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Use the regular main processing loop also in walsenders.

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The regular backend's main loop handles signal handling and error recovery
better than the current WAL sender command loop does. For example, if the
client hangs and a SIGTERM is received before starting streaming, the
walsender will now terminate immediately, rather than hang until the
connection times out.
pull/3/head
Heikki Linnakangas 13 years ago
parent 1997f34db4
commit fd5942c18f
4 changed files with 109 additions and 232 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 16
      src/backend/replication/basebackup.c
  2. 269
      src/backend/replication/walsender.c
  3. 51
      src/backend/tcop/postgres.c
  4. 5
      src/include/replication/walsender.h

16
src/backend/replication/basebackup.c
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@ -22,6 +22,7 @@
#include "lib/stringinfo.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
#include "nodes/pg_list.h"
#include "replication/basebackup.h"
#include "replication/walsender.h"
@ -30,7 +31,6 @@
#include "storage/ipc.h"
#include "utils/builtins.h"
#include "utils/elog.h"
#include "utils/memutils.h"
#include "utils/ps_status.h"
typedef struct
@ -370,19 +370,10 @@ void
SendBaseBackup(BaseBackupCmd *cmd)
{
DIR *dir;
MemoryContext backup_context;
MemoryContext old_context;
basebackup_options opt;
parse_basebackup_options(cmd->options, &opt);
backup_context = AllocSetContextCreate(CurrentMemoryContext,
"Streaming base backup context",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
old_context = MemoryContextSwitchTo(backup_context);
WalSndSetState(WALSNDSTATE_BACKUP);
if (update_process_title)
@ -403,9 +394,6 @@ SendBaseBackup(BaseBackupCmd *cmd)
perform_base_backup(&opt, dir);
FreeDir(dir);
MemoryContextSwitchTo(old_context);
MemoryContextDelete(backup_context);
}
static void
@ -606,7 +594,7 @@ sendDir(char *path, int basepathlen, bool sizeonly)
* error in that case. The error handler further up will call
* do_pg_abort_backup() for us.
*/
if (walsender_shutdown_requested || walsender_ready_to_stop)
if (ProcDiePending || walsender_ready_to_stop)
ereport(ERROR,
(errmsg("shutdown requested, aborting active base backup")));

269
src/backend/replication/walsender.c
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@ -78,6 +78,8 @@ bool am_walsender = false; /* Am I a walsender process ? */
bool am_cascading_walsender = false; /* Am I cascading WAL to
* another standby ? */
static bool replication_started = false; /* Started streaming yet? */
/* User-settable parameters for walsender */
int max_wal_senders = 0; /* the maximum number of concurrent walsenders */
int replication_timeout = 60 * 1000; /* maximum time to send one
@ -113,21 +115,16 @@ static TimestampTz last_reply_timestamp;
/* Flags set by signal handlers for later service in main loop */
static volatile sig_atomic_t got_SIGHUP = false;
volatile sig_atomic_t walsender_shutdown_requested = false;
volatile sig_atomic_t walsender_ready_to_stop = false;
/* Signal handlers */
static void WalSndSigHupHandler(SIGNAL_ARGS);
static void WalSndShutdownHandler(SIGNAL_ARGS);
static void WalSndQuickDieHandler(SIGNAL_ARGS);
static void WalSndXLogSendHandler(SIGNAL_ARGS);
static void WalSndLastCycleHandler(SIGNAL_ARGS);
/* Prototypes for private functions */
static bool HandleReplicationCommand(const char *cmd_string);
static void WalSndLoop(void) __attribute__((noreturn));
static void InitWalSnd(void);
static void WalSndHandshake(void);
static void InitWalSenderSlot(void);
static void WalSndKill(int code, Datum arg);
static void XLogSend(char *msgbuf, bool *caughtup);
static void IdentifySystem(void);
@ -139,147 +136,48 @@ static void ProcessRepliesIfAny(void);
static void WalSndKeepalive(char *msgbuf);
/* Main entry point for walsender process */
/* Initialize walsender process before entering the main command loop */
void
WalSenderMain(void)
InitWalSender(void)
{
MemoryContext walsnd_context;
am_cascading_walsender = RecoveryInProgress();
/* Create a per-walsender data structure in shared memory */
InitWalSnd();
/*
* Create a memory context that we will do all our work in. We do this so
* that we can reset the context during error recovery and thereby avoid
* possible memory leaks. Formerly this code just ran in
* TopMemoryContext, but resetting that would be a really bad idea.
