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Improve replication connection timeouts.

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Rename replication_timeout to wal_sender_timeout, and add a new setting
called wal_receiver_timeout that does the same at the walreceiver side.
There was previously no timeout in walreceiver, so if the network went down,
for example, the walreceiver could take a long time to notice that the
connection was lost. Now with the two settings, both sides of a replication
connection will detect a broken connection similarly.

It is no longer necessary to manually set wal_receiver_status_interval to
a value smaller than the timeout. Both wal sender and receiver now
automatically send a "ping" message if more than 1/2 of the configured
timeout has elapsed, and it hasn't received any messages from the other end.

Amit Kapila, heavily edited by me.
This commit is contained in:
Heikki Linnakangas 2012-10-11 17:39:52 +03:00
parent 8521d13194
commit 6f60fdd701
10 changed files with 191 additions and 68 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
doc/src/sgml/config.sgml
View File

@ -2236,10 +2236,10 @@ include 'filename'
</listitem>
</varlistentry>
<varlistentry id="guc-replication-timeout" xreflabel="replication_timeout">
<term><varname>replication_timeout</varname> (<type>integer</type>)</term>
<varlistentry id="guc-wal-sender-timeout" xreflabel="wal_sender_timeout">
<term><varname>wal_sender_timeout</varname> (<type>integer</type>)</term>
<indexterm>
<primary><varname>replication_timeout</> configuration parameter</primary>
<primary><varname>wal_sender_timeout</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
@ -2251,12 +2251,6 @@ include 'filename'
the <filename>postgresql.conf</> file or on the server command line.
The default value is 60 seconds.
</para>
<para>
To prevent connections from being terminated prematurely,
<xref linkend="guc-wal-receiver-status-interval">
must be enabled on the standby, and its value must be less than the
value of <varname>replication_timeout</>.
</para>
</listitem>
</varlistentry>
@ -2474,11 +2468,6 @@ include 'filename'
the <filename>postgresql.conf</> file or on the server command line.
The default value is 10 seconds.
</para>
<para>
When <xref linkend="guc-replication-timeout"> is enabled on a sending server,
<varname>wal_receiver_status_interval</> must be enabled, and its value
must be less than the value of <varname>replication_timeout</>.
</para>
</listitem>
</varlistentry>
@ -2507,6 +2496,25 @@ include 'filename'
</listitem>
</varlistentry>
<varlistentry id="guc-wal-receiver-timeout" xreflabel="wal_receiver_timeout">
<term><varname>wal_receiver_timeout</varname> (<type>integer</type>)</term>
<indexterm>
<primary><varname>wal_receiver_timeout</> configuration parameter</primary>
</indexterm>
<listitem>
<para>
Terminate replication connections that are inactive longer
than the specified number of milliseconds. This is useful for
the receiving standby server to detect a primary node crash or network
outage.
A value of zero disables the timeout mechanism. This parameter
can only be set in
the <filename>postgresql.conf</> file or on the server command line.
The default value is 60 seconds.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
</sect1>

2
doc/src/sgml/release-9.1.sgml
View File

@ -3322,7 +3322,7 @@
<listitem>
<para>
Add
<link linkend="guc-replication-timeout"><varname>replication_timeout</></link>
<varname>replication_timeout</>
setting (Fujii Masao, Heikki Linnakangas)
</para>

