (numkeys > (c->argc - 3)) {
+        addReplyError(c,"Number of keys can't be greater than number of args");
+        return;
+    } else if (numkeys < 0) {
+        addReplyError(c,"Number of keys can't be negative");
+        return;
+    }
+
+    /* We obtain the script SHA1, then check if this function is already
+     * defined into the Lua state */
+    funcname[0] = 'f';
+    funcname[1] = '_';
+    if (!evalsha) {
+        /* Hash the code if this is an EVAL call */
+        sha1hex(funcname+2,c->argv[1]->ptr,sdslen(c->argv[1]->ptr));
+    } else {
+        /* We already have the SHA if it is an EVALSHA */
+        int j;
+        char *sha = c->argv[1]->ptr;
+
+        /* Convert to lowercase. We don't use tolower since the function
+         * managed to always show up in the profiler output consuming
+         * a non trivial amount of time. */
+        for (j = 0; j < 40; j++)
+            funcname[j+2] = (sha[j] >= 'A' && sha[j] <= 'Z') ?
+                sha[j]+('a'-'A') : sha[j];
+        funcname[42] = '\0';
+    }
+
+    /* Push the pcall error handler function on the stack. */
+    lua_getglobal(lua, "__redis__err__handler");
+
+    /* Try to lookup the Lua function */
+    lua_getglobal(lua, funcname);
+    if (lua_isnil(lua,-1)) {
+        lua_pop(lua,1); /* remove the nil from the stack */
+        /* Function not defined... let's define it if we have the
+         * body of the function. If this is an EVALSHA call we can just
+         * return an error. */
+        if (evalsha) {
+            lua_pop(lua,1); /* remove the error handler from the stack. */
+            addReplyErrorObject(c, shared.noscripterr);
+            return;
+        }
+        if (luaCreateFunction(c,lua,c->argv[1]) == NULL) {
+            lua_pop(lua,1); /* remove the error handler from the stack. */
+            /* The error is sent to the client by luaCreateFunction()
+             * itself when it returns NULL. */
+            return;
+        }
+        /* Now the following is guaranteed to return non nil */
+        lua_getglobal(lua, funcname);
+        serverAssert(!lua_isnil(lua,-1));
+    }
+
+    /* Populate the argv and keys table accordingly to the arguments that
+     * EVAL received. */
+    luaSetGlobalArray(lua,"KEYS",c->argv+3,numkeys);
+    luaSetGlobalArray(lua,"ARGV",c->argv+3+numkeys,c->argc-3-numkeys);
+
+    /* Set a hook in order to be able to stop the script execution if it
+     * is running for too much time.
+     * We set the hook only if the time limit is enabled as the hook will
+     * make the Lua script execution slower.
+     *
+     * If we are debugging, we set instead a "line" hook so that the
+     * debugger is call-back at every line executed by the script. */
+    server.in_eval = 1;
+    server.lua_caller = c;
+    server.lua_cur_script = funcname + 2;
+    server.lua_time_start = getMonotonicUs();
+    server.lua_time_snapshot = mstime();
+    server.lua_kill = 0;
+    if (server.lua_time_limit > 0 && ldb.active == 0) {
+        lua_sethook(lua,luaMaskCountHook,LUA_MASKCOUNT,100000);
+        delhook = 1;
+    } else if (ldb.active) {
+        lua_sethook(server.lua,luaLdbLineHook,LUA_MASKLINE|LUA_MASKCOUNT,100000);
+        delhook = 1;
+    }
+
+    prepareLuaClient();
+
+    /* At this point whether this script was never seen before or if it was
+     * already defined, we can call it. We have zero arguments and expect
+     * a single return value. */
+    err = lua_pcall(lua,0,1,-2);
+
+    resetLuaClient();
+
+    /* Perform some cleanup that we need to do both on error and success. */
+    if (delhook) lua_sethook(lua,NULL,0,0); /* Disable hook */
+    if (server.lua_timedout) {
+        server.lua_timedout = 0;
+        blockingOperationEnds();
+        /* Restore the client that was protected when the script timeout
+         * was detected. */
+        unprotectClient(c);
+        if (server.masterhost && server.master)
+            queueClientForReprocessing(server.master);
+    }
+    server.in_eval = 0;
+    server.lua_caller = NULL;
+    server.lua_cur_script = NULL;
+
+    /* Call the Lua garbage collector from time to time to avoid a
+     * full cycle performed by Lua, which adds too latency.
+     *
+     * The call is performed every LUA_GC_CYCLE_PERIOD executed commands
+     * (and for LUA_GC_CYCLE_PERIOD collection steps) because calling it
+     * for every command uses too much CPU. */
+    #define LUA_GC_CYCLE_PERIOD 50
+    {
+        static long gc_count = 0;
+
+        gc_count++;
+        if (gc_count == LUA_GC_CYCLE_PERIOD) {
+            lua_gc(lua,LUA_GCSTEP,LUA_GC_CYCLE_PERIOD);
+            gc_count = 0;
+        }
+    }
+
+    if (err) {
+        addReplyErrorFormat(c,"Error running script (call to %s): %s\n",
+            funcname, lua_tostring(lua,-1));
+        lua_pop(lua,2); /* Consume the Lua reply and remove error handler. */
+    } else {
+        /* On success convert the Lua return value into Redis protocol, and
+         * send it to * the client. */
+        luaReplyToRedisReply(c,lua); /* Convert and consume the reply. */
+        lua_pop(lua,1); /* Remove the error handler. */
+    }
+
+    /* If we are using single commands replication, emit EXEC if there
+     * was at least a write. */
+    if (server.lua_replicate_commands) {
+        preventCommandPropagation(c);
+        if (server.lua_multi_emitted) {
+            execCommandPropagateExec(c->db->id);
+        }
+    }
+
+    /* EVALSHA should be propagated to Slave and AOF file as full EVAL, unless
+     * we are sure that the script was already in the context of all the
+     * attached slaves *and* the current AOF file if enabled.
+     *
+     * To do so we use a cache of SHA1s of scripts that we already propagated
+     * as full EVAL, that's called the Replication Script Cache.
