concourse-smuggler-resource: Concourse generic resource

Smuggler is a "generic-resource", that allows you to quickly implement any concourse resource with minimum boilerplate, even in the pipeline itself.

It allows you to run any random command/script into the resource container for the check/in/out.

Smuggler will basically:

1. parse the input JSON from concourse
2. set environment variables with the parameters
3. execute the provided shell script
4. parse the output and create a valid response for concourse.

Smuggler is ideal for PoC, prototyping, fast development or implementation of simple resources.

Basic example

The following resource definition will generate random numbers using the sh ${RANDOM} variable.

get in the job some_job writes the random number in the file specified by the parameter params.target_file. It also provides the current date in the metadata.

# Add the custom resource type
# See https://concourse.ci/configuring-resource-types.html
resource_types:
- name: smuggler
  type: docker-image
  source:
    repository: redfactorlabs/concourse-smuggler-resource
    tag: alpine

resources:
# A randon number generator
- name: random_number_generator
  type: smuggler
  source:
    smuggler_debug: true
    target_file: random_number_file
    commands:
      check: |
        echo "${RANDOM}" > ${SMUGGLER_OUTPUT_DIR}/versions
      in: |
        echo "${SMUGGLER_VERSION_ID}" > \
          ${SMUGGLER_DESTINATION_DIR}/${SMUGGLER_target_file}
        echo "date=$(date)" > ${SMUGGLER_OUTPUT_DIR}/metadata

jobs:
# A example job using our new resource
- name: some_job
  plan:
  - get: random_number_generator
    trigger: true
  - task: print_the_number
    config:
      platform: linux
      image_resource:
        type: docker-image
        source:
          repository: alpine
      inputs:
      - name: random_number_generator
        params:
          target_file: my_random_number_file
      run:
        path: sh
        args:
        - -ec
        - |
          cat random_number_generator/my_random_number_file

Other examples

Check the examples directory for examples of hacks and resources.

Some to highlight:

• ssh-keygen resource
• ssh-keygen-s3 resource: Generates a SSH key and stores it in S3.
• s3-with-default resource: Extends the official S3 resource to allow define a default value if the object is missing.

Using smuggler-concourse

Defining check/in/out commands

Use commands.check, commands.in or commands.out to provide the script to execute. All of them are optional:

• commands.check: Called to check and find new versions. Write the versions to ${SMUGGLER_OUTPUT_DIR}/versions, one line for each version.

• commands.in: called by the get step to fetch a resource. Write the data into ${SMUGGLER_DESTINATION_DIR}

• commands.out: called by the put step to upload the resource. The input files from previous steps in the job would be in ${SMUGGLER_SOURCES_DIR}

Input & output

The check/in/out scripts communicate with smuggler/concourse via:

• Environment variables:

  Variable	example	available in	description
  SMUGGLER_<param_name>	SMUGGLER_id_rsa	check/in/out	Parameters from source.* or params.*
  SMUGGLER_VERSION_<key>	SMUGGLER_VERSION_ID	check/in	Environment variable with the latest resource version retrieved. \ Not be defined in first run of check.
  SMUGGLER_OUTPUT_DIR		check/in/out	The directory to write versions and metadata.
  SMUGGLER_DESTINATION_DIR		in	The directory to write the retrieved data to.
  SMUGGLER_SOURCES_DIR		out	The directory with files from previous steps in the job

  Important: Note that SMUGGLER_OUTPUT_DIR with SMUGGLER_DESTINATION_DIR or SMUGGLER_SOURCES_DIR are different directories.

• ${SMUGGLER_OUTPUT_DIR}/versions: For check/in/out.

  • Optional, only processed if no json is written in stdout.
  • Smuggler will automatically add the default key ID.
  • Restrictions:
    • check: Your command must write here the versions found, one line per version.
    • in: Optional, if no version is written, smuggler will use the same as passed to the command as input. Only the first line is taken into account.
    • out: Mandatory, you must always specify a version for out, as concourse does not provide the version in the input. Only the first line is taken into account.

• ${SMUGGLER_OUTPUT_DIR}/metadata: For in/out Optional. the metadata for concourse as a multiline file with key=value pairs.

• ${SMUGGLER_DESTINATION_DIR}/: For in. The directory to write the retrieved data to.

• ${SMUGGLER_SOURCES_DIR}/*/*: For out. The directories with files from previous steps in the job.

• stdin: For check/in/out. Raw JSON with as it is sent from concourse and as described in the implementing concourse resources documentation.

