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kubernetes-elasticsearch-cluster's Introduction

kubernetes-elasticsearch-cluster

Elasticsearch (5.6.0) cluster on top of Kubernetes made easy.

Table of Contents

Abstract

Elasticsearch best-practices recommend to separate nodes in three roles:

  • Master nodes - intended for clustering management only, no data, no HTTP API
  • Client nodes - intended for client usage, no data, with HTTP API
  • Data nodes - intended for storing and indexing data, no HTTP API

Given this, I'm going to demonstrate how to provision a production grade scenario consisting of 3 master, 2 client and 2 data nodes.

(Very) Important notes

  • Elasticsearch pods need for an init-container to run in privileged mode, so it can set some VM options. For that to happen, the kubelet should be running with args --allow-privileged, otherwise the init-container will fail to run.

  • By default, ES_JAVA_OPTS is set to -Xms256m -Xmx256m. This is a very low value but many users, i.e. minikube users, were having issues with pods getting killed because hosts were out of memory. One can change this in the deployment descriptors available in this repository.

  • As of the moment, Kubernetes pod descriptors use an emptyDir for storing data in each data node container. This is meant to be for the sake of simplicity and should be adapted according to one's storage needs.

  • The stateful directory contains an example which deploys the data pods as a StatefulSet. These use a volumeClaimTemplates to provision persistent storage for each pod.

Pre-requisites

  • Kubernetes cluster with alpha features enabled (tested with v1.7.2 on top of Vagrant + CoreOS), thas's because curator is a CronJob object which comes from batch/v2alpha1, to enable it, just add --runtime-config=batch/v2alpha1=true into your kube-apiserver options.
  • kubectl configured to access the cluster master API Server

Build images (optional)

Providing one's own version of the images automatically built from this repository will not be supported. This is an optional step. One has been warned.

Test

Deploy

kubectl create -f es-discovery-svc.yaml
kubectl create -f es-svc.yaml
kubectl create -f es-master.yaml

Wait until es-master deployment is provisioned, and

kubectl create -f es-client.yaml
kubectl create -f es-data.yaml

Wait for containers to be in the Running state and check one of the Elasticsearch master nodes logs:

$ kubectl get svc,deployment,pods
NAME                          CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
svc/elasticsearch             10.100.169.170   <none>        9200/TCP   1m
svc/elasticsearch-discovery   10.100.186.247   <none>        9300/TCP   1m
svc/kubernetes                10.100.0.1       <none>        443/TCP    5h

NAME               DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
deploy/es-client   2         2         2            2           28s
deploy/es-data     2         2         2            2           21s
deploy/es-master   3         3         3            3           1m

NAME                            READY     STATUS    RESTARTS   AGE
po/es-client-3800087898-hm9jc   1/1       Running   0          28s
po/es-client-3800087898-xsr0f   1/1       Running   0          28s
po/es-data-369535600-5b0q2      1/1       Running   0          21s
po/es-data-369535600-t0w5c      1/1       Running   0          21s
po/es-master-275923172-lpcjb    1/1       Running   0          1m
po/es-master-275923172-ngnn1    1/1       Running   0          1m
po/es-master-275923172-nj8fb    1/1       Running   0          1m