+     *
+     * For replication, every time a new slave attaches to the master, we need to
+     * flush our cache of scripts that can be replicated as EVALSHA, while
+     * for AOF we need to do so every time we rewrite the AOF file. */
+    if (evalsha && !server.lua_replicate_commands) {
+        if (!replicationScriptCacheExists(c->argv[1]->ptr)) {
+            /* This script is not in our script cache, replicate it as
+             * EVAL, then add it into the script cache, as from now on
+             * slaves and AOF know about it. */
+            robj *script = dictFetchValue(server.lua_scripts,c->argv[1]->ptr);
+
+            replicationScriptCacheAdd(c->argv[1]->ptr);
+            serverAssertWithInfo(c,NULL,script != NULL);
+
+            /* If the script did not produce any changes in the dataset we want
+             * just to replicate it as SCRIPT LOAD, otherwise we risk running
+             * an aborted script on slaves (that may then produce results there)
+             * or just running a CPU costly read-only script on the slaves. */
+            if (server.dirty == initial_server_dirty) {
+                rewriteClientCommandVector(c,3,
+                    shared.script,
+                    shared.load,
+                    script);
+            } else {
+                rewriteClientCommandArgument(c,0,shared.eval);
+                rewriteClientCommandArgument(c,1,script);
+            }
+            forceCommandPropagation(c,PROPAGATE_REPL|PROPAGATE_AOF);
+        }
+    }
+}
+
+void evalCommand(client *c) {
+    /* Explicitly feed monitor here so that lua commands appear after their
+     * script command. */
+    replicationFeedMonitors(c,server.monitors,c->db->id,c->argv,c->argc);
+    if (!(c->flags & CLIENT_LUA_DEBUG))
+        evalGenericCommand(c,0);
+    else
+        evalGenericCommandWithDebugging(c,0);
+}
+
+void evalRoCommand(client *c) {
+    evalCommand(c);
+}
+
+void evalShaCommand(client *c) {
+    /* Explicitly feed monitor here so that lua commands appear after their
+     * script command. */
+    replicationFeedMonitors(c,server.monitors,c->db->id,c->argv,c->argc);
+    if (sdslen(c->argv[1]->ptr) != 40) {
+        /* We know that a match is not possible if the provided SHA is
+         * not the right length. So we return an error ASAP, this way
+         * evalGenericCommand() can be implemented without string length
+         * sanity check */
+        addReplyErrorObject(c, shared.noscripterr);
+        return;
+    }
+    if (!(c->flags & CLIENT_LUA_DEBUG))
+        evalGenericCommand(c,1);
+    else {
+        addReplyError(c,"Please use EVAL instead of EVALSHA for debugging");
+        return;
+    }
+}
+
+void evalShaRoCommand(client *c) {
+    evalShaCommand(c);
+}
+
+void scriptCommand(client *c) {
+    if (c->argc == 2 && !strcasecmp(c->argv[1]->ptr,"help")) {
+        const char *help[] = {
+"DEBUG (YES|SYNC|NO)",
+"    Set the debug mode for subsequent scripts executed.",
+"EXISTS <sha1> [<sha1> ...]",
+"    Return information about the existence of the scripts in the script cache.",
+"FLUSH [ASYNC|SYNC]",
+"    Flush the Lua scripts cache. Very dangerous on replicas.",
+"    When called without the optional mode argument, the behavior is determined by the",
+"    lazyfree-lazy-user-flush configuration directive. Valid modes are:",
+"    * ASYNC: Asynchronously flush the scripts cache.",
+"    * SYNC: Synchronously flush the scripts cache.",
+"KILL",
+"    Kill the currently executing Lua script.",
+"LOAD <script>",
+"    Load a script into the scripts cache without executing it.",
+NULL
+        };
+        addReplyHelp(c, help);
+    } else if (c->argc >= 2 && !strcasecmp(c->argv[1]->ptr,"flush")) {
+        int async = 0;
+        if (c->argc == 3 && !strcasecmp(c->argv[2]->ptr,"sync")) {
+            async = 0;
+        } else if (c->argc == 3 && !strcasecmp(c->argv[2]->ptr,"async")) {
+            async = 1;
+        } else if (c->argc == 2) {
+            async = server.lazyfree_lazy_user_flush ? 1 : 0;
+        } else {
+            addReplyError(c,"SCRIPT FLUSH only support SYNC|ASYNC option");
+            return;
+        }
+        scriptingReset(async);
+        addReply(c,shared.ok);
+        replicationScriptCacheFlush();
+        server.dirty++; /* Propagating this command is a good idea. */
+    } else if (c->argc >= 2 && !strcasecmp(c->argv[1]->ptr,"exists")) {
+        int j;
+
+        addReplyArrayLen(c, c->argc-2);
+        for (j = 2; j < c->argc; j++) {
+            if (dictFind(server.lua_scripts,c->argv[j]->ptr))
+                addReply(c,shared.cone);
+            else
+                addReply(c,shared.czero);
+        }
+    } else if (c->argc == 3 && !strcasecmp(c->argv[1]->ptr,"load")) {
+        sds sha = luaCreateFunction(c,server.lua,c->argv[2]);
+        if (sha == NULL) return; /* The error was sent by luaCreateFunction(). */
+        addReplyBulkCBuffer(c,sha,40);
+        forceCommandPropagation(c,PROPAGATE_REPL|PROPAGATE_AOF);
+    } else if (c->argc == 2 && !strcasecmp(c->argv[1]->ptr,"kill")) {
+        if (server.lua_caller == NULL) {
+            addReplyError(c,"-NOTBUSY No scripts in execution right now.");
+        } else if (server.lua_caller->flags & CLIENT_MASTER) {
+            addReplyError(c,"-UNKILLABLE The busy script was sent by a master instance in the context of replication and cannot be killed.");
+        } else if (server.lua_write_dirty) {
+            addReplyError(c,"-UNKILLABLE Sorry the script already executed write commands against the dataset. You can either wait the script termination or kill the server in a hard way using the SHUTDOWN NOSAVE command.");
+        } else {
+            server.lua_kill = 1;
+            addReply(c,shared.ok);
+        }
+    } else if (c->argc == 3 && !strcasecmp(c->argv[1]->ptr,"debug")) {
+        if (clientHasPendingReplies(c)) {
+            addReplyError(c,"SCRIPT DEBUG must be called outside a pipeline");
+            return;
+        }
+        if (!strcasecmp(c->argv[2]->ptr,"no")) {
+            ldbDisable(c);
+            addReply(c,shared.ok);
+        } else if (!strcasecmp(c->argv[2]->ptr,"yes")) {
+            ldbEnable(c);
+            addReply(c,shared.ok);
+        } else if (!strcasecmp(c->argv[2]->ptr,"sync")) {
+            ldbEnable(c);
+            addReply(c,shared.ok);
+            c->flags |= CLIENT_LUA_DEBUG_SYNC;
+        } else {
+            addReplyError(c,"Use SCRIPT DEBUG YES/SYNC/NO");
+            return;
+        }
+    } else {
+        addReplySubcommandSyntaxError(c);
+    }
+}
+
+/* ---------------------------------------------------------------------------
