Add FUNCTION DUMP and RESTORE. (#9938)

Follow the conclusions to support Functions in redis cluster (#9899)

Added 2 new FUNCTION sub-commands:
1. `FUNCTION DUMP` - dump a binary payload representation of all the functions.
2. `FUNCTION RESTORE <PAYLOAD> [FLUSH|APPEND|REPLACE]` - give the binary payload extracted
   using `FUNCTION DUMP`, restore all the functions on the given payload. Restore policy can be given to
   control how to handle existing functions (default is APPEND):
   * FLUSH: delete all existing functions.
   * APPEND: appends the restored functions to the existing functions. On collision, abort.
   * REPLACE: appends the restored functions to the existing functions. On collision,
     replace the old function with the new function.

Modify `redis-cli --cluster add-node` to use `FUNCTION DUMP` to get existing functions from
one of the nodes in the cluster, and `FUNCTION RESTORE` to load the same set of functions
to the new node. `redis-cli` will execute this step before sending the `CLUSTER MEET` command
to the new node. If `FUNCTION DUMP` returns an error, assume the current Redis version do not
support functions and skip `FUNCTION RESTORE`. If `FUNCTION RESTORE` fails, abort and do not send
the `CLUSTER MEET` command. If the new node already contains functions (before the `FUNCTION RESTORE`
is sent), abort and do not add the node to the cluster. Test was added to verify
`redis-cli --cluster add-node` works as expected. 

9 files changed, 367 insertions, 33 deletions

diff --git a/src/cluster.c b/src/cluster.c
index d44f41ad8..15d2fc38f 100644
--- a/src/cluster.c
+++ b/src/cluster.c
@@ -5398,8 +5398,9 @@ void createDumpPayload(rio *payload, robj *o, robj *key, int dbid) {
 /* Verify that the RDB version of the dump payload matches the one of this Redis
  * instance and that the checksum is ok.
  * If the DUMP payload looks valid C_OK is returned, otherwise C_ERR
- * is returned. */
-int verifyDumpPayload(unsigned char *p, size_t len) {
+ * is returned. If rdbver_ptr is not NULL, its populated with the value read
+ * from the input buffer. */
+int verifyDumpPayload(unsigned char *p, size_t len, uint16_t *rdbver_ptr) {
     unsigned char *footer;
     uint16_t rdbver;
     uint64_t crc;
@@ -5410,6 +5411,9 @@ int verifyDumpPayload(unsigned char *p, size_t len) {
 
     /* Verify RDB version */
     rdbver = (footer[1] << 8) | footer[0];
+    if (rdbver_ptr) {
+        *rdbver_ptr = rdbver;
+    }
     if (rdbver > RDB_VERSION) return C_ERR;
 
     if (server.skip_checksum_validation)
@@ -5499,7 +5503,7 @@ void restoreCommand(client *c) {
     }
 
     /* Verify RDB version and data checksum. */
-    if (verifyDumpPayload(c->argv[3]->ptr,sdslen(c->argv[3]->ptr)) == C_ERR)
+    if (verifyDumpPayload(c->argv[3]->ptr,sdslen(c->argv[3]->ptr),NULL) == C_ERR)
     {
         addReplyError(c,"DUMP payload version or checksum are wrong");
         return;
diff --git a/src/commands.c b/src/commands.c
index 0a07fb25f..2514c51b6 100644
--- a/src/commands.c
+++ b/src/commands.c
@@ -3064,6 +3064,14 @@ struct redisCommandArg FUNCTION_DELETE_Args[] = {
 {0}
 };
 
+/********** FUNCTION DUMP ********************/
+
+/* FUNCTION DUMP history */
+#define FUNCTION_DUMP_History NULL
+
+/* FUNCTION DUMP hints */
+#define FUNCTION_DUMP_Hints NULL
+
 /********** FUNCTION FLUSH ********************/
 
 /* FUNCTION FLUSH history */
@@ -3124,6 +3132,29 @@ struct redisCommandArg FUNCTION_INFO_Args[] = {
 /* FUNCTION LIST hints */
 #define FUNCTION_LIST_Hints NULL
 