*
* XXX: we don't actually attempt error recovery in walsender, we just
* close the connection and exit.
*/
walsnd_context = AllocSetContextCreate(TopMemoryContext,
"Wal Sender",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
MemoryContextSwitchTo(walsnd_context);
InitWalSenderSlot();
/* Set up resource owner */
CurrentResourceOwner = ResourceOwnerCreate(NULL, "walsender top-level resource owner");
/* Unblock signals (they were blocked when the postmaster forked us) */
PG_SETMASK(&UnBlockSig);
/*
* Use the recovery target timeline ID during recovery
*/
if (am_cascading_walsender)
ThisTimeLineID = GetRecoveryTargetTLI();
/* Tell the standby that walsender is ready for receiving commands */
ReadyForQuery(DestRemote);
/* Handle handshake messages before streaming */
WalSndHandshake();
/* Initialize shared memory status */
{
/* use volatile pointer to prevent code rearrangement */
volatile WalSnd *walsnd = MyWalSnd;
SpinLockAcquire(&walsnd->mutex);
walsnd->sentPtr = sentPtr;
SpinLockRelease(&walsnd->mutex);
}
SyncRepInitConfig();
/* Main loop of walsender */
WalSndLoop();
}
/*
* Execute commands from walreceiver, until we enter streaming mode.
* Clean up after an error.
*
* WAL sender processes don't use transactions like regular backends do.
* This function does any cleanup requited after an error in a WAL sender
* process, similar to what transaction abort does in a regular backend.
*/
static void
WalSndHandshake(void)
void
WalSndErrorCleanup()
{
StringInfoData input_message;
bool replication_started = false;
initStringInfo(&input_message);
while (!replication_started)
if (sendFile >= 0)
{
int firstchar;
WalSndSetState(WALSNDSTATE_STARTUP);
set_ps_display("idle", false);
/* Wait for a command to arrive */
firstchar = pq_getbyte();
/*
* Emergency bailout if postmaster has died. This is to avoid the
* necessity for manual cleanup of all postmaster children.
*/
if (!PostmasterIsAlive())
exit(1);
/*
* Check for any other interesting events that happened while we
* slept.
*/
if (got_SIGHUP)
{
got_SIGHUP = false;
ProcessConfigFile(PGC_SIGHUP);
}
if (firstchar != EOF)
{
/*
* Read the message contents. This is expected to be done without
* blocking because we've been able to get message type code.
*/
if (pq_getmessage(&input_message, 0))
firstchar = EOF; /* suitable message already logged */
}
/* Handle the very limited subset of commands expected in this phase */
switch (firstchar)
{
case 'Q': /* Query message */
{
const char *query_string;
query_string = pq_getmsgstring(&input_message);
pq_getmsgend(&input_message);
if (HandleReplicationCommand(query_string))
replication_started = true;
}
break;
case 'X':
/* standby is closing the connection */
proc_exit(0);
case EOF:
/* standby disconnected unexpectedly */
ereport(COMMERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg("unexpected EOF on standby connection")));
proc_exit(0);
default:
ereport(FATAL,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg("invalid standby handshake message type %d", firstchar)));
}
close(sendFile);
sendFile = -1;
}
/*
* Don't return back to the command loop after we've started replicating.
* We've already marked us as an actively streaming WAL sender in the
* PMSignal slot, and there's currently no way to undo that.
