redis slave won't sync with master

Question

The redis slave won't sync with the master.

Connectivity:

I can connect to the master when I issue

HOST_NAME=fakehost redis-cli -h $HOST_NAME 

and check the master status using a command like INFO, so connectivity is not an issue.

Settings:

From the slave box, I issued

SLAVEOF $HOST_NAME 6379 

And received an OK.

When I issue the INFO command on the slave, I get

# Replication role:slave master_host:<removed> master_port:6379 master_link_status:down master_last_io_seconds_ago:-1 master_sync_in_progress:0 master_link_down_since_seconds:1379450797 slave_priority:100 slave_read_only:1 connected_slaves:0 

On the master box, I issue info and get

# Replication role:master connected_slaves:0 

So obviously I'm not connected.

Logs

[11225] 17 Sep 14:31:33.225 * Connecting to MASTER... [11225] 17 Sep 14:31:33.226 * MASTER <-> SLAVE sync started [11225] 17 Sep 14:31:33.226 * Non blocking connect for SYNC fired the event. [11225] 17 Sep 14:31:33.226 * Master replied to PING, replication can continue... [11225] 17 Sep 14:31:33.227 # MASTER aborted replication with an error: ERR Unable to perform background save 

Tests

Test that dump.rdb is created on BGSAVE

BGSAVE > OK 

Test that dump.rdb is created on SAVE

SAVE > OK 

Thanks in advance.

Answer 1

I encountered a similar situation today. It seems that for systems that use sysctl, you might have to do:

sysctl vm.overcommit_memory=1 

and restart the slave redis server. This link might help.

Answer 2

This issue little tricky,

the reason that the slave can't sync is in the master itself,

pay attention to the Log output : MASTER aborted replication with an error: ERR Unable to perform background save

this is mean that the master can't do background saving due low memory reserve on the master machine,

to solve this issue I Restarted the master redis server , then all the slaves has been sync by themselves.