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Replace postmaster.c's own backend type codes with BackendType

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Introduce a separate BackendType for dead-end children, so that we
don't need a separate dead_end flag.

Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/a102f15f-eac4-4ff2-af02-f9ff209ec66f@iki.fi
This commit is contained in:
Heikki Linnakangas 2024-11-14 16:06:16 +02:00
parent a274bbb1b3
commit 18d67a8d7d
6 changed files with 168 additions and 116 deletions
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1
src/backend/postmaster/launch_backend.c
View File

@ -174,6 +174,7 @@ static child_process_kind child_process_kinds[] = {
[B_INVALID] = {"invalid", NULL, false},
[B_BACKEND] = {"backend", BackendMain, true},
[B_DEAD_END_BACKEND] = {"dead-end backend", BackendMain, true},
[B_AUTOVAC_LAUNCHER] = {"autovacuum launcher", AutoVacLauncherMain, true},
[B_AUTOVAC_WORKER] = {"autovacuum worker", AutoVacWorkerMain, true},
[B_BG_WORKER] = {"bgworker", BackgroundWorkerMain, true},

235
src/backend/postmaster/postmaster.c
View File

@ -126,15 +126,71 @@
/*
* Possible types of a backend. Beyond being the possible bkend_type values in
* struct bkend, these are OR-able request flag bits for SignalSomeChildren()
* and CountChildren().
* CountChildren and SignalChildren take a bitmask argument to represent
* BackendTypes to count or signal. Define a separate type and functions to
* work with the bitmasks, to avoid accidentally passing a plain BackendType
* in place of a bitmask or vice versa.
*/
#define BACKEND_TYPE_NORMAL 0x0001 /* normal backend */
#define BACKEND_TYPE_AUTOVAC 0x0002 /* autovacuum worker process */
#define BACKEND_TYPE_WALSND 0x0004 /* walsender process */
#define BACKEND_TYPE_BGWORKER 0x0008 /* bgworker process */
#define BACKEND_TYPE_ALL 0x000F /* OR of all the above */
typedef struct
{
uint32 mask;
} BackendTypeMask;
StaticAssertDecl(BACKEND_NUM_TYPES < 32, "too many backend types for uint32");
static const BackendTypeMask BTYPE_MASK_ALL = {(1 << BACKEND_NUM_TYPES) - 1};
#if 0 /* unused */
static const BackendTypeMask BTYPE_MASK_NONE = {0};
#endif
static inline BackendTypeMask
btmask(BackendType t)
{
BackendTypeMask mask = {.mask = 1 << t};
return mask;
}
#if 0 /* unused */
static inline BackendTypeMask
btmask_add(BackendTypeMask mask, BackendType t)
{
mask.mask |= 1 << t;
return mask;
}
#endif
static inline BackendTypeMask
btmask_del(BackendTypeMask mask, BackendType t)
{
mask.mask &= ~(1 << t);
return mask;
}
static inline BackendTypeMask
btmask_all_except(BackendType t)
{
BackendTypeMask mask = BTYPE_MASK_ALL;
mask = btmask_del(mask, t);
return mask;
}
static inline BackendTypeMask
btmask_all_except2(BackendType t1, BackendType t2)
{
BackendTypeMask mask = BTYPE_MASK_ALL;
mask = btmask_del(mask, t1);
mask = btmask_del(mask, t2);
return mask;
}
static inline bool
btmask_contains(BackendTypeMask mask, BackendType t)
{
return (mask.mask & (1 << t)) != 0;
}
/*
* List of active backends (or child processes anyway; we don't actually
@ -145,7 +201,7 @@
* As shown in the above set of backend types, this list includes not only
* "normal" client sessions, but also autovacuum workers, walsenders, and
* background workers. (Note that at the time of launch, walsenders are
* labeled BACKEND_TYPE_NORMAL; we relabel them to BACKEND_TYPE_WALSND
* labeled B_BACKEND; we relabel them to B_WAL_SENDER