+ * LDB: Redis Lua debugging facilities
+ * ------------------------------------------------------------------------- */
+
+/* Initialize Lua debugger data structures. */
+void ldbInit(void) {
+    ldb.conn = NULL;
+    ldb.active = 0;
+    ldb.logs = listCreate();
+    listSetFreeMethod(ldb.logs,(void (*)(void*))sdsfree);
+    ldb.children = listCreate();
+    ldb.src = NULL;
+    ldb.lines = 0;
+    ldb.cbuf = sdsempty();
+}
+
+/* Remove all the pending messages in the specified list. */
+void ldbFlushLog(list *log) {
+    listNode *ln;
+
+    while((ln = listFirst(log)) != NULL)
+        listDelNode(log,ln);
+}
+
+/* Enable debug mode of Lua scripts for this client. */
+void ldbEnable(client *c) {
+    c->flags |= CLIENT_LUA_DEBUG;
+    ldbFlushLog(ldb.logs);
+    ldb.conn = c->conn;
+    ldb.step = 1;
+    ldb.bpcount = 0;
+    ldb.luabp = 0;
+    sdsfree(ldb.cbuf);
+    ldb.cbuf = sdsempty();
+    ldb.maxlen = LDB_MAX_LEN_DEFAULT;
+    ldb.maxlen_hint_sent = 0;
+}
+
+/* Exit debugging mode from the POV of client. This function is not enough
+ * to properly shut down a client debugging session, see ldbEndSession()
+ * for more information. */
+void ldbDisable(client *c) {
+    c->flags &= ~(CLIENT_LUA_DEBUG|CLIENT_LUA_DEBUG_SYNC);
+}
+
+/* Append a log entry to the specified LDB log. */
+void ldbLog(sds entry) {
+    listAddNodeTail(ldb.logs,entry);
+}
+
+/* A version of ldbLog() which prevents producing logs greater than
+ * ldb.maxlen. The first time the limit is reached a hint is generated
+ * to inform the user that reply trimming can be disabled using the
+ * debugger "maxlen" command. */
+void ldbLogWithMaxLen(sds entry) {
+    int trimmed = 0;
+    if (ldb.maxlen && sdslen(entry) > ldb.maxlen) {
+        sdsrange(entry,0,ldb.maxlen-1);
+        entry = sdscatlen(entry," ...",4);
+        trimmed = 1;
+    }
+    ldbLog(entry);
+    if (trimmed && ldb.maxlen_hint_sent == 0) {
+        ldb.maxlen_hint_sent = 1;
+        ldbLog(sdsnew(
+        "<hint> The above reply was trimmed. Use 'maxlen 0' to disable trimming."));
+    }
+}
+
+/* Send ldb.logs to the debugging client as a multi-bulk reply
+ * consisting of simple strings. Log entries which include newlines have them
+ * replaced with spaces. The entries sent are also consumed. */
+void ldbSendLogs(void) {
+    sds proto = sdsempty();
+    proto = sdscatfmt(proto,"*%i\r\n", (int)listLength(ldb.logs));
+    while(listLength(ldb.logs)) {
+        listNode *ln = listFirst(ldb.logs);
+        proto = sdscatlen(proto,"+",1);
+        sdsmapchars(ln->value,"\r\n","  ",2);
+        proto = sdscatsds(proto,ln->value);
+        proto = sdscatlen(proto,"\r\n",2);
+        listDelNode(ldb.logs,ln);
+    }
+    if (connWrite(ldb.conn,proto,sdslen(proto)) == -1) {
+        /* Avoid warning. We don't check the return value of write()
+         * since the next read() will catch the I/O error and will
+         * close the debugging session. */
+    }
+    sdsfree(proto);
+}
+
+/* Start a debugging session before calling EVAL implementation.
+ * The technique we use is to capture the client socket file descriptor,
+ * in order to perform direct I/O with it from within Lua hooks. This
+ * way we don't have to re-enter Redis in order to handle I/O.
+ *
+ * The function returns 1 if the caller should proceed to call EVAL,
+ * and 0 if instead the caller should abort the operation (this happens
+ * for the parent in a forked session, since it's up to the children
+ * to continue, or when fork returned an error).
+ *
+ * The caller should call ldbEndSession() only if ldbStartSession()
+ * returned 1. */
+int ldbStartSession(client *c) {
+    ldb.forked = (c->flags & CLIENT_LUA_DEBUG_SYNC) == 0;
+    if (ldb.forked) {
+        pid_t cp = redisFork(CHILD_TYPE_LDB);
+        if (cp == -1) {
+            addReplyErrorFormat(c,"Fork() failed: can't run EVAL in debugging mode: %s", strerror(errno));
+            return 0;
+        } else if (cp == 0) {
+            /* Child. Let's ignore important signals handled by the parent. */
+            struct sigaction act;
+            sigemptyset(&act.sa_mask);
+            act.sa_flags = 0;
+            act.sa_handler = SIG_IGN;
+            sigaction(SIGTERM, &act, NULL);
+            sigaction(SIGINT, &act, NULL);
+
+            /* Log the creation of the child and close the listening
+             * socket to make sure if the parent crashes a reset is sent
+             * to the clients. */
+            serverLog(LL_WARNING,"Redis forked for debugging eval");
+        } else {
+            /* Parent */
+            listAddNodeTail(ldb.children,(void*)(unsigned long)cp);
+            freeClientAsync(c); /* Close the client in the parent side. */
+            return 0;
+        }
+    } else {
+        serverLog(LL_WARNING,
+            "Redis synchronous debugging eval session started");
+    }
+
+    /* Setup our debugging session. */
+    connBlock(ldb.conn);
+    connSendTimeout(ldb.conn,5000);
+    ldb.active = 1;
+
+    /* First argument of EVAL is the script itself. We split it into different
+     * lines since this is the way the debugger accesses the source code. */
+    sds srcstring = sdsdup(c->argv[1]->ptr);
+    size_t srclen = sdslen(srcstring);
+    while(srclen && (srcstring[srclen-1] == '\n' ||
+                     srcstring[srclen-1] == '\r'))
+    {
+        srcstring[--srclen] = '\0';
+    }
+    sdssetlen(srcstring,srclen);
+    ldb.src = sdssplitlen(srcstring,sdslen(srcstring),"\n",1,&ldb.lines);
+    sdsfree(srcstring);
+    return 1;
+}
+
+/* End a debugging session after the EVAL call with debugging enabled
+ * returned. */
+void ldbEndSession(client *c) {
+    /* Emit the remaining logs and an <endsession> mark. */
+    ldbLog(sdsnew("<endsession>"));
+    ldbSendLogs();
+
+    /* If it's a fork()ed session, we just exit. */
+    if (ldb.forked) {
+        writeToClient(c,0);
+        serverLog(LL_WARNING,"Lua debugging session child exiting");
+        exitFromChild(0);
+    } else {
+        serverLog(LL_WARNING,
+            "Redis synchronous debugging eval session ended");
+    }
+
+    /* Otherwise let's restore client's state. */
+    connNonBlock(ldb.conn);
+    connSendTimeout(ldb.conn,0);
+
+    /* Close the client connection after sending the final EVAL reply
+     * in order to signal the end of the debugging session. */
+    c->flags |= CLIENT_CLOSE_AFTER_REPLY;
+
+    /* Cleanup. */
+    sdsfreesplitres(ldb.src,ldb.lines);
+    ldb.lines = 0;
+    ldb.active = 0;
+}
+
+/* If the specified pid is among the list of children spawned for
+ * forked debugging sessions, it is removed from the children list.