94
src/backend/replication/walreceiver.c
View File

@ -55,6 +55,7 @@
/* GUC variables */
int wal_receiver_status_interval;
int wal_receiver_timeout;
bool hot_standby_feedback;
/* libpqreceiver hooks to these when loaded */
@ -121,7 +122,7 @@ static void WalRcvDie(int code, Datum arg);
static void XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len);
static void XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr);
static void XLogWalRcvFlush(bool dying);
static void XLogWalRcvSendReply(void);
static void XLogWalRcvSendReply(bool force, bool requestReply);
static void XLogWalRcvSendHSFeedback(void);
static void ProcessWalSndrMessage(XLogRecPtr walEnd, TimestampTz sendTime);
@ -170,9 +171,10 @@ WalReceiverMain(void)
{
char conninfo[MAXCONNINFO];
XLogRecPtr startpoint;
/* use volatile pointer to prevent code rearrangement */
volatile WalRcvData *walrcv = WalRcv;
TimestampTz last_recv_timestamp;
bool ping_sent;
/*
* WalRcv should be set up already (if we are a backend, we inherit this
@ -282,6 +284,10 @@ WalReceiverMain(void)
MemSet(&reply_message, 0, sizeof(reply_message));
MemSet(&feedback_message, 0, sizeof(feedback_message));
/* Initialize the last recv timestamp */
last_recv_timestamp = GetCurrentTimestamp();
ping_sent = false;
/* Loop until end-of-streaming or error */
for (;;)
{
@ -316,15 +322,23 @@ WalReceiverMain(void)
/* Wait a while for data to arrive */
if (walrcv_receive(NAPTIME_PER_CYCLE, &type, &buf, &len))
{
/* Something was received from master, so reset timeout */
last_recv_timestamp = GetCurrentTimestamp();
ping_sent = false;
/* Accept the received data, and process it */
XLogWalRcvProcessMsg(type, buf, len);
/* Receive any more data we can without sleeping */
while (walrcv_receive(0, &type, &buf, &len))
{
last_recv_timestamp = GetCurrentTimestamp();
ping_sent = false;
XLogWalRcvProcessMsg(type, buf, len);
}
/* Let the master know that we received some data. */
XLogWalRcvSendReply();
XLogWalRcvSendReply(false, false);
/*
* If we've written some records, flush them to disk and let the
@ -335,10 +349,48 @@ WalReceiverMain(void)
else
{
/*
* We didn't receive anything new, but send a status update to the
* master anyway, to report any progress in applying WAL.
* We didn't receive anything new. If we haven't heard anything
* from the server for more than wal_receiver_timeout / 2,
* ping the server. Also, if it's been longer than
* wal_receiver_status_interval since the last update we sent,
* send a status update to the master anyway, to report any
* progress in applying WAL.
*/
XLogWalRcvSendReply();
bool requestReply = false;
/*
* Check if time since last receive from standby has reached the
* configured limit.
*/
if (wal_receiver_timeout > 0)
{
TimestampTz now = GetCurrentTimestamp();
TimestampTz timeout;
timeout = TimestampTzPlusMilliseconds(last_recv_timestamp,
wal_receiver_timeout);
if (now >= timeout)
ereport(ERROR,
(errmsg("terminating walreceiver due to timeout")));
/*
* We didn't receive anything new, for half of receiver
* replication timeout. Ping the server.
*/
if (!ping_sent)
{
timeout = TimestampTzPlusMilliseconds(last_recv_timestamp,
(wal_receiver_timeout/2));
if (now >= timeout)
{
requestReply = true;
ping_sent = true;
}
}
}
XLogWalRcvSendReply(requestReply, requestReply);
XLogWalRcvSendHSFeedback();
}
}
@ -460,6 +512,10 @@ XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len)
memcpy(&keepalive, buf, sizeof(PrimaryKeepaliveMessage));
ProcessWalSndrMessage(keepalive.walEnd, keepalive.sendTime);
/* If the primary requested a reply, send one immediately */
if (keepalive.replyRequested)
XLogWalRcvSendReply(true, false);
break;
}
default:
@ -609,19 +665,25 @@ XLogWalRcvFlush(bool dying)
/* Also let the master know that we made some progress */
if (!dying)
{
XLogWalRcvSendReply();
XLogWalRcvSendHSFeedback();
}
XLogWalRcvSendReply(false, false);
}
}
/*
* Send reply message to primary, indicating our current XLOG positions and
* the current time.
* Send reply message to primary, indicating our current XLOG positions, oldest
* xmin and the current time.
*
* If 'force' is not set, the message is only sent if enough time has
* passed since last status update to reach wal_receiver_status_internal.
* If wal_receiver_status_interval is disabled altogether and 'force' is
* false, this is a no-op.
*
* If 'requestReply' is true, requests the server to reply immediately upon
* receiving this message. This is used for heartbearts, when approaching
* wal_receiver_timeout.
*/
static void
XLogWalRcvSendReply(void)
XLogWalRcvSendReply(bool force, bool requestReply)
{
char buf[sizeof(StandbyReplyMessage) + 1];
TimestampTz now;
@ -630,7 +692,7 @@ XLogWalRcvSendReply(void)
* If the user doesn't want status to be reported to the master, be sure
* to exit before doing anything at all.
*/
if (wal_receiver_status_interval <= 0)
if (!force && wal_receiver_status_interval <= 0)
return;
/* Get current timestamp. */
@ -645,7 +707,8 @@ XLogWalRcvSendReply(void)
* this is only for reporting purposes and only on idle systems, that's
* probably OK.
*/
if (XLByteEQ(reply_message.write, LogstreamResult.Write)
if (!force
&& XLByteEQ(reply_message.write, LogstreamResult.Write)
&& XLByteEQ(reply_message.flush, LogstreamResult.Flush)
&& !TimestampDifferenceExceeds(reply_message.sendTime, now,
wal_receiver_status_interval * 1000))
@ -656,6 +719,7 @@ XLogWalRcvSendReply(void)
reply_message.flush = LogstreamResult.Flush;
reply_message.apply = GetXLogReplayRecPtr(NULL);
reply_message.sendTime = now;
reply_message.replyRequested = requestReply;
elog(DEBUG2, "sending write %X/%X flush %X/%X apply %X/%X",
(uint32) (reply_message.write >> 32), (uint32) reply_message.write,