+/********** FUNCTION RESTORE ********************/
+
+/* FUNCTION RESTORE history */
+#define FUNCTION_RESTORE_History NULL
+
+/* FUNCTION RESTORE hints */
+#define FUNCTION_RESTORE_Hints NULL
+
+/* FUNCTION RESTORE policy argument table */
+struct redisCommandArg FUNCTION_RESTORE_policy_Subargs[] = {
+{"flush",ARG_TYPE_PURE_TOKEN,-1,"FLUSH",NULL,NULL,CMD_ARG_NONE},
+{"append",ARG_TYPE_PURE_TOKEN,-1,"APPEND",NULL,NULL,CMD_ARG_NONE},
+{"replace",ARG_TYPE_PURE_TOKEN,-1,"REPLACE",NULL,NULL,CMD_ARG_NONE},
+{0}
+};
+
+/* FUNCTION RESTORE argument table */
+struct redisCommandArg FUNCTION_RESTORE_Args[] = {
+{"serialized-value",ARG_TYPE_STRING,-1,NULL,NULL,NULL,CMD_ARG_NONE},
+{"policy",ARG_TYPE_ONEOF,-1,NULL,NULL,NULL,CMD_ARG_OPTIONAL,.subargs=FUNCTION_RESTORE_policy_Subargs},
+{0}
+};
+
 /********** FUNCTION STATS ********************/
 