+ * If the pid was found non-zero is returned. */
+int ldbRemoveChild(pid_t pid) {
+    listNode *ln = listSearchKey(ldb.children,(void*)(unsigned long)pid);
+    if (ln) {
+        listDelNode(ldb.children,ln);
+        return 1;
+    }
+    return 0;
+}
+
+/* Return the number of children we still did not receive termination
+ * acknowledge via wait() in the parent process. */
+int ldbPendingChildren(void) {
+    return listLength(ldb.children);
+}
+
+/* Kill all the forked sessions. */
+void ldbKillForkedSessions(void) {
+    listIter li;
+    listNode *ln;
+
+    listRewind(ldb.children,&li);
+    while((ln = listNext(&li))) {
+        pid_t pid = (unsigned long) ln->value;
+        serverLog(LL_WARNING,"Killing debugging session %ld",(long)pid);
+        kill(pid,SIGKILL);
+    }
+    listRelease(ldb.children);
+    ldb.children = listCreate();
+}
+
+/* Wrapper for EVAL / EVALSHA that enables debugging, and makes sure
+ * that when EVAL returns, whatever happened, the session is ended. */
+void evalGenericCommandWithDebugging(client *c, int evalsha) {
+    if (ldbStartSession(c)) {
+        evalGenericCommand(c,evalsha);
+        ldbEndSession(c);
+    } else {
+        ldbDisable(c);
+    }
+}
+
+/* Return a pointer to ldb.src source code line, considering line to be
+ * one-based, and returning a special string for out of range lines. */
+char *ldbGetSourceLine(int line) {
+    int idx = line-1;
+    if (idx < 0 || idx >= ldb.lines) return "<out of range source code line>";
+    return ldb.src[idx];
+}
+
+/* Return true if there is a breakpoint in the specified line. */
+int ldbIsBreakpoint(int line) {
+    int j;
+
+    for (j = 0; j < ldb.bpcount; j++)
+        if (ldb.bp[j] == line) return 1;
+    return 0;
+}
+
+/* Add the specified breakpoint. Ignore it if we already reached the max.
+ * Returns 1 if the breakpoint was added (or was already set). 0 if there is
+ * no space for the breakpoint or if the line is invalid. */
+int ldbAddBreakpoint(int line) {
+    if (line <= 0 || line > ldb.lines) return 0;
+    if (!ldbIsBreakpoint(line) && ldb.bpcount != LDB_BREAKPOINTS_MAX) {
+        ldb.bp[ldb.bpcount++] = line;
+        return 1;
+    }
+    return 0;
+}
+
+/* Remove the specified breakpoint, returning 1 if the operation was
+ * performed or 0 if there was no such breakpoint. */
+int ldbDelBreakpoint(int line) {
+    int j;
+
+    for (j = 0; j < ldb.bpcount; j++) {
+        if (ldb.bp[j] == line) {
+            ldb.bpcount--;
+            memmove(ldb.bp+j,ldb.bp+j+1,ldb.bpcount-j);
+            return 1;
+        }
+    }
+    return 0;
+}
+
+/* Expect a valid multi-bulk command in the debugging client query buffer.
+ * On success the command is parsed and returned as an array of SDS strings,
+ * otherwise NULL is returned and there is to read more buffer. */
+sds *ldbReplParseCommand(int *argcp, char** err) {
+    static char* protocol_error = "protocol error";
+    sds *argv = NULL;
+    int argc = 0;
+    if (sdslen(ldb.cbuf) == 0) return NULL;
+
+    /* Working on a copy is simpler in this case. We can modify it freely
+     * for the sake of simpler parsing. */
+    sds copy = sdsdup(ldb.cbuf);
+    char *p = copy;
+
+    /* This Redis protocol parser is a joke... just the simplest thing that
+     * works in this context. It is also very forgiving regarding broken
+     * protocol. */
+
+    /* Seek and parse *<count>\r\n. */
+    p = strchr(p,'*'); if (!p) goto protoerr;
+    char *plen = p+1; /* Multi bulk len pointer. */
+    p = strstr(p,"\r\n"); if (!p) goto keep_reading;
+    *p = '\0'; p += 2;
+    *argcp = atoi(plen);
+    if (*argcp <= 0 || *argcp > 1024) goto protoerr;
+
+    /* Parse each argument. */
+    argv = zmalloc(sizeof(sds)*(*argcp));
+    argc = 0;
+    while(argc < *argcp) {
+        /* reached the end but there should be more data to read */
+        if (*p == '\0') goto keep_reading;
+
+        if (*p != '$') goto protoerr;
+        plen = p+1; /* Bulk string len pointer. */
+        p = strstr(p,"\r\n"); if (!p) goto keep_reading;
+        *p = '\0'; p += 2;
+        int slen = atoi(plen); /* Length of this arg. */
+        if (slen <= 0 || slen > 1024) goto protoerr;
+        if ((size_t)(p + slen + 2 - copy) > sdslen(copy) ) goto keep_reading;
+        argv[argc++] = sdsnewlen(p,slen);
+        p += slen; /* Skip the already parsed argument. */
+        if (p[0] != '\r' || p[1] != '\n') goto protoerr;
+        p += 2; /* Skip \r\n. */
+    }
+    sdsfree(copy);
+    return argv;
+
+protoerr:
+    *err = protocol_error;
+keep_reading:
+    sdsfreesplitres(argv,argc);
+    sdsfree(copy);
+    return NULL;
+}
+
+/* Log the specified line in the Lua debugger output. */
+void ldbLogSourceLine(int lnum) {
+    char *line = ldbGetSourceLine(lnum);
+    char *prefix;
+    int bp = ldbIsBreakpoint(lnum);
+    int current = ldb.currentline == lnum;
+
+    if (current && bp)
+        prefix = "->#";
+    else if (current)
+        prefix = "-> ";
+    else if (bp)
+        prefix = "  #";
+    else
+        prefix = "   ";
+    sds thisline = sdscatprintf(sdsempty(),"%s%-3d %s", prefix, lnum, line);
+    ldbLog(thisline);
+}
+
+/* Implement the "list" command of the Lua debugger. If around is 0
+ * the whole file is listed, otherwise only a small portion of the file
+ * around the specified line is shown. When a line number is specified
+ * the amount of context (lines before/after) is specified via the
+ * 'context' argument. */
+void ldbList(int around, int context) {
+    int j;
+
+    for (j = 1; j <= ldb.lines; j++) {
+        if (around != 0 && abs(around-j) > context) continue;
+        ldbLogSourceLine(j);
+    }
+}
+
+/* Append a human readable representation of the Lua value at position 'idx'
+ * on the stack of the 'lua' state, to the SDS string passed as argument.
+ * The new SDS string with the represented value attached is returned.
+ * Used in order to implement ldbLogStackValue().
