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Running DynamoDB Local service container on CircleCI 2.0

tl;dr use a custom entrypoint in your CircleCI 2.0 config to limit Java memory to 1G.

The new CircleCI 2.0 docker configuration supports a "primary image" (listed first) which runs all the "steps" as well as zero or many "service images" (listed subsequently). The "service images", although not running in the same container as the primary present as if local to the primary.

It sort of feels like mixing many docker containers together.

Enough talk, in this example, I show how easy it is to run DynamoDB Local in a separate container but at the same time present it to the primary as 127.0.0.1:8000:

version: 2
workflows:
  version: 2
  tests:
    jobs:
      - test

jobs:

  test:

    working_directory: /go/src/github.com/remind101/r101-myapp

    docker:

      # Primary container image where all the steps run.
      - image: circleci/golang:1.8

      # Service container image made available to the primary container at `host: localhost`
      - image: dwmkerr/dynamodb:41
        # custom entrypoint to limit RAM to 1G to prevent OOM on CircleCI 2.0.
        # https://circleci.com/docs/2.0/configuration-reference/#docker--machine--macosexecutor
        entrypoint: ["java", "-Xmx1G", "-jar", "DynamoDBLocal.jar"]

    steps:
      - checkout
      - run: make test_verbose

Troubleshooting

When I first tried to use this image, any test which tried to reach out to DynamoDB via 127.0.0.1:8000 had the following exception:

Test Panicked
Error creating table group_associations: RequestError: send request failed
caused by: Post http://127.0.0.1:8000/: dial tcp 127.0.0.1:8000: getsockopt: connection refused
/usr/local/go/src/runtime/panic.go:489

It seems the docker-dynamodb (DynamoDB Local) container failed to start and exited like this:

Initializing DynamoDB Local with the following configuration:
Port: 8000
InMemory:     false
DbPath:       null
SharedDb:     false
shouldDelayTransientStatuses: false
CorsParams:   *


Exited with code 137

Apparently Exit code 137 is a classic Docker + Java error code caused by an OOM (out of memory).

By default, projects on CircleCI build in virtual environments with 4GB of RAM but this is shared and Java acts greedy when inside a container so it needs a limit by adding -Xmx1G to the entrypoint!

References:




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© Russell Ballestrini.