Elasticsearch service running on minikube cluster not reachable from within the cluster - elasticsearch

Question

I am using kompose to deploy this docker-compose.yaml
version: '3'
services:
webapp:
build:
context: ../../../
dockerfile: config/docker/dev/Dockerfile-dev
container_name: myWebApp-dev
command: ["/bin/sh", "-ec","sleep 1000"]
image: 'localhost:5002/webapp:1'
environment:
- ELASTICSEARCH_URL=http://elasticsearch:9200
- ELASTICSEARCH_HOST=elasticsearch
labels:
kompose.image-pull-policy: 'IfNotPresent'
kompose.service.type: nodeport
ports:
- "4000:4000"
- "3000:3000"
depends_on:
- elasticsearch
links:
- elasticsearch
elasticsearch:
image: docker.elastic.co/elasticsearch/elasticsearch:7.0.1
container_name: elasticsearch
command: ["/bin/sh", "-ec","sleep 1000"]
environment:
- node.name=elasticsearch
- discovery.seed_hosts=es02
- cluster.initial_master_nodes=elasticsearch,es02
- cluster.name=docker-cluster
- bootstrap.memory_lock=true
- "ES_JAVA_OPTS=-Xms512m -Xmx512m"
ulimits:
memlock:
soft: -1
hard: -1
volumes:
- esdata01:/usr/share/elasticsearch/data
ports:
- 9200:9200
- 9300:9300
es02:
image: docker.elastic.co/elasticsearch/elasticsearch:7.0.1
container_name: es02
command: ["/bin/sh", "-ec","sleep 1000"]
environment:
- node.name=es02
- discovery.seed_hosts=elasticsearch
- cluster.initial_master_nodes=elasticsearch,es02
- cluster.name=docker-cluster
- bootstrap.memory_lock=true
- "ES_JAVA_OPTS=-Xms512m -Xmx512m"
ulimits:
memlock:
soft: -1
hard: -1
volumes:
- esdata02:/usr/share/elasticsearch/data
to minikube.
The elasticsearch pod and service are running. However, the webapp cannot access the elasticsearch cluster as I get a connection refused error when curling from within the webapp pod -> curl: (7) Failed to connect to 10.108.5.31 port 9200: Connection refused. Does anyone know what the reason for this problem is and how to fix it?

Answer 1

In elasticsearch section, you have a shell command to sleep. And, never started any elasticsearch instances after that.
command: ["/bin/sh", "-ec","sleep 1000"]
So, looks like, there is no elasticsearch running inside the container and that's why connection refused is happening.
To Fix:
Get rid of command: of elasticsearch and es02, that way, default command will be used.
Note:
Now, When the elasticsearch starts, You will face two error (described below) with this compose yaml in kubernetes. These are unrelated to this post, But I will try to giving you direction where to look.
ERROR: [2] bootstrap checks failed
[1]: memory locking requested for elasticsearch process but memory is not locked
[2]: max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]
Here,
you need to update host system for vm.max_map_count. Exec into minikube virtualbox by minikube ssh and run sudo -s sysctl -w vm.max_map_count=262144 to change the map_count of host kernel. It will work, because docker/container doesn't provide kernel level isolation.
For minikube,
minikube ssh 'sudo -s sysctl -w vm.max_map_count=262144'
ulimit is not available in kompose. See issue here. So either you have to get rid of both, bootstrap.memory_lock=true from environment: sections, or you may need to update the docker image. This question is already asked here in stackoverflow.
So the improved kompose yaml (works well on minikube):
version: '3'
services:
webapp:
build:
context: ../../../
dockerfile: config/docker/dev/Dockerfile-dev
container_name: myWebApp-dev
command: ["/bin/sh", "-ec","sleep 1000"]
image: 'localhost:5002/webapp:1'
environment:
- ELASTICSEARCH_URL=http://elasticsearch:9200
- ELASTICSEARCH_HOST=elasticsearch
labels:
kompose.image-pull-policy: 'IfNotPresent'
kompose.service.type: nodeport
ports:
- "4000:4000"
- "3000:3000"
depends_on:
- elasticsearch
links:
- elasticsearch
elasticsearch:
image: docker.elastic.co/elasticsearch/elasticsearch:7.0.1
container_name: elasticsearch
environment:
- node.name=elasticsearch
- discovery.seed_hosts=es02
- cluster.initial_master_nodes=elasticsearch,es02
- cluster.name=docker-cluster
- "ES_JAVA_OPTS=-Xms512m -Xmx512m"
volumes:
- esdata01:/usr/share/elasticsearch/data
ports:
- 9200:9200
- 9300:9300
es02:
image: docker.elastic.co/elasticsearch/elasticsearch:7.0.1
container_name: es02
environment:
- node.name=es02
- discovery.seed_hosts=elasticsearch
- cluster.initial_master_nodes=elasticsearch,es02
- cluster.name=docker-cluster
- "ES_JAVA_OPTS=-Xms512m -Xmx512m"
volumes:
- esdata02:/usr/share/elasticsearch/data
However, I would suggest to follow the elasticsearch official doc instead of using compose to install elasticsearch in kubernetes.