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Allow background workers to be started dynamically.

Browse Source 
There is a new API, RegisterDynamicBackgroundWorker, which allows
an ordinary user backend to register a new background writer during
normal running.  This means that it's no longer necessary for all
background workers to be registered during processing of
shared_preload_libraries, although the option of registering workers
at that time remains available.

When a background worker exits and will not be restarted, the
slot previously used by that background worker is automatically
released and becomes available for reuse.  Slots used by background
workers that are configured for automatic restart can't (yet) be
released without shutting down the system.

This commit adds a new source file, bgworker.c, and moves some
of the existing control logic for background workers there.
Previously, there was little enough logic that it made sense to
keep everything in postmaster.c, but not any more.

This commit also makes the worker_spi contrib module into an
extension and adds a new function, worker_spi_launch, which can
be used to demonstrate the new facility.
This commit is contained in:
Robert Haas 2013-07-16 13:02:15 -04:00
parent 233bfe0673
commit 7f7485a0cd
13 changed files with 710 additions and 209 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
contrib/worker_spi/Makefile
View File

@ -2,6 +2,9 @@
MODULES = worker_spi
EXTENSION = worker_spi
DATA = worker_spi--1.0.sql
ifdef USE_PGXS
PG_CONFIG = pg_config
PGXS := $(shell $(PG_CONFIG) --pgxs)

9
contrib/worker_spi/worker_spi--1.0.sql Normal file
View File

@ -0,0 +1,9 @@
/* contrib/worker_spi/worker_spi--1.0.sql */
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
\echo Use "CREATE EXTENSION worker_spi" to load this file. \quit
CREATE FUNCTION worker_spi_launch(pg_catalog.int4)
RETURNS pg_catalog.bool STRICT
AS 'MODULE_PATHNAME'
LANGUAGE C;

66
contrib/worker_spi/worker_spi.c
View File

@ -42,8 +42,11 @@
#include "tcop/utility.h"
PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(worker_spi_launch);
void _PG_init(void);
void worker_spi_main(Datum);
Datum worker_spi_launch(PG_FUNCTION_ARGS);
/* flags set by signal handlers */
static volatile sig_atomic_t got_sighup = false;
@ -153,11 +156,22 @@ initialize_worker_spi(worktable *table)
pgstat_report_activity(STATE_IDLE, NULL);
}
static void
worker_spi_main(void *main_arg)
void
worker_spi_main(Datum main_arg)
{
worktable *table = (worktable *) main_arg;
int index = DatumGetInt32(main_arg);
worktable *table;
StringInfoData buf;
char name[20];
table = palloc(sizeof(worktable));
sprintf(name, "schema%d", index);
table->schema = pstrdup(name);
table->name = pstrdup("counted");
/* Establish signal handlers before unblocking signals. */
pqsignal(SIGHUP, worker_spi_sighup);
pqsignal(SIGTERM, worker_spi_sigterm);
/* We're now ready to receive signals */
BackgroundWorkerUnblockSignals();
@ -279,7 +293,7 @@ worker_spi_main(void *main_arg)
pgstat_report_activity(STATE_IDLE, NULL);
}
proc_exit(0);
proc_exit(1);
}
/*
@ -292,9 +306,7 @@ void
_PG_init(void)
{
BackgroundWorker worker;
worktable *table;
unsigned int i;
char name[20];
/* get the configuration */
DefineCustomIntVariable("worker_spi.naptime",
@ -309,6 +321,10 @@ _PG_init(void)
NULL,
NULL,
NULL);
if (!process_shared_preload_libraries_in_progress)
return;
DefineCustomIntVariable("worker_spi.total_workers",
"Number of workers.",
NULL,
@ -328,23 +344,41 @@ _PG_init(void)
worker.bgw_start_time = BgWorkerStart_RecoveryFinished;
worker.bgw_restart_time = BGW_NEVER_RESTART;
worker.bgw_main = worker_spi_main;
worker.bgw_sighup = worker_spi_sighup;
worker.bgw_sigterm = worker_spi_sigterm;
worker.bgw_sighup = NULL;
worker.bgw_sigterm = NULL;
/*
* Now fill in worker-specific data, and do the actual registrations.
*/
for (i = 1; i <= worker_spi_total_workers; i++)
{
sprintf(name, "worker %d", i);
worker.bgw_name = pstrdup(name);
table = palloc(sizeof(worktable));
sprintf(name, "schema%d", i);
table->schema = pstrdup(name);
table->name = pstrdup("counted");
worker.bgw_main_arg = (void *) table;
snprintf(worker.bgw_name, BGW_MAXLEN, "worker %d", i);
worker.bgw_main_arg = Int32GetDatum(i);
RegisterBackgroundWorker(&worker);
}
}
/*
* Dynamically launch an SPI worker.
*/
Datum
worker_spi_launch(PG_FUNCTION_ARGS)
{
int32 i = PG_GETARG_INT32(0);
BackgroundWorker worker;
worker.bgw_flags = BGWORKER_SHMEM_ACCESS |
BGWORKER_BACKEND_DATABASE_CONNECTION;
worker.bgw_start_time = BgWorkerStart_RecoveryFinished;
worker.bgw_restart_time = BGW_NEVER_RESTART;
worker.bgw_main = NULL; /* new worker might not have library loaded */
sprintf(worker.bgw_library_name, "worker_spi");
sprintf(worker.bgw_function_name, "worker_spi_main");
worker.bgw_sighup = NULL; /* new worker might not have library loaded */
worker.bgw_sigterm = NULL; /* new worker might not have library loaded */
snprintf(worker.bgw_name, BGW_MAXLEN, "worker %d", i);
worker.bgw_main_arg = Int32GetDatum(i);
PG_RETURN_BOOL(RegisterDynamicBackgroundWorker(&worker));
}