 /* FUNCTION STATS history */
@@ -3136,11 +3167,13 @@ struct redisCommandArg FUNCTION_INFO_Args[] = {
 struct redisCommand FUNCTION_Subcommands[] = {
 {"create","Create a function with the given arguments (name, code, description)","O(1) (considering compilation time is redundant)","7.0.0",CMD_DOC_NONE,NULL,NULL,COMMAND_GROUP_SCRIPTING,FUNCTION_CREATE_History,FUNCTION_CREATE_Hints,functionCreateCommand,-5,CMD_NOSCRIPT|CMD_WRITE,ACL_CATEGORY_SCRIPTING,.args=FUNCTION_CREATE_Args},
 {"delete","Delete a function by name","O(1)","7.0.0",CMD_DOC_NONE,NULL,NULL,COMMAND_GROUP_SCRIPTING,FUNCTION_DELETE_History,FUNCTION_DELETE_Hints,functionDeleteCommand,3,CMD_NOSCRIPT|CMD_WRITE,ACL_CATEGORY_SCRIPTING,.args=FUNCTION_DELETE_Args},
+{"dump","Dump all functions into a serialized binary payload","O(N) where N is the number of functions","7.0.0",CMD_DOC_NONE,NULL,NULL,COMMAND_GROUP_SCRIPTING,FUNCTION_DUMP_History,FUNCTION_DUMP_Hints,functionDumpCommand,2,CMD_NOSCRIPT,ACL_CATEGORY_SCRIPTING},
 {"flush","Deleting all functions","O(N) where N is the number of functions deleted","7.0.0",CMD_DOC_NONE,NULL,NULL,COMMAND_GROUP_SCRIPTING,FUNCTION_FLUSH_History,FUNCTION_FLUSH_Hints,functionFlushCommand,-2,CMD_NOSCRIPT|CMD_WRITE,ACL_CATEGORY_SCRIPTING,.args=FUNCTION_FLUSH_Args},
 {"help","Show helpful text about the different subcommands","O(1)","7.0.0",CMD_DOC_NONE,NULL,NULL,COMMAND_GROUP_SCRIPTING,FUNCTION_HELP_History,FUNCTION_HELP_Hints,functionHelpCommand,2,CMD_LOADING|CMD_STALE,ACL_CATEGORY_SCRIPTING},
 {"info","Return information about a function by function name","O(1)","7.0.0",CMD_DOC_NONE,NULL,NULL,COMMAND_GROUP_SCRIPTING,FUNCTION_INFO_History,FUNCTION_INFO_Hints,functionInfoCommand,-3,CMD_NOSCRIPT,ACL_CATEGORY_SCRIPTING,.args=FUNCTION_INFO_Args},
 {"kill","Kill the function currently in execution.","O(1)","7.0.0",CMD_DOC_NONE,NULL,NULL,COMMAND_GROUP_SCRIPTING,FUNCTION_KILL_History,FUNCTION_KILL_Hints,functionKillCommand,2,CMD_NOSCRIPT,ACL_CATEGORY_SCRIPTING},
 {"list","List information about all the functions","O(N) where N is the number of functions","7.0.0",CMD_DOC_NONE,NULL,NULL,COMMAND_GROUP_SCRIPTING,FUNCTION_LIST_History,FUNCTION_LIST_Hints,functionListCommand,2,CMD_NOSCRIPT,ACL_CATEGORY_SCRIPTING},
+{"restore","Restore all the functions on the given payload","O(N) where N is the number of functions on the payload","7.0.0",CMD_DOC_NONE,NULL,NULL,COMMAND_GROUP_SCRIPTING,FUNCTION_RESTORE_History,FUNCTION_RESTORE_Hints,functionRestoreCommand,-3,CMD_NOSCRIPT|CMD_WRITE,ACL_CATEGORY_SCRIPTING,.args=FUNCTION_RESTORE_Args},
 {"stats","Return information about the function currently running (name, description, duration)","O(1)","7.0.0",CMD_DOC_NONE,NULL,NULL,COMMAND_GROUP_SCRIPTING,FUNCTION_STATS_History,FUNCTION_STATS_Hints,functionStatsCommand,2,CMD_NOSCRIPT,ACL_CATEGORY_SCRIPTING},
 {0}
 };
diff --git a/src/commands/function-dump.json b/src/commands/function-dump.json
new file mode 100644
index 000000000..de402f589
--- /dev/null
+++ b/src/commands/function-dump.json
@@ -0,0 +1,17 @@
+{
+    "DUMP": {
+        "summary": "Dump all functions into a serialized binary payload",
+        "complexity": "O(N) where N is the number of functions",
+        "group": "scripting",
+        "since": "7.0.0",
+        "arity": 2,
+        "container": "FUNCTION",
+        "function": "functionDumpCommand",
+        "command_flags": [
+            "NOSCRIPT"
+        ],
+        "acl_categories": [
+            "SCRIPTING"
+        ]
+    }
+}
diff --git a/src/commands/function-restore.json b/src/commands/function-restore.json
new file mode 100644
index 000000000..bc9b32be4
--- /dev/null
+++ b/src/commands/function-restore.json
@@ -0,0 +1,46 @@
+{
+    "RESTORE": {
+        "summary": "Restore all the functions on the given payload",
+        "complexity": "O(N) where N is the number of functions on the payload",
+        "group": "scripting",
+        "since": "7.0.0",
+        "arity": -3,
+        "container": "FUNCTION",
+        "function": "functionRestoreCommand",
+        "command_flags": [
+            "NOSCRIPT",
+            "WRITE"
+        ],
+        "acl_categories": [
+            "SCRIPTING"
+        ],
+        "arguments": [
+            {
+                "name": "serialized-value",
+                "type": "string"
+            },
+            {
+                "name": "policy",
+                "type": "oneof",
+                "optional": true,
+                "arguments": [
+                    {
+                        "name": "flush",
+                        "type": "pure-token",
+                        "token": "FLUSH"
+                    },
+                    {
+                        "name": "append",
+                        "type": "pure-token",
+                        "token": "APPEND"
+                    },
+                    {
+                        "name": "replace",
+                        "type": "pure-token",
+                        "token": "REPLACE"
+                    }
+                ]
+            }
+        ]
+    }
+}
diff --git a/src/functions.c b/src/functions.c
index 8da845250..2da142ecb 100644
--- a/src/functions.c
+++ b/src/functions.c
@@ -33,6 +33,10 @@
 #include "adlist.h"
 #include "atomicvar.h"
 
+typedef enum {
+    restorePolicy_Flush, restorePolicy_Append, restorePolicy_Replace
+} restorePolicy;
+
 static size_t engine_cache_memory = 0;
 
