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Replica fail and retry the PSYNC if the master is unresponsive (#10726) 

We observed from our replication testing that when the master becomes unresponsive,
or the replication connection is broken during PSYNC so the replica doesn't get a
response from the master, it was not able to recognize that condition as a failure
and instead moved into the full-sync code path. This fix makes the replica fail and
retry the PSYNC with the master in such scenarios.
This commit is contained in:
Qu Chen 2022-05-16 02:08:19 -07:00 committed by GitHub
parent a7d6ca9770
commit 837c063baf
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 20 additions and 2 deletions
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22
src/replication.c
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@ -2223,8 +2223,8 @@ char *receiveSynchronousResponse(connection *conn) {
/* Read the reply from the server. */
if (connSyncReadLine(conn,buf,sizeof(buf),server.repl_syncio_timeout*1000) == -1)
{
return sdscatprintf(sdsempty(),"-Reading from master: %s",
strerror(errno));
serverLog(LL_WARNING, "Failed to read response from the server: %s", strerror(errno));
return NULL;
}
server.repl_transfer_lastio = server.unixtime;
return sdsnew(buf);
@ -2407,6 +2407,13 @@ int slaveTryPartialResynchronization(connection *conn, int read_reply) {
/* Reading half */
reply = receiveSynchronousResponse(conn);
/* Master did not reply to PSYNC */
if (reply == NULL) {
connSetReadHandler(conn, NULL);
serverLog(LL_WARNING, "Master did not reply to PSYNC, will try later");
return PSYNC_TRY_LATER;
}
if (sdslen(reply) == 0) {
/* The master may send empty newlines after it receives PSYNC
* and before to reply, just to keep the connection alive. */
@ -2566,6 +2573,9 @@ void syncWithMaster(connection *conn) {
if (server.repl_state == REPL_STATE_RECEIVE_PING_REPLY) {
err = receiveSynchronousResponse(conn);
/* The master did not reply */
if (err == NULL) goto no_response_error;
/* We accept only two replies as valid, a positive +PONG reply
* (we just check for "+") or an authentication error.
* Note that older versions of Redis replied with "operation not
@ -2652,6 +2662,7 @@ void syncWithMaster(connection *conn) {
/* Receive AUTH reply. */
if (server.repl_state == REPL_STATE_RECEIVE_AUTH_REPLY) {
err = receiveSynchronousResponse(conn);
if (err == NULL) goto no_response_error;
if (err[0] == '-') {
serverLog(LL_WARNING,"Unable to AUTH to MASTER: %s",err);
sdsfree(err);
@ -2666,6 +2677,7 @@ void syncWithMaster(connection *conn) {
/* Receive REPLCONF listening-port reply. */
if (server.repl_state == REPL_STATE_RECEIVE_PORT_REPLY) {
err = receiveSynchronousResponse(conn);
if (err == NULL) goto no_response_error;
/* Ignore the error if any, not all the Redis versions support
* REPLCONF listening-port. */
if (err[0] == '-') {
@ -2683,6 +2695,7 @@ void syncWithMaster(connection *conn) {
/* Receive REPLCONF ip-address reply. */
if (server.repl_state == REPL_STATE_RECEIVE_IP_REPLY) {
err = receiveSynchronousResponse(conn);
if (err == NULL) goto no_response_error;
/* Ignore the error if any, not all the Redis versions support
* REPLCONF ip-address. */
if (err[0] == '-') {
@ -2697,6 +2710,7 @@ void syncWithMaster(connection *conn) {
/* Receive CAPA reply. */
if (server.repl_state == REPL_STATE_RECEIVE_CAPA_REPLY) {
err = receiveSynchronousResponse(conn);
if (err == NULL) goto no_response_error;
/* Ignore the error if any, not all the Redis versions support
* REPLCONF capa. */
if (err[0] == '-') {
@ -2810,6 +2824,10 @@ void syncWithMaster(connection *conn) {
server.repl_transfer_lastio = server.unixtime;
return;
no_response_error: /* Handle receiveSynchronousResponse() error when master has no reply */
serverLog(LL_WARNING, "Master did not respond to command during SYNC handshake");
/* Fall through to regular error handling */
error:
if (dfd != -1) close(dfd);
connClose(conn);