Can Elasticsearch version 5.5.3 run on Kubernetes with StatefulSet?

Question

I've been trying to get Elasticsearch running on K8s using the newly-promoted-to-stable helm chart, which works fine, BTW, for elasticsearch v 6.4.2. However, we're tied to a grails app that requires elasticsearch v 5.5.3, for which we don't have the ability to upgrade. I've downgraded the elasticsearch image version in the chart to 5.5.3 (and also tried v 5.6.12) but it fails to start.

I looked into the elasticsearch operator, but it's currently set up to work with AWS S3 storage types, out of the box, and GCP with a little work (although no snapshot ability). Before I dive into this, I'd like to know if it will work with 5.5.3, to begin with.

Does anyone know if I can get elasticsearch v 5.5.3 running in a k8s cluster? I would say using a k8s StatefulSet at a minimum.

Thanks!

Update

I suppose I should have given the errors that the existing helm chart is having when downgrading elasticsearch image to 5.5.3.

master-0 pod fails to start with:

Error injecting constructor, ElasticsearchException[java.io.IOException: failed to read [id:15, legacy:false, file:/usr/share/elasticsearch/data/nodes/0/_state/global-15.st]]; nested: IOException[failed to read [id:15, legacy:false, file:/usr/share/elasticsearch/data/nodes/0/_state/global-15.st]]; nested: ElasticsearchException[Unknown license version found, please upgrade all nodes to the latest elasticsearch-license plugin]; at org.elasticsearch.gateway.GatewayMetaState.<init>(Unknown Source) while locating org.elasticsearch.gateway.GatewayMetaState for parameter 4 at org.elasticsearch.gateway.GatewayService.<init>(Unknown Source) while locating org.elasticsearch.gateway.GatewayService Caused by: ElasticsearchException[java.io.IOException: failed to read [id:15, legacy:false, file:/usr/share/elasticsearch/data/nodes/0/_state/global-15.st]]; nested: IOException[failed to read [id:15, legacy:false, file:/usr/share/elasticsearch/data/nodes/0/_state/global-15.st]]; nested: ElasticsearchException[Unknown license version found, please upgrade all nodes to the latest elasticsearch-license plugin];

The client pods fail with:

[2018-10-22T17:52:51,835][WARN ][o.e.d.z.UnicastZenPing ] [elasticsearch-client-6bf954c595-7zlpc] failed to resolve host [elasticsearch-discovery] java.net.UnknownHostException: elasticsearch-discovery

Clearly, it's expecting a later elasticsearch version.

Answer 1

The short answer here is that ElasticSearch 5.5.3 should work with Kubernetes. Note the configs for 5.5.3 are slightly different, I believe they changed after 5.6 where for example the made x-pack enabled by default, and yes use a StatefulSet or start from the existing stable Helm chart.