5
contrib/worker_spi/worker_spi.control Normal file
View File

@ -0,0 +1,5 @@
# worker_spi extension
comment = 'Sample background worker'
default_version = '1.0'
module_pathname = '$libdir/worker_spi'
relocatable = true

55
doc/src/sgml/bgworker.sgml
View File

@ -30,23 +30,35 @@
</warning>
<para>
Only modules listed in <varname>shared_preload_libraries</> can run
background workers. A module wishing to run a background worker needs
to register it by calling
Background workers can be initialized at the time that
<productname>PostgreSQL</> is started including the module name in
<varname>shared_preload_libraries</>. A module wishing to run a background
worker can register it by calling
<function>RegisterBackgroundWorker(<type>BackgroundWorker *worker</type>)</function>
from its <function>_PG_init()</>.
from its <function>_PG_init()</>. Background workers can also be started
after the system is up and running by calling the function
<function>RegisterDynamicBackgroundWorker</function>(<type>BackgroundWorker
*worker</type>). Unlike <function>RegisterBackgroundWorker</>, which can
only be called from within the postmaster,
<function>RegisterDynamicBackgroundWorker</function> must be called from
a regular backend.
</para>
<para>
The structure <structname>BackgroundWorker</structname> is defined thus:
<programlisting>
typedef void (*bgworker_main_type)(void *main_arg);
typedef void (*bgworker_sighdlr_type)(SIGNAL_ARGS);
typedef struct BackgroundWorker
{
char *bgw_name;
char bgw_name[BGW_MAXLEN];
int bgw_flags;
BgWorkerStartTime bgw_start_time;
int bgw_restart_time; /* in seconds, or BGW_NEVER_RESTART */
bgworker_main_type bgw_main;
void *bgw_main_arg;
bgworker_main_type bgw_main;
char bgw_library_name[BGW_MAXLEN]; /* only if bgw_main is NULL */
char bgw_function_name[BGW_MAXLEN]; /* only if bgw_main is NULL */
Datum bgw_main_arg;
bgworker_sighdlr_type bgw_sighup;
bgworker_sighdlr_type bgw_sigterm;
} BackgroundWorker;
@ -101,7 +113,29 @@ typedef struct BackgroundWorker
<structfield>bgw_main_arg</structfield> will be passed to it as its only
argument. Note that the global variable <literal>MyBgworkerEntry</literal>
points to a copy of the <structname>BackgroundWorker</structname> structure
passed at registration time.
passed at registration time. <structfield>bgw_main</structfield> may be
NULL; in that case, <structfield>bgw_library_name</structfield> and
<structfield>bgw_function_name</structfield> will be used to determine
the entrypoint. This is useful for background workers launched after
postmaster startup, where the postmaster does not have the requisite
library loaded.
</para>
<para>
<structfield>bgw_library_name</structfield> is the name of a library in
which the initial entrypoint for the background worker should be sought.
It is ignored unless <structfield>bgw_main</structfield> is NULL.
But if <structfield>bgw_main</structfield> is NULL, then the named library
will be dynamically loaded by the worker process and
<structfield>bgw_function_name</structfield> will be used to identify
the function to be called.
</para>
<para>
<structfield>bgw_function_name</structfield> is the name of a function in
a dynamically loaded library which should be used as the initial entrypoint
for a new background worker. It is ignored unless
<structfield>bgw_main</structfield> is NULL.
</para>
<para>
@ -109,7 +143,10 @@ typedef struct BackgroundWorker
pointers to functions that will be installed as signal handlers for the new
process. If <structfield>bgw_sighup</> is NULL, then <literal>SIG_IGN</>
is used; if <structfield>bgw_sigterm</> is NULL, a handler is installed that
will terminate the process after logging a suitable message.
will terminate the process after logging a suitable message. These
fields should not be used if <structfield>bgw_main</> is NULL; instead,
the worker process should set its own signal handlers before calling
<function>BackgroundWorkerUnblockSignals()</function>.
</para>
<para>Once running, the process can connect to a database by calling

4
src/backend/postmaster/Makefile
View File

@ -12,7 +12,7 @@ subdir = src/backend/postmaster
top_builddir = ../../..
include $(top_builddir)/src/Makefile.global
OBJS = autovacuum.o bgwriter.o fork_process.o pgarch.o pgstat.o postmaster.o \
startup.o syslogger.o walwriter.o checkpointer.o
OBJS = autovacuum.o bgworker.o bgwriter.o checkpointer.o fork_process.o \
pgarch.o pgstat.o postmaster.o startup.o syslogger.o walwriter.o
include $(top_srcdir)/src/backend/common.mk

