docker compose: No assignment of host names when bridge is used - docker

Question

In order to make every container part of the default bridge, I added network_mode: bridge in every service. These became part of bridge but the containers are not getting attached with the hostnames. Below is the config.
docker-compose.yml
version: '2'
services:
elasticsearch:
build:
context: elasticsearch/
args:
ELK_VERSION: $ELK_VERSION
volumes:
- ./elasticsearch/config/elasticsearch.yml:/usr/share/elasticsearch/config/elasticsearch.yml:ro
ports:
- "9200:9200"
- "9300:9300"
environment:
ES_JAVA_OPTS: "-Xmx256m -Xms256m"
network_mode: bridge
hostname: elasticsearch
logstash:
build:
context: logstash/
args:
ELK_VERSION: $ELK_VERSION
volumes:
- ./logstash/config/logstash.yml:/usr/share/logstash/config/logstash.yml:ro
- ./logstash/pipeline:/usr/share/logstash/pipeline:ro
ports:
- "5000:5000"
- "9600:9600"
environment:
LS_JAVA_OPTS: "-Xmx256m -Xms256m"
network_mode: bridge
depends_on:
- elasticsearch
kibana:
build:
context: kibana/
args:
ELK_VERSION: $ELK_VERSION
volumes:
- ./kibana/config/:/usr/share/kibana/config:ro
ports:
- "5601:5601"
network_mode: bridge
depends_on:
- elasticsearch
Docker compose up
$ docker-compose up -d
Creating docker-elk_elasticsearch_1 ... done
Creating docker-elk_kibana_1 ... done
Creating docker-elk_logstash_1 ... done
Docker network inspect
$ docker network inspect bridge
[
{
"Name": "bridge",
"Id": "f561a85fb2b22bbf251545c7021d57020cf152bd3a5c3c061c7d6b0cb4e267e5",
"Created": "2018-09-19T07:02:49.36259364Z",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "172.17.0.0/16",
"Gateway": "172.17.0.1"
}
]
},
"Internal": false,
"Attachable": false,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {
"0aedc2ce900b8a51f028e58a85c8db9480fd2816874a608540a899a4daab32fd": {
"Name": "docker-elk_kibana_1",
"EndpointID": "df3af338e0accb880ccc44323e5581064ee8ef84574485f1928d12dc415b598e",
"MacAddress": "02:42:ac:11:00:05",
"IPv4Address": "172.17.0.5/16",
"IPv6Address": ""
},
"3f2088847bd8e958a047093b1af879c91c4071f57f0105bb7bf80fb8df832d41": {
"Name": "docker-elk_logstash_1",
"EndpointID": "6588b7eece43144833ae2f9ffe753e3cc6c70d0891a587c3e9a4e9ca84993532",
"MacAddress": "02:42:ac:11:00:06",
"IPv4Address": "172.17.0.6/16",
"IPv6Address": ""
},
"ace35bb6fadd50823f64e9075b5972e6e3b24e8b73273a41e7a48f9eeff89da1": {
"Name": "roach",
"EndpointID": "dd058e3e9f46b2459f14a2e5bdf96eae277e81dcf7ac2e6ac1c97d8220ead30d",
"MacAddress": "02:42:ac:11:00:03",
"IPv4Address": "172.17.0.3/16",
"IPv6Address": ""
},
"f90378063d2a0157110b77af39f2526347f1ea9634839e0d2c0c584fb14ff957": {
"Name": "docker-elk_elasticsearch_1",
"EndpointID": "294a2f67196788135f370bbf83526395ba4401afb25db9eb0b59fba7fd358912",
"MacAddress": "02:42:ac:11:00:04",
"IPv4Address": "172.17.0.4/16",
"IPv6Address": ""
},
"f954c218e5ab15c83c2a0e2c848549c18879613f6f46d07f7ebf71cc89b6e55b": {
"Name": "rabbitmq",
"EndpointID": "e675ddc6076fe2256553e8b367a82aa36f488457e06ae6cf969c2e04feeb9fb8",
"MacAddress": "02:42:ac:11:00:02",
"IPv4Address": "172.17.0.2/16",
"IPv6Address": ""
}
},
"Options": {
"com.docker.network.bridge.default_bridge": "true",
"com.docker.network.bridge.enable_icc": "true",
"com.docker.network.bridge.enable_ip_masquerade": "true",
"com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
"com.docker.network.bridge.name": "docker0",