 /* Forward declaration */
@@ -81,6 +85,9 @@ static size_t functionMallocSize(functionInfo *fi) {
 /* Dispose function memory */
 static void engineFunctionDispose(dict *d, void *obj) {
     UNUSED(d);
+    if (!obj) {
+        return;
+    }
     functionInfo *fi = obj;
     sdsfree(fi->code);
     sdsfree(fi->name);
@@ -377,6 +384,156 @@ void fcallroCommand(client *c) {
     fcallCommandGeneric(c, 1);
 }
 
+/*
+ * FUNCTION DUMP
+ *
+ * Returns a binary payload representing all the functions.
+ * Can be loaded using FUNCTION RESTORE
+ *
+ * The payload structure is the same as on RDB. Each function
+ * is saved separately with the following information:
+ * * Function name
+ * * Engine name
+ * * Function description
+ * * Function code
+ * RDB_OPCODE_FUNCTION is saved before each function to present
+ * that the payload is a function.
+ * RDB version and crc64 is saved at the end of the payload.
+ * The RDB version is saved for backward compatibility.
+ * crc64 is saved so we can verify the payload content.
+ */
+void functionDumpCommand(client *c) {
+    unsigned char buf[2];
+    uint64_t crc;
+    rio payload;
+    rioInitWithBuffer(&payload, sdsempty());
+
+    functionsSaveRio(&payload);
+
+    /* RDB version */
+    buf[0] = RDB_VERSION & 0xff;
+    buf[1] = (RDB_VERSION >> 8) & 0xff;
+    payload.io.buffer.ptr = sdscatlen(payload.io.buffer.ptr, buf, 2);
+
+    /* CRC64 */
+    crc = crc64(0, (unsigned char*) payload.io.buffer.ptr,
+                sdslen(payload.io.buffer.ptr));
+    memrev64ifbe(&crc);
+    payload.io.buffer.ptr = sdscatlen(payload.io.buffer.ptr, &crc, 8);
+
+    addReplyBulkSds(c, payload.io.buffer.ptr);
+}
+
+/*
+ * FUNCTION RESTORE <payload> [FLUSH|APPEND|REPLACE]
+ *
+ * Restore the functions represented by the give payload.
+ * Restore policy to can be given to control how to handle existing functions (default APPEND):
+ * * FLUSH: delete all existing functions.
+ * * APPEND: appends the restored functions to the existing functions. On collision, abort.
+ * * REPLACE: appends the restored functions to the existing functions.
+ *   On collision, replace the old function with the new function.
+ */
+void functionRestoreCommand(client *c) {
+    if (c->argc > 4) {
+        addReplySubcommandSyntaxError(c);
+        return;
+    }
+
+    restorePolicy restore_replicy = restorePolicy_Append; /* default policy: APPEND */
+    sds data = c->argv[2]->ptr;
+    size_t data_len = sdslen(data);
+    rio payload;
+    dictIterator *iter = NULL;
+    sds err = NULL;
+
+    if (c->argc == 4) {
+        const char *restore_policy_str = c->argv[3]->ptr;
+        if (!strcasecmp(restore_policy_str, "append")) {
+            restore_replicy = restorePolicy_Append;
+        } else if (!strcasecmp(restore_policy_str, "replace")) {
+            restore_replicy = restorePolicy_Replace;
+        } else if (!strcasecmp(restore_policy_str, "flush")) {
+            restore_replicy = restorePolicy_Flush;
+        } else {
+            addReplyError(c, "Wrong restore policy given, value should be either FLUSH, APPEND or REPLACE.");
+            return;
+        }
+    }
+
+    uint16_t rdbver;
+    if (verifyDumpPayload((unsigned char*)data, data_len, &rdbver) != C_OK) {
+        addReplyError(c, "DUMP payload version or checksum are wrong");
+        return;
+    }
+
+    functionsCtx *f_ctx = functionsCtxCreate();
+    rioInitWithBuffer(&payload, data);
+
+    /* Read until reaching last 10 bytes that should contain RDB version and checksum. */
+    while (data_len - payload.io.buffer.pos > 10) {
+        int type;
+        if ((type = rdbLoadType(&payload)) == -1) {
+            err = sdsnew("can not read data type");
+            goto load_error;
+        }
+        if (type != RDB_OPCODE_FUNCTION) {
+            err = sdsnew("given type is not a function");
+            goto load_error;
+        }
+        if (rdbFunctionLoad(&payload, rdbver, f_ctx, RDBFLAGS_NONE, &err) != C_OK) {
+            if (!err) {
+                err = sdsnew("failed loading the given functions payload");
+            }
+            goto load_error;
+        }
+    }
+
+    if (restore_replicy == restorePolicy_Flush) {
+        functionsCtxSwapWithCurrent(f_ctx);
+        f_ctx = NULL; /* avoid releasing the f_ctx in the end */
+    } else {
+        if (restore_replicy == restorePolicy_Append) {
+            /* First make sure there is only new functions */
+            iter = dictGetIterator(f_ctx->functions);
+            dictEntry *entry = NULL;
+            while ((entry = dictNext(iter))) {
+                functionInfo *fi = dictGetVal(entry);
+                if (dictFetchValue(functions_ctx->functions, fi->name)) {
+                    /* function already exists, failed the restore. */
+                    err = sdscatfmt(sdsempty(), "Function %s already exists", fi->name);
+                    goto load_error;
+                }
+            }
+            dictReleaseIterator(iter);
+        }
+        iter = dictGetIterator(f_ctx->functions);
+        dictEntry *entry = NULL;
+        while ((entry = dictNext(iter))) {
+            functionInfo *fi = dictGetVal(entry);
+            dictReplace(functions_ctx->functions, fi->name, fi);
+            dictSetVal(f_ctx->functions, entry, NULL); /* make sure value will not be disposed */
+        }
+    }
+
+    /* Indicate that the command changed the data so it will be replicated and
+     * counted as a data change (for persistence configuration) */
+    server.dirty++;
+
+load_error:
+    if (err) {
+        addReplyErrorSds(c, err);
+    } else {
+        addReply(c, shared.ok);
+    }
+    if (iter) {
+        dictReleaseIterator(iter);
+    }
+    if (f_ctx) {
+        functionsCtxFree(f_ctx);
+    }
+}
+
 void functionFlushCommand(client *c) {
     if (c->argc > 3) {
         addReplySubcommandSyntaxError(c);
@@ -434,6 +591,15 @@ void functionHelpCommand(client *c) {
 "    lazyfree-lazy-user-flush configuration directive. Valid modes are:",
 "    * ASYNC: Asynchronously flush the functions.",
 "    * SYNC: Synchronously flush the functions.",
+"DUMP",
+"    Returns a serialized payload representing the current functions, can be restored using FUNCTION RESTORE command",
+"RESTORE <PAYLOAD> [FLUSH|APPEND|REPLACE]",
+"    Restore the functions represented by the given payload, it is possible to give a restore policy to",
+"    control how to handle existing functions (default APPEND):",
+"    * FLUSH: delete all existing functions.",
+"    * APPEND: appends the restored functions to the existing functions. On collision, abort.",
+"    * REPLACE: appends the restored functions to the existing functions, On collision, replace the old",
+"      function with the new function.",
 NULL };
     addReplyHelp(c, help);
 }
diff --git a/src/rdb.c b/src/rdb.c
index 108804741..2126d6e6d 100644
--- a/src/rdb.c
+++ b/src/rdb.c
@@ -1214,6 +1214,30 @@ ssize_t rdbSaveSingleModuleAux(rio *rdb, int when, moduleType *mt) {
     return io.bytes;
 }
 