90
src/backend/replication/walsender.c
View File

@ -82,7 +82,7 @@ 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
int wal_sender_timeout = 60 * 1000; /* maximum time to send one
* WAL data message */
/*
* State for WalSndWakeupRequest
@ -103,15 +103,20 @@ static uint32 sendOff = 0;
*/
static XLogRecPtr sentPtr = 0;
/*
* Buffer for processing reply messages.
*/
/* Buffer for processing reply messages. */
static StringInfoData reply_message;
/*
* Buffer for constructing outgoing messages.
* (1 + sizeof(WalDataMessageHeader) + MAX_SEND_SIZE bytes)
*/
static char *output_message;
/*
* Timestamp of the last receipt of the reply from the standby.
*/
static TimestampTz last_reply_timestamp;
/* Have we sent a heartbeat message asking for reply, since last reply? */
static bool ping_sent = false;
/* Flags set by signal handlers for later service in main loop */
static volatile sig_atomic_t got_SIGHUP = false;
@ -126,14 +131,14 @@ static void WalSndLastCycleHandler(SIGNAL_ARGS);
static void WalSndLoop(void) __attribute__((noreturn));
static void InitWalSenderSlot(void);
static void WalSndKill(int code, Datum arg);
static void XLogSend(char *msgbuf, bool *caughtup);
static void XLogSend(bool *caughtup);
static void IdentifySystem(void);
static void StartReplication(StartReplicationCmd *cmd);
static void ProcessStandbyMessage(void);
static void ProcessStandbyReplyMessage(void);
static void ProcessStandbyHSFeedbackMessage(void);
static void ProcessRepliesIfAny(void);
static void WalSndKeepalive(char *msgbuf);
static void WalSndKeepalive(bool requestReply);
/* Initialize walsender process before entering the main command loop */
@ -465,7 +470,10 @@ ProcessRepliesIfAny(void)
* Save the last reply timestamp if we've received at least one reply.
*/
if (received)
{
last_reply_timestamp = GetCurrentTimestamp();
ping_sent = false;
}
}
/*
@ -527,6 +535,10 @@ ProcessStandbyReplyMessage(void)
(uint32) (reply.flush >> 32), (uint32) reply.flush,
(uint32) (reply.apply >> 32), (uint32) reply.apply);
/* Send a reply if the standby requested one. */
if (reply.replyRequested)
WalSndKeepalive(false);
/*
* Update shared state for this WalSender process based on reply data from
* standby.
@ -620,7 +632,6 @@ ProcessStandbyHSFeedbackMessage(void)
static void
WalSndLoop(void)
{
char *output_message;
bool caughtup = false;
/*
@ -638,6 +649,7 @@ WalSndLoop(void)
/* Initialize the last reply timestamp */
last_reply_timestamp = GetCurrentTimestamp();
ping_sent = false;
/* Loop forever, unless we get an error */
for (;;)
@ -672,7 +684,7 @@ WalSndLoop(void)
* caught up.
*/
if (!pq_is_send_pending())
XLogSend(output_message, &caughtup);
XLogSend(&caughtup);
else
caughtup = false;
@ -708,7 +720,7 @@ WalSndLoop(void)
if (walsender_ready_to_stop)
{
/* ... let's just be real sure we're caught up ... */
XLogSend(output_message, &caughtup);
XLogSend(&caughtup);
if (caughtup && !pq_is_send_pending())
{
/* Inform the standby that XLOG streaming is done */
@ -738,23 +750,34 @@ WalSndLoop(void)
if (pq_is_send_pending())
wakeEvents |= WL_SOCKET_WRITEABLE;
else if (MyWalSnd->sendKeepalive)
else if (wal_sender_timeout > 0 && !ping_sent)
{
WalSndKeepalive(output_message);
/* Try to flush pending output to the client */
if (pq_flush_if_writable() != 0)
break;
/*
* If half of wal_sender_timeout has lapsed without receiving
* any reply from standby, send a keep-alive message to standby
* requesting an immediate reply.
*/
timeout = TimestampTzPlusMilliseconds(last_reply_timestamp,
wal_sender_timeout / 2);
