NATS and Docker

NATS Server Containerization

The NATS server is provided as a Docker image on Docker Hub that you can run using the Docker daemon. The NATS server Docker image is extremely lightweight, coming in under 10 MB in size.
Synadia actively maintains and supports the NATS server Docker image.

Usage

To use the Docker container image, install Docker and pull the public image:
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docker pull nats
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Run the NATS server image:
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docker run nats
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By default the NATS server exposes multiple ports:
  • 4222 is for clients.
  • 8222 is an HTTP management port for information reporting.
  • 6222 is a routing port for clustering.
  • Use -p or -P to customize.
To run a server with the ports exposed on a docker network:
First create the 'docker network' nats
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docker network create nats
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And start the server
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docker run --name nats --network nats --rm -p 4222:4222 -p 8222:8222 nats --http_port 8222
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Creating a NATS Cluster

First run a server with the ports exposed on the 'nats' docker network:
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docker run --name nats --network nats --rm -p 4222:4222 -p 8222:8222 nats --http_port 8222 --cluster_name NATS --cluster nats://0.0.0.0:6222
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[1] 2021/09/28 09:21:56.554756 [INF] Starting nats-server
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[1] 2021/09/28 09:21:56.554864 [INF] Version: 2.6.1
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[1] 2021/09/28 09:21:56.554878 [INF] Git: [c91f0fe]
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[1] 2021/09/28 09:21:56.554894 [INF] Name: NDIQLLD2UGGPSAEYBKHW3S2JB2DXIAFHMIWWRUBAX7FC4RTQX4ET2JNQ
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[1] 2021/09/28 09:21:56.555001 [INF] ID: NDIQLLD2UGGPSAEYBKHW3S2JB2DXIAFHMIWWRUBAX7FC4RTQX4ET2JNQ
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[1] 2021/09/28 09:21:56.557658 [INF] Starting http monitor on 0.0.0.0:8222
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[1] 2021/09/28 09:21:56.557967 [INF] Listening for client connections on 0.0.0.0:4222
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[1] 2021/09/28 09:21:56.559224 [INF] Server is ready
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[1] 2021/09/28 09:21:56.559375 [INF] Cluster name is NATS
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[1] 2021/09/28 09:21:56.559433 [INF] Listening for route connections on 0.0.0.0:6222
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Next, start another couple of servers and point them to the seed server to make them form a cluster:
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docker run --name nats-1 --network nats --rm nats --cluster_name NATS --cluster nats://0.0.0.0:6222 --routes=nats://ruser:[email protected]:6222
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docker run --name nats-2 --network nats --rm nats --cluster_name NATS --cluster nats://0.0.0.0:6222 --routes=nats://ruser:[email protected]:6222
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NOTE Since the Docker image protects routes using credentials we need to provide them above. Extracted from Docker image configuration
To verify the routes are connected, you can make a request to the monitoring endpoint on /routez as follows and confirm that there are now 2 routes:
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curl http://127.0.0.1:8222/routez
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{
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"server_id": "NDIQLLD2UGGPSAEYBKHW3S2JB2DXIAFHMIWWRUBAX7FC4RTQX4ET2JNQ",
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"now": "2021-09-28T09:22:15.8019785Z",
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"num_routes": 2,
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"routes": [
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{
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"rid": 5,
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"remote_id": "NBRAUY3YSVFYU7BFWI2YF5VPQFGO2XCKKAHYZ7ETCMGB3SQY3FDFTYOQ",
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"did_solicit": false,
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"is_configured": false,
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"ip": "172.18.0.3",
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"port": 59092,
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"pending_size": 0,
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"rtt": "1.2505ms",
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"in_msgs": 4,
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"out_msgs": 3,
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"in_bytes": 2714,
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"out_bytes": 1943,
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"subscriptions": 35
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},
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{
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"rid": 6,
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"remote_id": "NA5STTST5GYFCD22M2I3VDJ57LQKOU35ZVWKQY3O5QRFGOPC3RFDIDVJ",
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"did_solicit": false,
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"is_configured": false,
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"ip": "172.18.0.4",
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"port": 47424,
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"pending_size": 0,
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"rtt": "1.2008ms",
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"in_msgs": 4,
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"out_msgs": 1,
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"in_bytes": 2930,
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"out_bytes": 833,
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"subscriptions": 35
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}
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]
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}
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Creating a NATS Cluster with Docker Compose