+int functionsSaveRio(rio *rdb) {
+    int ret = C_ERR;
+    dict *functions = functionsGet();
+    dictIterator *iter = dictGetIterator(functions);
+    dictEntry *entry = NULL;
+    while ((entry = dictNext(iter))) {
+        rdbSaveType(rdb, RDB_OPCODE_FUNCTION);
+        functionInfo *fi = dictGetVal(entry);
+        if (rdbSaveRawString(rdb, (unsigned char *) fi->name, sdslen(fi->name)) == -1) goto done;
+        if (rdbSaveRawString(rdb, (unsigned char *) fi->ei->name, sdslen(fi->ei->name)) == -1) goto done;
+        if (fi->desc) {
+            if (rdbSaveLen(rdb, 1) == -1) goto done; /* desc exists */
+            if (rdbSaveRawString(rdb, (unsigned char *) fi->desc, sdslen(fi->desc)) == -1) goto done;
+        } else {
+            if (rdbSaveLen(rdb, 0) == -1) goto done; /* desc not exists */
+        }
+        if (rdbSaveRawString(rdb, (unsigned char *) fi->code, sdslen(fi->code)) == -1) goto done;
+    }
+    ret = C_OK;
+done:
+    dictReleaseIterator(iter);
+    return ret;
+}
+
 /* Produces a dump of the database in RDB format sending it to the specified
  * Redis I/O channel. On success C_OK is returned, otherwise C_ERR
  * is returned and part of the output, or all the output, can be
@@ -1240,24 +1264,7 @@ int rdbSaveRio(rio *rdb, int *error, int rdbflags, rdbSaveInfo *rsi) {
     if (rdbSaveInfoAuxFields(rdb,rdbflags,rsi) == -1) goto werr;
     if (rdbSaveModulesAux(rdb, REDISMODULE_AUX_BEFORE_RDB) == -1) goto werr;
 