483
src/backend/postmaster/bgworker.c Normal file
View File

@ -0,0 +1,483 @@
/*--------------------------------------------------------------------
* bgworker.c
* POSTGRES pluggable background workers implementation
*
* Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/postmaster/bgworker.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "miscadmin.h"
#include "postmaster/bgworker_internals.h"
#include "storage/barrier.h"
#include "storage/lwlock.h"
#include "storage/pmsignal.h"
#include "storage/shmem.h"
#include "utils/ascii.h"
/*
* The postmaster's list of registered background workers, in private memory.
*/
slist_head BackgroundWorkerList = SLIST_STATIC_INIT(BackgroundWorkerList);
/*
* BackgroundWorkerSlots exist in shared memory and can be accessed (via
* the BackgroundWorkerArray) by both the postmaster and by regular backends.
* However, the postmaster cannot take locks, even spinlocks, because this
* might allow it to crash or become wedged if shared memory gets corrupted.
* Such an outcome is intolerable. Therefore, we need a lockless protocol
* for coordinating access to this data.
*
* The 'in_use' flag is used to hand off responsibility for the slot between
* the postmaster and the rest of the system. When 'in_use' is false,
* the postmaster will ignore the slot entirely, except for the 'in_use' flag
* itself, which it may read. In this state, regular backends may modify the
* slot. Once a backend sets 'in_use' to true, the slot becomes the
* responsibility of the postmaster. Regular backends may no longer modify it,
* but the postmaster may examine it. Thus, a backend initializing a slot
* must fully initialize the slot - and insert a write memory barrier - before
* marking it as in use.
*
* In addition to coordinating with the postmaster, backends modifying this
* data structure must coordinate with each other. Since they can take locks,
* this is straightforward: any backend wishing to manipulate a slot must
* take BackgroundWorkerLock in exclusive mode. Backends wishing to read
* data that might get concurrently modified by other backends should take
* this lock in shared mode. No matter what, backends reading this data
* structure must be able to tolerate concurrent modifications by the
* postmaster.
*/
typedef struct BackgroundWorkerSlot
{
bool in_use;
BackgroundWorker worker;
} BackgroundWorkerSlot;
typedef struct BackgroundWorkerArray
{
int total_slots;
BackgroundWorkerSlot slot[FLEXIBLE_ARRAY_MEMBER];
} BackgroundWorkerArray;
BackgroundWorkerArray *BackgroundWorkerData;
/*
* Calculate shared memory needed.
*/
Size
BackgroundWorkerShmemSize(void)
{
Size size;
/* Array of workers is variably sized. */
size = offsetof(BackgroundWorkerArray, slot);
size = add_size(size, mul_size(max_worker_processes,
sizeof(BackgroundWorkerSlot)));
return size;
}
/*
* Initialize shared memory.
*/
void
BackgroundWorkerShmemInit(void)
{
bool found;
BackgroundWorkerData = ShmemInitStruct("Background Worker Data",
BackgroundWorkerShmemSize(),
&found);
if (!IsUnderPostmaster)
{
slist_iter siter;
int slotno = 0;
BackgroundWorkerData->total_slots = max_worker_processes;
/*
* Copy contents of worker list into shared memory. Record the
* shared memory slot assigned to each worker. This ensures
* a 1-to-1 correspondence betwen the postmaster's private list and
* the array in shared memory.
*/
slist_foreach(siter, &BackgroundWorkerList)
{
BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
RegisteredBgWorker *rw;
rw = slist_container(RegisteredBgWorker, rw_lnode, siter.cur);
Assert(slotno < max_worker_processes);
slot->in_use = true;
rw->rw_shmem_slot = slotno;
memcpy(&slot->worker, &rw->rw_worker, sizeof(BackgroundWorker));
++slotno;
}
/*
* Mark any remaining slots as not in use.
*/
while (slotno < max_worker_processes)
{
BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
slot->in_use = false;
++slotno;
}
}
else
Assert(found);
}
static RegisteredBgWorker *
FindRegisteredWorkerBySlotNumber(int slotno)
{
slist_iter siter;
/*
* Copy contents of worker list into shared memory. Record the
* shared memory slot assigned to each worker. This ensures
* a 1-to-1 correspondence betwen the postmaster's private list and
* the array in shared memory.
*/
slist_foreach(siter, &BackgroundWorkerList)
{
RegisteredBgWorker *rw;
