proxy: pull chunks into individual c files

now's a good time to at least shove functional subsections of code into
their own files. Some further work to clearly separate the API's will
help but looks not too terrible.

Big bonus is getting the backend handling code away from the frontend
handling code, which should make it easier to follow.

1 files changed, 421 insertions, 0 deletions

diff --git a/proxy_config.c b/proxy_config.c
new file mode 100644
index 0000000..caddbff
--- /dev/null
+++ b/proxy_config.c
@@ -0,0 +1,421 @@
+/* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
+// Functions related to the configuration management threads and VM
+// TODO (v2): move worker thread related code back out of here.
+
+#include "proxy.h"
+
+struct _dumpbuf {
+    size_t size;
+    size_t used;
+    char *buf;
+};
+
+static int _dump_helper(lua_State *L, const void *p, size_t sz, void *ud) {
+    (void)L;
+    struct _dumpbuf *db = ud;
+    if (db->used + sz > db->size) {
+        db->size *= 2;
+        char *nb = realloc(db->buf, db->size);
+        if (nb == NULL) {
+            return -1;
+        }
+        db->buf = nb;
+    }
+    memcpy(db->buf + db->used, (const char *)p, sz);
+    db->used += sz;
+    return 0;
+}
+
+static const char * _load_helper(lua_State *L, void *data, size_t *size) {
+    (void)L;
+    struct _dumpbuf *db = data;
+    if (db->used == 0) {
+        *size = 0;
+        return NULL;
+    }
+    *size = db->used;
+    db->used = 0;
+    return db->buf;
+}
+
+void proxy_start_reload(void *arg) {
+    proxy_ctx_t *ctx = arg;
+    if (pthread_mutex_trylock(&ctx->config_lock) == 0) {
+        pthread_cond_signal(&ctx->config_cond);
+        pthread_mutex_unlock(&ctx->config_lock);
+    }
+}
+
+// Manages a queue of inbound objects destined to be deallocated.
+static void *_proxy_manager_thread(void *arg) {
+    proxy_ctx_t *ctx = arg;
+    pool_head_t head;
+
+    pthread_mutex_lock(&ctx->manager_lock);
+    while (1) {
+        STAILQ_INIT(&head);
+        while (STAILQ_EMPTY(&ctx->manager_head)) {
+            pthread_cond_wait(&ctx->manager_cond, &ctx->manager_lock);
+        }
+
+        // pull dealloc queue into local queue.
+        STAILQ_CONCAT(&head, &ctx->manager_head);
+        pthread_mutex_unlock(&ctx->manager_lock);
+
+        // Config lock is required for using config VM.
+        pthread_mutex_lock(&ctx->config_lock);
+        lua_State *L = ctx->proxy_state;
+        mcp_pool_t *p;
+        STAILQ_FOREACH(p, &head, next) {
+            // we let the pool object _gc() handle backend references.
+
+            luaL_unref(L, LUA_REGISTRYINDEX, p->phc_ref);
+            // need to... unref self.
+            // NOTE: double check if we really need to self-reference.
+            // this is a backup here to ensure the external refcounts hit zero
+            // before lua garbage collects the object. other things hold a
+            // reference to the object though.
+            luaL_unref(L, LUA_REGISTRYINDEX, p->self_ref);
+        }
+        pthread_mutex_unlock(&ctx->config_lock);
+
+        // done.
+        pthread_mutex_lock(&ctx->manager_lock);
+    }
+
+    return NULL;
+}
+
+// Thread handling the configuration reload sequence.
+// TODO (v2): get a logger instance.
+// TODO (v2): making this "safer" will require a few phases of work.
+// 1) JFDI
+// 2) "test VM" -> from config thread, test the worker reload portion.
+// 3) "unit testing" -> from same temporary worker VM, execute set of
+// integration tests that must pass.
+// 4) run update on each worker, collecting new mcp.attach() hooks.
+//    Once every worker has successfully executed and set new hooks, roll
+//    through a _second_ time to actually swap the hook structures and unref
+//    the old structures where marked dirty.
+static void *_proxy_config_thread(void *arg) {
+    proxy_ctx_t *ctx = arg;
+
+    logger_create();
+    pthread_mutex_lock(&ctx->config_lock);
+    while (1) {
+        pthread_cond_wait(&ctx->config_cond, &ctx->config_lock);
+        LOGGER_LOG(NULL, LOG_PROXYEVENTS, LOGGER_PROXY_CONFIG, NULL, "start");
+        STAT_INCR(ctx, config_reloads, 1);
+        lua_State *L = ctx->proxy_state;
+        lua_settop(L, 0); // clear off any crud that could have been left on the stack.