$ kubectl logs po/es-master-275923172-lpcjb
[2017-09-12T16:20:47,413][INFO ][o.e.n.Node               ] [es-master-275923172-lpcjb] initializing ...
[2017-09-12T16:20:47,575][INFO ][o.e.e.NodeEnvironment    ] [es-master-275923172-lpcjb] using [1] data paths, mounts [[/data (/dev/sda9)]], net usable_space [13.7gb], net total_space [15.5gb], spins? [possibly], types [ext4]
[2017-09-12T16:20:47,577][INFO ][o.e.e.NodeEnvironment    ] [es-master-275923172-lpcjb] heap size [247.5mb], compressed ordinary object pointers [true]
[2017-09-12T16:20:47,580][INFO ][o.e.n.Node               ] [es-master-275923172-lpcjb] node name [es-master-275923172-lpcjb], node ID [A9M6aaPzRuS-SVOLl7Vj9A]
[2017-09-12T16:20:47,581][INFO ][o.e.n.Node               ] [es-master-275923172-lpcjb] version[5.6.0], pid[25], build[781a835/2017-09-07T03:09:58.087Z], OS[Linux/4.13.0-coreos/amd64], JVM[Oracle Corporation/OpenJDK 64-Bit Server VM/1.8.0_131/25.131-b11]
[2017-09-12T16:20:47,582][INFO ][o.e.n.Node               ] [es-master-275923172-lpcjb] JVM arguments [-XX:+UseConcMarkSweepGC, -XX:CMSInitiatingOccupancyFraction=75, -XX:+UseCMSInitiatingOccupancyOnly, -XX:+DisableExplicitGC, -XX:+AlwaysPreTouch, -Xss1m, -Djava.awt.headless=true, -Dfile.encoding=UTF-8, -Djna.nosys=true, -Djdk.io.permissionsUseCanonicalPath=true, -Dio.netty.noUnsafe=true, -Dio.netty.noKeySetOptimization=true, -Dlog4j.shutdownHookEnabled=false, -Dlog4j2.disable.jmx=true, -Dlog4j.skipJansi=true, -XX:+HeapDumpOnOutOfMemoryError, -Xms256m, -Xmx256m, -Des.path.home=/elasticsearch]
[2017-09-12T16:20:49,008][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [aggs-matrix-stats]
[2017-09-12T16:20:49,008][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [ingest-common]
[2017-09-12T16:20:49,009][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [lang-expression]
[2017-09-12T16:20:49,009][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [lang-groovy]
[2017-09-12T16:20:49,009][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [lang-mustache]
[2017-09-12T16:20:49,009][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [lang-painless]
[2017-09-12T16:20:49,010][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [parent-join]
[2017-09-12T16:20:49,011][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [percolator]
[2017-09-12T16:20:49,011][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [reindex]
[2017-09-12T16:20:49,011][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [transport-netty3]
[2017-09-12T16:20:49,012][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] loaded module [transport-netty4]
[2017-09-12T16:20:49,013][INFO ][o.e.p.PluginsService     ] [es-master-275923172-lpcjb] no plugins loaded
[2017-09-12T16:20:51,356][INFO ][o.e.d.DiscoveryModule    ] [es-master-275923172-lpcjb] using discovery type [zen]
[2017-09-12T16:20:52,237][INFO ][o.e.n.Node               ] [es-master-275923172-lpcjb] initialized
[2017-09-12T16:20:52,241][INFO ][o.e.n.Node               ] [es-master-275923172-lpcjb] starting ...
[2017-09-12T16:20:52,618][INFO ][o.e.t.TransportService   ] [es-master-275923172-lpcjb] publish_address {10.244.48.2:9300}, bound_addresses {10.244.48.2:9300}
[2017-09-12T16:20:52,648][INFO ][o.e.b.BootstrapChecks    ] [es-master-275923172-lpcjb] bound or publishing to a non-loopback or non-link-local address, enforcing bootstrap checks
[2017-09-12T16:20:55,954][INFO ][o.e.c.s.ClusterService   ] [es-master-275923172-lpcjb] new_master {es-master-275923172-lpcjb}{A9M6aaPzRuS-SVOLl7Vj9A}{akW5Qz09RoeBHV16KUnPJg}{10.244.48.2}{10.244.48.2:9300}, added {{es-master-275923172-nj8fb}{wsmiXLlWRrSEhhN4NPcRMQ}{FmQuB67SSUSKke9w7CQjjA}{10.244.14.3}{10.244.14.3:9300},}, reason: zen-disco-elected-as-master ([1] nodes joined)[{es-master-275923172-nj8fb}{wsmiXLlWRrSEhhN4NPcRMQ}{FmQuB67SSUSKke9w7CQjjA}{10.244.14.3}{10.244.14.3:9300}]
[2017-09-12T16:20:55,995][INFO ][o.e.n.Node               ] [es-master-275923172-lpcjb] started
[2017-09-12T16:20:56,079][INFO ][o.e.g.GatewayService     ] [es-master-275923172-lpcjb] recovered [0] indices into cluster_state
[2017-09-12T16:20:56,278][INFO ][o.e.c.s.ClusterService   ] [es-master-275923172-lpcjb] added {{es-master-275923172-ngnn1}{GZdGXETmQOy3Qi0Ylb82Sg}{Hu9QRDpTRF6FuIJE7rmfMA}{10.244.68.2}{10.244.68.2:9300},}, reason: zen-disco-node-join[{es-master-275923172-ngnn1}{GZdGXETmQOy3Qi0Ylb82Sg}{Hu9QRDpTRF6FuIJE7rmfMA}{10.244.68.2}{10.244.68.2:9300}]
[2017-09-12T16:21:16,850][INFO ][o.e.c.s.ClusterService   ] [es-master-275923172-lpcjb] added {{es-client-3800087898-hm9jc}{7qP40AKVRKmBwilpkZkepw}{Y7GGJeawSDqUwrf8TgaoEQ}{10.244.48.3}{10.244.48.3:9300},}, reason: zen-disco-node-join[{es-client-3800087898-hm9jc}{7qP40AKVRKmBwilpkZkepw}{Y7GGJeawSDqUwrf8TgaoEQ}{10.244.48.3}{10.244.48.3:9300}]
[2017-09-12T16:21:17,154][INFO ][o.e.c.s.ClusterService   ] [es-master-275923172-lpcjb] added {{es-client-3800087898-xsr0f}{70HsVVjQQ8yrBlnGwyOIRg}{OB6x3fdRSbeQB4hz3e5hXg}{10.244.14.4}{10.244.14.4:9300},}, reason: zen-disco-node-join[{es-client-3800087898-xsr0f}{70HsVVjQQ8yrBlnGwyOIRg}{OB6x3fdRSbeQB4hz3e5hXg}{10.244.14.4}{10.244.14.4:9300}]
[2017-09-12T16:21:24,380][INFO ][o.e.c.s.ClusterService   ] [es-master-275923172-lpcjb] added {{es-data-369535600-t0w5c}{Q7z4j40fQeOTZP8SlKrmaw}{3GSJruvaTTCL2rEl3uEPOw}{10.244.68.3}{10.244.68.3:9300},}, reason: zen-disco-node-join[{es-data-369535600-t0w5c}{Q7z4j40fQeOTZP8SlKrmaw}{3GSJruvaTTCL2rEl3uEPOw}{10.244.68.3}{10.244.68.3:9300}]
[2017-09-12T16:21:25,228][INFO ][o.e.c.s.ClusterService   ] [es-master-275923172-lpcjb] added {{es-data-369535600-5b0q2}{I2_SC1kfSbCFZ_FvTPHGNw}{AlG4-saZRU6r4Hd4CufRyg}{10.244.14.5}{10.244.14.5:9300},}, reason: zen-disco-node-join[{es-data-369535600-5b0q2}{I2_SC1kfSbCFZ_FvTPHGNw}{AlG4-saZRU6r4Hd4CufRyg}{10.244.14.5}{10.244.14.5:9300}]