-    /* save functions */
-    dict *functions = functionsGet();
-    dictIterator *iter = dictGetIterator(functions);
-    dictEntry *entry = NULL;
-    while ((entry = dictNext(iter))) {
-        rdbSaveType(rdb, RDB_OPCODE_FUNCTION);
-        functionInfo* fi = dictGetVal(entry);
-        if (rdbSaveRawString(rdb, (unsigned char *) fi->name, sdslen(fi->name)) == -1) goto werr;
-        if (rdbSaveRawString(rdb, (unsigned char *) fi->ei->name, sdslen(fi->ei->name)) == -1) goto werr;
-        if (fi->desc) {
-            if (rdbSaveLen(rdb, 1) == -1) goto werr; /* desc exists */
-            if (rdbSaveRawString(rdb, (unsigned char *) fi->desc, sdslen(fi->desc)) == -1) goto werr;
-        } else {
-            if (rdbSaveLen(rdb, 0) == -1) goto werr; /* desc not exists */
-        }
-        if (rdbSaveRawString(rdb, (unsigned char *) fi->code, sdslen(fi->code)) == -1) goto werr;
-    }
-    dictReleaseIterator(iter);
+    if (functionsSaveRio(rdb) != C_OK) goto werr;
 
     for (j = 0; j < server.dbnum; j++) {
         redisDb *db = server.db+j;
@@ -2697,42 +2704,48 @@ void rdbLoadProgressCallback(rio *r, const void *buf, size_t len) {
     }
 }
 
-static int rdbFunctionLoad(rio *rdb, int ver, functionsCtx* functions_ctx, int rdbflags) {
+/* Save the given functions_ctx to the rdb.
+ * The err output parameter is optional and will be set with relevant error
+ * message on failure, it is the caller responsibility to free the error
+ * message on failure. */
+int rdbFunctionLoad(rio *rdb, int ver, functionsCtx* functions_ctx, int rdbflags, sds *err) {
     UNUSED(ver);
     sds name = NULL;
     sds engine_name = NULL;
     sds desc = NULL;
     sds blob = NULL;
-    sds err = NULL;
     uint64_t has_desc;
+    sds error = NULL;
     int res = C_ERR;
     if (!(name = rdbGenericLoadStringObject(rdb, RDB_LOAD_SDS, NULL))) {
-        serverLog(LL_WARNING, "Failed loading function name");
+        error = sdsnew("Failed loading function name");
         goto error;
     }
 
     if (!(engine_name = rdbGenericLoadStringObject(rdb, RDB_LOAD_SDS, NULL))) {
-        serverLog(LL_WARNING, "Failed loading engine name");
+        error = sdsnew("Failed loading engine name");
         goto error;
     }
 
     if ((has_desc = rdbLoadLen(rdb, NULL)) == RDB_LENERR) {
-        serverLog(LL_WARNING, "Failed loading function desc indicator");
+        error = sdsnew("Failed loading function description indicator");
         goto error;
     }
 
