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proxy_config.c
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proxy_config.c
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/* -*- 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_TBOOLEAN:
lua_pushboolean(to, lua_toboolean(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;
}