database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-09-03 15:22:11 +03:00
Code Activity

Make pg_receivexlog and pg_basebackup -X stream work across timeline switches.

Browse Source 
This mirrors the changes done earlier to the server in standby mode. When
receivelog reaches the end of a timeline, as reported by the server, it
fetches the timeline history file of the next timeline, and restarts
streaming from the new timeline by issuing a new START_STREAMING command.

When pg_receivexlog crosses a timeline, it leaves the .partial suffix on the
last segment on the old timeline. This helps you to tell apart a partial
segment left in the directory because of a timeline switch, and a completed
segment. If you just follow a single server, it won't make a difference, but
it can be significant in more complicated scenarios where new WAL is still
generated on the old timeline.

This includes two small changes to the streaming replication protocol:
First, when you reach the end of timeline while streaming, the server now
sends the TLI of the next timeline in the server's history to the client.
pg_receivexlog uses that as the next timeline, so that it doesn't need to
parse the timeline history file like a standby server does. Second, when
BASE_BACKUP command sends the begin and end WAL positions, it now also sends
the timeline IDs corresponding the positions.
This commit is contained in:
Heikki Linnakangas
2013-01-17 20:23:00 +02:00
parent 8ae35e9180
commit 0b6329130e
12 changed files with 699 additions and 312 deletions
Download Patch File Download Diff File Expand all files Collapse all files

50
src/backend/replication/walsender.c
View File

@@ -117,6 +117,7 @@ static uint32 sendOff = 0;
* history forked off from that timeline at sendTimeLineValidUpto.
*/
static TimeLineID sendTimeLine = 0;
static TimeLineID sendTimeLineNextTLI = 0;
static bool sendTimeLineIsHistoric = false;
static XLogRecPtr sendTimeLineValidUpto = InvalidXLogRecPtr;
@@ -449,7 +450,8 @@ StartReplication(StartReplicationCmd *cmd)
* requested start location is on that timeline.
*/
timeLineHistory = readTimeLineHistory(ThisTimeLineID);
switchpoint = tliSwitchPoint(cmd->timeline, timeLineHistory);
switchpoint = tliSwitchPoint(cmd->timeline, timeLineHistory,
&sendTimeLineNextTLI);
list_free_deep(timeLineHistory);
/*
@@ -496,8 +498,7 @@ StartReplication(StartReplicationCmd *cmd)
streamingDoneSending = streamingDoneReceiving = false;
/* If there is nothing to stream, don't even enter COPY mode */
if (!sendTimeLineIsHistoric ||
cmd->startpoint < sendTimeLineValidUpto)
if (!sendTimeLineIsHistoric || cmd->startpoint < sendTimeLineValidUpto)
{
/*
* When we first start replication the standby will be behind the primary.
@@ -554,10 +555,46 @@ StartReplication(StartReplicationCmd *cmd)
if (walsender_ready_to_stop)
proc_exit(0);
WalSndSetState(WALSNDSTATE_STARTUP);
Assert(streamingDoneSending && streamingDoneReceiving);
}
/* Get out of COPY mode (CommandComplete). */
EndCommand("COPY 0", DestRemote);
/*
* Copy is finished now. Send a single-row result set indicating the next
* timeline.
*/
if (sendTimeLineIsHistoric)
{
char str[11];
snprintf(str, sizeof(str), "%u", sendTimeLineNextTLI);
pq_beginmessage(&buf, 'T'); /* RowDescription */
pq_sendint(&buf, 1, 2); /* 1 field */
/* Field header */
pq_sendstring(&buf, "next_tli");
pq_sendint(&buf, 0, 4); /* table oid */
pq_sendint(&buf, 0, 2); /* attnum */
/*
* int8 may seem like a surprising data type for this, but in theory
* int4 would not be wide enough for this, as TimeLineID is unsigned.
*/
pq_sendint(&buf, INT8OID, 4); /* type oid */
pq_sendint(&buf, -1, 2);
pq_sendint(&buf, 0, 4);
pq_sendint(&buf, 0, 2);
pq_endmessage(&buf);
/* Data row */
pq_beginmessage(&buf, 'D');
pq_sendint(&buf, 1, 2); /* number of columns */
pq_sendint(&buf, strlen(str), 4); /* length */
pq_sendbytes(&buf, str, strlen(str));
pq_endmessage(&buf);
}
/* Send CommandComplete message */
pq_puttextmessage('C', "START_STREAMING");
}
/*
@@ -1377,8 +1414,9 @@ XLogSend(bool *caughtup)
List *history;
history = readTimeLineHistory(ThisTimeLineID);
sendTimeLineValidUpto = tliSwitchPoint(sendTimeLine, history);
sendTimeLineValidUpto = tliSwitchPoint(sendTimeLine, history, &sendTimeLineNextTLI);
Assert(sentPtr <= sendTimeLineValidUpto);
Assert(sendTimeLine < sendTimeLineNextTLI);
list_free_deep(history);
/* the current send pointer should be <= the switchpoint */