     if (has_desc && !(desc = rdbGenericLoadStringObject(rdb, RDB_LOAD_SDS, NULL))) {
-        serverLog(LL_WARNING, "Failed loading function desc");
+        error = sdsnew("Failed loading function description");
         goto error;
     }
 
     if (!(blob = rdbGenericLoadStringObject(rdb, RDB_LOAD_SDS, NULL))) {
-        serverLog(LL_WARNING, "Failed loading function blob");
+        error = sdsnew("Failed loading function blob");
         goto error;
     }
 
-    if (functionsCreateWithFunctionCtx(name, engine_name, desc, blob, rdbflags & RDBFLAGS_ALLOW_DUP, &err, functions_ctx) != C_OK) {
-        serverLog(LL_WARNING, "Failed compiling and saving the function %s", err);
+    if (functionsCreateWithFunctionCtx(name, engine_name, desc, blob, rdbflags & RDBFLAGS_ALLOW_DUP, &error, functions_ctx) != C_OK) {
+        if (!error) {
+            error = sdsnew("Failed creating the function");
+        }
         goto error;
     }
 
@@ -2743,7 +2756,14 @@ error:
     if (engine_name) sdsfree(engine_name);
     if (desc) sdsfree(desc);
     if (blob) sdsfree(blob);
-    if (err)  sdsfree(err);
+    if (error) {
+        if (err) {
+            *err = error;
+        } else {
+            serverLog(LL_WARNING, "Failed creating function, %s", error);
+            sdsfree(error);
+        }
+    }
     return res;
 }
 
@@ -2964,8 +2984,10 @@ int rdbLoadRioWithLoadingCtx(rio *rdb, int rdbflags, rdbSaveInfo *rsi, rdbLoadin
                 continue; /* Read next opcode. */
             }
         } else if (type == RDB_OPCODE_FUNCTION) {
-            if (rdbFunctionLoad(rdb, rdbver, rdb_loading_ctx->functions_ctx, rdbflags) != C_OK) {
-                serverLog(LL_WARNING,"Failed loading function");
+            sds err = NULL;
+            if (rdbFunctionLoad(rdb, rdbver, rdb_loading_ctx->functions_ctx, rdbflags, &err) != C_OK) {
+                serverLog(LL_WARNING,"Failed loading function, %s", err);
+                sdsfree(err);
                 goto eoferr;
             }
             continue;
diff --git a/src/rdb.h b/src/rdb.h
index 66496bcec..5942c4333 100644
--- a/src/rdb.h
+++ b/src/rdb.h
@@ -169,7 +169,9 @@ int rdbSaveBinaryFloatValue(rio *rdb, float val);
 int rdbLoadBinaryFloatValue(rio *rdb, float *val);
 int rdbLoadRio(rio *rdb, int rdbflags, rdbSaveInfo *rsi);
 int rdbLoadRioWithLoadingCtx(rio *rdb, int rdbflags, rdbSaveInfo *rsi, rdbLoadingCtx *rdb_loading_ctx);
+int rdbFunctionLoad(rio *rdb, int ver, functionsCtx* functions_ctx, int rdbflags, sds *err);
 int rdbSaveRio(rio *rdb, int *error, int rdbflags, rdbSaveInfo *rsi);
+int functionsSaveRio(rio *rdb);
 rdbSaveInfo *rdbPopulateSaveInfo(rdbSaveInfo *rsi);
 
 #endif
diff --git a/src/redis-cli.c b/src/redis-cli.c
index 81e4f4883..24e8fe562 100644
--- a/src/redis-cli.c
+++ b/src/redis-cli.c
@@ -5880,6 +5880,8 @@ cleanup:
 static int clusterManagerCommandAddNode(int argc, char **argv) {
     int success = 1;
     redisReply *reply = NULL;
+    redisReply *function_restore_reply = NULL;
+    redisReply *function_list_reply = NULL;
     char *ref_ip = NULL, *ip = NULL;
     int ref_port = 0, port = 0;
     if (!getClusterHostFromCmdArgs(argc - 1, argv + 1, &ref_ip, &ref_port))
@@ -5944,6 +5946,43 @@ static int clusterManagerCommandAddNode(int argc, char **argv) {
     listAddNodeTail(cluster_manager.nodes, new_node);
     added = 1;
 
