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Introduce cron_shutdown function for stopping the main background worker #381

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Introduce cron_shutdown function for stopping the main background worker #381

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8 changes: 7 additions & 1 deletion pg_cron--1.5--1.6.sql
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Original file line number Diff line number Diff line change
@@ -1 +1,7 @@
/* no SQL changes in 1.6 */
DROP FUNCTION IF EXISTS cron.shutdown();
CREATE FUNCTION cron.shutdown()
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this would require a new SQL script (1.7), otherwise existing 1.6 users will never get the function.

RETURNS bool
LANGUAGE C STRICT
AS 'MODULE_PATHNAME', $$cron_shutdown$$;
COMMENT ON FUNCTION cron.shutdown()
IS 'shutdown pg_cron';
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should also revoke execute from public, to ensure only superuser can call this (or grant privileges)

81 changes: 79 additions & 2 deletions src/pg_cron.c
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Expand Up @@ -149,6 +149,9 @@ static bool jobStartupTimeout(CronTask *task, TimestampTz currentTime);
static char* pg_cron_cmdTuples(char *msg);
static void bgw_generate_returned_message(StringInfoData *display_msg, ErrorData edata);

/* SQL-callable functions */
PG_FUNCTION_INFO_V1(cron_shutdown);

/* global settings */
char *CronTableDatabaseName = "postgres";
static bool CronLogStatement = true;
Expand All @@ -169,6 +172,9 @@ static bool UseBackgroundWorkers = false;

char *cron_timezone = NULL;

static shmem_request_hook_type prev_shmem_request_hook = NULL;
static shmem_startup_hook_type prev_shmem_startup_hook = NULL;

static const struct config_enum_entry cron_message_level_options[] = {
{"debug5", DEBUG5, false},
{"debug4", DEBUG4, false},
Expand All @@ -188,6 +194,63 @@ static const struct config_enum_entry cron_message_level_options[] = {

static const char *cron_error_severity(int elevel);

struct scheduler_shared_data_t {
pid_t scheduler_pid;
bool restart_scheduler;
LWLockId lock;
};

static struct scheduler_shared_data_t* scheduler_shared_data = NULL;

Datum
cron_shutdown(PG_FUNCTION_ARGS)
{
bool result = false;
Oid funcid;
pid_t pid;

LWLockAcquire(scheduler_shared_data->lock, LW_EXCLUSIVE);
pid = scheduler_shared_data->scheduler_pid;
scheduler_shared_data->scheduler_pid = 0;
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the code style should be adapted to the rest of the project

(except the Vixie cron logic in entry.c/misc.c)

scheduler_shared_data->restart_scheduler = false;
LWLockRelease(scheduler_shared_data->lock);

funcid = fmgr_internal_function("pg_terminate_backend");
if (funcid == InvalidOid) {
ereport(ERROR, (errmsg("Function pg_terminate_backend not found")));
}
result = DatumGetBool(OidFunctionCall1(funcid, Int32GetDatum(pid)));
PG_RETURN_BOOL(result);
}

static void cron_shmem_request(void)
{
if (prev_shmem_request_hook) {
prev_shmem_request_hook();
}

RequestNamedLWLockTranche("cron", 1);
}

static void cron_shmem_startup(void)
{
bool found;
if (prev_shmem_startup_hook) {
prev_shmem_startup_hook();
}

LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
InitShmemIndex();
scheduler_shared_data = (struct scheduler_shared_data_t*)
ShmemInitStruct("cron_scheduler_shared_data", sizeof(struct scheduler_shared_data_t), &found);
if (!found) {
scheduler_shared_data->scheduler_pid = 0;
scheduler_shared_data->restart_scheduler = true;
scheduler_shared_data->lock = &(GetNamedLWLockTranche("cron"))->lock;
}
LWLockRelease(AddinShmemInitLock);
}

/*
* _PG_init gets called when the extension is loaded.
*/
Expand All @@ -211,6 +274,12 @@ _PG_init(void)
/* watch for invalidation events */
CacheRegisterRelcacheCallback(InvalidateJobCacheCallback, (Datum) 0);

prev_shmem_request_hook = shmem_request_hook;
shmem_request_hook = cron_shmem_request;

prev_shmem_startup_hook = shmem_startup_hook;
shmem_startup_hook = cron_shmem_startup;

DefineCustomStringVariable(
"cron.database_name",
gettext_noop("Database in which pg_cron metadata is kept."),
Expand Down Expand Up @@ -560,6 +629,11 @@ PgCronLauncherMain(Datum arg)
{
MemoryContext CronLoopContext = NULL;
struct rlimit limit;
int retcode;

LWLockAcquire(scheduler_shared_data->lock, LW_EXCLUSIVE);
scheduler_shared_data->scheduler_pid = MyProcPid;
LWLockRelease(scheduler_shared_data->lock);

/* Establish signal handlers before unblocking signals. */
pqsignal(SIGHUP, pg_cron_sighup);
Expand Down Expand Up @@ -670,8 +744,11 @@ PgCronLauncherMain(Datum arg)

ereport(LOG, (errmsg("pg_cron scheduler shutting down")));

/* return error code to trigger restart */
proc_exit(1);
/* return error code to trigger restart unless shutting down cron scheduler */
LWLockAcquire(scheduler_shared_data->lock, LW_EXCLUSIVE);
retcode = (int)scheduler_shared_data->restart_scheduler;
LWLockRelease(scheduler_shared_data->lock);
proc_exit((int)retcode);
}


Expand Down