* upon noticing they've changed their PMChildFlags entry. Hence that check
* must be done before any operation that needs to distinguish walsenders
* from normal backends.)
@ -154,7 +210,7 @@
* the purpose of sending a friendly rejection message to a would-be client.
* We must track them because they are attached to shared memory, but we know
* they will never become live backends. dead_end children are not assigned a
* PMChildSlot. dead_end children have bkend_type NORMAL.
* PMChildSlot. dead_end children have bkend_type B_DEAD_END_BACKEND.
*
* "Special" children such as the startup, bgwriter, autovacuum launcher, and
* slot sync worker tasks are not in this list. They are tracked via StartupPID
@ -166,8 +222,7 @@ typedef struct bkend
{
pid_t pid; /* process id of backend */
int child_slot; /* PMChildSlot for this backend, if any */
int bkend_type; /* child process flavor, see above */
bool dead_end; /* is it going to send an error and quit? */
BackendType bkend_type; /* child process flavor, see above */
RegisteredBgWorker *rw; /* bgworker info, if this is a bgworker */
bool bgworker_notify; /* gets bgworker start/stop notifications */
dlist_node elem; /* list link in BackendList */
@ -404,15 +459,12 @@ static void ExitPostmaster(int status) pg_attribute_noreturn();
static int ServerLoop(void);
static int BackendStartup(ClientSocket *client_sock);
static void report_fork_failure_to_client(ClientSocket *client_sock, int errnum);
static CAC_state canAcceptConnections(int backend_type);
static CAC_state canAcceptConnections(BackendType backend_type);
static void signal_child(pid_t pid, int signal);
static void sigquit_child(pid_t pid);
static bool SignalSomeChildren(int signal, int target);
static bool SignalChildren(int signal, BackendTypeMask targetMask);
static void TerminateChildren(int signal);
#define SignalChildren(sig) SignalSomeChildren(sig, BACKEND_TYPE_ALL)
static int CountChildren(int target);
static int CountChildren(BackendTypeMask targetMask);
static Backend *assign_backendlist_entry(void);
static void LaunchMissingBackgroundProcesses(void);
static void maybe_start_bgworkers(void);
@ -1751,12 +1803,12 @@ ServerLoop(void)
/*
* canAcceptConnections --- check to see if database state allows connections
* of the specified type. backend_type can be BACKEND_TYPE_NORMAL,
* BACKEND_TYPE_AUTOVAC, or BACKEND_TYPE_BGWORKER. (Note that we don't yet
* know whether a NORMAL connection might turn into a walsender.)
* of the specified type. backend_type can be B_BACKEND, B_AUTOVAC_WORKER, or
* B_BG_WORKER. (Note that we don't yet know whether a normal B_BACKEND
* connection might turn into a walsender.)
*/
static CAC_state
canAcceptConnections(int backend_type)
canAcceptConnections(BackendType backend_type)
{
CAC_state result = CAC_OK;
@ -1767,7 +1819,7 @@ canAcceptConnections(int backend_type)
* bgworker_should_start_now() decided whether the DB state allows them.
*/
if (pmState != PM_RUN && pmState != PM_HOT_STANDBY &&
backend_type != BACKEND_TYPE_BGWORKER)
backend_type != B_BG_WORKER)
{
if (Shutdown > NoShutdown)
return CAC_SHUTDOWN; /* shutdown is pending */
@ -1784,7 +1836,7 @@ canAcceptConnections(int backend_type)
* "Smart shutdown" restrictions are applied only to normal connections,
* not to autovac workers or bgworkers.
*/
if (!connsAllowed && backend_type == BACKEND_TYPE_NORMAL)
if (!connsAllowed && backend_type == B_BACKEND)