+ *
+ * The element is not automatically removed from the stack, nor it is
+ * converted to a different type. */
+#define LDB_MAX_VALUES_DEPTH (LUA_MINSTACK/2)
+sds ldbCatStackValueRec(sds s, lua_State *lua, int idx, int level) {
+    int t = lua_type(lua,idx);
+
+    if (level++ == LDB_MAX_VALUES_DEPTH)
+        return sdscat(s,"<max recursion level reached! Nested table?>");
+
+    switch(t) {
+    case LUA_TSTRING:
+        {
+        size_t strl;
+        char *strp = (char*)lua_tolstring(lua,idx,&strl);
+        s = sdscatrepr(s,strp,strl);
+        }
+        break;
+    case LUA_TBOOLEAN:
+        s = sdscat(s,lua_toboolean(lua,idx) ? "true" : "false");
+        break;
+    case LUA_TNUMBER:
+        s = sdscatprintf(s,"%g",(double)lua_tonumber(lua,idx));
+        break;
+    case LUA_TNIL:
+        s = sdscatlen(s,"nil",3);
+        break;
+    case LUA_TTABLE:
+        {
+        int expected_index = 1; /* First index we expect in an array. */
+        int is_array = 1; /* Will be set to null if check fails. */
+        /* Note: we create two representations at the same time, one
+         * assuming the table is an array, one assuming it is not. At the
+         * end we know what is true and select the right one. */
+        sds repr1 = sdsempty();
+        sds repr2 = sdsempty();
+        lua_pushnil(lua); /* The first key to start the iteration is nil. */
+        while (lua_next(lua,idx-1)) {
+            /* Test if so far the table looks like an array. */
+            if (is_array &&
+                (lua_type(lua,-2) != LUA_TNUMBER ||
+                 lua_tonumber(lua,-2) != expected_index)) is_array = 0;
+            /* Stack now: table, key, value */
+            /* Array repr. */
+            repr1 = ldbCatStackValueRec(repr1,lua,-1,level);
+            repr1 = sdscatlen(repr1,"; ",2);
+            /* Full repr. */
+            repr2 = sdscatlen(repr2,"[",1);
+            repr2 = ldbCatStackValueRec(repr2,lua,-2,level);
+            repr2 = sdscatlen(repr2,"]=",2);
+            repr2 = ldbCatStackValueRec(repr2,lua,-1,level);
+            repr2 = sdscatlen(repr2,"; ",2);
+            lua_pop(lua,1); /* Stack: table, key. Ready for next iteration. */
+            expected_index++;
+        }
+        /* Strip the last " ;" from both the representations. */
+        if (sdslen(repr1)) sdsrange(repr1,0,-3);
+        if (sdslen(repr2)) sdsrange(repr2,0,-3);
+        /* Select the right one and discard the other. */
+        s = sdscatlen(s,"{",1);
+        s = sdscatsds(s,is_array ? repr1 : repr2);
+        s = sdscatlen(s,"}",1);
+        sdsfree(repr1);
+        sdsfree(repr2);
+        }
+        break;
+    case LUA_TFUNCTION:
+    case LUA_TUSERDATA:
+    case LUA_TTHREAD:
+    case LUA_TLIGHTUSERDATA:
+        {
+        const void *p = lua_topointer(lua,idx);
+        char *typename = "unknown";
+        if (t == LUA_TFUNCTION) typename = "function";
+        else if (t == LUA_TUSERDATA) typename = "userdata";
+        else if (t == LUA_TTHREAD) typename = "thread";
+        else if (t == LUA_TLIGHTUSERDATA) typename = "light-userdata";
+        s = sdscatprintf(s,"\"%s@%p\"",typename,p);
+        }
+        break;
+    default:
+        s = sdscat(s,"\"<unknown-lua-type>\"");
+        break;
+    }
+    return s;
+}
+
+/* Higher level wrapper for ldbCatStackValueRec() that just uses an initial
+ * recursion level of '0'. */
+sds ldbCatStackValue(sds s, lua_State *lua, int idx) {
+    return ldbCatStackValueRec(s,lua,idx,0);
+}
+
+/* Produce a debugger log entry representing the value of the Lua object
+ * currently on the top of the stack. The element is not popped nor modified.
+ * Check ldbCatStackValue() for the actual implementation. */
+void ldbLogStackValue(lua_State *lua, char *prefix) {
+    sds s = sdsnew(prefix);
+    s = ldbCatStackValue(s,lua,-1);
+    ldbLogWithMaxLen(s);
+}
+
+char *ldbRedisProtocolToHuman_Int(sds *o, char *reply);
+char *ldbRedisProtocolToHuman_Bulk(sds *o, char *reply);
+char *ldbRedisProtocolToHuman_Status(sds *o, char *reply);
+char *ldbRedisProtocolToHuman_MultiBulk(sds *o, char *reply);
+char *ldbRedisProtocolToHuman_Set(sds *o, char *reply);
+char *ldbRedisProtocolToHuman_Map(sds *o, char *reply);
+char *ldbRedisProtocolToHuman_Null(sds *o, char *reply);
+char *ldbRedisProtocolToHuman_Bool(sds *o, char *reply);
+char *ldbRedisProtocolToHuman_Double(sds *o, char *reply);
+
+/* Get Redis protocol from 'reply' and appends it in human readable form to
+ * the passed SDS string 'o'.
