コード例 #1
0
ファイル: walsender.c プロジェクト: a1exsh/postgres
static void
WalSndKeepalive(char *msgbuf)
{
	PrimaryKeepaliveMessage keepalive_message;

	/* Construct a new message */
	keepalive_message.walEnd = sentPtr;
	keepalive_message.sendTime = GetCurrentTimestamp();

	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);
}
コード例 #2
0
ファイル: walsender.c プロジェクト: ibejoeb/postgres
/*
 * Read up to MAX_SEND_SIZE bytes of WAL that's been flushed to disk,
 * 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)
{
	XLogRecPtr	SendRqstPtr;
	XLogRecPtr	startptr;
	XLogRecPtr	endptr;
	Size		nbytes;
	WalDataMessageHeader msghdr;

	/*
	 * Attempt to send all data that's already been written out and fsync'd to
	 * disk.  We cannot go further than what's been written out given the
	 * current implementation of XLogRead().  And in any case it's unsafe to
	 * send WAL that is not securely down to disk on the master: if the master
	 * subsequently crashes and restarts, slaves must not have applied any WAL
	 * that gets lost on the master.
	 */
	SendRqstPtr = am_cascading_walsender ? GetStandbyFlushRecPtr() : GetFlushRecPtr();

	/* Quick exit if nothing to do */
	if (XLByteLE(SendRqstPtr, sentPtr))
	{
		*caughtup = true;
		return;
	}

	/*
	 * Figure out how much to send in one message. If there's no more than
	 * MAX_SEND_SIZE bytes to send, send everything. Otherwise send
	 * MAX_SEND_SIZE bytes, but round back to logfile or page boundary.
	 *
	 * The rounding is not only for performance reasons. Walreceiver relies on
	 * the fact that we never split a WAL record across two messages. Since a
	 * long WAL record is split at page boundary into continuation records,
	 * page boundary is always a safe cut-off point. We also assume that
	 * SendRqstPtr never points to the middle of a WAL record.
	 */
	startptr = sentPtr;
	if (startptr.xrecoff >= XLogFileSize)
	{
		/*
		 * crossing a logid boundary, skip the non-existent last log segment
		 * in previous logical log file.
		 */
		startptr.xlogid += 1;
		startptr.xrecoff = 0;
	}

	endptr = startptr;
	XLByteAdvance(endptr, MAX_SEND_SIZE);
	if (endptr.xlogid != startptr.xlogid)
	{
		/* Don't cross a logfile boundary within one message */
		Assert(endptr.xlogid == startptr.xlogid + 1);
		endptr.xlogid = startptr.xlogid;
		endptr.xrecoff = XLogFileSize;
	}

	/* if we went beyond SendRqstPtr, back off */
	if (XLByteLE(SendRqstPtr, endptr))
	{
		endptr = SendRqstPtr;
		*caughtup = true;
	}
	else
	{
		/* round down to page boundary. */
		endptr.xrecoff -= (endptr.xrecoff % XLOG_BLCKSZ);
		*caughtup = false;
	}

	nbytes = endptr.xrecoff - startptr.xrecoff;
	Assert(nbytes <= MAX_SEND_SIZE);

	/*
	 * OK to read and send the slice.
	 */
	msgbuf[0] = 'w';

	/*
	 * Read the log directly into the output buffer to avoid extra memcpy
	 * calls.
	 */
	XLogRead(msgbuf + 1 + sizeof(WalDataMessageHeader), startptr, nbytes);

	/*
	 * We fill the message header last so that the send timestamp is taken as
	 * late as possible.
	 */
	msghdr.dataStart = startptr;
	msghdr.walEnd = SendRqstPtr;
	msghdr.sendTime = GetCurrentTimestamp();

	memcpy(msgbuf + 1, &msghdr, sizeof(WalDataMessageHeader));

	pq_putmessage_noblock('d', msgbuf, 1 + sizeof(WalDataMessageHeader) + nbytes);

	sentPtr = endptr;

	/* Update shared memory status */
	{
		/* use volatile pointer to prevent code rearrangement */
		volatile WalSnd *walsnd = MyWalSnd;

		SpinLockAcquire(&walsnd->mutex);
		walsnd->sentPtr = sentPtr;
		SpinLockRelease(&walsnd->mutex);
	}

	/* Report progress of XLOG streaming in PS display */
	if (update_process_title)
	{
		char		activitymsg[50];

		snprintf(activitymsg, sizeof(activitymsg), "streaming %X/%X",
				 sentPtr.xlogid, sentPtr.xrecoff);
		set_ps_display(activitymsg, false);
	}

	return;
}