+    if (!master_node) {
+        /* Send functions to the new node, if new node is a replica it will get the functions from its primary. */
+        clusterManagerLogInfo(">>> Getting functions from cluster\n");
+        reply = CLUSTER_MANAGER_COMMAND(refnode, "FUNCTION DUMP");
+        if (!clusterManagerCheckRedisReply(refnode, reply, &err)) {
+            clusterManagerLogInfo(">>> Failed retrieving Functions from the cluster, "
+                    "skip this step as Redis version do not support function command (error = '%s')\n", err? err : "NULL reply");
+            if (err) zfree(err);
+        } else {
+            assert(reply->type == REDIS_REPLY_STRING);
+            clusterManagerLogInfo(">>> Send FUNCTION LIST to %s:%d to verify there is no functions in it\n", ip, port);
+            function_list_reply = CLUSTER_MANAGER_COMMAND(new_node, "FUNCTION LIST");
+            if (!clusterManagerCheckRedisReply(new_node, function_list_reply, &err)) {
+                clusterManagerLogErr(">>> Failed on CLUSTER LIST (error = '%s')\r\n", err? err : "NULL reply");
+                if (err) zfree(err);
+                success = 0;
+                goto cleanup;
+            }
+            assert(function_list_reply->type == REDIS_REPLY_ARRAY);
+            if (function_list_reply->elements > 0) {
+                clusterManagerLogErr(">>> New node already contains functions and can not be added to the cluster. Use FUNCTION FLUSH and try again.\r\n");
+                success = 0;
+                goto cleanup;
+            }
+            clusterManagerLogInfo(">>> Send FUNCTION RESTORE to %s:%d\n", ip, port);
+            function_restore_reply = CLUSTER_MANAGER_COMMAND(new_node, "FUNCTION RESTORE %b", reply->str, reply->len);
+            if (!clusterManagerCheckRedisReply(new_node, function_restore_reply, &err)) {
+                clusterManagerLogErr(">>> Failed loading functions to the new node (error = '%s')\r\n", err? err : "NULL reply");
+                if (err) zfree(err);
+                success = 0;
+                goto cleanup;
+            }
+        }
+    }
+
+    if (reply) freeReplyObject(reply);
+
     // Send CLUSTER MEET command to the new node
     clusterManagerLogInfo(">>> Send CLUSTER MEET to node %s:%d to make it "
                           "join the cluster.\n", ip, port);
@@ -5968,6 +6007,8 @@ static int clusterManagerCommandAddNode(int argc, char **argv) {
 cleanup:
     if (!added && new_node) freeClusterManagerNode(new_node);
     if (reply) freeReplyObject(reply);
+    if (function_restore_reply) freeReplyObject(function_restore_reply);
+    if (function_list_reply) freeReplyObject(function_list_reply);
     return success;
 invalid_args:
     fprintf(stderr, CLUSTER_MANAGER_INVALID_HOST_ARG);
diff --git a/src/server.h b/src/server.h
index 8e4d8d902..471e8c72a 100644
--- a/src/server.h
+++ b/src/server.h
@@ -3162,6 +3162,7 @@ void migrateCommand(client *c);
 void askingCommand(client *c);
 void readonlyCommand(client *c);
 void readwriteCommand(client *c);
+int verifyDumpPayload(unsigned char *p, size_t len, uint16_t *rdbver_ptr);
 void dumpCommand(client *c);
 void objectCommand(client *c);
 void memoryCommand(client *c);
@@ -3182,6 +3183,8 @@ void functionInfoCommand(client *c);
 void functionListCommand(client *c);
 void functionHelpCommand(client *c);
 void functionFlushCommand(client *c);
+void functionRestoreCommand(client *c);
+void functionDumpCommand(client *c);
 void timeCommand(client *c);
 void bitopCommand(client *c);
 void bitcountCommand(client *c);