+ *
+ * Note that the SDS string is passed by reference (pointer of pointer to
+ * char*) so that we can return a modified pointer, as for SDS semantics. */
+char *ldbRedisProtocolToHuman(sds *o, char *reply) {
+    char *p = reply;
+    switch(*p) {
+    case ':': p = ldbRedisProtocolToHuman_Int(o,reply); break;
+    case '$': p = ldbRedisProtocolToHuman_Bulk(o,reply); break;
+    case '+': p = ldbRedisProtocolToHuman_Status(o,reply); break;
+    case '-': p = ldbRedisProtocolToHuman_Status(o,reply); break;
+    case '*': p = ldbRedisProtocolToHuman_MultiBulk(o,reply); break;
+    case '~': p = ldbRedisProtocolToHuman_Set(o,reply); break;
+    case '%': p = ldbRedisProtocolToHuman_Map(o,reply); break;
+    case '_': p = ldbRedisProtocolToHuman_Null(o,reply); break;
+    case '#': p = ldbRedisProtocolToHuman_Bool(o,reply); break;
+    case ',': p = ldbRedisProtocolToHuman_Double(o,reply); break;
+    }
+    return p;
+}
+
+/* The following functions are helpers for ldbRedisProtocolToHuman(), each
+ * take care of a given Redis return type. */
+
+char *ldbRedisProtocolToHuman_Int(sds *o, char *reply) {
+    char *p = strchr(reply+1,'\r');
+    *o = sdscatlen(*o,reply+1,p-reply-1);
+    return p+2;
+}
+
+char *ldbRedisProtocolToHuman_Bulk(sds *o, char *reply) {
+    char *p = strchr(reply+1,'\r');
+    long long bulklen;
+
+    string2ll(reply+1,p-reply-1,&bulklen);
+    if (bulklen == -1) {
+        *o = sdscatlen(*o,"NULL",4);
+        return p+2;
+    } else {
+        *o = sdscatrepr(*o,p+2,bulklen);
+        return p+2+bulklen+2;
+    }
+}
+
+char *ldbRedisProtocolToHuman_Status(sds *o, char *reply) {
+    char *p = strchr(reply+1,'\r');
+
+    *o = sdscatrepr(*o,reply,p-reply);
+    return p+2;
+}
+
+char *ldbRedisProtocolToHuman_MultiBulk(sds *o, char *reply) {
+    char *p = strchr(reply+1,'\r');
+    long long mbulklen;
+    int j = 0;
+
+    string2ll(reply+1,p-reply-1,&mbulklen);
+    p += 2;
+    if (mbulklen == -1) {
+        *o = sdscatlen(*o,"NULL",4);
+        return p;
+    }
+    *o = sdscatlen(*o,"[",1);
+    for (j = 0; j < mbulklen; j++) {
+        p = ldbRedisProtocolToHuman(o,p);
+        if (j != mbulklen-1) *o = sdscatlen(*o,",",1);
+    }
+    *o = sdscatlen(*o,"]",1);
+    return p;
+}
+
+char *ldbRedisProtocolToHuman_Set(sds *o, char *reply) {
+    char *p = strchr(reply+1,'\r');
+    long long mbulklen;
+    int j = 0;
+
+    string2ll(reply+1,p-reply-1,&mbulklen);
+    p += 2;
+    *o = sdscatlen(*o,"~(",2);
+    for (j = 0; j < mbulklen; j++) {
+        p = ldbRedisProtocolToHuman(o,p);
+        if (j != mbulklen-1) *o = sdscatlen(*o,",",1);
+    }
+    *o = sdscatlen(*o,")",1);
+    return p;
+}
+
+char *ldbRedisProtocolToHuman_Map(sds *o, char *reply) {
+    char *p = strchr(reply+1,'\r');
+    long long mbulklen;
+    int j = 0;
+
+    string2ll(reply+1,p-reply-1,&mbulklen);
+    p += 2;
+    *o = sdscatlen(*o,"{",1);
+    for (j = 0; j < mbulklen; j++) {
+        p = ldbRedisProtocolToHuman(o,p);
+        *o = sdscatlen(*o," => ",4);
+        p = ldbRedisProtocolToHuman(o,p);
+        if (j != mbulklen-1) *o = sdscatlen(*o,",",1);
+    }
+    *o = sdscatlen(*o,"}",1);
+    return p;
+}
+
+char *ldbRedisProtocolToHuman_Null(sds *o, char *reply) {
+    char *p = strchr(reply+1,'\r');
+    *o = sdscatlen(*o,"(null)",6);
+    return p+2;
+}
+
+char *ldbRedisProtocolToHuman_Bool(sds *o, char *reply) {
+    char *p = strchr(reply+1,'\r');
+    if (reply[1] == 't')
+        *o = sdscatlen(*o,"#true",5);
+    else
+        *o = sdscatlen(*o,"#false",6);
+    return p+2;
+}
+
+char *ldbRedisProtocolToHuman_Double(sds *o, char *reply) {
+    char *p = strchr(reply+1,'\r');
+    *o = sdscatlen(*o,"(double) ",9);
+    *o = sdscatlen(*o,reply+1,p-reply-1);
+    return p+2;
+}
+
+/* Log a Redis reply as debugger output, in a human readable format.
+ * If the resulting string is longer than 'len' plus a few more chars
+ * used as prefix, it gets truncated. */
+void ldbLogRedisReply(char *reply) {
+    sds log = sdsnew("<reply> ");
+    ldbRedisProtocolToHuman(&log,reply);
+    ldbLogWithMaxLen(log);
+}
+
+/* Implements the "print <var>" command of the Lua debugger. It scans for Lua
+ * var "varname" starting from the current stack frame up to the top stack
+ * frame. The first matching variable is printed. */
+void ldbPrint(lua_State *lua, char *varname) {
+    lua_Debug ar;
+
+    int l = 0; /* Stack level. */
+    while (lua_getstack(lua,l,&ar) != 0) {
+        l++;
+        const char *name;
+        int i = 1; /* Variable index. */
+        while((name = lua_getlocal(lua,&ar,i)) != NULL) {
+            i++;
+            if (strcmp(varname,name) == 0) {
+                ldbLogStackValue(lua,"<value> ");
+                lua_pop(lua,1);
+                return;
+            } else {
+                lua_pop(lua,1); /* Discard the var name on the stack. */
+            }
+        }
+    }
+
+    /* Let's try with global vars in two selected cases */
+    if (!strcmp(varname,"ARGV") || !strcmp(varname,"KEYS")) {
+        lua_getglobal(lua, varname);
+        ldbLogStackValue(lua,"<value> ");
+        lua_pop(lua,1);
+    } else {
+        ldbLog(sdsnew("No such variable."));
+    }
+}
+
+/* Implements the "print" command (without arguments) of the Lua debugger.