return CAC_SHUTDOWN; /* shutdown is pending */
/*
@ -1799,7 +1851,7 @@ canAcceptConnections(int backend_type)
* The limit here must match the sizes of the per-child-process arrays;
* see comments for MaxLivePostmasterChildren().
*/
if (CountChildren(BACKEND_TYPE_ALL) >= MaxLivePostmasterChildren())
if (CountChildren(btmask_all_except(B_DEAD_END_BACKEND)) >= MaxLivePostmasterChildren())
result = CAC_TOOMANY;
return result;
@ -1968,7 +2020,7 @@ process_pm_reload_request(void)
ereport(LOG,
(errmsg("received SIGHUP, reloading configuration files")));
ProcessConfigFile(PGC_SIGHUP);
SignalChildren(SIGHUP);
SignalChildren(SIGHUP, btmask_all_except(B_DEAD_END_BACKEND));
if (StartupPID != 0)
signal_child(StartupPID, SIGHUP);
if (BgWriterPID != 0)
@ -2386,7 +2438,7 @@ process_pm_child_exit(void)
* Waken walsenders for the last time. No regular backends
* should be around anymore.
*/
SignalChildren(SIGUSR2);
SignalChildren(SIGUSR2, btmask(B_WAL_SENDER));
pmState = PM_SHUTDOWN_2;
}
@ -2552,23 +2604,19 @@ CleanupBackend(Backend *bp,
int exitstatus) /* child's exit status. */
{
char namebuf[MAXPGPATH];
char *procname;
const char *procname;
bool crashed = false;
bool logged = false;
/* Construct a process name for log message */
if (bp->dead_end)
{
procname = _("dead end backend");
}
else if (bp->bkend_type == BACKEND_TYPE_BGWORKER)
/* Construct a process name for the log message */
if (bp->bkend_type == B_BG_WORKER)
{
snprintf(namebuf, MAXPGPATH, _("background worker \"%s\""),
bp->rw->rw_worker.bgw_type);
procname = namebuf;
}
else
procname = _("server process");
procname = _(GetBackendTypeDesc(bp->bkend_type));
/*
* If a backend dies in an ugly way then we must signal all other backends
@ -2600,7 +2648,7 @@ CleanupBackend(Backend *bp,
* If the process attached to shared memory, check that it detached
* cleanly.
*/
if (!bp->dead_end)
if (bp->bkend_type != B_DEAD_END_BACKEND)
{
if (!ReleasePostmasterChildSlot(bp->child_slot))
{
@ -2633,7 +2681,7 @@ CleanupBackend(Backend *bp,
* If it was a background worker, also update its RegisteredBgWorker
* entry.
*/
if (bp->bkend_type == BACKEND_TYPE_BGWORKER)
if (bp->bkend_type == B_BG_WORKER)
{
RegisteredBgWorker *rw = bp->rw;
@ -2861,7 +2909,7 @@ PostmasterStateMachine(void)
* This state ends when we have no normal client backends running.
* Then we're ready to stop other children.
*/
if (CountChildren(BACKEND_TYPE_NORMAL) == 0)
if (CountChildren(btmask(B_BACKEND)) == 0)
pmState = PM_STOP_BACKENDS;
}
}
@ -2880,9 +2928,8 @@ PostmasterStateMachine(void)
*/
ForgetUnstartedBackgroundWorkers();
/* Signal all backend children except walsenders */
SignalSomeChildren(SIGTERM,
BACKEND_TYPE_ALL - BACKEND_TYPE_WALSND);
/* Signal all backend children except walsenders and dead-end backends */
SignalChildren(SIGTERM, btmask_all_except2(B_WAL_SENDER, B_DEAD_END_BACKEND));
/* and the autovac launcher too */
if (AutoVacPID != 0)
signal_child(AutoVacPID, SIGTERM);
@ -2924,7 +2971,7 @@ PostmasterStateMachine(void)
* here. Walsenders and archiver are also disregarded, they will be
* terminated later after writing the checkpoint record.
*/
if (CountChildren(BACKEND_TYPE_ALL - BACKEND_TYPE_WALSND) == 0 &&
if (CountChildren(btmask_all_except2(B_WAL_SENDER, B_DEAD_END_BACKEND)) == 0 &&
StartupPID == 0 &&
WalReceiverPID == 0 &&
WalSummarizerPID == 0 &&
@ -2982,7 +3029,7 @@ PostmasterStateMachine(void)
pmState = PM_WAIT_DEAD_END;