+
+        // The main stages of config reload are:
+        // - load and execute the config file
+        // - run mcp_config_pools()
+        // - for each worker:
+        //   - copy and execute new lua code
+        //   - copy selector table
+        //   - run mcp_config_routes()
+
+        if (proxy_load_config(ctx) != 0) {
+            // Failed to load. log and wait for a retry.
+            STAT_INCR(ctx, config_reload_fails, 1);
+            LOGGER_LOG(NULL, LOG_PROXYEVENTS, LOGGER_PROXY_CONFIG, NULL, "failed");
+            continue;
+        }
+
+        // TODO (v2): create a temporary VM to test-load the worker code into.
+        // failing to load partway through the worker VM reloads can be
+        // critically bad if we're not careful about references.
+        // IE: the config VM _must_ hold references to selectors and backends
+        // as long as they exist in any worker for any reason.
+
+        for (int x = 0; x < settings.num_threads; x++) {
+            LIBEVENT_THREAD *thr = get_worker_thread(x);
+
+            pthread_mutex_lock(&ctx->worker_lock);
+            ctx->worker_done = false;
+            ctx->worker_failed = false;
+            proxy_reload_notify(thr);
+            while (!ctx->worker_done) {
+                // in case of spurious wakeup.
+                pthread_cond_wait(&ctx->worker_cond, &ctx->worker_lock);
+            }
+            pthread_mutex_unlock(&ctx->worker_lock);
+
+            // Code load bailed.
+            if (ctx->worker_failed) {
+                STAT_INCR(ctx, config_reload_fails, 1);
+                LOGGER_LOG(NULL, LOG_PROXYEVENTS, LOGGER_PROXY_CONFIG, NULL, "failed");
+                continue;
+            }
+        }
+        LOGGER_LOG(NULL, LOG_PROXYEVENTS, LOGGER_PROXY_CONFIG, NULL, "done");
+    }
+
+    return NULL;
+}
+
+int _start_proxy_config_threads(proxy_ctx_t *ctx) {
+    int ret;
+
+    pthread_mutex_lock(&ctx->config_lock);
+    if ((ret = pthread_create(&ctx->config_tid, NULL,
+                    _proxy_config_thread, ctx)) != 0) {
+        fprintf(stderr, "Failed to start proxy configuration thread: %s\n",
+                strerror(ret));
+        pthread_mutex_unlock(&ctx->config_lock);
+        return -1;
+    }
+    pthread_mutex_unlock(&ctx->config_lock);
+
+    pthread_mutex_lock(&ctx->manager_lock);
+    if ((ret = pthread_create(&ctx->manager_tid, NULL,
+                    _proxy_manager_thread, ctx)) != 0) {
+        fprintf(stderr, "Failed to start proxy configuration thread: %s\n",
+                strerror(ret));
+        pthread_mutex_unlock(&ctx->manager_lock);
+        return -1;
+    }
+    pthread_mutex_unlock(&ctx->manager_lock);
+
+    return 0;
+}
+
+int proxy_load_config(void *arg) {
+    proxy_ctx_t *ctx = arg;
+    lua_State *L = ctx->proxy_state;
+    int res = luaL_loadfile(L, settings.proxy_startfile);
+    if (res != LUA_OK) {
+        fprintf(stderr, "ERROR: Failed to load proxy_startfile: %s\n", lua_tostring(L, -1));
+        return -1;
+    }
+    // LUA_OK, LUA_ERRSYNTAX, LUA_ERRMEM, LUA_ERRFILE
+
+    // Now we need to dump the compiled code into bytecode.
+    // This will then get loaded into worker threads.
+    struct _dumpbuf *db = malloc(sizeof(struct _dumpbuf));
+    db->size = 16384;
+    db->used = 0;
+    db->buf = malloc(db->size);
+    lua_dump(L, _dump_helper, db, 0);
+    // 0 means no error.
+    ctx->proxy_code = db;
+
+    // now we complete the data load by calling the function.
+    res = lua_pcall(L, 0, LUA_MULTRET, 0);
+    if (res != LUA_OK) {
+        fprintf(stderr, "ERROR: Failed to load data into lua config state: %s\n", lua_tostring(L, -1));
+        exit(EXIT_FAILURE);
+    }
+
+    // call the mcp_config_pools function to get the central backends.