+ * Prints all the variables in the current stack frame. */
+void ldbPrintAll(lua_State *lua) {
+    lua_Debug ar;
+    int vars = 0;
+
+    if (lua_getstack(lua,0,&ar) != 0) {
+        const char *name;
+        int i = 1; /* Variable index. */
+        while((name = lua_getlocal(lua,&ar,i)) != NULL) {
+            i++;
+            if (!strstr(name,"(*temporary)")) {
+                sds prefix = sdscatprintf(sdsempty(),"<value> %s = ",name);
+                ldbLogStackValue(lua,prefix);
+                sdsfree(prefix);
+                vars++;
+            }
+            lua_pop(lua,1);
+        }
+    }
+
+    if (vars == 0) {
+        ldbLog(sdsnew("No local variables in the current context."));
+    }
+}
+
+/* Implements the break command to list, add and remove breakpoints. */
+void ldbBreak(sds *argv, int argc) {
+    if (argc == 1) {
+        if (ldb.bpcount == 0) {
+            ldbLog(sdsnew("No breakpoints set. Use 'b <line>' to add one."));
+            return;
+        } else {
+            ldbLog(sdscatfmt(sdsempty(),"%i breakpoints set:",ldb.bpcount));
+            int j;
+            for (j = 0; j < ldb.bpcount; j++)
+                ldbLogSourceLine(ldb.bp[j]);
+        }
+    } else {
+        int j;
+        for (j = 1; j < argc; j++) {
+            char *arg = argv[j];
+            long line;
+            if (!string2l(arg,sdslen(arg),&line)) {
+                ldbLog(sdscatfmt(sdsempty(),"Invalid argument:'%s'",arg));
+            } else {
+                if (line == 0) {
+                    ldb.bpcount = 0;
+                    ldbLog(sdsnew("All breakpoints removed."));
+                } else if (line > 0) {
+                    if (ldb.bpcount == LDB_BREAKPOINTS_MAX) {
+                        ldbLog(sdsnew("Too many breakpoints set."));
+                    } else if (ldbAddBreakpoint(line)) {
+                        ldbList(line,1);
+                    } else {
+                        ldbLog(sdsnew("Wrong line number."));
+                    }
+                } else if (line < 0) {
+                    if (ldbDelBreakpoint(-line))
+                        ldbLog(sdsnew("Breakpoint removed."));
+                    else
+                        ldbLog(sdsnew("No breakpoint in the specified line."));
+                }
+            }
+        }
+    }
+}
+
+/* Implements the Lua debugger "eval" command. It just compiles the user
+ * passed fragment of code and executes it, showing the result left on
+ * the stack. */
+void ldbEval(lua_State *lua, sds *argv, int argc) {
+    /* Glue the script together if it is composed of multiple arguments. */
+    sds code = sdsjoinsds(argv+1,argc-1," ",1);
+    sds expr = sdscatsds(sdsnew("return "),code);
+
+    /* Try to compile it as an expression, prepending "return ". */
+    if (luaL_loadbuffer(lua,expr,sdslen(expr),"@ldb_eval")) {
+        lua_pop(lua,1);
+        /* Failed? Try as a statement. */
+        if (luaL_loadbuffer(lua,code,sdslen(code),"@ldb_eval")) {
+            ldbLog(sdscatfmt(sdsempty(),"<error> %s",lua_tostring(lua,-1)));
+            lua_pop(lua,1);
+            sdsfree(code);
+            sdsfree(expr);
+            return;
+        }
+    }
+
+    /* Call it. */
+    sdsfree(code);
+    sdsfree(expr);
+    if (lua_pcall(lua,0,1,0)) {
+        ldbLog(sdscatfmt(sdsempty(),"<error> %s",lua_tostring(lua,-1)));
+        lua_pop(lua,1);
+        return;
+    }
+    ldbLogStackValue(lua,"<retval> ");
+    lua_pop(lua,1);
+}
+
+/* Implement the debugger "redis" command. We use a trick in order to make
+ * the implementation very simple: we just call the Lua redis.call() command
+ * implementation, with ldb.step enabled, so as a side effect the Redis command
+ * and its reply are logged. */
+void ldbRedis(lua_State *lua, sds *argv, int argc) {
+    int j, saved_rc = server.lua_replicate_commands;
+
+    if (!lua_checkstack(lua, argc + 1)) {
+        /* Increase the Lua stack if needed to make sure there is enough room
+         * to push 'argc + 1' elements to the stack. On failure, return error.
+         * Notice that we need, in worst case, 'argc + 1' elements because we push all the arguments
+         * given by the user (without the first argument) and we also push the 'redis' global table and
+         * 'redis.call' function so:
+         * (1 (redis table)) + (1 (redis.call function)) + (argc - 1 (all arguments without the first)) = argc + 1*/
+        ldbLogRedisReply("max lua stack reached");
+        return;
+    }
+
+    lua_getglobal(lua,"redis");
+    lua_pushstring(lua,"call");
+    lua_gettable(lua,-2);       /* Stack: redis, redis.call */
+    for (j = 1; j < argc; j++)
+        lua_pushlstring(lua,argv[j],sdslen(argv[j]));
+    ldb.step = 1;               /* Force redis.call() to log. */
+    server.lua_replicate_commands = 1;
+    lua_pcall(lua,argc-1,1,0);  /* Stack: redis, result */
+    ldb.step = 0;               /* Disable logging. */
+    server.lua_replicate_commands = saved_rc;
+    lua_pop(lua,2);             /* Discard the result and clean the stack. */
+}
+
+/* Implements "trace" command of the Lua debugger. It just prints a backtrace
+ * querying Lua starting from the current callframe back to the outer one. */
+void ldbTrace(lua_State *lua) {
+    lua_Debug ar;
+    int level = 0;
+
+    while(lua_getstack(lua,level,&ar)) {
+        lua_getinfo(lua,"Snl",&ar);
+        if(strstr(ar.short_src,"user_script") != NULL) {
+            ldbLog(sdscatprintf(sdsempty(),"%s %s:",
+                (level == 0) ? "In" : "From",
+                ar.name ? ar.name : "top level"));
+            ldbLogSourceLine(ar.currentline);
+        }
+        level++;
+    }
+    if (level == 0) {
+        ldbLog(sdsnew("<error> Can't retrieve Lua stack."));
+    }
+}
+
+/* Implements the debugger "maxlen" command. It just queries or sets the
+ * ldb.maxlen variable. */
+void ldbMaxlen(sds *argv, int argc) {
+    if (argc == 2) {
+        int newval = atoi(argv[1]);
+        ldb.maxlen_hint_sent = 1; /* User knows about this command. */
+        if (newval != 0 && newval <= 60) newval = 60;
+        ldb.maxlen = newval;
+    }
+    if (ldb.maxlen) {
+        ldbLog(sdscatprintf(sdsempty(),"<value> replies are truncated at %d bytes.",(int)ldb.maxlen));
+    } else {
+        ldbLog(sdscatprintf(sdsempty(),"<value> replies are unlimited."));
+    }
+}
+
+/* Read debugging commands from client.