/* Kill the walsenders and archiver too */
SignalChildren(SIGQUIT);
SignalChildren(SIGQUIT, btmask_all_except(B_DEAD_END_BACKEND));
if (PgArchPID != 0)
signal_child(PgArchPID, SIGQUIT);
}
@ -2998,7 +3045,7 @@ PostmasterStateMachine(void)
* left by now anyway; what we're really waiting for is walsenders and
* archiver.
*/
if (PgArchPID == 0 && CountChildren(BACKEND_TYPE_ALL) == 0)
if (PgArchPID == 0 && CountChildren(btmask_all_except(B_DEAD_END_BACKEND)) == 0)
{
pmState = PM_WAIT_DEAD_END;
}
@ -3296,11 +3343,10 @@ sigquit_child(pid_t pid)
}
/*
* Send a signal to the targeted children (but NOT special children;
* dead_end children are never signaled, either).
* Send a signal to the targeted children (but NOT special children).
*/
static bool
SignalSomeChildren(int signal, int target)
SignalChildren(int signal, BackendTypeMask targetMask)
{
dlist_iter iter;
bool signaled = false;
@ -3309,30 +3355,24 @@ SignalSomeChildren(int signal, int target)
{
Backend *bp = dlist_container(Backend, elem, iter.cur);
if (bp->dead_end)
continue;
/*
* Since target == BACKEND_TYPE_ALL is the most common case, we test
* it first and avoid touching shared memory for every child.
* If we need to distinguish between B_BACKEND and B_WAL_SENDER, check
* if any B_BACKEND backends have recently announced that they are
* actually WAL senders.
*/
if (target != BACKEND_TYPE_ALL)
if (btmask_contains(targetMask, B_WAL_SENDER) != btmask_contains(targetMask, B_BACKEND) &&
bp->bkend_type == B_BACKEND)
{
/*
* Assign bkend_type for any recently announced WAL Sender
* processes.
*/
if (bp->bkend_type == BACKEND_TYPE_NORMAL &&
IsPostmasterChildWalSender(bp->child_slot))
bp->bkend_type = BACKEND_TYPE_WALSND;
if (!(target & bp->bkend_type))
continue;
if (IsPostmasterChildWalSender(bp->child_slot))
bp->bkend_type = B_WAL_SENDER;
}
if (!btmask_contains(targetMask, bp->bkend_type))
continue;
ereport(DEBUG4,
(errmsg_internal("sending signal %d to process %d",
signal, (int) bp->pid)));
(errmsg_internal("sending signal %d to %s process %d",
signal, GetBackendTypeDesc(bp->bkend_type), (int) bp->pid)));
signal_child(bp->pid, signal);
signaled = true;
}
@ -3346,7 +3386,7 @@ SignalSomeChildren(int signal, int target)
static void
TerminateChildren(int signal)
{
SignalChildren(signal);
SignalChildren(signal, btmask_all_except(B_DEAD_END_BACKEND));
if (StartupPID != 0)
{
signal_child(StartupPID, signal);
@ -3399,22 +3439,27 @@ BackendStartup(ClientSocket *client_sock)
}
/* Pass down canAcceptConnections state */
startup_data.canAcceptConnections = canAcceptConnections(BACKEND_TYPE_NORMAL);
bn->dead_end = (startup_data.canAcceptConnections != CAC_OK);
startup_data.canAcceptConnections = canAcceptConnections(B_BACKEND);
bn->rw = NULL;
/*
* Unless it's a dead_end child, assign it a child slot number
*/
if (!bn->dead_end)
if (startup_data.canAcceptConnections == CAC_OK)
{
bn->bkend_type = B_BACKEND; /* Can change later to B_WAL_SENDER */
bn->child_slot = MyPMChildSlot = AssignPostmasterChildSlot();
}
else
{
bn->bkend_type = B_DEAD_END_BACKEND;
bn->child_slot = 0;
}
/* Hasn't asked to be notified about any bgworkers yet */
bn->bgworker_notify = false;
pid = postmaster_child_launch(B_BACKEND,
pid = postmaster_child_launch(bn->bkend_type,
(char *) &startup_data, sizeof(startup_data),
client_sock);
if (pid < 0)
@ -3422,7 +3467,7 @@ BackendStartup(ClientSocket *client_sock)
/* in parent, fork failed */
int save_errno = errno;
