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
parent
47c5b8f558
commit
808969d0e7
@ -1,4 +1,4 @@
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<!-- $PostgreSQL: pgsql/doc/src/sgml/protocol.sgml,v 1.77 2010/01/15 09:18:59 heikki Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/protocol.sgml,v 1.78 2010/02/03 09:47:19 heikki Exp $ -->
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<chapter id="protocol">
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<title>Frontend/Backend Protocol</title>
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@ -4179,12 +4179,65 @@ The commands accepted in walsender mode are:
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already been recycled. On success, server responds with a
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CopyOutResponse message, and backend starts to stream WAL as CopyData
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messages.
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The payload in CopyData message consists of the following format.
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</para>
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<para>
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The payload in each CopyData message consists of an XLogRecPtr,
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indicating the starting point of the WAL in the message, immediately
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followed by the WAL data itself.
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<variablelist>
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<varlistentry>
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<term>
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XLogData (B)
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</term>
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<listitem>
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<para>
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<variablelist>
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<varlistentry>
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<term>
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Byte1('w')
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</term>
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<listitem>
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<para>
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Identifies the message as WAL data.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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Int32
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</term>
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<listitem>
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<para>
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The log file number of the LSN, indicating the starting point of
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the WAL in the message.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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Int32
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</term>
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<listitem>
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<para>
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The byte offset of the LSN, indicating the starting point of
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the WAL in the message.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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Byte<replaceable>n</replaceable>
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</term>
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<listitem>
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<para>
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Data that forms part of WAL data stream.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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A single WAL record is never split across two CopyData messages. When
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@ -10,7 +10,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c,v 1.2 2010/01/20 11:58:44 heikki Exp $
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* $PostgreSQL: pgsql/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c,v 1.3 2010/02/03 09:47:19 heikki Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -48,8 +48,8 @@ static char *recvBuf = NULL;
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/* Prototypes for interface functions */
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static bool libpqrcv_connect(char *conninfo, XLogRecPtr startpoint);
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static bool libpqrcv_receive(int timeout, XLogRecPtr *recptr, char **buffer,
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int *len);
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static bool libpqrcv_receive(int timeout, unsigned char *type,
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char **buffer, int *len);
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static void libpqrcv_disconnect(void);
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/* Prototypes for private functions */
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@ -236,13 +236,13 @@ libpqrcv_disconnect(void)
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}
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/*
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* Receive any WAL records available from XLOG stream, blocking for
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* Receive a message available from XLOG stream, blocking for
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* maximum of 'timeout' ms.
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*
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* Returns:
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*
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* True if data was received. *recptr, *buffer and *len are set to
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* the WAL location of the received data, buffer holding it, and length,
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* True if data was received. *type, *buffer and *len are set to
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* the type of the received data, buffer holding it, and length,
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* respectively.
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*
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* False if no data was available within timeout, or wait was interrupted
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@ -254,7 +254,7 @@ libpqrcv_disconnect(void)
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* ereports on error.
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*/
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static bool
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libpqrcv_receive(int timeout, XLogRecPtr *recptr, char **buffer, int *len)
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libpqrcv_receive(int timeout, unsigned char *type, char **buffer, int *len)
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{
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int rawlen;
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@ -275,14 +275,14 @@ libpqrcv_receive(int timeout, XLogRecPtr *recptr, char **buffer, int *len)
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if (PQconsumeInput(streamConn) == 0)
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ereport(ERROR,
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(errmsg("could not read xlog records: %s",
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(errmsg("could not receive data from XLOG stream: %s",
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PQerrorMessage(streamConn))));
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}
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justconnected = false;
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/* Receive CopyData message */
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rawlen = PQgetCopyData(streamConn, &recvBuf, 1);
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if (rawlen == 0) /* no records available yet, then return */
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if (rawlen == 0) /* no data available yet, then return */
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return false;
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if (rawlen == -1) /* end-of-streaming or error */
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{
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@ -297,22 +297,18 @@ libpqrcv_receive(int timeout, XLogRecPtr *recptr, char **buffer, int *len)
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}
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PQclear(res);
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ereport(ERROR,
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(errmsg("could not read xlog records: %s",
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(errmsg("could not receive data from XLOG stream: %s",
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PQerrorMessage(streamConn))));
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}
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if (rawlen < -1)
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ereport(ERROR,
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(errmsg("could not read xlog records: %s",
