⚠️ Repo Archive Notice

As of Nov 13, 2020, charts in this repo will no longer be updated. For more information, see the Helm Charts Deprecation and Archive Notice, and Update.

Redis-cache

This chart will allow us to use redis as a pure in-memory cache, this uses a special utility to perform master-slave promotion which overcomes this problem, K8s could restart the master way before it is detected and agreed among the redis-sentinels.

DEPRECATION NOTICE

This chart is deprecated and no longer supported.

###Prerequisites

Kubernetes 1.10+

Install Redis-cache chart as an in-memory cache.

Uses 7MB redis:4.0.12-alpine image which is extremely light weight
Uses redis-sentinel-k8s for automatic slave promotion if master fails, feel free to fork.
Super fast caching as no persistence involved
Has Pod Disruption Budget
Uses Statefulset
Has Anti-Affinity Configured

Quick Benchmark comparison between redis with and without persistence enabled, as you can notice the writes are at least 3 times slower.

Redis persistence enabled

$ k exec -i -t ${REPLICA-NAME} -c redis -- redis-benchmark -q -h ${REPLICA-NAME}.${POD-NAME}.${NAMESPACE} -p 6379 -t set,get -n 100000 -d 100 -r 1000000
SET: 22026.43 requests per second
GET: 76161.46 requests per second

Redis without persistence

$ k exec -i -t ${REPLICA-NAME} -c redis -- redis-benchmark -q -h ${REPLICA-NAME}.${POD-NAME}.${NAMESPACE} -p 6379 -t set,get -n 100000 -d 100 -r 1000000
SET: 60060.06 requests per second
GET: 89285.71 requests per second

Here is a sample demo of master slave promotion.

Install this chart

$helm install -n dev incubator/redis-cache/
NAME:   dev
LAST DEPLOYED: Wed Apr 12 23:25:56 2017
NAMESPACE: default
STATUS: DEPLOYED

RESOURCES:
==> v1/Service
NAME    CLUSTER-IP  EXTERNAL-IP  PORT(S)   AGE
rd-dev  None        <none>       6379/TCP  0s

==> policy/v1beta1/PodDisruptionBudget
NAME    MIN-AVAILABLE  ALLOWED-DISRUPTIONS  AGE
rd-dev  2              0                    0s

==> apps/v1beta1/StatefulSet
NAME    DESIRED  CURRENT  AGE
rd-dev  3        0        0s


NOTES:
1. To Find which replica is the master
  kubectl exec -i -t rd-dev-0 -c redis -- redis-cli -h rd-dev-0.rd-dev.default -p 6379 info replication

Wait until the PODs are created and check which replica is the master (by default it creates 3 replicas with 1 master and 2 slaves)

$kubectl get pods
NAME                  READY     STATUS    RESTARTS   AGE
rd-dev-0              2/2       Running   0          57s
rd-dev-1              2/2       Running   0          41s
rd-dev-2              2/2       Running   0          29s

$kubectl exec -i -t rd-dev-0 -c redis -- redis-cli -h rd-dev-0.rd-dev.default -p 6379 info replication
# Replication
role:master
connected_slaves:2
slave0:ip=10.244.2.18,port=6379,state=online,offset=29,lag=0
slave1:ip=10.244.1.16,port=6379,state=online,offset=29,lag=0
master_repl_offset:29
repl_backlog_active:1
repl_backlog_size:1048576
repl_backlog_first_byte_offset:2
repl_backlog_histlen:28

Set a Key

$kubectl exec -i -t rd-dev-0 -c redis -- redis-cli -h rd-dev-0.rd-dev.default -p 6379 set foo bar
OK

Check if that is replicated in any of the slaves

$kubectl exec -i -t rd-dev-0 -c redis -- redis-cli -h rd-dev-2.rd-dev.default -p 6379 get foo
"bar"

Kill the master

$kubectl delete po/rd-dev-0
pod "rd-dev-0" deleted

Wait until the kubernetes restarts rd-dev-0, once this is up you can check sentinel-micro's logs to find out which of the slave is now elected as the new master.

$kubectl logs rd-dev-0 sentinel-micro
I0412 18:07:08.633263       1 redis_sentinel_k8s.go:368] Available endpoints are [rd-dev-2.rd-dev.default.svc.cluster.local rd-dev-1.rd-dev.default.svc.cluster.local]
I0412 18:07:08.633392       1 redis_sentinel_k8s.go:194] Processing rd-dev-2.rd-dev.default.svc.cluster.local
I0412 18:07:08.633446       1 redis_sentinel_k8s.go:194] Processing rd-dev-1.rd-dev.default.svc.cluster.local
R=&{ slave -1 7 937 rd-dev-0.rd-dev.default 6379 100 false <nil>}
R=&{ slave -1 7 937 rd-dev-0.rd-dev.default 6379 100 false <nil>}
I0412 18:07:08.645222       1 redis_sentinel_k8s.go:382] OldMaster=<nil> NewMaster=&{rd-dev-1.rd-dev.default:6379 slave -1 7 937 rd-dev-0.rd-dev.default 6379 100 false 0xc42000e300}
I0412 18:07:08.646876       1 redis_sentinel_k8s.go:398] New Master is rd-dev-1.rd-dev.default:6379, All the slaves are re-configured to replicate from this
I0412 18:07:08.647040       1 redis_sentinel_k8s.go:421] Redis-Sentinal-micro Finished

As you can see rd-dev-1 is the new master while rd-dev-0 and rd-dev-2 are its slaves Lets check if our original key foo is retained across master restarts

$kubectl exec -i -t rd-dev-0 -c redis -- redis-cli -h rd-dev-0.rd-dev.default -p 6379 get foo
"bar"

Note: Care should be taken when you scale down the number of replicas of this statefulset. Please make sure that current redis-master is not among to be scaled down replicas.