if (!bn->dead_end)
if (bn->child_slot != 0)
(void) ReleasePostmasterChildSlot(bn->child_slot);
pfree(bn);
errno = save_errno;
@ -3434,7 +3479,8 @@ BackendStartup(ClientSocket *client_sock)
/* in parent, successful fork */
ereport(DEBUG2,
(errmsg_internal("forked new backend, pid=%d socket=%d",
(errmsg_internal("forked new %s, pid=%d socket=%d",
GetBackendTypeDesc(bn->bkend_type),
(int) pid, (int) client_sock->sock)));
/*
@ -3442,7 +3488,6 @@ BackendStartup(ClientSocket *client_sock)
* of backends.
*/
bn->pid = pid;
bn->bkend_type = BACKEND_TYPE_NORMAL; /* Can change later to WALSND */
dlist_push_head(&BackendList, &bn->elem);
return STATUS_OK;
@ -3676,11 +3721,11 @@ dummy_handler(SIGNAL_ARGS)
}
/*
* Count up number of child processes of specified types (dead_end children
* are always excluded).
* Count up number of child processes of specified types (but NOT special
* children).
*/
static int
CountChildren(int target)
CountChildren(BackendTypeMask targetMask)
{
dlist_iter iter;
int cnt = 0;
@ -3689,27 +3734,21 @@ CountChildren(int target)
{
Backend *bp = dlist_container(Backend, elem, iter.cur);
if (bp->dead_end)
continue;
/*
* Since target == BACKEND_TYPE_ALL is the most common case, we test
* it first and avoid touching shared memory for every child.
* If we need to distinguish between B_BACKEND and B_WAL_SENDER, check
* if any B_BACKEND backends have recently announced that they are
* actually WAL senders.
*/
if (target != BACKEND_TYPE_ALL)
if (btmask_contains(targetMask, B_WAL_SENDER) != btmask_contains(targetMask, B_BACKEND) &&
bp->bkend_type == B_BACKEND)
{
/*
* Assign bkend_type for any recently announced WAL Sender
* processes.
*/
if (bp->bkend_type == BACKEND_TYPE_NORMAL &&
IsPostmasterChildWalSender(bp->child_slot))
bp->bkend_type = BACKEND_TYPE_WALSND;
if (!(target & bp->bkend_type))
continue;
if (IsPostmasterChildWalSender(bp->child_slot))
bp->bkend_type = B_WAL_SENDER;
}
if (!btmask_contains(targetMask, bp->bkend_type))
continue;
cnt++;
}
return cnt;
@ -3773,13 +3812,13 @@ StartAutovacuumWorker(void)
* we have to check to avoid race-condition problems during DB state
* changes.
*/
if (canAcceptConnections(BACKEND_TYPE_AUTOVAC) == CAC_OK)
if (canAcceptConnections(B_AUTOVAC_WORKER) == CAC_OK)
{
bn = (Backend *) palloc_extended(sizeof(Backend), MCXT_ALLOC_NO_OOM);
if (bn)
{
/* Autovac workers are not dead_end and need a child slot */
bn->dead_end = false;
/* Autovac workers need a child slot */
bn->bkend_type = B_AUTOVAC_WORKER;
bn->child_slot = MyPMChildSlot = AssignPostmasterChildSlot();
bn->bgworker_notify = false;
bn->rw = NULL;
@ -3787,7 +3826,6 @@ StartAutovacuumWorker(void)
bn->pid = StartChildProcess(B_AUTOVAC_WORKER);
if (bn->pid > 0)
{
bn->bkend_type = BACKEND_TYPE_AUTOVAC;
dlist_push_head(&BackendList, &bn->elem);
/* all OK */
return;
@ -3993,7 +4031,7 @@ assign_backendlist_entry(void)
* only possible failure is CAC_TOOMANY, so we just log an error message
* based on that rather than checking the error code precisely.
*/
if (canAcceptConnections(BACKEND_TYPE_BGWORKER) != CAC_OK)
if (canAcceptConnections(B_BG_WORKER) != CAC_OK)
{
ereport(LOG,
(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
@ -4011,8 +4049,7 @@ assign_backendlist_entry(void)
}
bn->child_slot = MyPMChildSlot = AssignPostmasterChildSlot();
bn->bkend_type = BACKEND_TYPE_BGWORKER;
bn->dead_end = false;
bn->bkend_type = B_BG_WORKER;
bn->bgworker_notify = false;
return bn;

