examples.md

Example LRPs

We provide some full examples of DesiredLRPCreateRequest JSON payloads for different types of LRPs below.

Web server via bash and nc

This DesiredLRP runs an extremely simple HTTP server on port 8080 via bash and nc, in the preloaded cflinuxfs2 as its distinguished unprivileged user, vcap:

{
  "process_guid": "my-nc-server-def456",
  "domain": "my-fresh-domain",
  "rootfs": "preloaded:cflinuxfs2",
  "instances": 1,
  "action": {
    "run": {
      "path": "bash",
      "args": [
        "-c",
        "set -e; mkfifo request; while true; do\n{\nread < request\n\necho -n -e \"HTTP/1.1 200 OK\\r\\nContent-Length: ${#INSTANCE_INDEX}\\r\\n\\r\\n${INSTANCE_INDEX}\"\n} | nc -l 0.0.0.0 $PORT > request;\ndone\n}"
      ],
      "env": [{"name":"PORT", "value":"8080"}],
      "user": "vcap"
    }
  },
  "ports": [
    8080
  ]
}

This example is based on an LRP used in Diego's inigo integration test suite.

Redis docker image

This DesiredLRP runs one instance of a Redis server via the official Redis Docker image:

{
  "process_guid": "my-redis-server-abc123",
  "domain": "my-fresh-domain",
  "rootfs": "docker:///redis",
  "instances": 1,
  "action": {
    "run": {
      "path": "/entrypoint.sh",
      "args": [
        "redis-server"
      ],
      "dir": "/data",
      "user": "root"
    }
  },
  "ports": [
    6379
  ]
}

Many elements of the LRP specification were determined from the redis 3.0 Dockerfile:

• The rootfs field itself refers to the official redis Docker image on Docker Hub.
• The RunAction takes its path and args values from the ENTRYPOINT and CMD directives in the Dockerfile, and its dir value from the WORKDIR directive. For the user value, we provide root, since this is the implicit user for a Docker image that does not specify a USER directive in its Dockerfile.
• The ports field corresponds to the ports listed in the EXPOSE directives in the Dockerfile.

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