+ * Return C_OK if the debugging session is continuing, otherwise
+ * C_ERR if the client closed the connection or is timing out. */
+int ldbRepl(lua_State *lua) {
+    sds *argv;
+    int argc;
+    char* err = NULL;
+
+    /* We continue processing commands until a command that should return
+     * to the Lua interpreter is found. */
+    while(1) {
+        while((argv = ldbReplParseCommand(&argc, &err)) == NULL) {
+            char buf[1024];
+            if (err) {
+                lua_pushstring(lua, err);
+                lua_error(lua);
+            }
+            int nread = connRead(ldb.conn,buf,sizeof(buf));
+            if (nread <= 0) {
+                /* Make sure the script runs without user input since the
+                 * client is no longer connected. */
+                ldb.step = 0;
+                ldb.bpcount = 0;
+                return C_ERR;
+            }
+            ldb.cbuf = sdscatlen(ldb.cbuf,buf,nread);
+            /* after 1M we will exit with an error
+             * so that the client will not blow the memory
+             */
+            if (sdslen(ldb.cbuf) > 1<<20) {
+                sdsfree(ldb.cbuf);
+                ldb.cbuf = sdsempty();
+                lua_pushstring(lua, "max client buffer reached");
+                lua_error(lua);
+            }
+        }
+
+        /* Flush the old buffer. */
+        sdsfree(ldb.cbuf);
+        ldb.cbuf = sdsempty();
+
+        /* Execute the command. */
+        if (!strcasecmp(argv[0],"h") || !strcasecmp(argv[0],"help")) {
+ldbLog(sdsnew("Redis Lua debugger help:"));
+ldbLog(sdsnew("[h]elp               Show this help."));
+ldbLog(sdsnew("[s]tep               Run current line and stop again."));
+ldbLog(sdsnew("[n]ext               Alias for step."));
+ldbLog(sdsnew("[c]ontinue           Run till next breakpoint."));
+ldbLog(sdsnew("[l]ist               List source code around current line."));
+ldbLog(sdsnew("[l]ist [line]        List source code around [line]."));
+ldbLog(sdsnew("                     line = 0 means: current position."));
+ldbLog(sdsnew("[l]ist [line] [ctx]  In this form [ctx] specifies how many lines"));
+ldbLog(sdsnew("                     to show before/after [line]."));
+ldbLog(sdsnew("[w]hole              List all source code. Alias for 'list 1 1000000'."));
+ldbLog(sdsnew("[p]rint              Show all the local variables."));
+ldbLog(sdsnew("[p]rint <var>        Show the value of the specified variable."));
+ldbLog(sdsnew("                     Can also show global vars KEYS and ARGV."));
+ldbLog(sdsnew("[b]reak              Show all breakpoints."));
+ldbLog(sdsnew("[b]reak <line>       Add a breakpoint to the specified line."));
+ldbLog(sdsnew("[b]reak -<line>      Remove breakpoint from the specified line."));
+ldbLog(sdsnew("[b]reak 0            Remove all breakpoints."));
+ldbLog(sdsnew("[t]race              Show a backtrace."));
+ldbLog(sdsnew("[e]val <code>        Execute some Lua code (in a different callframe)."));
+ldbLog(sdsnew("[r]edis <cmd>        Execute a Redis command."));
+ldbLog(sdsnew("[m]axlen [len]       Trim logged Redis replies and Lua var dumps to len."));
+ldbLog(sdsnew("                     Specifying zero as <len> means unlimited."));
+ldbLog(sdsnew("[a]bort              Stop the execution of the script. In sync"));
+ldbLog(sdsnew("                     mode dataset changes will be retained."));
+ldbLog(sdsnew(""));
+ldbLog(sdsnew("Debugger functions you can call from Lua scripts:"));
+ldbLog(sdsnew("redis.debug()        Produce logs in the debugger console."));
+ldbLog(sdsnew("redis.breakpoint()   Stop execution like if there was a breakpoint in the"));
+ldbLog(sdsnew("                     next line of code."));
+            ldbSendLogs();
+        } else if (!strcasecmp(argv[0],"s") || !strcasecmp(argv[0],"step") ||
+                   !strcasecmp(argv[0],"n") || !strcasecmp(argv[0],"next")) {
+            ldb.step = 1;
+            break;
+        } else if (!strcasecmp(argv[0],"c") || !strcasecmp(argv[0],"continue")){
+            break;
+        } else if (!strcasecmp(argv[0],"t") || !strcasecmp(argv[0],"trace")) {
+            ldbTrace(lua);
+            ldbSendLogs();
+        } else if (!strcasecmp(argv[0],"m") || !strcasecmp(argv[0],"maxlen")) {
+            ldbMaxlen(argv,argc);
+            ldbSendLogs();
+        } else if (!strcasecmp(argv[0],"b") || !strcasecmp(argv[0],"break")) {
+            ldbBreak(argv,argc);
+            ldbSendLogs();
+        } else if (!strcasecmp(argv[0],"e") || !strcasecmp(argv[0],"eval")) {
+            ldbEval(lua,argv,argc);
+            ldbSendLogs();
+        } else if (!strcasecmp(argv[0],"a") || !strcasecmp(argv[0],"abort")) {
+            lua_pushstring(lua, "script aborted for user request");
+            lua_error(lua);
+        } else if (argc > 1 &&
+                   (!strcasecmp(argv[0],"r") || !strcasecmp(argv[0],"redis"))) {
+            ldbRedis(lua,argv,argc);
+            ldbSendLogs();
+        } else if ((!strcasecmp(argv[0],"p") || !strcasecmp(argv[0],"print"))) {
+            if (argc == 2)
+                ldbPrint(lua,argv[1]);
+            else
+                ldbPrintAll(lua);
+            ldbSendLogs();
+        } else if (!strcasecmp(argv[0],"l") || !strcasecmp(argv[0],"list")){
+            int around = ldb.currentline, ctx = 5;
+            if (argc > 1) {
+                int num = atoi(argv[1]);
+                if (num > 0) around = num;
+            }
+            if (argc > 2) ctx = atoi(argv[2]);
+            ldbList(around,ctx);
+            ldbSendLogs();
+        } else if (!strcasecmp(argv[0],"w") || !strcasecmp(argv[0],"whole")){
+            ldbList(1,1000000);
+            ldbSendLogs();
+        } else {
+            ldbLog(sdsnew("<error> Unknown Redis Lua debugger command or "
+                          "wrong number of arguments."));
+            ldbSendLogs();
+        }
+
+        /* Free the command vector. */
+        sdsfreesplitres(argv,argc);
+    }
+
+    /* Free the current command argv if we break inside the while loop. */
+    sdsfreesplitres(argv,argc);
+    return C_OK;
+}
+
+/* This is the core of our Lua debugger, called each time Lua is about
+ * to start executing a new line. */
+void luaLdbLineHook(lua_State *lua, lua_Debug *ar) {
+    lua_getstack(lua,0,ar);
+    lua_getinfo(lua,"Sl",ar);
+    ldb.currentline = ar->currentline;
+
+    int bp = ldbIsBreakpoint(ldb.currentline) || ldb.luabp;
+    int timeout = 0;
+
+    /* Events outside our script are not interesting. */
+    if(strstr(ar->short_src,"user_script") == NULL) return;
+
+    /* Check if a timeout occurred. */
+    if (ar->event == LUA_HOOKCOUNT && ldb.step == 0 && bp == 0) {
+        mstime_t elapsed = elapsedMs(server.lua_time_start);
+        mstime_t timelimit = server.lua_time_limit ?
+                             server.lua_time_limit : 5000;
+        if (elapsed >= timelimit) {
+            timeout = 1;
+            ldb.step = 1;
+        } else {
+            return; /* No timeout, ignore the COUNT event. */
+        }
+    }
+
+    if (ldb.step || bp) {
+        char *reason = "step over";
+        if (bp) reason = ldb.luabp ? "redis.breakpoint() called" :
+                                     "break point";
+        else if (timeout) reason = "timeout reached, infinite loop?";
+        ldb.step = 0;
+        ldb.luabp = 0;
+        ldbLog(sdscatprintf(sdsempty(),
+            "* Stopped at %d, stop reason = %s",
+            ldb.currentline, reason));
+        ldbLogSourceLine(ldb.currentline);
+        ldbSendLogs();
+        if (ldbRepl(lua) == C_ERR && timeout) {
+            /* If the client closed the connection and we have a timeout
+             * connection, let's kill the script otherwise the process
+             * will remain blocked indefinitely. */
+            lua_pushstring(lua, "timeout during Lua debugging with client closing connection");
+            lua_error(lua);
+        }
+        server.lua_time_start = getMonotonicUs();
+        server.lua_time_snapshot = mstime();
+    }
+}