3
src/backend/utils/activity/pgstat_io.c
View File

@ -330,6 +330,8 @@ pgstat_io_snapshot_cb(void)
*
* The following BackendTypes do not participate in the cumulative stats
* subsystem or do not perform IO on which we currently track:
* - Dead-end backend because it is not connected to shared memory and
* doesn't do any IO
* - Syslogger because it is not connected to shared memory
* - Archiver because most relevant archiving IO is delegated to a
* specialized command or module
@ -352,6 +354,7 @@ pgstat_tracks_io_bktype(BackendType bktype)
switch (bktype)
{
case B_INVALID:
case B_DEAD_END_BACKEND:
case B_ARCHIVER:
case B_LOGGER:
case B_WAL_RECEIVER:

43
src/backend/utils/init/miscinit.c
View File

@ -260,60 +260,69 @@ SwitchBackToLocalLatch(void)
SetLatch(MyLatch);
}
/*
* Return a human-readable string representation of a BackendType.
*
* The string is not localized here, but we mark the strings for translation
* so that callers can invoke _() on the result.
*/
const char *
GetBackendTypeDesc(BackendType backendType)
{
const char *backendDesc = "unknown process type";
const char *backendDesc = gettext_noop("unknown process type");
switch (backendType)
{
case B_INVALID:
backendDesc = "not initialized";
backendDesc = gettext_noop("not initialized");
break;
case B_ARCHIVER:
backendDesc = "archiver";
backendDesc = gettext_noop("archiver");
break;
case B_AUTOVAC_LAUNCHER:
backendDesc = "autovacuum launcher";
backendDesc = gettext_noop("autovacuum launcher");
break;
case B_AUTOVAC_WORKER:
backendDesc = "autovacuum worker";
backendDesc = gettext_noop("autovacuum worker");
break;
case B_BACKEND:
backendDesc = "client backend";
backendDesc = gettext_noop("client backend");
break;
case B_DEAD_END_BACKEND:
backendDesc = gettext_noop("dead-end client backend");
break;
case B_BG_WORKER:
backendDesc = "background worker";
backendDesc = gettext_noop("background worker");
break;
case B_BG_WRITER:
backendDesc = "background writer";
backendDesc = gettext_noop("background writer");
break;
case B_CHECKPOINTER:
backendDesc = "checkpointer";
backendDesc = gettext_noop("checkpointer");
break;
case B_LOGGER:
backendDesc = "logger";
backendDesc = gettext_noop("logger");
break;
case B_SLOTSYNC_WORKER:
backendDesc = "slotsync worker";
backendDesc = gettext_noop("slotsync worker");
break;
case B_STANDALONE_BACKEND:
backendDesc = "standalone backend";
backendDesc = gettext_noop("standalone backend");
break;
case B_STARTUP:
backendDesc = "startup";
backendDesc = gettext_noop("startup");
break;
case B_WAL_RECEIVER:
backendDesc = "walreceiver";
backendDesc = gettext_noop("walreceiver");
break;
case B_WAL_SENDER:
backendDesc = "walsender";
backendDesc = gettext_noop("walsender");
break;
case B_WAL_SUMMARIZER:
backendDesc = "walsummarizer";
backendDesc = gettext_noop("walsummarizer");
break;
case B_WAL_WRITER:
backendDesc = "walwriter";
backendDesc = gettext_noop("walwriter");
break;
}

1
src/include/miscadmin.h
View File

@ -333,6 +333,7 @@ typedef enum BackendType
/* Backends and other backend-like processes */
B_BACKEND,
B_DEAD_END_BACKEND,
B_AUTOVAC_LAUNCHER,
B_AUTOVAC_WORKER,
B_BG_WORKER,

1
src/tools/pgindent/typedefs.list
View File

@ -235,6 +235,7 @@ BackendParameters
BackendStartupData
BackendState
BackendType
BackendTypeMask
BackgroundWorker
BackgroundWorkerArray
BackgroundWorkerHandle