rw = slist_container(RegisteredBgWorker, rw_lnode, siter.cur);
if (rw->rw_shmem_slot == slotno)
return rw;
}
return NULL;
}
/*
* Notice changes to shared_memory made by other backends. This code
* runs in the postmaster, so we must be very careful not to assume that
* shared memory contents are sane. Otherwise, a rogue backend could take
* out the postmaster.
*/
void
BackgroundWorkerStateChange(void)
{
int slotno;
/*
* The total number of slots stored in shared memory should match our
* notion of max_worker_processes. If it does not, something is very
* wrong. Further down, we always refer to this value as
* max_worker_processes, in case shared memory gets corrupted while
* we're looping.
*/
if (max_worker_processes != BackgroundWorkerData->total_slots)
{
elog(LOG,
"inconsistent background worker state (max_worker_processes=%d, total_slots=%d",
max_worker_processes,
BackgroundWorkerData->total_slots);
return;
}
/*
* Iterate through slots, looking for newly-registered workers or
* workers who must die.
*/
for (slotno = 0; slotno < max_worker_processes; ++slotno)
{
BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
RegisteredBgWorker *rw;
if (!slot->in_use)
continue;
/*
* Make sure we don't see the in_use flag before the updated slot
* contents.
*/
pg_read_barrier();
/*
* See whether we already know about this worker. If not, we need
* to update our backend-private BackgroundWorkerList to match shared
* memory.
*/
rw = FindRegisteredWorkerBySlotNumber(slotno);
if (rw != NULL)
continue;
/*
* Copy the registration data into the registered workers list.
*/
rw = malloc(sizeof(RegisteredBgWorker));
if (rw == NULL)
{
ereport(LOG,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory")));
return;
}
/*
* Copy strings in a paranoid way. If shared memory is corrupted,
* the source data might not even be NUL-terminated.
*/
ascii_safe_strlcpy(rw->rw_worker.bgw_name,
slot->worker.bgw_name, BGW_MAXLEN);
ascii_safe_strlcpy(rw->rw_worker.bgw_library_name,
slot->worker.bgw_library_name, BGW_MAXLEN);
ascii_safe_strlcpy(rw->rw_worker.bgw_function_name,
slot->worker.bgw_function_name, BGW_MAXLEN);
/*
* Copy remaining fields.
*
* flags, start_time, and restart_time are examined by the
* postmaster, but nothing too bad will happen if they are
* corrupted. The remaining fields will only be examined by the
* child process. It might crash, but we won't.
*/
rw->rw_worker.bgw_flags = slot->worker.bgw_flags;
rw->rw_worker.bgw_start_time = slot->worker.bgw_start_time;
rw->rw_worker.bgw_restart_time = slot->worker.bgw_restart_time;
rw->rw_worker.bgw_main = slot->worker.bgw_main;
rw->rw_worker.bgw_main_arg = slot->worker.bgw_main_arg;
rw->rw_worker.bgw_sighup = slot->worker.bgw_sighup;
rw->rw_worker.bgw_sigterm = slot->worker.bgw_sigterm;
/* Initialize postmaster bookkeeping. */
rw->rw_backend = NULL;
rw->rw_pid = 0;
rw->rw_child_slot = 0;
rw->rw_crashed_at = 0;
rw->rw_shmem_slot = slotno;
/* Log it! */
ereport(LOG,
(errmsg("registering background worker: %s",
rw->rw_worker.bgw_name)));
slist_push_head(&BackgroundWorkerList, &rw->rw_lnode);
}
}
/*
* Forget about a background worker that's no longer needed.
*
* At present, this only happens when a background worker marked
* BGW_NEVER_RESTART exits. This function should only be invoked in
* the postmaster.
*/
void
ForgetBackgroundWorker(RegisteredBgWorker *rw)
{
BackgroundWorkerSlot *slot;
Assert(rw->rw_shmem_slot < max_worker_processes);
slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
slot->in_use = false;
ereport(LOG,
(errmsg("unregistering background worker: %s",
rw->rw_worker.bgw_name)));
slist_delete(&BackgroundWorkerList, &rw->rw_lnode);
free(rw);
}
#ifdef EXEC_BACKEND
/*
* In EXEC_BACKEND mode, workers use this to retrieve their details from
* shared memory.
*/
BackgroundWorker *
BackgroundWorkerEntry(int slotno)
{
BackgroundWorkerSlot *slot;
Assert(slotno < BackgroundWorkerData->total_slots);
slot = &BackgroundWorkerData->slot[slotno];
Assert(slot->in_use);
return &slot->worker; /* can't become free while we're still here */
}
#endif
/*
* Complain about the BackgroundWorker definition using error level elevel.
* Return true if it looks ok, false if not (unless elevel >= ERROR, in
* which case we won't return at all in the not-OK case).
*/
static bool