+    lua_getglobal(L, "mcp_config_pools");
+
+    if (lua_isnil(L, -1)) {
+        fprintf(stderr, "ERROR: Configuration file missing 'mcp_config_pools' function\n");
+        exit(EXIT_FAILURE);
+    }
+    lua_pushnil(L); // no "old" config yet.
+    if (lua_pcall(L, 1, 1, 0) != LUA_OK) {
+        fprintf(stderr, "ERROR: Failed to execute mcp_config_pools: %s\n", lua_tostring(L, -1));
+        exit(EXIT_FAILURE);
+    }
+
+    // result is our main config.
+    return 0;
+}
+
+static int _copy_pool(lua_State *from, lua_State *to) {
+    // from, -3 should have he userdata.
+    mcp_pool_t *p = luaL_checkudata(from, -3, "mcp.pool");
+    size_t size = sizeof(mcp_pool_proxy_t);
+    mcp_pool_proxy_t *pp = lua_newuserdatauv(to, size, 0);
+    luaL_setmetatable(to, "mcp.pool_proxy");
+
+    pp->main = p;
+    pthread_mutex_lock(&p->lock);
+    p->refcount++;
+    pthread_mutex_unlock(&p->lock);
+    return 0;
+}
+
+static void _copy_config_table(lua_State *from, lua_State *to);
+// (from, -1) is the source value
+// should end with (to, -1) being the new value.
+static void _copy_config_table(lua_State *from, lua_State *to) {
+    int type = lua_type(from, -1);
+    bool found = false;
+    luaL_checkstack(from, 4, "configuration error: table recursion too deep");
+    luaL_checkstack(to, 4, "configuration error: table recursion too deep");
+    switch (type) {
+        case LUA_TNIL:
+            lua_pushnil(to);
+            break;
+        case LUA_TUSERDATA:
+            // see dump_stack() - check if it's something we handle.
+            if (lua_getmetatable(from, -1) != 0) {
+                lua_pushstring(from, "__name");
+                if (lua_rawget(from, -2) != LUA_TNIL) {
+                    const char *name = lua_tostring(from, -1);
+                    if (strcmp(name, "mcp.pool") == 0) {
+                        _copy_pool(from, to);
+                        found = true;
+                    }
+                }
+                lua_pop(from, 2);
+            }
+            if (!found) {
+                proxy_lua_ferror(from, "unhandled userdata type in configuration table\n");
+            }
+            break;
+        case LUA_TNUMBER:
+            if (lua_isinteger(from, -1)) {
+                lua_pushinteger(to, lua_tointeger(from, -1));
+            } else {
+                lua_pushnumber(to, lua_tonumber(from, -1));
+            }
+            break;
+        case LUA_TSTRING:
+            lua_pushlstring(to, lua_tostring(from, -1), lua_rawlen(from, -1));
+            break;
+        case LUA_TTABLE:
+            // TODO (v2): copy the metatable first?
+            // TODO (v2): size narr/nrec from old table and use createtable to
+            // pre-allocate.
+            lua_newtable(to); // throw new table on worker
+            int t = lua_absindex(from, -1); // static index of table to copy.
+            int nt = lua_absindex(to, -1); // static index of new table.
+            lua_pushnil(from); // start iterator for main
+            while (lua_next(from, t) != 0) {
+                // (key, -2), (val, -1)
+                int keytype = lua_type(from, -2);
+                // to intentionally limit complexity and allow for future
+                // optimizations we restrict what types may be used as keys
+                // for sub-tables.
+                switch (keytype) {
+                    case LUA_TSTRING:
+                        // to[l]string converts the actual key in the table
+                        // into a string, so we must not do that unless it
+                        // already is one.
+                        lua_pushlstring(to, lua_tostring(from, -2), lua_rawlen(from, -2));
+                        break;
+                    case LUA_TNUMBER:
+                        if (lua_isinteger(from, -1)) {
+                            lua_pushinteger(to, lua_tointeger(from, -1));
+                        } else {
+                            lua_pushnumber(to, lua_tonumber(from, -1));
+                        }
+                        break;
+                    default:
+                        proxy_lua_error(from, "configuration table keys must be strings or numbers");
+                }
+                // lua_settable(to, n) - n being the table
+                // takes -2 key -1 value, pops both.
+                // use lua_absindex(L, -1) and so to convert easier?