*/
if (replication_started)
proc_exit(0);
}
/*
@ -350,15 +248,13 @@ IdentifySystem(void)
pq_sendbytes(&buf, (char *) xpos, strlen(xpos));
pq_endmessage(&buf);
/* Send CommandComplete and ReadyForQuery messages */
EndCommand("SELECT", DestRemote);
ReadyForQuery(DestRemote);
/* ReadyForQuery did pq_flush for us */
}
/*
* START_REPLICATION
* Handle START_REPLICATION command.
*
* At the moment, this never returns, but an ereport(ERROR) will take us back
* to the main loop.
*/
static void
StartReplication(StartReplicationCmd *cmd)
@ -374,6 +270,7 @@ StartReplication(StartReplicationCmd *cmd)
*/
MarkPostmasterChildWalSender();
SendPostmasterSignal(PMSIGNAL_ADVANCE_STATE_MACHINE);
replication_started = true;
/*
* When promoting a cascading standby, postmaster sends SIGUSR2 to any
@ -435,15 +332,29 @@ StartReplication(StartReplicationCmd *cmd)
* be shipped from that position
*/
sentPtr = cmd->startpoint;
/* Also update the start position status in shared memory */
{
/* use volatile pointer to prevent code rearrangement */
volatile WalSnd *walsnd = MyWalSnd;
SpinLockAcquire(&walsnd->mutex);
walsnd->sentPtr = sentPtr;
SpinLockRelease(&walsnd->mutex);
}
SyncRepInitConfig();
/* Main loop of walsender */
WalSndLoop();
}
/*
* Execute an incoming replication command.
*/
static bool
HandleReplicationCommand(const char *cmd_string)
void
exec_replication_command(const char *cmd_string)
{
bool replication_started = false;
int parse_rc;
Node *cmd_node;
MemoryContext cmd_context;
@ -451,6 +362,8 @@ HandleReplicationCommand(const char *cmd_string)
elog(DEBUG1, "received replication command: %s", cmd_string);
CHECK_FOR_INTERRUPTS();
cmd_context = AllocSetContextCreate(CurrentMemoryContext,
"Replication command context",
ALLOCSET_DEFAULT_MINSIZE,
@ -476,18 +389,10 @@ HandleReplicationCommand(const char *cmd_string)
case T_StartReplicationCmd:
StartReplication((StartReplicationCmd *) cmd_node);
/* break out of the loop */
replication_started = true;
break;
case T_BaseBackupCmd:
SendBaseBackup((BaseBackupCmd *) cmd_node);
/* Send CommandComplete and ReadyForQuery messages */
EndCommand("SELECT", DestRemote);
ReadyForQuery(DestRemote);
/* ReadyForQuery did pq_flush for us */
break;
default:
@ -500,7 +405,8 @@ HandleReplicationCommand(const char *cmd_string)
MemoryContextSwitchTo(old_context);
MemoryContextDelete(cmd_context);
return replication_started;
/* Send CommandComplete message */
EndCommand("SELECT", DestRemote);
}
/*
@ -710,7 +616,7 @@ ProcessStandbyHSFeedbackMessage(void)
MyPgXact->xmin = reply.xmin;
}
/* Main loop of walsender process */
/* Main loop of walsender process that streams the WAL over Copy messages. */
static void
WalSndLoop(void)
{
@ -754,15 +660,7 @@ WalSndLoop(void)
SyncRepInitConfig();
}
/* Normal exit from the walsender is here */
if (walsender_shutdown_requested)
{
/* Inform the standby that XLOG streaming is done */
pq_puttextmessage('C', "COPY 0");
pq_flush();
proc_exit(0);
}
CHECK_FOR_INTERRUPTS();
/* Check for input from the client */
ProcessRepliesIfAny();
@ -813,7 +711,7 @@ WalSndLoop(void)
XLogSend(output_message, &caughtup);
if (caughtup && !pq_is_send_pending())
{
walsender_shutdown_requested = true;
ProcDiePending = true;
continue; /* don't want to wait more */
}
}
@ -854,8 +752,11 @@ WalSndLoop(void)
}
/* Sleep until something happens or replication timeout */
ImmediateInterruptOK = true;
CHECK_FOR_INTERRUPTS();
WaitLatchOrSocket(&MyWalSnd->latch, wakeEvents,
MyProcPort->sock, sleeptime);
ImmediateInterruptOK = false;
/*
* Check for replication timeout. Note we ignore the corner case
@ -892,7 +793,7 @@ WalSndLoop(void)
/* Initialize a per-walsender data structure for this walsender process */
static void
InitWalSnd(void)
InitWalSenderSlot(void)
{
int i;
@ -1284,58 +1185,6 @@ WalSndSigHupHandler(SIGNAL_ARGS)
errno = save_errno;
}
/* SIGTERM: set flag to shut down */
static void
WalSndShutdownHandler(SIGNAL_ARGS)
{
int save_errno = errno;
walsender_shutdown_requested = true;
if (MyWalSnd)
SetLatch(&MyWalSnd->latch);
/*
* Set the standard (non-walsender) state as well, so that we can abort
* things like do_pg_stop_backup().