SanityCheckBackgroundWorker(BackgroundWorker *worker, int elevel)
{
/* sanity check for flags */
if (worker->bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION)
{
if (!(worker->bgw_flags & BGWORKER_SHMEM_ACCESS))
{
ereport(elevel,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("background worker \"%s\": must attach to shared memory in order to request a database connection",
worker->bgw_name)));
return false;
}
if (worker->bgw_start_time == BgWorkerStart_PostmasterStart)
{
ereport(elevel,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("background worker \"%s\": cannot request database access if starting at postmaster start",
worker->bgw_name)));
return false;
}
/* XXX other checks? */
}
if ((worker->bgw_restart_time < 0 &&
worker->bgw_restart_time != BGW_NEVER_RESTART) ||
(worker->bgw_restart_time > USECS_PER_DAY / 1000))
{
ereport(elevel,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("background worker \"%s\": invalid restart interval",
worker->bgw_name)));
return false;
}
return true;
}
/*
* Register a new background worker while processing shared_preload_libraries.
*
* This can only be called in the _PG_init function of a module library
* that's loaded by shared_preload_libraries; otherwise it has no effect.
*/
void
RegisterBackgroundWorker(BackgroundWorker *worker)
{
RegisteredBgWorker *rw;
static int numworkers = 0;
if (!IsUnderPostmaster)
ereport(LOG,
(errmsg("registering background worker: %s", worker->bgw_name)));
if (!process_shared_preload_libraries_in_progress)
{
if (!IsUnderPostmaster)
ereport(LOG,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("background worker \"%s\": must be registered in shared_preload_libraries",
worker->bgw_name)));
return;
}
if (!SanityCheckBackgroundWorker(worker, LOG))
return;
/*
* Enforce maximum number of workers. Note this is overly restrictive: we
* could allow more non-shmem-connected workers, because these don't count
* towards the MAX_BACKENDS limit elsewhere. For now, it doesn't seem
* important to relax this restriction.
*/
if (++numworkers > max_worker_processes)
{
ereport(LOG,
(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
errmsg("too many background workers"),
errdetail_plural("Up to %d background worker can be registered with the current settings.",
"Up to %d background workers can be registered with the current settings.",
max_worker_processes,
max_worker_processes),
errhint("Consider increasing the configuration parameter \"max_worker_processes\".")));
return;
}
/*
* Copy the registration data into the registered workers list.
*/
rw = malloc(sizeof(RegisteredBgWorker));
if (rw == NULL)
{
ereport(LOG,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory")));
return;
}
rw->rw_worker = *worker;
rw->rw_backend = NULL;
rw->rw_pid = 0;
rw->rw_child_slot = 0;
rw->rw_crashed_at = 0;
slist_push_head(&BackgroundWorkerList, &rw->rw_lnode);
}
/*
* Register a new background worker from a regular backend.
*
* Returns true on success and false on failure. Failure typically indicates
* that no background worker slots are currently available.
*/
bool
RegisterDynamicBackgroundWorker(BackgroundWorker *worker)
{
int slotno;
bool success = false;
/*
* We can't register dynamic background workers from the postmaster.
* If this is a standalone backend, we're the only process and can't
* start any more. In a multi-process environement, it might be
* theoretically possible, but we don't currently support it due to
* locking considerations; see comments on the BackgroundWorkerSlot
* data structure.
*/
if (!IsUnderPostmaster)
return false;
if (!SanityCheckBackgroundWorker(worker, ERROR))
return false;
LWLockAcquire(BackgroundWorkerLock, LW_EXCLUSIVE);
/*
* Look for an unused slot. If we find one, grab it.
*/
for (slotno = 0; slotno < BackgroundWorkerData->total_slots; ++slotno)
{
BackgroundWorkerSlot *slot = &BackgroundWorkerData->slot[slotno];
if (!slot->in_use)
{
memcpy(&slot->worker, worker, sizeof(BackgroundWorker));
/*
* Make sure postmaster doesn't see the slot as in use before
* it sees the new contents.
*/
pg_write_barrier();
slot->in_use = true;
success = true;
break;
}
}
LWLockRelease(BackgroundWorkerLock);
/* If we found a slot, tell the postmaster to notice the change. */
if (success)
SendPostmasterSignal(PMSIGNAL_BACKGROUND_WORKER_CHANGE);
return success;
}

