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Module API for Forking

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* create module API for forking child processes.
* refactor duplicate code around creating and tracking forks by AOF and RDB.
* child processes listen to SIGUSR1 and dies exitFromChild in order to
  eliminate a valgrind warning of unhandled signal.
* note that BGSAVE error reply has changed.

valgrind error is:
  Process terminating with default action of signal 10 (SIGUSR1)
This commit is contained in:
Oran Agra
2019-07-17 08:51:02 +03:00
parent 4b2579a064
commit 56258c6b7d
15 changed files with 342 additions and 91 deletions
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90
src/server.c
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@ -1447,12 +1447,18 @@ int incrementallyRehash(int dbid) {
* for dict.c to resize the hash tables accordingly to the fact we have o not
* running childs. */
void updateDictResizePolicy(void) {
if (server.rdb_child_pid == -1 && server.aof_child_pid == -1)
if (!hasForkChild())
dictEnableResize();
else
dictDisableResize();
}
int hasForkChild() {
return server.rdb_child_pid != -1 ||
server.aof_child_pid != -1 ||
server.module_child_pid != -1;
}
/* ======================= Cron: called every 100 ms ======================== */
/* Add a sample to the operations per second array of samples. */
@ -1689,7 +1695,7 @@ void databasesCron(void) {
/* Perform hash tables rehashing if needed, but only if there are no
* other processes saving the DB on disk. Otherwise rehashing is bad
* as will cause a lot of copy-on-write of memory pages. */
if (server.rdb_child_pid == -1 && server.aof_child_pid == -1) {
if (!hasForkChild()) {
/* We use global counters so if we stop the computation at a given
* DB we'll be able to start from the successive in the next
* cron loop iteration. */
@ -1886,15 +1892,14 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
/* Start a scheduled AOF rewrite if this was requested by the user while
* a BGSAVE was in progress. */
if (server.rdb_child_pid == -1 && server.aof_child_pid == -1 &&
if (!hasForkChild() &&
server.aof_rewrite_scheduled)
{
rewriteAppendOnlyFileBackground();
}
/* Check if a background saving or AOF rewrite in progress terminated. */
if (server.rdb_child_pid != -1 || server.aof_child_pid != -1 ||
ldbPendingChildren())
if (hasForkChild() || ldbPendingChildren())
{
int statloc;
pid_t pid;
@ -1907,16 +1912,20 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
if (pid == -1) {
serverLog(LL_WARNING,"wait3() returned an error: %s. "
"rdb_child_pid = %d, aof_child_pid = %d",
"rdb_child_pid = %d, aof_child_pid = %d, module_child_pid = %d",
strerror(errno),
(int) server.rdb_child_pid,
(int) server.aof_child_pid);
(int) server.aof_child_pid,
(int) server.module_child_pid);
} else if (pid == server.rdb_child_pid) {
backgroundSaveDoneHandler(exitcode,bysignal);
if (!bysignal && exitcode == 0) receiveChildInfo();
} else if (pid == server.aof_child_pid) {
backgroundRewriteDoneHandler(exitcode,bysignal);
if (!bysignal && exitcode == 0) receiveChildInfo();
} else if (pid == server.module_child_pid) {
ModuleForkDoneHandler(exitcode,bysignal);
if (!bysignal && exitcode == 0) receiveChildInfo();
} else {
if (!ldbRemoveChild(pid)) {
serverLog(LL_WARNING,
@ -1954,8 +1963,7 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
/* Trigger an AOF rewrite if needed. */
if (server.aof_state == AOF_ON &&
