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Add a message type header to the CopyData messages sent from primary 

to standby in streaming replication. While we only have one message type
at the moment, adding a message type header makes this easier to extend.
This commit is contained in:
Heikki Linnakangas 2010-02-03 09:47:19 +00:00
parent 47c5b8f558
commit 808969d0e7
5 changed files with 117 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

61
doc/src/sgml/protocol.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/protocol.sgml,v 1.77 2010/01/15 09:18:59 heikki Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/protocol.sgml,v 1.78 2010/02/03 09:47:19 heikki Exp $ -->
<chapter id="protocol">
<title>Frontend/Backend Protocol</title>
@ -4179,12 +4179,65 @@ The commands accepted in walsender mode are:
already been recycled. On success, server responds with a
CopyOutResponse message, and backend starts to stream WAL as CopyData
messages.
The payload in CopyData message consists of the following format.
</para>
<para>
The payload in each CopyData message consists of an XLogRecPtr,
indicating the starting point of the WAL in the message, immediately
followed by the WAL data itself.
<variablelist>
<varlistentry>
<term>
XLogData (B)
</term>
<listitem>
<para>
<variablelist>
<varlistentry>
<term>
Byte1('w')
</term>
<listitem>
<para>
Identifies the message as WAL data.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Int32
</term>
<listitem>
<para>
The log file number of the LSN, indicating the starting point of
the WAL in the message.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Int32
</term>
<listitem>
<para>
The byte offset of the LSN, indicating the starting point of
the WAL in the message.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
Byte<replaceable>n</replaceable>
</term>
<listitem>
<para>
Data that forms part of WAL data stream.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
A single WAL record is never split across two CopyData messages. When

34
src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
View File

@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c,v 1.2 2010/01/20 11:58:44 heikki Exp $
* $PostgreSQL: pgsql/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c,v 1.3 2010/02/03 09:47:19 heikki Exp $
*
*-------------------------------------------------------------------------
*/
@ -48,8 +48,8 @@ static char *recvBuf = NULL;
/* Prototypes for interface functions */
static bool libpqrcv_connect(char *conninfo, XLogRecPtr startpoint);
static bool libpqrcv_receive(int timeout, XLogRecPtr *recptr, char **buffer,
int *len);
static bool libpqrcv_receive(int timeout, unsigned char *type,
char **buffer, int *len);
static void libpqrcv_disconnect(void);
/* Prototypes for private functions */
@ -236,13 +236,13 @@ libpqrcv_disconnect(void)
}
/*
* Receive any WAL records available from XLOG stream, blocking for
* Receive a message available from XLOG stream, blocking for
* maximum of 'timeout' ms.
*
* Returns:
*
* True if data was received. *recptr, *buffer and *len are set to
* the WAL location of the received data, buffer holding it, and length,
* True if data was received. *type, *buffer and *len are set to
* the type of the received data, buffer holding it, and length,
* respectively.
*
* False if no data was available within timeout, or wait was interrupted
@ -254,7 +254,7 @@ libpqrcv_disconnect(void)
* ereports on error.
*/
static bool
libpqrcv_receive(int timeout, XLogRecPtr *recptr, char **buffer, int *len)
libpqrcv_receive(int timeout, unsigned char *type, char **buffer, int *len)
{
int rawlen;
@ -275,14 +275,14 @@ libpqrcv_receive(int timeout, XLogRecPtr *recptr, char **buffer, int *len)
if (PQconsumeInput(streamConn) == 0)
ereport(ERROR,
(errmsg("could not read xlog records: %s",
(errmsg("could not receive data from XLOG stream: %s",
PQerrorMessage(streamConn))));
}
justconnected = false;
/* Receive CopyData message */
rawlen = PQgetCopyData(streamConn, &recvBuf, 1);
if (rawlen == 0) /* no records available yet, then return */
if (rawlen == 0) /* no data available yet, then return */
return false;
if (rawlen == -1) /* end-of-streaming or error */
{
@ -297,22 +297,18 @@ libpqrcv_receive(int timeout, XLogRecPtr *recptr, char **buffer, int *len)
}
PQclear(res);
ereport(ERROR,
(errmsg("could not read xlog records: %s",
(errmsg("could not receive data from XLOG stream: %s",
PQerrorMessage(streamConn))));
}
if (rawlen < -1)
ereport(ERROR,
(errmsg("could not read xlog records: %s",
(errmsg("could not receive data from XLOG stream: %s",
PQerrorMessage(streamConn))));
if (rawlen < sizeof(XLogRecPtr))
ereport(ERROR,
(errmsg("invalid WAL message received from primary")));
/* Return received WAL records to caller */
*recptr = *((XLogRecPtr *) recvBuf);
*buffer = recvBuf + sizeof(XLogRecPtr);
*len = rawlen - sizeof(XLogRecPtr);
/* Return received messages to caller */
*type = *((unsigned char *) recvBuf);
*buffer = recvBuf + sizeof(*type);
*len = rawlen - sizeof(*type);
return true;
}