227
src/backend/postmaster/postmaster.c
View File

@ -103,7 +103,7 @@
#include "miscadmin.h"
#include "pgstat.h"
#include "postmaster/autovacuum.h"
#include "postmaster/bgworker.h"
#include "postmaster/bgworker_internals.h"
#include "postmaster/fork_process.h"
#include "postmaster/pgarch.h"
#include "postmaster/postmaster.h"
@ -117,6 +117,7 @@
#include "tcop/tcopprot.h"
#include "utils/builtins.h"
#include "utils/datetime.h"
#include "utils/dynamic_loader.h"
#include "utils/memutils.h"
#include "utils/ps_status.h"
#include "utils/timeout.h"
@ -178,29 +179,6 @@ static dlist_head BackendList = DLIST_STATIC_INIT(BackendList);
static Backend *ShmemBackendArray;
#endif
/*
* List of background workers.
*
* A worker that requests a database connection during registration will have
* rw_backend set, and will be present in BackendList. Note: do not rely on
* rw_backend being non-NULL for shmem-connected workers!
*/
typedef struct RegisteredBgWorker
{
BackgroundWorker rw_worker; /* its registry entry */
Backend *rw_backend; /* its BackendList entry, or NULL */
pid_t rw_pid; /* 0 if not running */
int rw_child_slot;
TimestampTz rw_crashed_at; /* if not 0, time it last crashed */
#ifdef EXEC_BACKEND
int rw_cookie;
#endif
slist_node rw_lnode; /* list link */
} RegisteredBgWorker;
static slist_head BackgroundWorkerList = SLIST_STATIC_INIT(BackgroundWorkerList);
BackgroundWorker *MyBgworkerEntry = NULL;
@ -532,8 +510,6 @@ static bool save_backend_variables(BackendParameters *param, Port *port,
static void ShmemBackendArrayAdd(Backend *bn);
static void ShmemBackendArrayRemove(Backend *bn);
static BackgroundWorker *find_bgworker_entry(int cookie);
#endif /* EXEC_BACKEND */
#define StartupDataBase() StartChildProcess(StartupProcess)
@ -1456,7 +1432,7 @@ DetermineSleepTime(struct timeval * timeout)
if (HaveCrashedWorker)
{
slist_iter siter;
slist_mutable_iter siter;
/*
* When there are crashed bgworkers, we sleep just long enough that
@ -1464,7 +1440,7 @@ DetermineSleepTime(struct timeval * timeout)
* determine the minimum of all wakeup times according to most recent
* crash time and requested restart interval.
*/
slist_foreach(siter, &BackgroundWorkerList)
slist_foreach_modify(siter, &BackgroundWorkerList)
{
RegisteredBgWorker *rw;
TimestampTz this_wakeup;
@ -1475,7 +1451,10 @@ DetermineSleepTime(struct timeval * timeout)
continue;
if (rw->rw_worker.bgw_restart_time == BGW_NEVER_RESTART)
{
ForgetBackgroundWorker(rw);
continue;
}
this_wakeup = TimestampTzPlusMilliseconds(rw->rw_crashed_at,
1000L * rw->rw_worker.bgw_restart_time);
@ -4619,7 +4598,7 @@ SubPostmasterMain(int argc, char *argv[])
}
if (strncmp(argv[1], "--forkbgworker=", 15) == 0)
{
int cookie;
int shmem_slot;
/* Close the postmaster's sockets */
ClosePostmasterPorts(false);
@ -4633,8 +4612,8 @@ SubPostmasterMain(int argc, char *argv[])
/* Attach process to shared data structures */
CreateSharedMemoryAndSemaphores(false, 0);
cookie = atoi(argv[1] + 15);
MyBgworkerEntry = find_bgworker_entry(cookie);
shmem_slot = atoi(argv[1] + 15);
MyBgworkerEntry = BackgroundWorkerEntry(shmem_slot);
do_start_bgworker();
}
if (strcmp(argv[1], "--forkarch") == 0)
@ -4697,9 +4676,17 @@ static void
sigusr1_handler(SIGNAL_ARGS)
{
int save_errno = errno;
bool start_bgworker = false;
PG_SETMASK(&BlockSig);
/* Process background worker state change. */
if (CheckPostmasterSignal(PMSIGNAL_BACKGROUND_WORKER_CHANGE))
{
BackgroundWorkerStateChange();
start_bgworker = true;
}
/*
* RECOVERY_STARTED and BEGIN_HOT_STANDBY signals are ignored in
* unexpected states. If the startup process quickly starts up, completes
@ -4737,11 +4724,13 @@ sigusr1_handler(SIGNAL_ARGS)
(errmsg("database system is ready to accept read only connections")));
pmState = PM_HOT_STANDBY;
/* Some workers may be scheduled to start now */
StartOneBackgroundWorker();
start_bgworker = true;
}
if (start_bgworker)
StartOneBackgroundWorker();
if (CheckPostmasterSignal(PMSIGNAL_WAKEN_ARCHIVER) &&
PgArchPID != 0)
{
@ -5214,126 +5203,6 @@ MaxLivePostmasterChildren(void)
max_worker_processes);
}
/*
* Register a new background worker.
*
* This can only be called in the _PG_init function of a module library
* that's loaded by shared_preload_libraries; otherwise it has no effect.
*/
void
RegisterBackgroundWorker(BackgroundWorker *worker)
{
RegisteredBgWorker *rw;
int namelen = strlen(worker->bgw_name);
static int numworkers = 0;
#ifdef EXEC_BACKEND
/*
* Use 1 here, not 0, to avoid confusing a possible bogus cookie read by
* atoi() in SubPostmasterMain.
*/
static int BackgroundWorkerCookie = 1;
#endif
if (!IsUnderPostmaster)
ereport(LOG,
(errmsg("registering background worker: %s", worker->bgw_name)));
if (!process_shared_preload_libraries_in_progress)
{
if (!IsUnderPostmaster)
ereport(LOG,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("background worker \"%s\": must be registered in shared_preload_libraries",
worker->bgw_name)));
return;
}
/* sanity check for flags */
if (worker->bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION)
{
if (!(worker->bgw_flags & BGWORKER_SHMEM_ACCESS))
{
if (!IsUnderPostmaster)
