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PSYNC2: stop sending newlines to sub-slaves when master is down.

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This actually includes two changes:

1) No newlines to take the master-slave link up when the upstream master
is down. Doing this is dangerous because the sub-slave often is received
replication protocol for an half-command, so can't receive newlines
without desyncing the replication link, even with the code in order to
cancel out the bytes that PSYNC2 was using. Moreover this is probably
also not needed/sane, because anyway the slave can keep serving
requests, and because if it's configured to don't serve stale data, it's
a good idea, actually, to break the link.

2) When a +CONTINUE with a different ID is received, we now break
connection with the sub-slaves: they need to be notified as well. This
was part of the original specification but for some reason it was not
implemented in the code, and was alter found as a PSYNC2 bug in the
integration testing.
This commit is contained in:
antirez 2016-11-28 17:54:04 +01:00
parent 16559a02fc
commit eab865a0a1
3 changed files with 6 additions and 30 deletions
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12
src/networking.c
View File

@ -1031,7 +1031,7 @@ int processInlineBuffer(client *c) {
char *newline;
int argc, j;
sds *argv, aux;
size_t querylen, protolen;
size_t querylen;
/* Search for end of line */
newline = strchr(c->querybuf,'\n');
@ -1044,7 +1044,6 @@ int processInlineBuffer(client *c) {
}
return C_ERR;
}
protolen = (newline - c->querybuf)+1; /* Total protocol bytes of command. */
/* Handle the \r\n case. */
if (newline && newline != c->querybuf && *(newline-1) == '\r')
@ -1067,15 +1066,6 @@ int processInlineBuffer(client *c) {
if (querylen == 0 && c->flags & CLIENT_SLAVE)
c->repl_ack_time = server.unixtime;
/* Newline from masters can be used to prevent timeouts, but should
* not affect the replication offset since they are always sent
* "out of band" directly writing to the socket and without passing
* from the output buffers. */
if (querylen == 0 && c->flags & CLIENT_MASTER) {
c->reploff -= protolen;
while (protolen--) chopReplicationBacklog();
}
/* Leave data after the first line of the query in the buffer */
sdsrange(c->querybuf,querylen+2,-1);

23
src/replication.c
View File

@ -148,22 +148,6 @@ void feedReplicationBacklog(void *ptr, size_t len) {
server.repl_backlog_histlen + 1;
}
/* Remove the last byte from the replication backlog. This
* is useful when we receive an out of band "\n" to keep the connection
* alive but don't want to count it as replication stream.
*
* As a side effect this function adjusts the master replication offset
* of this instance to account for the missing byte. */
void chopReplicationBacklog(void) {
if (!server.repl_backlog || !server.repl_backlog_histlen) return;
if (server.repl_backlog_idx == 0)
server.repl_backlog_idx = server.repl_backlog_size-1;
else
server.repl_backlog_idx--;
server.master_repl_offset--;
server.repl_backlog_histlen--;
}
/* Wrapper for feedReplicationBacklog() that takes Redis string objects
* as input. */
void feedReplicationBacklogWithObject(robj *o) {
@ -1530,6 +1514,9 @@ int slaveTryPartialResynchronization(int fd, int read_reply) {
* new one. */
memcpy(server.replid,new,sizeof(server.replid));
memcpy(server.cached_master->replid,new,sizeof(server.replid));
/* Disconnect all the sub-slaves: they need to be notified. */
disconnectSlaves();
}
}
@ -2553,10 +2540,8 @@ void replicationCron(void) {
(slave->replstate == SLAVE_STATE_WAIT_BGSAVE_START ||
(slave->replstate == SLAVE_STATE_WAIT_BGSAVE_END &&
server.rdb_child_type != RDB_CHILD_TYPE_SOCKET));
int is_subslave = server.masterhost && server.master == NULL &&
slave->replstate == SLAVE_STATE_ONLINE;
if (is_presync || is_subslave) {
if (is_presync) {
if (write(slave->fd, "\n", 1) == -1) {
/* Don't worry about socket errors, it's just a ping. */
}

1
tests/integration/psync2.tcl
View File

@ -87,6 +87,7 @@ start_server {} {
set slave_id [randomInt 5]
if {$disconnect} {
$R($slave_id) client kill type master
puts "+++ Breaking link for slave #$slave_id"
}
}
}