49
src/backend/replication/walreceiver.c
View File

@ -29,7 +29,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/replication/walreceiver.c,v 1.2 2010/01/27 15:27:51 heikki Exp $
* $PostgreSQL: pgsql/src/backend/replication/walreceiver.c,v 1.3 2010/02/03 09:47:19 heikki Exp $
*
*-------------------------------------------------------------------------
*/
@ -135,6 +135,7 @@ static void WalRcvQuickDieHandler(SIGNAL_ARGS);
/* Prototypes for private functions */
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(void);
@ -258,7 +259,7 @@ WalReceiverMain(void)
/* Loop until end-of-streaming or error */
for (;;)
{
XLogRecPtr recptr;
unsigned char type;
char *buf;
int len;
@ -287,17 +288,17 @@ WalReceiverMain(void)
}
/* Wait a while for data to arrive */
if (walrcv_receive(NAPTIME_PER_CYCLE, &recptr, &buf, &len))
if (walrcv_receive(NAPTIME_PER_CYCLE, &type, &buf, &len))
{
/* Write received WAL records to disk */
XLogWalRcvWrite(buf, len, recptr);
/* Accept the received data, and process it */
XLogWalRcvProcessMsg(type, buf, len);
/* Receive any more WAL records we can without sleeping */
while(walrcv_receive(0, &recptr, &buf, &len))
XLogWalRcvWrite(buf, len, recptr);
/* Receive any more data we can without sleeping */
while(walrcv_receive(0, &type, &buf, &len))
XLogWalRcvProcessMsg(type, buf, len);
/*
* Now that we've written some records, flush them to disk and
* If we've written some records, flush them to disk and
* let the startup process know about them.
*/
XLogWalRcvFlush();
@ -375,6 +376,36 @@ WalRcvQuickDieHandler(SIGNAL_ARGS)
exit(2);
}
/*
* Accept the message from XLOG stream, and process it.
*/
static void
XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len)
{
switch (type)
{
case 'w': /* WAL records */
{
XLogRecPtr recptr;
if (len < sizeof(XLogRecPtr))
ereport(ERROR,
(errmsg("invalid WAL message received from primary")));
recptr = *((XLogRecPtr *) buf);
buf += sizeof(XLogRecPtr);
len -= sizeof(XLogRecPtr);
XLogWalRcvWrite(buf, len, recptr);
break;
}
default:
ereport(ERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg("invalid replication message type %d",
type)));
}
}
/*
* Write XLOG data to disk.
*/

3
src/backend/replication/walsender.c
View File

@ -30,7 +30,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/replication/walsender.c,v 1.4 2010/01/27 16:41:09 heikki Exp $
* $PostgreSQL: pgsql/src/backend/replication/walsender.c,v 1.5 2010/02/03 09:47:19 heikki Exp $
*
*-------------------------------------------------------------------------
*/
@ -659,6 +659,7 @@ XLogSend(StringInfo outMsg)
* have the same byte order. If they have different byte order, we
* don't reach here.
*/
pq_sendbyte(outMsg, 'w');
pq_sendbytes(outMsg, (char *) &startptr, sizeof(startptr));
if (endptr.xlogid != startptr.xlogid)

5
src/include/replication/walreceiver.h
View File

@ -5,7 +5,7 @@
*
* Portions Copyright (c) 2010-2010, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/include/replication/walreceiver.h,v 1.5 2010/01/27 15:27:51 heikki Exp $
* $PostgreSQL: pgsql/src/include/replication/walreceiver.h,v 1.6 2010/02/03 09:47:19 heikki Exp $
*
*-------------------------------------------------------------------------
*/
@ -66,7 +66,8 @@ extern WalRcvData *WalRcv;
typedef bool (*walrcv_connect_type) (char *conninfo, XLogRecPtr startpoint);
extern PGDLLIMPORT walrcv_connect_type walrcv_connect;
typedef bool (*walrcv_receive_type) (int timeout, XLogRecPtr *recptr, char **buffer, int *len);
typedef bool (*walrcv_receive_type) (int timeout, unsigned char *type,
char **buffer, int *len);
extern PGDLLIMPORT walrcv_receive_type walrcv_receive;
typedef void (*walrcv_disconnect_type) (void);