ereport(LOG,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("background worker \"%s\": must attach to shared memory in order to request a database connection",
worker->bgw_name)));
return;
}
if (worker->bgw_start_time == BgWorkerStart_PostmasterStart)
{
if (!IsUnderPostmaster)
ereport(LOG,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("background worker \"%s\": cannot request database access if starting at postmaster start",
worker->bgw_name)));
return;
}
/* XXX other checks? */
}
if ((worker->bgw_restart_time < 0 &&
worker->bgw_restart_time != BGW_NEVER_RESTART) ||
(worker->bgw_restart_time > USECS_PER_DAY / 1000))
{
if (!IsUnderPostmaster)
ereport(LOG,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("background worker \"%s\": invalid restart interval",
worker->bgw_name)));
return;
}
/*
* Enforce maximum number of workers. Note this is overly restrictive: we
* could allow more non-shmem-connected workers, because these don't count
* towards the MAX_BACKENDS limit elsewhere. For now, it doesn't seem
* important to relax this restriction.
*/
if (++numworkers > max_worker_processes)
{
ereport(LOG,
(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
errmsg("too many background workers"),
errdetail_plural("Up to %d background worker can be registered with the current settings.",
"Up to %d background workers can be registered with the current settings.",
max_worker_processes,
max_worker_processes),
errhint("Consider increasing the configuration parameter \"max_worker_processes\".")));
return;
}
/*
* Copy the registration data into the registered workers list.
*/
rw = malloc(sizeof(RegisteredBgWorker) + namelen + 1);
if (rw == NULL)
{
ereport(LOG,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory")));
return;
}
rw->rw_worker = *worker;
rw->rw_worker.bgw_name = ((char *) rw) + sizeof(RegisteredBgWorker);
strlcpy(rw->rw_worker.bgw_name, worker->bgw_name, namelen + 1);
rw->rw_backend = NULL;
rw->rw_pid = 0;
rw->rw_child_slot = 0;
rw->rw_crashed_at = 0;
#ifdef EXEC_BACKEND
rw->rw_cookie = BackgroundWorkerCookie++;
#endif
slist_push_head(&BackgroundWorkerList, &rw->rw_lnode);
}
/*
* Connect background worker to a database.
*/
@ -5372,25 +5241,6 @@ BackgroundWorkerUnblockSignals(void)
PG_SETMASK(&UnBlockSig);
}
#ifdef EXEC_BACKEND
static BackgroundWorker *
find_bgworker_entry(int cookie)
{
slist_iter iter;
slist_foreach(iter, &BackgroundWorkerList)
{
RegisteredBgWorker *rw;
rw = slist_container(RegisteredBgWorker, rw_lnode, iter.cur);
if (rw->rw_cookie == cookie)
return &rw->rw_worker;
}
return NULL;
}
#endif
static void
bgworker_quickdie(SIGNAL_ARGS)
{
@ -5453,6 +5303,7 @@ do_start_bgworker(void)
sigjmp_buf local_sigjmp_buf;
char buf[MAXPGPATH];
BackgroundWorker *worker = MyBgworkerEntry;
bgworker_main_type entrypt;
if (worker == NULL)
elog(FATAL, "unable to find bgworker entry");
@ -5568,6 +5419,23 @@ do_start_bgworker(void)
InitProcess();
#endif
/*
* If bgw_main is set, we use that value as the initial entrypoint.
* However, if the library containing the entrypoint wasn't loaded at
* postmaster startup time, passing it as a direct function pointer is
* not possible. To work around that, we allow callers for whom a
* function pointer is not available to pass a library name (which will
* be loaded, if necessary) and a function name (which will be looked up
* in the named library).
*/
if (worker->bgw_main != NULL)
entrypt = worker->bgw_main;
else
entrypt = (bgworker_main_type)
load_external_function(worker->bgw_library_name,
worker->bgw_function_name,
true, NULL);
/*
* Note that in normal processes, we would call InitPostgres here. For a
* worker, however, we don't know what database to connect to, yet; so we
@ -5578,7 +5446,7 @@ do_start_bgworker(void)
/*
* Now invoke the user-defined worker code
*/
worker->bgw_main(worker->bgw_main_arg);
entrypt(worker->bgw_main_arg);
/* ... and if it returns, we're done */
proc_exit(0);
@ -5586,13 +5454,13 @@ do_start_bgworker(void)
#ifdef EXEC_BACKEND
static pid_t
bgworker_forkexec(int cookie)
bgworker_forkexec(int shmem_slot)
{
char *av[10];
int ac = 0;
char forkav[MAXPGPATH];
snprintf(forkav, MAXPGPATH, "--forkbgworker=%d", cookie);
snprintf(forkav, MAXPGPATH, "--forkbgworker=%d", shmem_slot);
av[ac++] = "postgres";
av[ac++] = forkav;
@ -5621,7 +5489,7 @@ start_bgworker(RegisteredBgWorker *rw)
rw->rw_worker.bgw_name)));
#ifdef EXEC_BACKEND
switch ((worker_pid = bgworker_forkexec(rw->rw_cookie)))
switch ((worker_pid = bgworker_forkexec(rw->rw_shmem_slot)))
#else
switch ((worker_pid = fork_process()))
#endif
@ -5749,7 +5617,7 @@ assign_backendlist_entry(RegisteredBgWorker *rw)
static void
StartOneBackgroundWorker(void)
{
slist_iter iter;
slist_mutable_iter iter;
TimestampTz now = 0;
if (FatalError)
@ -5761,7 +5629,7 @@ StartOneBackgroundWorker(void)
HaveCrashedWorker = false;
slist_foreach(iter, &BackgroundWorkerList)
slist_foreach_modify(iter, &BackgroundWorkerList)
{
RegisteredBgWorker *rw;
@ -5781,7 +5649,10 @@ StartOneBackgroundWorker(void)
if (rw->rw_crashed_at != 0)
{
if (rw->rw_worker.bgw_restart_time == BGW_NEVER_RESTART)
{
ForgetBackgroundWorker(rw);
continue;
}
if (now == 0)
now = GetCurrentTimestamp();