*/
InterruptPending = true;
ProcDiePending = true;
errno = save_errno;
}
/*
* WalSndQuickDieHandler() occurs when signalled SIGQUIT by the postmaster.
*
* Some backend has bought the farm,
* so we need to stop what we're doing and exit.
*/
static void
WalSndQuickDieHandler(SIGNAL_ARGS)
{
PG_SETMASK(&BlockSig);
/*
* We DO NOT want to run proc_exit() callbacks -- we're here because
* shared memory may be corrupted, so we don't want to try to clean up our
* transaction. Just nail the windows shut and get out of town. Now that
* there's an atexit callback to prevent third-party code from breaking
* things by calling exit() directly, we have to reset the callbacks
* explicitly to make this work as intended.
*/
on_exit_reset();
/*
* Note we do exit(2) not exit(0). This is to force the postmaster into a
* system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
* backend. This is necessary precisely because we don't clean up our
* shared memory state. (The "dead man switch" mechanism in pmsignal.c
* should ensure the postmaster sees this as a crash, too, but no harm in
* being doubly sure.)
*/
exit(2);
}
/* SIGUSR1: set flag to send WAL records */
static void
WalSndXLogSendHandler(SIGNAL_ARGS)
@ -1368,8 +1217,8 @@ WalSndSignals(void)
pqsignal(SIGHUP, WalSndSigHupHandler); /* set flag to read config
* file */
pqsignal(SIGINT, SIG_IGN); /* not used */
pqsignal(SIGTERM, WalSndShutdownHandler); /* request shutdown */
pqsignal(SIGQUIT, WalSndQuickDieHandler); /* hard crash time */
pqsignal(SIGTERM, die); /* request shutdown */
pqsignal(SIGQUIT, quickdie); /* hard crash time */
InitializeTimeouts(); /* establishes SIGALRM handler */
pqsignal(SIGPIPE, SIG_IGN);
pqsignal(SIGUSR1, WalSndXLogSendHandler); /* request WAL sending */

51
src/backend/tcop/postgres.c
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@ -192,6 +192,7 @@ static int InteractiveBackend(StringInfo inBuf);
static int interactive_getc(void);
static int SocketBackend(StringInfo inBuf);
static int ReadCommand(StringInfo inBuf);
static void forbidden_in_wal_sender(char firstchar);
static List *pg_rewrite_query(Query *query);
static bool check_log_statement(List *stmt_list);
static int errdetail_execute(List *raw_parsetree_list);
@ -3720,12 +3721,9 @@ PostgresMain(int argc, char *argv[], const char *username)
if (IsUnderPostmaster && Log_disconnections)
on_proc_exit(log_disconnections, 0);
/* If this is a WAL sender process, we're done with initialization. */
/* Perform initialization specific to a WAL sender process. */
if (am_walsender)
{
WalSenderMain(); /* does not return */
abort();
}
InitWalSender();
/*
* process any libraries that should be preloaded at backend start (this
@ -3835,6 +3833,9 @@ PostgresMain(int argc, char *argv[], const char *username)
*/
AbortCurrentTransaction();
if (am_walsender)
WalSndErrorCleanup();
/*
* Now return to normal top-level context and clear ErrorContext for
* next time.