As we can assert, the cluster is up and running. Easy, wasn't it?

Access the service

Don't forget that services in Kubernetes are only acessible from containers in the cluster. For different behavior one should configure the creation of an external load-balancer. While it's supported within this example service descriptor, its usage is out of scope of this document, for now.

$ kubectl get svc elasticsearch
NAME            CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
elasticsearch   10.100.169.170   <none>        9200/TCP   1m

From any host on the Kubernetes cluster (that's running kube-proxy or similar), run:

$ curl http://10.100.169.170:9200

One should see something similar to the following:

{
  "name" : "es-client-3800087898-xsr0f",
  "cluster_name" : "myesdb",
  "cluster_uuid" : "9BYou_7nTiuz-PMcplEJuw",
  "version" : {
    "number" : "5.6.0",
    "build_hash" : "781a835",
    "build_date" : "2017-09-07T03:09:58.087Z",
    "build_snapshot" : false,
    "lucene_version" : "6.6.0"
  },
  "tagline" : "You Know, for Search"
}

Or if one wants to see cluster information:

$ curl http://10.100.169.170:9200/_cluster/health?pretty

One should see something similar to the following:

{
  "cluster_name" : "myesdb",
  "status" : "green",
  "timed_out" : false,
  "number_of_nodes" : 7,
  "number_of_data_nodes" : 2,
  "active_primary_shards" : 0,
  "active_shards" : 0,
  "relocating_shards" : 0,
  "initializing_shards" : 0,
  "unassigned_shards" : 0,
  "delayed_unassigned_shards" : 0,
  "number_of_pending_tasks" : 0,
  "number_of_in_flight_fetch" : 0,
  "task_max_waiting_in_queue_millis" : 0,
  "active_shards_percent_as_number" : 100.0
}

Pod anti-affinity

One of the main advantages of running Elasticsearch on top of Kubernetes is how resilient the cluster becomes, particularly during node restarts. However if all data pods are scheduled onto the same node(s), this advantage decreases significantly and may even result in no data pods being available.