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(errmsg("could not receive data from XLOG stream: %s",
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PQerrorMessage(streamConn))));
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if (rawlen < sizeof(XLogRecPtr))
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ereport(ERROR,
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(errmsg("invalid WAL message received from primary")));
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/* Return received WAL records to caller */
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*recptr = *((XLogRecPtr *) recvBuf);
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*buffer = recvBuf + sizeof(XLogRecPtr);
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*len = rawlen - sizeof(XLogRecPtr);
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/* Return received messages to caller */
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*type = *((unsigned char *) recvBuf);
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*buffer = recvBuf + sizeof(*type);
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*len = rawlen - sizeof(*type);
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return true;
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}
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@ -29,7 +29,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/replication/walreceiver.c,v 1.2 2010/01/27 15:27:51 heikki Exp $
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* $PostgreSQL: pgsql/src/backend/replication/walreceiver.c,v 1.3 2010/02/03 09:47:19 heikki Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -135,6 +135,7 @@ static void WalRcvQuickDieHandler(SIGNAL_ARGS);
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/* Prototypes for private functions */
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static void WalRcvDie(int code, Datum arg);
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static void XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len);
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static void XLogWalRcvWrite(char *buf, Size nbytes, XLogRecPtr recptr);
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static void XLogWalRcvFlush(void);
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@ -258,7 +259,7 @@ WalReceiverMain(void)
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/* Loop until end-of-streaming or error */
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for (;;)
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{
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XLogRecPtr recptr;
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unsigned char type;
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char *buf;
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int len;
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@ -287,17 +288,17 @@ WalReceiverMain(void)
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}
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/* Wait a while for data to arrive */
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if (walrcv_receive(NAPTIME_PER_CYCLE, &recptr, &buf, &len))
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if (walrcv_receive(NAPTIME_PER_CYCLE, &type, &buf, &len))
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{
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/* Write received WAL records to disk */
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XLogWalRcvWrite(buf, len, recptr);
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/* Accept the received data, and process it */
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XLogWalRcvProcessMsg(type, buf, len);
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/* Receive any more WAL records we can without sleeping */
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while(walrcv_receive(0, &recptr, &buf, &len))
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XLogWalRcvWrite(buf, len, recptr);
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/* Receive any more data we can without sleeping */
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while(walrcv_receive(0, &type, &buf, &len))
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XLogWalRcvProcessMsg(type, buf, len);
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/*
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* Now that we've written some records, flush them to disk and
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* If we've written some records, flush them to disk and
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* let the startup process know about them.
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*/
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XLogWalRcvFlush();
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@ -375,6 +376,36 @@ WalRcvQuickDieHandler(SIGNAL_ARGS)
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exit(2);
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}
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/*
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* Accept the message from XLOG stream, and process it.
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*/
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static void
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XLogWalRcvProcessMsg(unsigned char type, char *buf, Size len)
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{
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switch (type)
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{
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case 'w': /* WAL records */
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{
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XLogRecPtr recptr;
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if (len < sizeof(XLogRecPtr))
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ereport(ERROR,
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(errmsg("invalid WAL message received from primary")));
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recptr = *((XLogRecPtr *) buf);
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buf += sizeof(XLogRecPtr);
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len -= sizeof(XLogRecPtr);
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XLogWalRcvWrite(buf, len, recptr);
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break;
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}
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default:
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ereport(ERROR,
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(errcode(ERRCODE_PROTOCOL_VIOLATION),
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errmsg("invalid replication message type %d",
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type)));
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}
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}
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/*
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* Write XLOG data to disk.
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*/
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@ -30,7 +30,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/replication/walsender.c,v 1.4 2010/01/27 16:41:09 heikki Exp $
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* $PostgreSQL: pgsql/src/backend/replication/walsender.c,v 1.5 2010/02/03 09:47:19 heikki Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -659,6 +659,7 @@ XLogSend(StringInfo outMsg)
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* have the same byte order. If they have different byte order, we
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* don't reach here.
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*/
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pq_sendbyte(outMsg, 'w');
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pq_sendbytes(outMsg, (char *) &startptr, sizeof(startptr));
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if (endptr.xlogid != startptr.xlogid)
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@ -5,7 +5,7 @@
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*
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* Portions Copyright (c) 2010-2010, PostgreSQL Global Development Group
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*
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* $PostgreSQL: pgsql/src/include/replication/walreceiver.h,v 1.5 2010/01/27 15:27:51 heikki Exp $
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* $PostgreSQL: pgsql/src/include/replication/walreceiver.h,v 1.6 2010/02/03 09:47:19 heikki Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -66,7 +66,8 @@ extern WalRcvData *WalRcv;
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typedef bool (*walrcv_connect_type) (char *conninfo, XLogRecPtr startpoint);
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extern PGDLLIMPORT walrcv_connect_type walrcv_connect;
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typedef bool (*walrcv_receive_type) (int timeout, XLogRecPtr *recptr, char **buffer, int *len);
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typedef bool (*walrcv_receive_type) (int timeout, unsigned char *type,
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char **buffer, int *len);
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extern PGDLLIMPORT walrcv_receive_type walrcv_receive;
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typedef void (*walrcv_disconnect_type) (void);
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