More strict checks and better comments in flushSlaveOutputBuffers().

Related to #6296.
This commit is contained in:
antirez 2019-08-31 14:46:21 +02:00
parent 2303ba1441
commit e57067b677

View File

@ -2468,15 +2468,26 @@ void flushSlavesOutputBuffers(void) {
listRewind(server.slaves,&li);
while((ln = listNext(&li))) {
client *slave = listNodeValue(ln);
int events = aeGetFileEvents(server.el,slave->fd);
int can_receive_writes = (events & AE_WRITABLE) ||
(slave->flags & CLIENT_PENDING_WRITE);
/* Note that the following will not flush output buffers of slaves
* in STATE_ONLINE but having put_online_on_ack set to true: in this
* case the writable event is never installed, since the purpose
* of put_online_on_ack is to postpone the moment it is installed.
* This is what we want since slaves in this state should not receive
* writes before the first ACK (to know the reason, grep for this
* flag in this file). */
/* We don't want to send the pending data to the replica in a few
* cases:
*
* 1. For some reason there is neither the write handler installed
* nor the client is flagged as to have pending writes: for some
* reason this replica may not be set to receive data. This is
* just for the sake of defensive programming.
*
* 2. The put_online_on_ack flag is true. To know why we don't want
* to send data to the replica in this case, please grep for the
* flag for this flag.
*
* 3. Obviously if the slave is not ONLINE.
*/
if (slave->replstate == SLAVE_STATE_ONLINE &&
can_receive_writes &&
!slave->repl_put_online_on_ack &&
clientHasPendingReplies(slave))
{