After some readings, it seems there is no sustainable solution for auto-scaling Redis on Kubernetes without adding a controller like Maestro. Unfortunatly the project seems a bit dead.
What are some alternatives for autoscaling Redis ?
Edit: Redis is a statefull app.
If you want to autoscale anything on Kubernetes, it requires some type of controller. For general autoscaling, the community is rallying around the Horizontal Pod Autoscaler. By default, you configure it to scale based on CPU utilization.
If you want to scale based on metrics other than CPU utilization and you're using the Redis helm chart, you can easily configure it to run a Prometheus metric sidecar and can set the autoscaler to scale based on one of those values.
Related
Currently hazelcast is using cloud discovery for communication.
So if there are 4 kubernetes pods and each of them is having in-memory hazelcast. whenever hazelcast cache is updated in one of the pod, it gets updated in one of the other pod. but in case both of these pods get downscaled and get terminated, the data which is only in these 2 pods is lost. Can we have something like redis where we can provide server, port of the hazelcast cluster and it will be independent of kubernetes pod
Please check the following Blog Post ("Scale without Data Loss!" section) to read how to scale Hazelcast cluster on Kubernetes to avoid data loss.
Also, you can check the official README of hazelcast/hazelcast-kubernetes plugin. There is a section dedicated to scaling there.
I need an HA redis solution instead of a single instance. Should I use cluster or Sentinel? I have tried to find out the difference between them, there is no official document about this, thanks a lot.
Well, for a HA redis solution , it depends upon the number of nodes you want to configure.
According to offical Redis documentation on Redis-cluster and Redis-sentinel both provides HA Solution but.....
Redis Sentinel provides high availability for Redis. In practical terms this means that using Sentinel you can create a Redis deployment that resists without human intervention to certain kind of failures.
Redis Cluster provides a way to run a Redis installation where data is automatically sharded across multiple Redis nodes.
Redis Cluster also provides some degree of availability during partitions, that is in practical terms the ability to continue the operations when some nodes fail or are not able to communicate. However the cluster stops to operate in the event of larger failures (for example when the majority of masters are unavailable).
For more information please refer the official docs :)
Cheers
For a large online application, use k8s to run it. The scale maybe daily activity user 500,000.
The application inside k8s need messaging feature - Pub/Sub, there are these options:
Kafka
RabbitMQ
Redis
Kafka
It needs zookeeper and good to run on os depends on disk I/O. So if install it into k8s cluster, how? The performance will be worse?
And, if keep Kafka outside of the k8s cluster, connect Kafka from application inside the k8s cluster, how about that performance? They are in the different layer, won't be slow?
RabbitMQ
It's slow than Kafka, but for a daily activity user 500,000 application, is it good enough? If so, maybe it's a good choice.
Redis
It's another option. Maybe the most simple one. But from the internet I got that it will lose message sometimes. If true, that's terrible.
So, the most important thing is, use Kafka(also with zookeeper) on k8s, good or not in this use case?
Yes, running Kafka on Kubernetes is great. Check out this example: https://github.com/Yolean/kubernetes-kafka. It includes ZooKeeper and Kafka as StatefulSets.
PS. Running any of the services in your question on Kubernetes will be pleasant. You can Google the name of the service and "kubernetes" and find example manifests. Many examples here: https://github.com/kubernetes/charts.
For Kafka, you can find some suggestion here. Kubernetes 1.7+ supports local persistent volume, which may be good for Kafka deployment.
You can also take a look to the following project :
https://github.com/EnMasseProject/barnabas
It's about running Kafka on Kubernetes and OpenShift as well. It provides deploying with StatefulSets with persistent volumes or just in memory (for developing or just testing purpose). It provides deploying for Kafka Connect and Prometheus metrics as well.
Another simple configuration of Kafka/Zookeeper on Kubernetes in DigitalOcean with external access:
https://github.com/StanislavKo/k8s_digitalocean_kafka
You can connect to Kafka from outside of AWS/DO/GCE by regular binary protocol. Connection is PLAINTEXT or SASL_PLAINTEXT (user/password).
Kafka cluster is StatefulSet, so you can scale cluster easily.
I am currently setting up an infrastructure for an App in AWS. App is written in Django and is using Redis for some transactions. High availability is key for this application and I am having a hard time trying to get my head around how to configure Redis for High availability.
Application level changes are not an option.
Ideally I would like to have a redis setup, to which I can write and read and replicate and scale when required.
Current Setup is a Redis Fail-over scenario with HAProxy --> Redis Master --> Replica Slave.
Could someone guide me understand various options ? and how to scale redis for high availability !
Use AWS ElastiCache Redis Cluster with Multi-AZ. They provides automatic fail-over. It provides endpoint to access master node.
If master goes down AWS route your endpoint to another node. everything happens automatically, you don't have to do anything.
Just make sure that if you are doing DNS to IP caching in your application, its set to 60 seconds or so instead of default.
http://docs.aws.amazon.com/AmazonElastiCache/latest/UserGuide/AutoFailover.html
Thanks,
KS
Since scaling and high availability are usually different concepts (Unless you opt for a load balancing fault tolerance scheme), I hoped Redis would support both. However to my understanding, we cant mix Redis cluster with Sentinel? If so how do I create a deployment which will have multiple partitions and is also managed by Sentinel?
Is there a guide that describes how this is done?
Redis' cluster does its own failover, hence Sentinel is unneeded when operating in cluster mode: http://redis.io/topics/cluster-spec#availability