I have deployed my application on SAP Cloud Foundary which creates connection with Redis Multinode instance running on the cloud.
The application can push and fetch data from Redis successfully.
Now I want to check high availability of Redis Nodes by crashing nodes of redis one by one (cloud has the instance of Redis with 3 nodes, 1 being master and other 2 as its slave).
I have been trying to crash anyone of the nodes by using redis-cli, ssh connection but could not get success in that.
Can anyone please help me to know how to crash any single node of Redis cluster in SAP cloud environment?
Any help would be appreciated.
Thanks :)
Related
A smart client for Redis cluster will "take persistent connections to many nodes, will cache hashslot -> node info, and will update the table when they receive a -MOVED error".
I checked numerous documents but can't find a definitive answer on whether Stackexchange.Redis is a smart client. Can anyone advice? Thanks.
I am using Stackexchange.Redis client in my web application to connect to Redis cluster having 6 instances of Redis servers. Stackexchange.Redis client works perfectly with Redis cluster and we did not get -MOVED error.
I am using Redis Cluster on 3 Linux servers (CentOS 7). I have standard configuration i.e. 6 nodes, 3 master instances, and 3 slave instances (one master have one slave) distributed on these 3 Linux servers. I am using this setup for my web application for data caching, HTTP response caching. My aim is to read primary and write secondary i.e. Read operation should not fail or delayed.
Now I would like to ask is it necessary to configure any load balancer before by 3 Linux servers so that my web application requests to Redis cluster instances can be distributed properly on these Redis servers? Or Redis cluster itself able to handle the load distribution?
If Yes, then please mention any reference link to configure the same. I have checked official documentation Redis Cluster but it does not specify anything regarding load balancer setup.
If you're running Redis in "Cluster Mode" you don't need a load balancer. Your Redis client (assuming it's any good) should contact Redis for a list of which slots are on which nodes when your application starts up. It will hash keys locally (in your application) and send requests directly to the node which owns the slot for that key (which avoids the extra call to Redis which results in a MOVED response).
You should be able to configure your client to do reads on slave and writes on master - or to do both reads and writes on only masters. In addition to configuring your client, if you want to do reads on slaves, check out the READONLY command: https://redis.io/commands/readonly .
We have 2 app/web servers running HA application, we need to setup redis with high availability/replication to support our app.
Considering the minimum sentinel setup requirement of 3 nodes.
We are planning to prepare the first app serve with redis master and 1 sentinel, the second app server will have the redis slave and 1 sentinel, we plan to add one additional server to hold the third sentinel node to achieve the 2 quorum sentinel setup.
Is this a valid setup ? what could be the risks ?
Thanks ,,,
Well it looks its not recommended to put the redis nodes on the app servers (where it is recommended to put the sentinel nodes there).
We ended with a setup for KeyDB (a fork from Redis) which claimed to be faster and support high availability/replication (and much more) to create two nodes within the app servers.
Of course We had to modify little in the client side to support some advance Lua scripts (There is some binary serialized data not getting replicated to the other node).
But after some effort, it worked ! as expected.
Hope this helps ...
How to get all connected clients of a redis cluster?
I am using AWS elasticCache redis with non cluster mode and redission as my redis client.
My Use Case:
I need to run specific code from only 1 connected redis client.
Thanks
redis has command about client information like CLIENT LIST, check out this page .
you could checkout this page for the command redisson has not supported yet.
I am planning on adding Redis to our application as a session and cache store. I have been looking at how to make Redis highly available on an on-premise hosted solution.
The standard approach appears to be to set up Redis as a 3 node replica and use Sentinel for the monitoring and automatic failover.
Redis 2.8 introduces Redis cluster. Does that mean it brings in automatic failover etc and we no longer need to use Sentinel?
No, Cluster and Failover are different scenarios. Also Cluster is in 3.0, not 2.8.
The standard (and minimum) setup for HA is a master and one slave (aka "a pod"), with a separate set of three nodes which run Sentinel and monitor the pod.
This is to ensure failover of the server. However, either your client library has to support using Sentinel to discover master and reconnect on failure, you implement it in your code, or you set up a TCP load balancer and a sentinel monitoring daemon to update your load balancer configuration when a failover occurs at which point the client code doesn't know or care about sentinel.
Cluster isn't there to provide HA, it is there for server-side sharding of data. For Cluster you're looking at 6-7 nodes minimum (3 master, 3 slave, 1 spare) as well as Cluster support in the client and restrictions about commands and Lua script which need to access multiple keys.