+                _copy_config_table(from, to); // push next value.
+                lua_settable(to, nt);
+                lua_pop(from, 1); // drop value, keep key.
+            }
+            // top of from is now the original table.
+            // top of to should be the new table.
+            break;
+        default:
+            proxy_lua_error(from, "unhandled data type in configuration table\n");
+    }
+}
+
+// Run from proxy worker to coordinate code reload.
+// config_lock must be held first.
+void proxy_worker_reload(void *arg, LIBEVENT_THREAD *thr) {
+    proxy_ctx_t *ctx = arg;
+    pthread_mutex_lock(&ctx->worker_lock);
+    if (proxy_thread_loadconf(thr) != 0) {
+        ctx->worker_failed = true;
+    }
+    ctx->worker_done = true;
+    pthread_cond_signal(&ctx->worker_cond);
+    pthread_mutex_unlock(&ctx->worker_lock);
+}
+
+// FIXME (v2): need to test how to recover from an actual error here. error message
+// needs to go somewhere useful, counters added, etc.
+int proxy_thread_loadconf(LIBEVENT_THREAD *thr) {
+    lua_State *L = thr->L;
+    // load the precompiled config function.
+    proxy_ctx_t *ctx = settings.proxy_ctx;
+    struct _dumpbuf *db = ctx->proxy_code;
+    struct _dumpbuf db2; // copy because the helper modifies it.
+    memcpy(&db2, db, sizeof(struct _dumpbuf));
+
+    lua_load(L, _load_helper, &db2, "config", NULL);
+    // LUA_OK + all errs from loadfile except LUA_ERRFILE.
+    //dump_stack(L);
+    // - pcall the func (which should load it)
+    int res = lua_pcall(L, 0, LUA_MULTRET, 0);
+    if (res != LUA_OK) {
+        // FIXME (v2): don't exit here!
+        fprintf(stderr, "Failed to load data into worker thread\n");
+        return -1;
+    }
+
+    lua_getglobal(L, "mcp_config_routes");
+    // create deepcopy of argument to pass into mcp_config_routes.
+    // FIXME (v2): to avoid lua SIGABRT'ing on errors we need to protect the call
+    // normal pattern:
+    // lua_pushcfunction(L, &_copy_config_table);
+    // lua_pushlightuserdata(L, &L2);
+    // res = la_pcall(L, etc);
+    // ... but since this is cross-VM we could get errors from not the
+    // protected VM, breaking setjmp/etc.
+    // for this part of the code we should override lua_atpanic(),
+    // allowing us to specifically recover and bail.
+    // However, again, this will require the next version of the config reload
+    // code since we are re-using the VM's and a panic can leave us in a
+    // broken state.
+    // If the setjump/longjump combos are compatible a pcall for from and
+    // atpanic for to might work best, since the config VM is/should be long
+    // running and worker VM's should be rotated.
+    _copy_config_table(ctx->proxy_state, L);
+
+    // copied value is in front of route function, now call it.
+    if (lua_pcall(L, 1, 1, 0) != LUA_OK) {
+        fprintf(stderr, "Failed to execute mcp_config_routes: %s\n", lua_tostring(L, -1));
+        return -1;
+    }
+
+    // update user stats
+    STAT_L(ctx);
+    struct proxy_user_stats *us = &ctx->user_stats;
+    struct proxy_user_stats *tus = NULL;
+    if (us->num_stats != 0) {
+        pthread_mutex_lock(&thr->stats.mutex);
+        if (thr->proxy_user_stats == NULL) {
+            tus = calloc(1, sizeof(struct proxy_user_stats));
+            thr->proxy_user_stats = tus;
+        } else {
+            tus = thr->proxy_user_stats;
+        }
+
+        // originally this was a realloc routine but it felt fragile.
+        // that might still be a better idea; still need to zero out the end.
+        uint64_t *counters = calloc(us->num_stats, sizeof(uint64_t));
+
+        // note that num_stats can _only_ grow in size.
+        // we also only care about counters on the worker threads.
+        if (tus->counters) {
+            assert(tus->num_stats <= us->num_stats);
+            memcpy(counters, tus->counters, tus->num_stats * sizeof(uint64_t));
+            free(tus->counters);
+        }
+
+        tus->counters = counters;
+        tus->num_stats = us->num_stats;
+        pthread_mutex_unlock(&thr->stats.mutex);
+    }
+    STAT_UL(ctx);
+
+    return 0;
+}
+
+