It is then highly recommended, in the context of the solution described in this repository, that one adopts pod anti-affinity in order to guarantee that two data pods will never run on the same node.

Here's an example:

spec:
  affinity:
    podAntiAffinity:
      preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 100
        podAffinityTerm:
          labelSelector:
            matchExpressions:
            - key: role
              operator: In
              values:
              - data
          topologyKey: kubernetes.io/hostname
  containers:
  - (...)

Deploying with Helm

Helm charts for a basic (non-stateful) ElasticSearch deployment are maintained at https://github.com/clockworksoul/helm-elasticsearch. With Helm properly installed and configured, standing up a complete cluster is almost trivial:

$ git clone https://github.com/clockworksoul/helm-elasticsearch.git
$ helm install helm-elasticsearch

Install plug-ins

The image used in this repo is very minimalist. However, one can install additional plug-ins at will by simply specifying the ES_PLUGINS_INSTALL environment variable in the desired pod descriptors. For instance, to install Google Cloud Storage and X-Pack plug-ins it would be like follows:

- name: "ES_PLUGINS_INSTALL"
  value: "repository-gcs,x-pack"

Clean up with Curator

Additionally, one can run a CronJob that will periodically run Curator to clean up indices (or do other actions on the Elasticsearch cluster).

kubectl create -f es-curator-config.yaml
kubectl create -f es-curator.yaml

Please, confirm the job has been created.

$ kubectl get cronjobs
NAME      SCHEDULE    SUSPEND   ACTIVE    LAST-SCHEDULE
curator   1 0 * * *   False     0         <none>

The job is configured to run once a day at 1 minute past midnight and delete indices that are older than 3 days.

Notes

  • One can change the schedule by editing the cron notation in es-curator.yaml.
  • One can change the action (e.g. delete older than 3 days) by editing the es-curator-config.yaml.
  • The definition of the action_file.yaml is quite self-explaining for simple set-ups. For more advanced configuration options, please consult the Curator Documentation.

If one wants to remove the curator job, just run:

kubectl delete cronjob curator
kubectl delete configmap curator-config

Various parameters of the cluster, including replica count and memory allocations, can be adjusted by editing the helm-elasticsearch/values.yaml file. For information about Helm, please consult the complete Helm documentation.

<a id="kibana>

Kibana

Additionally, one can also add Kibana to the mix. In order to do so, one must use a container image of Kibana without x-pack, as it's not supported by the Elasticsearch container images used in this repository.

An image is already provided but one can build their own like follows:

FROM docker.elastic.co/kibana/kibana:5.5.1
RUN bin/kibana-plugin remove x-pack

If ones does provide their own image, one must make sure to alter the following files before deploying:

kubectl create -f kibana.yaml
kubectl create -f kibana-svc.yaml

Kibana will be available through service kibana, and one will be able to access it from within the cluster or proxy it through the Kubernetes API Server, as follows:

https://<API_SERVER_URL>/api/v1/proxy/namespaces/default/services/kibana/proxy

One can also create an Ingress to expose the service publicly or simly use the service nodeport. In the case one proceeds to do so, one must change the environment variable SERVER_BASEPATH to the match their environment.

FAQ

Why does NUMBER_OF_MASTERS differ from number of master-replicas?

The default value for this environment variable is 2, meaning a cluster will need a minimum of 2 master nodes to operate. If a cluster has 3 masters and one dies, the cluster still works. Minimum master nodes are usually n/2 + 1, where n is the number of master nodes in a cluster. If a cluster has 5 master nodes, one should have a minimum of 3, less than that and the cluster stops. If one scales the number of masters, make sure to update the minimum number of master nodes through the Elasticsearch API as setting environment variable will only work on cluster setup. More info: https://www.elastic.co/guide/en/elasticsearch/guide/1.x/_important_configuration_changes.html#_minimum_master_nodes

How can I customize elasticsearch.yaml?