server.rdb_child_pid == -1 &&
server.aof_child_pid == -1 &&
!hasForkChild() &&
server.aof_rewrite_perc &&
server.aof_current_size > server.aof_rewrite_min_size)
{
@ -2013,7 +2021,7 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
* Note: this code must be after the replicationCron() call above so
* make sure when refactoring this file to keep this order. This is useful
* because we want to give priority to RDB savings for replication. */
if (server.rdb_child_pid == -1 && server.aof_child_pid == -1 &&
if (!hasForkChild() &&
server.rdb_bgsave_scheduled &&
(server.unixtime-server.lastbgsave_try > CONFIG_BGSAVE_RETRY_DELAY ||
server.lastbgsave_status == C_OK))
@ -2784,6 +2792,7 @@ void initServer(void) {
server.cronloops = 0;
server.rdb_child_pid = -1;
server.aof_child_pid = -1;
server.module_child_pid = -1;
server.rdb_child_type = RDB_CHILD_TYPE_NONE;
server.rdb_bgsave_scheduled = 0;
server.child_info_pipe[0] = -1;
@ -2802,6 +2811,7 @@ void initServer(void) {
server.stat_peak_memory = 0;
server.stat_rdb_cow_bytes = 0;
server.stat_aof_cow_bytes = 0;
server.stat_module_cow_bytes = 0;
server.cron_malloc_stats.zmalloc_used = 0;
server.cron_malloc_stats.process_rss = 0;
server.cron_malloc_stats.allocator_allocated = 0;
@ -4040,7 +4050,9 @@ sds genRedisInfoString(char *section) {
"aof_current_rewrite_time_sec:%jd\r\n"
"aof_last_bgrewrite_status:%s\r\n"
"aof_last_write_status:%s\r\n"
"aof_last_cow_size:%zu\r\n",
"aof_last_cow_size:%zu\r\n"
"module_fork_in_progress:%d\r\n"
"module_fork_last_cow_size:%zu\r\n",
server.loading,
server.dirty,
server.rdb_child_pid != -1,
@ -4058,7 +4070,9 @@ sds genRedisInfoString(char *section) {
-1 : time(NULL)-server.aof_rewrite_time_start),
(server.aof_lastbgrewrite_status == C_OK) ? "ok" : "err",
(server.aof_last_write_status == C_OK) ? "ok" : "err",
server.stat_aof_cow_bytes);
server.stat_aof_cow_bytes,
server.module_child_pid != -1,
server.stat_module_cow_bytes);
if (server.aof_enabled) {
info = sdscatprintf(info,
@ -4554,6 +4568,58 @@ void setupSignalHandlers(void) {
return;
}
static void sigKillChildHandler(int sig) {
UNUSED(sig);
/* this handler is needed to resolve a valgrind warning */
serverLogFromHandler(LL_WARNING, "Received SIGUSR1 in child, exiting now.");
exitFromChild(1);
}
void setupChildSignalHandlers(void) {
struct sigaction act;
/* When the SA_SIGINFO flag is set in sa_flags then sa_sigaction is used.
* Otherwise, sa_handler is used. */
sigemptyset(&act.sa_mask);
act.sa_flags = 0;
act.sa_handler = sigKillChildHandler;
sigaction(SIGUSR1, &act, NULL);
return;
}
int redisFork() {
int childpid;
long long start = ustime();
if ((childpid = fork()) == 0) {
/* Child */
closeListeningSockets(0);
setupChildSignalHandlers();
} else {
/* Parent */
server.stat_fork_time = ustime()-start;
server.stat_fork_rate = (double) zmalloc_used_memory() * 1000000 / server.stat_fork_time / (1024*1024*1024); /* GB per second. */
latencyAddSampleIfNeeded("fork",server.stat_fork_time/1000);
if (childpid == -1) {
return -1;
}
updateDictResizePolicy();
}
return childpid;
}
void sendChildCOWInfo(int ptype, char *pname) {
size_t private_dirty = zmalloc_get_private_dirty(-1);
if (private_dirty) {
serverLog(LL_NOTICE,
"%s: %zu MB of memory used by copy-on-write",
pname, private_dirty/(1024*1024));
}
server.child_info_data.cow_size = private_dirty;
sendChildInfo(ptype);
}
void memtest(size_t megabytes, int passes);
/* Returns 1 if there is --sentinel among the arguments or if