diff options
Diffstat (limited to 'src/backend/replication/walsender.c')
| -rw-r--r-- | src/backend/replication/walsender.c | 57 |
1 files changed, 48 insertions, 9 deletions
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c index ba138e73da3..10e40506965 100644 --- a/src/backend/replication/walsender.c +++ b/src/backend/replication/walsender.c @@ -110,6 +110,9 @@ static int sendFile = -1; static XLogSegNo sendSegNo = 0; static uint32 sendOff = 0; +/* Timeline ID of the currently open file */ +static TimeLineID curFileTimeLine = 0; + /* * These variables keep track of the state of the timeline we're currently * sending. sendTimeLine identifies the timeline. If sendTimeLineIsHistoric, @@ -1201,8 +1204,8 @@ WalSndKill(int code, Datum arg) * always be one descriptor left open until the process ends, but never * more than one. */ -void -XLogRead(char *buf, TimeLineID tli, XLogRecPtr startptr, Size count) +static void +XLogRead(char *buf, XLogRecPtr startptr, Size count) { char *p; XLogRecPtr recptr; @@ -1222,7 +1225,7 @@ retry: startoff = recptr % XLogSegSize; - if (sendFile < 0 || !XLByteInSeg(recptr, sendSegNo) || sendTimeLine != tli) + if (sendFile < 0 || !XLByteInSeg(recptr, sendSegNo)) { char path[MAXPGPATH]; @@ -1230,9 +1233,45 @@ retry: if (sendFile >= 0) close(sendFile); - sendTimeLine = tli; XLByteToSeg(recptr, sendSegNo); - XLogFilePath(path, sendTimeLine, sendSegNo); + + /*------- + * When reading from a historic timeline, and there is a timeline + * switch within this segment, read from the WAL segment belonging + * to the new timeline. + * + * For example, imagine that this server is currently on timeline + * 5, and we're streaming timeline 4. The switch from timeline 4 + * to 5 happened at 0/13002088. In pg_xlog, we have these files: + * + * ... + * 000000040000000000000012 + * 000000040000000000000013 + * 000000050000000000000013 + * 000000050000000000000014 + * ... + * + * In this situation, when requested to send the WAL from + * segment 0x13, on timeline 4, we read the WAL from file + * 000000050000000000000013. Archive recovery prefers files from + * newer timelines, so if the segment was restored from the + * archive on this server, the file belonging to the old timeline, + * 000000040000000000000013, might not exist. Their contents are + * equal up to the switchpoint, because at a timeline switch, the + * used portion of the old segment is copied to the new file. + *------- + */ + curFileTimeLine = sendTimeLine; + if (sendTimeLineIsHistoric) + { + XLogSegNo endSegNo; + + XLByteToSeg(sendTimeLineValidUpto, endSegNo); + if (sendSegNo == endSegNo) + curFileTimeLine = sendTimeLineNextTLI; + } + + XLogFilePath(path, curFileTimeLine, sendSegNo); sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0); if (sendFile < 0) @@ -1246,7 +1285,7 @@ retry: ereport(ERROR, (errcode_for_file_access(), errmsg("requested WAL segment %s has already been removed", - XLogFileNameP(sendTimeLine, sendSegNo)))); + XLogFileNameP(curFileTimeLine, sendSegNo)))); else ereport(ERROR, (errcode_for_file_access(), @@ -1263,7 +1302,7 @@ retry: ereport(ERROR, (errcode_for_file_access(), errmsg("could not seek in log segment %s to offset %u: %m", - XLogFileNameP(sendTimeLine, sendSegNo), + XLogFileNameP(curFileTimeLine, sendSegNo), startoff))); sendOff = startoff; } @@ -1280,7 +1319,7 @@ retry: ereport(ERROR, (errcode_for_file_access(), errmsg("could not read from log segment %s, offset %u, length %lu: %m", - XLogFileNameP(sendTimeLine, sendSegNo), + XLogFileNameP(curFileTimeLine, sendSegNo), sendOff, (unsigned long) segbytes))); } @@ -1524,7 +1563,7 @@ XLogSend(bool *caughtup) * calls. */ enlargeStringInfo(&output_message, nbytes); - XLogRead(&output_message.data[output_message.len], sendTimeLine, startptr, nbytes); + XLogRead(&output_message.data[output_message.len], startptr, nbytes); output_message.len += nbytes; output_message.data[output_message.len] = '\0'; |