@ -3969,7 +3970,10 @@ PostgresMain(int argc, char *argv[], const char *username)
query_string = pq_getmsgstring(&input_message);
pq_getmsgend(&input_message);
exec_simple_query(query_string);
if (am_walsender)
exec_replication_command(query_string);
else
exec_simple_query(query_string);
send_ready_for_query = true;
}
@ -3982,6 +3986,8 @@ PostgresMain(int argc, char *argv[], const char *username)
int numParams;
Oid *paramTypes = NULL;
forbidden_in_wal_sender(firstchar);
/* Set statement_timestamp() */
SetCurrentStatementStartTimestamp();
@ -4004,6 +4010,8 @@ PostgresMain(int argc, char *argv[], const char *username)
break;
case 'B': /* bind */
forbidden_in_wal_sender(firstchar);
/* Set statement_timestamp() */
SetCurrentStatementStartTimestamp();
@ -4019,6 +4027,8 @@ PostgresMain(int argc, char *argv[], const char *username)
const char *portal_name;
int max_rows;
forbidden_in_wal_sender(firstchar);
/* Set statement_timestamp() */
SetCurrentStatementStartTimestamp();
@ -4031,6 +4041,8 @@ PostgresMain(int argc, char *argv[], const char *username)
break;
case 'F': /* fastpath function call */
forbidden_in_wal_sender(firstchar);
/* Set statement_timestamp() */
SetCurrentStatementStartTimestamp();
@ -4078,6 +4090,8 @@ PostgresMain(int argc, char *argv[], const char *username)
int close_type;
const char *close_target;
forbidden_in_wal_sender(firstchar);
close_type = pq_getmsgbyte(&input_message);
close_target = pq_getmsgstring(&input_message);
pq_getmsgend(&input_message);
@ -4120,6 +4134,8 @@ PostgresMain(int argc, char *argv[], const char *username)
int describe_type;
const char *describe_target;
forbidden_in_wal_sender(firstchar);
/* Set statement_timestamp() (needed for xact) */
SetCurrentStatementStartTimestamp();
@ -4201,6 +4217,29 @@ PostgresMain(int argc, char *argv[], const char *username)
} /* end of input-reading loop */
}
/*
* Throw an error if we're a WAL sender process.
*
* This is used to forbid anything else than simple query protocol messages
* in a WAL sender process. 'firstchar' specifies what kind of a forbidden
* message was received, and is used to construct the error message.
*/
static void
forbidden_in_wal_sender(char firstchar)
{
if (am_walsender)
{
if (firstchar == 'F')
ereport(ERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg("fastpath function calls not supported in a replication connection")));
else
ereport(ERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg("extended query protocol not supported in a replication connection")));
}
}
/*
* Obtain platform stack depth limit (in bytes)

5
src/include/replication/walsender.h
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@ -19,7 +19,6 @@
/* global state */
extern bool am_walsender;
extern bool am_cascading_walsender;
extern volatile sig_atomic_t walsender_shutdown_requested;
extern volatile sig_atomic_t walsender_ready_to_stop;
extern bool wake_wal_senders;
@ -27,7 +26,9 @@ extern bool wake_wal_senders;
extern int max_wal_senders;
extern int replication_timeout;
extern void WalSenderMain(void) __attribute__((noreturn));
extern void InitWalSender(void);
extern void exec_replication_command(const char *query_string);
extern void WalSndErrorCleanup(void);
extern void WalSndSignals(void);
extern Size WalSndShmemSize(void);
extern void WalSndShmemInit(void);

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