Should I use exact mirror of redis.conf on slave, if it would be promoted as master when failover activates.
For example should I appendonly yes to slave ?
The slaves configuration are different than the master one, so you will need to have 1 config file per server, plus one sentinel config file. Here you have a nice tutorial to make it work (basically) https://seanmcgary.com/posts/how-to-build-a-fault-tolerant-redis-cluster-with-sentinel
Related
When adding a master to Sentinel, I always add the entries by editing sentinel.conf, but I often find out that application is being rewritten by another user (Sentinel).
I'm wondering if there is a more appropriate and an efficient way to add hosts to Sentinel without the need to edit the config file manually.
You can configure sentinel to monitor a new master at runtime.
Example:
SENTINEL MONITOR {cluster_name} {master_ip} {master_port} {quorum}
SENTINEL SET {cluster_name} auth-pass {password}
SENTINEL FLUSHCONFIG # Force Sentinel to rewrite its configuration file
For additional information check out the Redis Sentinel docs:
https://redis.io/topics/sentinel#reconfiguring-sentinel-at-runtime
Hope that helps!
I've installed stablest redis(ver 3.2). Everything work fine until I renamed CONFIG command of redis, sentinel could not promote slave to be master.
Think the problem is sentinel still use CONFIG command (has been renamed) to change configuration of redis.
Is there any way to change configuration of sentinel (via redis-cli or configuration files sentinel.conf) to adapt redis configuration (renamed config command). If there isn't, how about changing source code?
Thanks
After google, I found solution for this problem.
I replace redis/src/sentinel.c via this redis github, rebuild and install redis from source.
Then I could add a directive to sentinel.conf to configure sentinel use renamed config command.
sentinel config-command mymaster <renamed-command>
Hi i have create a cluster Redis with sentinel composed by 3 aws instances, i have configured sentinel to have an HA redis cluster and work, but if i simulate a crash of master (shutdown of master instance), sentinel installed on slaves, not locate sentinel of master and the election fail.
My sentinel configuration is:
sentinel monitor master ip-master 6379 2
sentinel down-after-milliseconds master 5000
sentinel failover-timeout master 10000
sentinel parallel-syncs master 1
Same file to all instaces
There are issues when running sentinel on the same node as the master and attempting to trigger a failover. Try it w/o running Sentinel on the master. Ultimately this means not running Sentinel on the same nodes as the Redis instances.
In your case your dead-node simulation is showing why you should not run Sentinel on the same node as Redis: If the node dies you lose one of your sentinels. In theory it should still work but as you and others have seen it isn't certain to work. I have some theories why but I've not yet confirmed them.
In a sense Sentinel is partly a monitoring system. Running a monitoring solution on the same nodes as are being monitored is generally unadvisable anyway, so you should be using off-node sentinels anyway. As Sentinel is resource efficient you don't necessarily need dedicated machines or large VMs. Indeed if you have a static set of application servers (where your client code runs), you should run Sentinel there, keeping in mind you want 3 minimum and a quorum of 50%+1.
recent redis version introduced the "protected-mode" option, which defaults to yes.
with protected-mode set to yes, redis instances, without a password set will not allow remote clients to execute commands.
this also affects sentinels master election.
try it with setting "protected-mode no" in the sentinels. this will allow them to talk to each other.
If you don't want to set protected-mode as no. you'd better set masterauth myredis in redis.conf and use sentinel auth-pass mymaster myredis in sentinel.conf
I have a redis master and slave configuration. What I'm finding is that if I restart the slave while there is a dump.rdb file in the directory, the instance starts as a master with no connected slaves rather than obeying the slaveof command in the config file. If I restart the service after deleting the dump.rdb, then the slave will come back online and connect to the master as expected.
Is this expected behavior? If so, is there a way to allow a slave to be restarted and go directly into slave mode?
Edit: This is running on Windows.
How does one upgrade to a newer version of Redis with zero downtime? Redis slaves are read-only, so it seems like you'd have to take down the master and your site would be read-only for 45 seconds or more while you waited for it to reload the DB.
Is there a way around this?
Redis Team has very good documentation on this
Core Steps:
Setup your new Redis instance as a slave for your current Redis instance. In order to do so you need a different server, or a server that has enough RAM to keep two instances of Redis running at the same time.
If you use a single server, make sure that the slave is started in a different port than the master instance, otherwise the slave will not be able to start at all.
Wait for the replication initial synchronization to complete (check the slave log file).
Make sure using INFO that there are the same number of keys in the master and in the slave. Check with redis-cli that the slave is working as you wish and is replying to your commands.
Configure all your clients in order to use the new instance (that is, the slave).
Once you are sure that the master is no longer receiving any query (you can check this with the MONITOR command), elect the slave to master using the SLAVEOF NO ONE command, and shut down your master.
Full Documentation:
Upgrading or restarting a Redis instance without downtime
When taking the node offline, promote the slave to master using the SLAVEOF command, then when you bring it back online you set it up as a slave and it will copy all data from the online node.
You may also need to make sure your client can handle changed/missing master nodes appropriately.
If you want to get really fancy, you can set up your client to promote a slave if it detects an error writing to the master.
You can use Redis Sentinel for doing this, the sentinel will automatically promote a slave as new master.
you can find more info here http://redis.io/topics/sentinel.
Sentinel is a system used to manage redis servers , it monitors the redis master and slaves continuously, and whenever a master goes down it will automatically promote a slave in to master. and when the old master is UP it will be made as slave of the new master.
Here there will be no downtime or manual configuration of config file is needed.
You can visit above link to find out how to configure sentinel for your redis servers.
Note, you may have to check and set the following config to write to your slave.
("Since Redis 2.6 by default slaves are read-only")
redis-cli config set slave-read-only no
-- Example
-bash-4.1$ redis-cli info
Server
redis_version:2.6.9
-bash-4.1$ redis-cli slaveof admin2.mypersonalsite.com 6379
OK
-bash-4.1$ redis-cli set temp 42
(error) READONLY You can't write against a read only slave.
-bash-4.1$ redis-cli slaveof no one
OK
-bash-4.1$ redis-cli set temp 42
OK
-bash-4.1$ redis-cli get temp
"42"
-bash-4.1$ redis-cli config set slave-read-only no
OK
-bash-4.1$ redis-cli slaveof admin2.mypersonalsite.com 6379
OK
-bash-4.1$ redis-cli set temp 42
OK
-bash-4.1$ redis-cli get temp
"42"