"com.docker.network.driver.mtu": "1500"
},
"Labels": {}
}
]
Docker inspect elasticsearch
$ docker inspect docker-elk_elasticsearch_1
"NetworkSettings": {
"Bridge": "",
"SandboxID": "31a438f8fcb3dd8efca37260e77d346f21239b36d8bb30f5f08db4b79880a5c9",
"HairpinMode": false,
"LinkLocalIPv6Address": "",
"LinkLocalIPv6PrefixLen": 0,
"Ports": {
"9200/tcp": [
{
"HostIp": "0.0.0.0",
"HostPort": "9200"
}
],
"9300/tcp": [
{
"HostIp": "0.0.0.0",
"HostPort": "9300"
}
]
},
"SandboxKey": "/var/run/docker/netns/31a438f8fcb3",
"SecondaryIPAddresses": null,
"SecondaryIPv6Addresses": null,
"EndpointID": "294a2f67196788135f370bbf83526395ba4401afb25db9eb0b59fba7fd358912",
"Gateway": "172.17.0.1",
"GlobalIPv6Address": "",
"GlobalIPv6PrefixLen": 0,
"IPAddress": "172.17.0.4",
"IPPrefixLen": 16,
"IPv6Gateway": "",
"MacAddress": "02:42:ac:11:00:04",
"Networks": {
"bridge": {
"IPAMConfig": null,
"Links": null,
"Aliases": null,
"NetworkID": "f561a85fb2b22bbf251545c7021d57020cf152bd3a5c3c061c7d6b0cb4e267e5",
"EndpointID": "294a2f67196788135f370bbf83526395ba4401afb25db9eb0b59fba7fd358912",
"Gateway": "172.17.0.1",
"IPAddress": "172.17.0.4",
"IPPrefixLen": 16,
"IPv6Gateway": "",
"GlobalIPv6Address": "",
"GlobalIPv6PrefixLen": 0,
"MacAddress": "02:42:ac:11:00:04",
"DriverOpts": null
}
}
}
Kibana Logs where elastic search is inaccessible:
$ docker logs docker-elk_kibana_1
{"type":"log","#timestamp":"2018-09-20T05:27:05Z","tags":["warning","elasticsearch","admin"],"pid":1,"message":"Unable to revive connection: http://elasticsearch:9200/"}
{"type":"log","#timestamp":"2018-09-20T05:27:05Z","tags":["warning","elasticsearch","admin"],"pid":1,"message":"No living connections"}
However, everything works fine with below config where I haven't provided any network related config.
version: '2'
services:
elasticsearch:
build:
context: elasticsearch/
args:
ELK_VERSION: $ELK_VERSION
volumes:
- ./elasticsearch/config/elasticsearch.yml:/usr/share/elasticsearch/config/elasticsearch.yml:ro
ports:
- "9200:9200"
- "9300:9300"
environment:
ES_JAVA_OPTS: "-Xmx256m -Xms256m"
logstash:
build:
context: logstash/
args:
ELK_VERSION: $ELK_VERSION
volumes:
- ./logstash/config/logstash.yml:/usr/share/logstash/config/logstash.yml:ro
- ./logstash/pipeline:/usr/share/logstash/pipeline:ro
ports:
- "5000:5000"
- "9600:9600"
environment:
LS_JAVA_OPTS: "-Xmx256m -Xms256m"
depends_on:
- elasticsearch
kibana:
build:
context: kibana/
args:
ELK_VERSION: $ELK_VERSION
volumes:
- ./kibana/config/:/usr/share/kibana/config:ro
ports:
- "5601:5601"
depends_on:
- elasticsearch

Answer 1

Containers on the default bridge network cannot refer each other by host name, they can only refer each other by IP. You can find this in the docs here https://docs.docker.com/network/bridge/#differences-between-user-defined-bridges-and-the-default-bridge.
Containers on the default bridge network can only access each other by IP addresses, unless you use the --link option, which is considered legacy. On a user-defined bridge network, containers can resolve each other by name or alias.
The solution is to define your custom bridge network in the Compose file with networks as described here https://docs.docker.com/compose/compose-file/#networks and add every container to this user defined network. On this network containers can resolve each other by name.