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:

  1. docker pull nats

Run the NATS server image:

  1. docker run nats

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

  1. docker network create nats

And start the server

  1. docker run --name nats --network nats --rm -p 4222:4222 -p 8222:8222 nats --http_port 8222

Creating a NATS Cluster

First run a server with the ports exposed on the ‘nats’ docker network:

  1. 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
  1. [1] 2021/09/28 09:21:56.554756 [INF] Starting nats-server
  2. [1] 2021/09/28 09:21:56.554864 [INF]   Version:  2.6.1
  3. [1] 2021/09/28 09:21:56.554878 [INF]   Git:      [c91f0fe]
  4. [1] 2021/09/28 09:21:56.554894 [INF]   Name:     NDIQLLD2UGGPSAEYBKHW3S2JB2DXIAFHMIWWRUBAX7FC4RTQX4ET2JNQ
  5. [1] 2021/09/28 09:21:56.555001 [INF]   ID:       NDIQLLD2UGGPSAEYBKHW3S2JB2DXIAFHMIWWRUBAX7FC4RTQX4ET2JNQ
  6. [1] 2021/09/28 09:21:56.557658 [INF] Starting http monitor on 0.0.0.0:8222
  7. [1] 2021/09/28 09:21:56.557967 [INF] Listening for client connections on 0.0.0.0:4222
  8. [1] 2021/09/28 09:21:56.559224 [INF] Server is ready
  9. [1] 2021/09/28 09:21:56.559375 [INF] Cluster name is NATS
  10. [1] 2021/09/28 09:21:56.559433 [INF] Listening for route connections on 0.0.0.0:6222

Next, start another couple of servers and point them to the seed server to make them form a cluster:

  1. docker run --name nats-1 --network nats --rm nats --cluster_name NATS --cluster nats://0.0.0.0:6222 --routes=nats://ruser:T0pS3cr3t@nats:6222
  2. docker run --name nats-2 --network nats --rm nats --cluster_name NATS --cluster nats://0.0.0.0:6222 --routes=nats://ruser:T0pS3cr3t@nats:6222

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:

  1. curl http://127.0.0.1:8222/routez
  1. {
  2.   "server_id": "NDIQLLD2UGGPSAEYBKHW3S2JB2DXIAFHMIWWRUBAX7FC4RTQX4ET2JNQ",
  3.   "now": "2021-09-28T09:22:15.8019785Z",
  4.   "num_routes": 2,
  5.   "routes": [
  6.     {
  7.       "rid": 5,
  8.       "remote_id": "NBRAUY3YSVFYU7BFWI2YF5VPQFGO2XCKKAHYZ7ETCMGB3SQY3FDFTYOQ",
  9.       "did_solicit": false,
  10.       "is_configured": false,
  11.       "ip": "172.18.0.3",
  12.       "port": 59092,
  13.       "pending_size": 0,
  14.       "rtt": "1.2505ms",
  15.       "in_msgs": 4,
  16.       "out_msgs": 3,
  17.       "in_bytes": 2714,
  18.       "out_bytes": 1943,
  19.       "subscriptions": 35
  20.     },
  21.     {
  22.       "rid": 6,
  23.       "remote_id": "NA5STTST5GYFCD22M2I3VDJ57LQKOU35ZVWKQY3O5QRFGOPC3RFDIDVJ",
  24.       "did_solicit": false,
  25.       "is_configured": false,
  26.       "ip": "172.18.0.4",
  27.       "port": 47424,
  28.       "pending_size": 0,
  29.       "rtt": "1.2008ms",
  30.       "in_msgs": 4,
  31.       "out_msgs": 1,
  32.       "in_bytes": 2930,
  33.       "out_bytes": 833,
  34.       "subscriptions": 35
  35.     }
  36.   ]
  37. }

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.

  1. version: "3.5"
  2. services:
  3.   nats:
  4.     image: nats
  5.     ports:
  6.       - "8222:8222"
  7.     command: "--cluster_name NATS --cluster nats://0.0.0.0:6222 --http_port 8222 "
  8.     networks: ["nats"]
  9.   nats-1:
  10.     image: nats
  11.     command: "--cluster_name NATS --cluster nats://0.0.0.0:6222 --routes=nats://ruser:T0pS3cr3t@nats:6222"
  12.     networks: ["nats"]
  13.     depends_on: ["nats"]
  14.   nats-2:
  15.     image: nats
  16.     command: "--cluster_name NATS --cluster nats://0.0.0.0:6222 --routes=nats://ruser:T0pS3cr3t@nats:6222"
  17.     networks: ["nats"]
  18.     depends_on: ["nats"]
  20. networks:
  21.   nats:
  22.     name: nats

Now we use Docker Compose to create the cluster that will be using the nats network:

