I have Redis server running on CentOS as a service. I can stop the server using service redis stop or redis-cli SHUTDOWN.
What is the difference between the two options and which one I should be using in Production environment?
You should check your init script since it may precisely perform a shutdown on stop and not a killproc, e.g:
ExecStop=/usr/bin/redis-cli shutdown
(from Fedora package: redis-server.service)
Using shutdown is the recommended way to stop Redis if persistence matters as stated by the documentation:
If persistence is enabled this commands makes sure that Redis is switched off without the lost of any data.
Related
We have 3 node Gridgain server and there are 3 client nodes deployed in GCP Kubernetes engine. Cluster is native persistence enabled. Also <property name="shutdownPolicy" value="GRACEFUL"/> as shutdown policy. There is one backup for each cache. After automatic cluster restart getting partition loss. Need to reset these partitions by executing control commands.
Can you provide proper solution for this. We have around 60GB persistent data.
<property name="shutdownPolicy" value="GRACEFUL"/> is supposed to protect from partition loss if certain conditions are met:
The caches must be either PARTITIONED with backups > 0 or REPLICATED. Check your configs. Default cache config in Ignite is PARTITIONED with backups = 0 (for historical reasons), so the defaults won't work.
There must be more than one baseline node (only baseline nodes store data!). Here is the doc.
You must stop the nodes in a graceful way. This is a bit tricky since you don't always control this.
If you stop with a kill to the process, make sure it uses SIGTERM and not SIGKILL because the later always kills the process immediately
If you stop with Ignite.close() this should just work
If you stop with Java System.exit() it'll work, but if you use System.halt() - it won't (because halt() is not graceful)
If you use orchestrators such as Kubernetes, you need to make sure they'll stop the nodes gracefully. For example, in Kubernetes you normally have to set terminationGracePeriodSeconds to a high value so that Kubernetes waits for the nodes to finish graceful shutdown instead of killing them.
If you use custom startup scripts, you need to make sure they forward signals to the Ignite process.
To debug this, check the points above. I would normally start by looking at the server logs (with IGNITE_QUIET=false!) to see if "Invoking shutdown hook" message is there. If it isn't there then your shutdown hook isn't getting called, and the problem is one of the points under 3. Otherwise, there should be other log messages explaining the situation.
Recently, I started to have some trouble with one of me Redis cluster. used_memroy and used_memory_rss increasing constantly.
According to some Googling, I found following discussion:
https://github.com/antirez/redis/issues/4570
Now I am wandering if it is safe to run SCRIPT FLUSH command on my production Redis cluster?
Yes - you can run the SCRIPT FLUSH command safely in a production cluster. The only potential side effect is blocking the server while it executes. Note, however, that you'll want to call it in each of your nodes.
I have set up a Celery task that is using RabbitMQ as the broker and Redis as the backend. After running I noticed that my Redis server was still using a lot of memory. Upon inspection I found that there were still keys for each task that was created.
Is there a way to get Celery to clean up these keys only after the response has been received? I know some MessageBrokers use acks, is there an equivalent for a redis backend in Celery?
Yes, use result_expires. Please note that celery beat should run as well, as written in the documentation:
A built-in periodic task will delete the results after this time (celery.backend_cleanup), assuming that celery beat is enabled. The task runs daily at 4am.
Unfortunately Celery doesn't have acks for its backend, so the best solution for my project was to call forget on my responses after I was done with them.
I was wondering why do we need Redis server for running CKAN.
If needed, why? And How do I configure it with CKAN?
p.s
I am running my ckan instance in RHEL7.
Update: Redis has been a requirement since CKAN 2.7, when a new system for asynchronous background jobs was introduced which relies on Redis. You can configure the Redis connection using the ckan.redis.url option.
Redis is not required for the current version of CKAN (2.6.2 at the time of this writing), it's not even mentioned in the CKAN 2.6.2 documentation.
However, the upcoming 2.7 release will require Redis for its new system of asynchronous background jobs. Redis will be configured using the new ckan.redis.url option.
I want to write script for restarting weblogics managed servers, which would do the following:
It would contain loop ,which would restart first nodes of all clusters at one time.
a.)FORCE_SHUTDOWN
b.)wait for status: SHUTDOWN
c.)START managed servers
d.)wait for status: RUNNING
e.)move to next node of each cluster and repeat until all managed servers are restarted.
So in first iteration it would restart all first nodes of each cluster, in second iteration it would restart the second nodes of each cluster and repeat this action until all managed servers are restarted.
I have not started to writing the script yet, I am newbie with weblogic and this is just concept. Do you have any suggestions how to achieve that goal?
Why reinvent the wheel?
rollingRestart
Category: Control Commands
Use with WLST: Online
Description Initiates a rolling restart of all servers in a domain or all servers in a specific cluster or clusters without interrupting
the service. This command provides the ability to sequentially restart
servers.
This operation involves the graceful shutdown of the servers, and the
servers being restarted without interrupting the service for the user.
Syntax
rollingRestart(target, [options])