if (GetCurrentTimestamp() >= timeout)
{
WalSndKeepalive(true);
ping_sent = true;
/* Try to flush pending output to the client */
if (pq_flush_if_writable() != 0)
break;
}
}
/* Determine time until replication timeout */
if (replication_timeout > 0)
if (wal_sender_timeout > 0)
{
timeout = TimestampTzPlusMilliseconds(last_reply_timestamp,
replication_timeout);
sleeptime = 1 + (replication_timeout / 10);
wal_sender_timeout);
sleeptime = 1 + (wal_sender_timeout / 10);
}
/* Sleep until something happens or replication timeout */
/* Sleep until something happens or we time out */
ImmediateInterruptOK = true;
CHECK_FOR_INTERRUPTS();
WaitLatchOrSocket(&MyWalSnd->latch, wakeEvents,
@ -766,8 +789,7 @@ WalSndLoop(void)
* possibility that the client replied just as we reached the
* timeout ... he's supposed to reply *before* that.
*/
if (replication_timeout > 0 &&
GetCurrentTimestamp() >= timeout)
if (wal_sender_timeout > 0 && GetCurrentTimestamp() >= timeout)
{
/*
* Since typically expiration of replication timeout means
@ -1016,15 +1038,11 @@ retry:
* but not yet sent to the client, and buffer it in the libpq output
* buffer.
*
* msgbuf is a work area in which the output message is constructed. It's
* passed in just so we can avoid re-palloc'ing the buffer on each cycle.
* It must be of size 1 + sizeof(WalDataMessageHeader) + MAX_SEND_SIZE.
*
* If there is no unsent WAL remaining, *caughtup is set to true, otherwise
* *caughtup is set to false.
*/
static void
XLogSend(char *msgbuf, bool *caughtup)
XLogSend(bool *caughtup)
{
XLogRecPtr SendRqstPtr;
XLogRecPtr startptr;
@ -1107,13 +1125,13 @@ XLogSend(char *msgbuf, bool *caughtup)
/*
* OK to read and send the slice.
*/
msgbuf[0] = 'w';
output_message[0] = 'w';
/*
* Read the log directly into the output buffer to avoid extra memcpy
* calls.
*/
XLogRead(msgbuf + 1 + sizeof(WalDataMessageHeader), startptr, nbytes);
XLogRead(output_message + 1 + sizeof(WalDataMessageHeader), startptr, nbytes);
/*
* We fill the message header last so that the send timestamp is taken as
@ -1123,9 +1141,9 @@ XLogSend(char *msgbuf, bool *caughtup)
msghdr.walEnd = SendRqstPtr;
msghdr.sendTime = GetCurrentTimestamp();
memcpy(msgbuf + 1, &msghdr, sizeof(WalDataMessageHeader));
memcpy(output_message + 1, &msghdr, sizeof(WalDataMessageHeader));
pq_putmessage_noblock('d', msgbuf, 1 + sizeof(WalDataMessageHeader) + nbytes);
pq_putmessage_noblock('d', output_message, 1 + sizeof(WalDataMessageHeader) + nbytes);
sentPtr = endptr;
@ -1492,21 +1510,27 @@ pg_stat_get_wal_senders(PG_FUNCTION_ARGS)
return (Datum) 0;
}
/*
* This function is used to send keepalive message to standby.
* If requestReply is set, sets a flag in the message requesting the standby
* to send a message back to us, for heartbeat purposes.
*/
static void
WalSndKeepalive(char *msgbuf)
WalSndKeepalive(bool requestReply)
{
PrimaryKeepaliveMessage keepalive_message;
/* Construct a new message */
keepalive_message.walEnd = sentPtr;
keepalive_message.sendTime = GetCurrentTimestamp();
keepalive_message.replyRequested = requestReply;
elog(DEBUG2, "sending replication keepalive");
/* Prepend with the message type and send it. */
msgbuf[0] = 'k';
memcpy(msgbuf + 1, &keepalive_message, sizeof(PrimaryKeepaliveMessage));
pq_putmessage_noblock('d', msgbuf, sizeof(PrimaryKeepaliveMessage) + 1);
output_message[0] = 'k';
memcpy(output_message + 1, &keepalive_message, sizeof(PrimaryKeepaliveMessage));
pq_putmessage_noblock('d', output_message, sizeof(PrimaryKeepaliveMessage) + 1);
}
/*