  1. docker-compose -f nats-cluster.yaml up
  1. [+] Running 3/3
  2.  ⠿ Container xxx_nats_1    Created
  3.  ⠿ Container xxx_nats-1_1  Created
  4.  ⠿ Container xxx_nats-2_1  Created
  5. Attaching to nats-1_1, nats-2_1, nats_1
  6. nats_1    | [1] 2021/09/28 10:42:36.742844 [INF] Starting nats-server
  7. nats_1    | [1] 2021/09/28 10:42:36.742898 [INF]   Version:  2.6.1
  8. nats_1    | [1] 2021/09/28 10:42:36.742913 [INF]   Git:      [c91f0fe]
  9. nats_1    | [1] 2021/09/28 10:42:36.742929 [INF]   Name:     NCZIIQ6QT4KT5K5WBP7H2RRBM4MSYD4C2TVSRZOZN57EHX6VTF4EWXAU
  10. nats_1    | [1] 2021/09/28 10:42:36.742954 [INF]   ID:       NCZIIQ6QT4KT5K5WBP7H2RRBM4MSYD4C2TVSRZOZN57EHX6VTF4EWXAU
  11. nats_1    | [1] 2021/09/28 10:42:36.745289 [INF] Starting http monitor on 0.0.0.0:8222
  12. nats_1    | [1] 2021/09/28 10:42:36.745737 [INF] Listening for client connections on 0.0.0.0:4222
  13. nats_1    | [1] 2021/09/28 10:42:36.750381 [INF] Server is ready
  14. nats_1    | [1] 2021/09/28 10:42:36.750669 [INF] Cluster name is NATS
  15. nats_1    | [1] 2021/09/28 10:42:36.751444 [INF] Listening for route connections on 0.0.0.0:6222
  16. nats-1_1  | [1] 2021/09/28 10:42:37.709888 [INF] Starting nats-server
  17. nats-1_1  | [1] 2021/09/28 10:42:37.709977 [INF]   Version:  2.6.1
  18. nats-1_1  | [1] 2021/09/28 10:42:37.709999 [INF]   Git:      [c91f0fe]
  19. nats-1_1  | [1] 2021/09/28 10:42:37.710023 [INF]   Name:     NBHTXXY3HYZVPXITYQ73BSDA5CQZINTKYRM23XFI46RWWTTUP5TAXQMB
  20. nats-1_1  | [1] 2021/09/28 10:42:37.710042 [INF]   ID:       NBHTXXY3HYZVPXITYQ73BSDA5CQZINTKYRM23XFI46RWWTTUP5TAXQMB
  21. nats-1_1  | [1] 2021/09/28 10:42:37.711646 [INF] Listening for client connections on 0.0.0.0:4222
  22. nats-1_1  | [1] 2021/09/28 10:42:37.712197 [INF] Server is ready
  23. nats-1_1  | [1] 2021/09/28 10:42:37.712376 [INF] Cluster name is NATS
  24. nats-1_1  | [1] 2021/09/28 10:42:37.712469 [INF] Listening for route connections on 0.0.0.0:6222
  25. nats_1    | [1] 2021/09/28 10:42:37.718918 [INF] 172.18.0.4:52950 - rid:4 - Route connection created
  26. nats-1_1  | [1] 2021/09/28 10:42:37.719906 [INF] 172.18.0.3:6222 - rid:4 - Route connection created
  27. nats-2_1  | [1] 2021/09/28 10:42:37.731357 [INF] Starting nats-server
  28. nats-2_1  | [1] 2021/09/28 10:42:37.731518 [INF]   Version:  2.6.1
  29. nats-2_1  | [1] 2021/09/28 10:42:37.731531 [INF]   Git:      [c91f0fe]
  30. nats-2_1  | [1] 2021/09/28 10:42:37.731543 [INF]   Name:     NCG6UQ2N3IHE6OS76TL46RNZBAPHNUCQSA64FDFHG5US2LLJOQLD5ZK2
  31. nats-2_1  | [1] 2021/09/28 10:42:37.731554 [INF]   ID:       NCG6UQ2N3IHE6OS76TL46RNZBAPHNUCQSA64FDFHG5US2LLJOQLD5ZK2
  32. nats-2_1  | [1] 2021/09/28 10:42:37.732893 [INF] Listening for client connections on 0.0.0.0:4222
  33. nats-2_1  | [1] 2021/09/28 10:42:37.733431 [INF] Server is ready
  34. nats-2_1  | [1] 2021/09/28 10:42:37.733491 [INF] Cluster name is NATS
  35. nats-2_1  | [1] 2021/09/28 10:42:37.733835 [INF] Listening for route connections on 0.0.0.0:6222
  36. nats_1    | [1] 2021/09/28 10:42:37.740860 [INF] 172.18.0.5:54616 - rid:5 - Route connection created
  37. nats-2_1  | [1] 2021/09/28 10:42:37.741557 [INF] 172.18.0.3:6222 - rid:4 - Route connection created
  38. nats-1_1  | [1] 2021/09/28 10:42:37.743981 [INF] 172.18.0.5:6222 - rid:5 - Route connection created
  39. nats-2_1  | [1] 2021/09/28 10:42:37.744332 [INF] 172.18.0.4:40250 - rid:5 - Route connection created

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.

  1. docker run --network nats --rm -it synadia/nats-box

Inside the container

  1. nats sub -s nats://nats:4222 hello &
  2. nats pub -s "nats://nats-1:4222" hello first
  3. nats pub -s "nats://nats-2:4222" hello second

Also stopping the seed node to which the subscription was done, should trigger an automatic failover to the other nodes:

  1. docker-compose -f nats-cluster.yaml stop nats

Output extract

  1. ... 
  2. 16e55f1c4f3c:~# 10:47:28 Disconnected due to: EOF, will attempt reconnect
  3. 10:47:28 Disconnected due to: EOF, will attempt reconnect
  4. 10:47:28 Reconnected [nats://172.18.0.4:4222]

Publishing again will continue to work after the reconnection:

  1. nats pub -s "nats://nats-1:4222" hello again
  2. nats pub -s "nats://nats-2:4222" hello again

Tutorial

See the NATS Docker tutorial for more instructions on using the NATS server Docker image.