It is also straightforward to create a cluster using Docker Compose. Below is a simple example that uses a network named nats to create a full mesh cluster.
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version: "3.5"
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services:
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nats:
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image: nats
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ports:
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- "8222:8222"
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command: "--cluster_name NATS --cluster nats://0.0.0.0:6222 --http_port 8222 "
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networks: ["nats"]
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nats-1:
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image: nats
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command: "--cluster_name NATS --cluster nats://0.0.0.0:6222 --routes=nats://ruser:[email protected]:6222"
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networks: ["nats"]
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depends_on: ["nats"]
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nats-2:
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image: nats
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command: "--cluster_name NATS --cluster nats://0.0.0.0:6222 --routes=nats://ruser:[email protected]:6222"
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networks: ["nats"]
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depends_on: ["nats"]
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networks:
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nats:
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name: nats
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Now we use Docker Compose to create the cluster that will be using the nats network:
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docker-compose -f nats-cluster.yaml up
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[+] Running 3/3
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⠿ Container xxx_nats_1 Created
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⠿ Container xxx_nats-1_1 Created
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⠿ Container xxx_nats-2_1 Created
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Attaching to nats-1_1, nats-2_1, nats_1
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nats_1 | [1] 2021/09/28 10:42:36.742844 [INF] Starting nats-server
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nats_1 | [1] 2021/09/28 10:42:36.742898 [INF] Version: 2.6.1
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nats_1 | [1] 2021/09/28 10:42:36.742913 [INF] Git: [c91f0fe]
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nats_1 | [1] 2021/09/28 10:42:36.742929 [INF] Name: NCZIIQ6QT4KT5K5WBP7H2RRBM4MSYD4C2TVSRZOZN57EHX6VTF4EWXAU
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nats_1 | [1] 2021/09/28 10:42:36.742954 [INF] ID: NCZIIQ6QT4KT5K5WBP7H2RRBM4MSYD4C2TVSRZOZN57EHX6VTF4EWXAU
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nats_1 | [1] 2021/09/28 10:42:36.745289 [INF] Starting http monitor on 0.0.0.0:8222
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nats_1 | [1] 2021/09/28 10:42:36.745737 [INF] Listening for client connections on 0.0.0.0:4222
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nats_1 | [1] 2021/09/28 10:42:36.750381 [INF] Server is ready
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nats_1 | [1] 2021/09/28 10:42:36.750669 [INF] Cluster name is NATS
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nats_1 | [1] 2021/09/28 10:42:36.751444 [INF] Listening for route connections on 0.0.0.0:6222
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nats-1_1 | [1] 2021/09/28 10:42:37.709888 [INF] Starting nats-server
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nats-1_1 | [1] 2021/09/28 10:42:37.709977 [INF] Version: 2.6.1
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nats-1_1 | [1] 2021/09/28 10:42:37.709999 [INF] Git: [c91f0fe]
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nats-1_1 | [1] 2021/09/28 10:42:37.710023 [INF] Name: NBHTXXY3HYZVPXITYQ73BSDA5CQZINTKYRM23XFI46RWWTTUP5TAXQMB
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nats-1_1 | [1] 2021/09/28 10:42:37.710042 [INF] ID: NBHTXXY3HYZVPXITYQ73BSDA5CQZINTKYRM23XFI46RWWTTUP5TAXQMB
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nats-1_1 | [1] 2021/09/28 10:42:37.711646 [INF] Listening for client connections on 0.0.0.0:4222
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nats-1_1 | [1] 2021/09/28 10:42:37.712197 [INF] Server is ready
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nats-1_1 | [1] 2021/09/28 10:42:37.712376 [INF] Cluster name is NATS
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nats-1_1 | [1] 2021/09/28 10:42:37.712469 [INF] Listening for route connections on 0.0.0.0:6222
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nats_1 | [1] 2021/09/28 10:42:37.718918 [INF] 172.18.0.4:52950 - rid:4 - Route connection created
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nats-1_1 | [1] 2021/09/28 10:42:37.719906 [INF] 172.18.0.3:6222 - rid:4 - Route connection created
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nats-2_1 | [1] 2021/09/28 10:42:37.731357 [INF] Starting nats-server
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nats-2_1 | [1] 2021/09/28 10:42:37.731518 [INF] Version: 2.6.1
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nats-2_1 | [1] 2021/09/28 10:42:37.731531 [INF] Git: [c91f0fe]
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nats-2_1 | [1] 2021/09/28 10:42:37.731543 [INF] Name: NCG6UQ2N3IHE6OS76TL46RNZBAPHNUCQSA64FDFHG5US2LLJOQLD5ZK2
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nats-2_1 | [1] 2021/09/28 10:42:37.731554 [INF] ID: NCG6UQ2N3IHE6OS76TL46RNZBAPHNUCQSA64FDFHG5US2LLJOQLD5ZK2
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nats-2_1 | [1] 2021/09/28 10:42:37.732893 [INF] Listening for client connections on 0.0.0.0:4222
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nats-2_1 | [1] 2021/09/28 10:42:37.733431 [INF] Server is ready
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nats-2_1 | [1] 2021/09/28 10:42:37.733491 [INF] Cluster name is NATS
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nats-2_1 | [1] 2021/09/28 10:42:37.733835 [INF] Listening for route connections on 0.0.0.0:6222
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nats_1 | [1] 2021/09/28 10:42:37.740860 [INF] 172.18.0.5:54616 - rid:5 - Route connection created
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nats-2_1 | [1] 2021/09/28 10:42:37.741557 [INF] 172.18.0.3:6222 - rid:4 - Route connection created
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nats-1_1 | [1] 2021/09/28 10:42:37.743981 [INF] 172.18.0.5:6222 - rid:5 - Route connection created
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nats-2_1 | [1] 2021/09/28 10:42:37.744332 [INF] 172.18.0.4:40250 - rid:5 - Route connection created
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Testing the Clusters

Now, the following should work: make a subscription on one of the nodes and publish it from another node. You should be able to receive the message without problems.
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docker run --network nats --rm -it synadia/nats-box
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Inside the container
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nats sub -s nats://nats:4222 hello &
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nats pub -s "nats://nats-1:4222" hello first
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nats pub -s "nats://nats-2:4222" hello second
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Also stopping the seed node to which the subscription was done, should trigger an automatic failover to the other nodes:
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docker-compose -f nats-cluster.yaml stop nats
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Output extract
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...
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16e55f1c4f3c:~# 10:47:28 Disconnected due to: EOF, will attempt reconnect
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10:47:28 Disconnected due to: EOF, will attempt reconnect
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10:47:28 Reconnected [nats://172.18.0.4:4222]
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Publishing again will continue to work after the reconnection:
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nats pub -s "nats://nats-1:4222" hello again
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nats pub -s "nats://nats-2:4222" hello again
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Tutorial

See the NATS Docker tutorial for more instructions on using the NATS server Docker image.
Last modified 11d ago