15
src/backend/utils/misc/guc.c
View File

@ -1595,6 +1595,17 @@ static struct config_int ConfigureNamesInt[] =
NULL, NULL, NULL
},
{
{"wal_receiver_timeout", PGC_SIGHUP, REPLICATION_STANDBY,
gettext_noop("Sets the maximum wait time to receive data from master."),
NULL,
GUC_UNIT_MS
},
&wal_receiver_timeout,
60 * 1000, 0, INT_MAX,
NULL, NULL, NULL
},
{
{"max_connections", PGC_POSTMASTER, CONN_AUTH_SETTINGS,
gettext_noop("Sets the maximum number of concurrent connections."),
@ -2019,12 +2030,12 @@ static struct config_int ConfigureNamesInt[] =
},
{
{"replication_timeout", PGC_SIGHUP, REPLICATION_SENDING,
{"wal_sender_timeout", PGC_SIGHUP, REPLICATION_SENDING,
gettext_noop("Sets the maximum time to wait for WAL replication."),
NULL,
GUC_UNIT_MS
},
&replication_timeout,
&wal_sender_timeout,
60 * 1000, 0, INT_MAX,
NULL, NULL, NULL
},

5
src/backend/utils/misc/postgresql.conf.sample
View File

@ -210,7 +210,7 @@
#max_wal_senders = 0 # max number of walsender processes
# (change requires restart)
#wal_keep_segments = 0 # in logfile segments, 16MB each; 0 disables
#replication_timeout = 60s # in milliseconds; 0 disables
#wal_sender_timeout = 60s # in milliseconds; 0 disables
# - Master Server -
@ -237,6 +237,9 @@
# 0 disables
#hot_standby_feedback = off # send info from standby to prevent
# query conflicts
#wal_receiver_timeout = 60s # time that receiver waits for
# communication from master
# in milliseconds; 0 disables
#------------------------------------------------------------------------------

12
src/include/replication/walprotocol.h
View File

@ -27,6 +27,12 @@ typedef struct
/* Sender's system clock at the time of transmission */
TimestampTz sendTime;
/*
* If replyRequested is set, the client should reply immediately to this
* message, to avoid a timeout disconnect.
*/
bool replyRequested;
} WalSndrMessage;
@ -80,6 +86,12 @@ typedef struct
/* Sender's system clock at the time of transmission */
TimestampTz sendTime;
/*
* If replyRequested is set, the server should reply immediately to this
* message, to avoid a timeout disconnect.
*/
bool replyRequested;
} StandbyReplyMessage;
/*

2
src/include/replication/walreceiver.h
View File

@ -17,7 +17,9 @@
#include "storage/spin.h"
#include "pgtime.h"
/* user-settable parameters */
extern int wal_receiver_status_interval;
extern int wal_receiver_timeout;
extern bool hot_standby_feedback;
/*

2
src/include/replication/walsender.h
View File

@ -24,7 +24,7 @@ extern bool wake_wal_senders;
/* user-settable parameters */
extern int max_wal_senders;
extern int replication_timeout;
extern int wal_sender_timeout;
extern void InitWalSender(void);
extern void exec_replication_command(const char *query_string);

1
src/include/replication/walsender_private.h
View File

@ -37,7 +37,6 @@ typedef struct WalSnd
XLogRecPtr sentPtr; /* WAL has been sent up to this point */
bool needreload; /* does currently-open file need to be
* reloaded? */
bool sendKeepalive; /* do we send keepalives on this connection? */
/*
* The xlog locations that have been written, flushed, and applied by