3
src/backend/storage/ipc/ipci.c
View File

@ -24,6 +24,7 @@
#include "miscadmin.h"
#include "pgstat.h"
#include "postmaster/autovacuum.h"
#include "postmaster/bgworker_internals.h"
#include "postmaster/bgwriter.h"
#include "postmaster/postmaster.h"
#include "replication/walreceiver.h"
@ -113,6 +114,7 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
size = add_size(size, CLOGShmemSize());
size = add_size(size, SUBTRANSShmemSize());
size = add_size(size, TwoPhaseShmemSize());
size = add_size(size, BackgroundWorkerShmemSize());
size = add_size(size, MultiXactShmemSize());
size = add_size(size, LWLockShmemSize());
size = add_size(size, ProcArrayShmemSize());
@ -214,6 +216,7 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
CreateSharedProcArray();
CreateSharedBackendStatus();
TwoPhaseShmemInit();
BackgroundWorkerShmemInit();
/*
* Set up shared-inval messaging

14
src/include/postmaster/bgworker.h
View File

@ -52,7 +52,7 @@
#define BGWORKER_BACKEND_DATABASE_CONNECTION 0x0002
typedef void (*bgworker_main_type) (void *main_arg);
typedef void (*bgworker_main_type) (Datum main_arg);
typedef void (*bgworker_sighdlr_type) (SIGNAL_ARGS);
/*
@ -67,22 +67,28 @@ typedef enum
#define BGW_DEFAULT_RESTART_INTERVAL 60
#define BGW_NEVER_RESTART -1
#define BGW_MAXLEN 64
typedef struct BackgroundWorker
{
char *bgw_name;
char bgw_name[BGW_MAXLEN];
int bgw_flags;
BgWorkerStartTime bgw_start_time;
int bgw_restart_time; /* in seconds, or BGW_NEVER_RESTART */
bgworker_main_type bgw_main;
void *bgw_main_arg;
char bgw_library_name[BGW_MAXLEN]; /* only if bgw_main is NULL */
char bgw_function_name[BGW_MAXLEN]; /* only if bgw_main is NULL */
Datum bgw_main_arg;
bgworker_sighdlr_type bgw_sighup;
bgworker_sighdlr_type bgw_sigterm;
} BackgroundWorker;
/* Register a new bgworker */
/* Register a new bgworker during shared_preload_libraries */
extern void RegisterBackgroundWorker(BackgroundWorker *worker);
/* Register a new bgworker from a regular backend */
extern bool RegisterDynamicBackgroundWorker(BackgroundWorker *worker);
/* This is valid in a running worker */
extern BackgroundWorker *MyBgworkerEntry;

48
src/include/postmaster/bgworker_internals.h Normal file
View File

@ -0,0 +1,48 @@
/*--------------------------------------------------------------------
* bgworker_internals.h
* POSTGRES pluggable background workers internals
*
* Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/include/postmaster/bgworker.h
*--------------------------------------------------------------------
*/
#ifndef BGWORKER_INTERNALS_H
#define BGWORKER_INTERNALS_H
#include "datatype/timestamp.h"
#include "lib/ilist.h"
#include "postmaster/bgworker.h"
/*
* List of background workers, private to postmaster.
*
* A worker that requests a database connection during registration will have
* rw_backend set, and will be present in BackendList. Note: do not rely on
* rw_backend being non-NULL for shmem-connected workers!
*/
typedef struct RegisteredBgWorker
{
BackgroundWorker rw_worker; /* its registry entry */
struct bkend *rw_backend; /* its BackendList entry, or NULL */
pid_t rw_pid; /* 0 if not running */
int rw_child_slot;
TimestampTz rw_crashed_at; /* if not 0, time it last crashed */
int rw_shmem_slot;
slist_node rw_lnode; /* list link */
} RegisteredBgWorker;
extern slist_head BackgroundWorkerList;
extern Size BackgroundWorkerShmemSize(void);
extern void BackgroundWorkerShmemInit(void);
extern void BackgroundWorkerStateChange(void);
extern void ForgetBackgroundWorker(RegisteredBgWorker *);
#ifdef EXEC_BACKEND
extern BackgroundWorker *BackgroundWorkerEntry(int slotno);
#endif
#endif /* BGWORKER_INTERNLS_H */

1
src/include/storage/lwlock.h
View File

@ -79,6 +79,7 @@ typedef enum LWLockId
SerializablePredicateLockListLock,
OldSerXidLock,
SyncRepLock,
BackgroundWorkerLock,
/* Individual lock IDs end here */
FirstBufMappingLock,
FirstLockMgrLock = FirstBufMappingLock + NUM_BUFFER_PARTITIONS,

1
src/include/storage/pmsignal.h
View File

@ -28,6 +28,7 @@ typedef enum
PMSIGNAL_ROTATE_LOGFILE, /* send SIGUSR1 to syslogger to rotate logfile */
PMSIGNAL_START_AUTOVAC_LAUNCHER, /* start an autovacuum launcher */
PMSIGNAL_START_AUTOVAC_WORKER, /* start an autovacuum worker */
PMSIGNAL_BACKGROUND_WORKER_CHANGE, /* background worker state change */
PMSIGNAL_START_WALRECEIVER, /* start a walreceiver */
PMSIGNAL_ADVANCE_STATE_MACHINE, /* advance postmaster's state machine */