Read a different config file by settings env var path.conf=/path/to/my/config/. Another option would be to build one's own image from this repository

Troubleshooting

No up-and-running site-local

One of the errors one may come across when running the setup is the following error:

[2016-11-29T01:28:36,515][WARN ][o.e.b.ElasticsearchUncaughtExceptionHandler] [] uncaught exception in thread [main]
org.elasticsearch.bootstrap.StartupException: java.lang.IllegalArgumentException: No up-and-running site-local (private) addresses found, got [name:lo (lo), name:eth0 (eth0)]
	at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:116) ~[elasticsearch-5.0.1.jar:5.0.1]
	at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:103) ~[elasticsearch-5.0.1.jar:5.0.1]
	at org.elasticsearch.cli.SettingCommand.execute(SettingCommand.java:54) ~[elasticsearch-5.0.1.jar:5.0.1]
	at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:96) ~[elasticsearch-5.0.1.jar:5.0.1]
	at org.elasticsearch.cli.Command.main(Command.java:62) ~[elasticsearch-5.0.1.jar:5.0.1]
	at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:80) ~[elasticsearch-5.0.1.jar:5.0.1]
	at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:73) ~[elasticsearch-5.0.1.jar:5.0.1]
Caused by: java.lang.IllegalArgumentException: No up-and-running site-local (private) addresses found, got [name:lo (lo), name:eth0 (eth0)]
	at org.elasticsearch.common.network.NetworkUtils.getSiteLocalAddresses(NetworkUtils.java:187) ~[elasticsearch-5.0.1.jar:5.0.1]
	at org.elasticsearch.common.network.NetworkService.resolveInternal(NetworkService.java:246) ~[elasticsearch-5.0.1.jar:5.0.1]
 	at org.elasticsearch.common.network.NetworkService.resolveInetAddresses(NetworkService.java:220) ~[elasticsearch-5.0.1.jar:5.0.1]
 	at org.elasticsearch.common.network.NetworkService.resolveBindHostAddresses(NetworkService.java:130) ~[elasticsearch-5.0.1.jar:5.0.1]
 	at org.elasticsearch.transport.TcpTransport.bindServer(TcpTransport.java:575) ~[elasticsearch-5.0.1.jar:5.0.1]
 	at org.elasticsearch.transport.netty4.Netty4Transport.doStart(Netty4Transport.java:182) ~[?:?]
 	at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:68) ~[elasticsearch-5.0.1.jar:5.0.1]
 	at org.elasticsearch.transport.TransportService.doStart(TransportService.java:182) ~[elasticsearch-5.0.1.jar:5.0.1]
 	at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:68) ~[elasticsearch-5.0.1.jar:5.0.1]
 	at org.elasticsearch.node.Node.start(Node.java:525) ~[elasticsearch-5.0.1.jar:5.0.1]
 	at org.elasticsearch.bootstrap.Bootstrap.start(Bootstrap.java:211) ~[elasticsearch-5.0.1.jar:5.0.1]
 	at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:288) ~[elasticsearch-5.0.1.jar:5.0.1]
 	at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:112) ~[elasticsearch-5.0.1.jar:5.0.1]
 	... 6 more
[2016-11-29T01:28:37,448][INFO ][o.e.n.Node               ] [kIEYQSE] stopping ...
[2016-11-29T01:28:37,451][INFO ][o.e.n.Node               ] [kIEYQSE] stopped
[2016-11-29T01:28:37,452][INFO ][o.e.n.Node               ] [kIEYQSE] closing ...
[2016-11-29T01:28:37,464][INFO ][o.e.n.Node               ] [kIEYQSE] closed

This is related to how the container binds to network ports (defaults to _local_). It will need to match the actual node network interface name, which depends on what OS and infrastructure provider one uses. For instance, if the primary interface on the node is p1p1 then that is the value that needs to be set for the NETWORK_HOST environment variable. Please see the documentation for reference of options.

In order to workaround this, set NETWORK_HOST environment variable in the pod descriptors as follows:

- name: "NETWORK_HOST"
  value: "_eth0_" #_p1p1_ if interface name is p1p1, _ens4_ if interface name is ens4, and so on.

(IPv6) org.elasticsearch.bootstrap.StartupException: BindTransportException

Intermittent failures occur when the local network interface has both IPv4 and IPv6 addresses, and Elasticsearch tries to bind to the IPv6 address first. If the IPv4 address is chosen first, Elasticsearch starts correctly.

In order to workaround this, set NETWORK_HOST environment variable in the pod descriptors as follows:

- name: "NETWORK_HOST"
  value: "_eth0:ipv4_" #_p1p1:ipv4_ if interface name is p1p1, _ens4:ipv4_ if interface name is ens4, and so on.

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