  This allows your command parse the request directly, or pass it to a wrapped resource.

  Note: If filter_raw_request: true, all the specific smuggler configuration will be filtered out (source.commands, source.smuggler_params, params.smuggler_params, etc.).

• stdout: For check/in/out, Optional. verbatim JSON response request as described in the implementing concourse resources documentation.

  Note: if you print anything to stdout that is not JSON, the output will be not be passed to concourse, but instead dump to stderr.

Resource parameters

Any additional parameter in the source of the definition, or passed to the get or put step as params, would be passed as environment variables to the script with the prefix SMUGGLER_. e.g.SMUGGLER_param1=value1, SMUGGLER_param2=value2.

For example in this definition:

resources:
- name: random_number_generator
  type: smuggler
  source:
    commands:
      check: |
        ...
      in: |
        ...
    global_config_entry: value1

jobs:
- name: some_job
  plan:
  - get: random_number_generator
    trigger: true
    params:
      specific_get_config_entry: value2

Smuggler would set SMUGGLER_global_config_entry for check and in, and SMUGGLER_specific_get_config_entry for the in command.

Smuggler specific parameters

Smuggler understands these parameters:

• commands.{check,in,out} to define the commands as described above.

• smuggler_debug: [true|false]. Optional. it will print debugging information to the stderr.

• filter_raw_request: [true|false]: Optional. Would remove the smuggler specific parameters from the JSON passed via stdin to the script.

• smuggler_params.<param>: Optional. Allows group the parameters so they can filtered out with filter_raw_request.

Parameter priorities

Parameters can be defined in different places so parameters with the same name would be overridden depending where they are declared (first has more priority)

1. /opt/resource/smuggler.yml in the docker image.
2. resource definition, source.smuggler_params.<param>
3. resource definition, source.<param>
4. get/put step, params.smuggler_params.<param>
5. get/put step, params.<param>

This allows easily define default values for parameters in your resources.

Logging and troubleshooting

All the operations would log into /tmp/smuggler.log in the container. Use the parameter smuggler_debug: true to print the log to stderr that would display the log in the concourse UI.

You can intercept the container to read the log or interact with the commands directly:

fly -t demo intercept -c pipeline_name/resource_name # intercept a check

fly -t demo intercept -j pipeline_name/job_nome # intercept a get/put

In /tmp/smuggler.log you can find the exact command used to call the resource, so you can execute it again by copy&paste for quick troubleshooting:

2017/09/27 23:23:32 [INFO] Smuggler command called as:
/opt/resource/in /tmp/build/get <<"EOF"
{
  "source": {
    "commands": {
      "check": "echo \"${RANDOM}\" \u003e ${SMUGGLER_OUTPUT_DIR}/versions\n",
      "in": "echo \"${SMUGGLER_VERSION_ID}\" \u003e ${SMUGGLER_DESTINATION_DIR}/random_number\n"
    },
    "smuggler_debug": true
  },
  "version": {
    "ID": "1480"
  }
}
EOF

Advanced usage

Bundle smuggler configuration into the docker image

You can optionally write the same configuration of the source section in the resource container image, in /opt/resource/smuggler.yml.

The content of that file will be merged with the request, so that any parameter and command defined in the pipeline, will override the ones defined in smuggler.yml.

This way smuggler becomes a framework to create any kind of resource with very little boilerplate.

Wrapping other resources with smuggler

Smuggler passes the raw JSON request from concourse from stdin and returns back the response from stdout (if it is a valid response).

Additionally, with source.filter_raw_request all the smuggler config will be strip from the request in stdin.

This way it is really easy to wrap any third party resource and change their behaviour. Simply copy the other resource commands in your image and call them directly.

For example, use S3 resource to generate some default content if the file is not in the bucket, and behave as usual otherwise:

---
filter_raw_request: true
commands:
  check: |
    /opt/resource/wrapped/s3/check > response.json
    # If it is the first run, just dispatch a - string to for 'in' to be triggered
    jq 'if . == [] then [{ "version_id":"-"}] else . end' < response.json

  in: |
    if [ "${SMUGGLER_VERSION_version_id}" == "-" ]; then
      # First run, simply print the default content
      echo "${SMUGGLER_default_content}" > ${SMUGGLER_DESTINATION_DIR}/${SMUGGLER_versioned_file}
    else
      # First run, simply print the default content
      /opt/resource/wrapped/s3/in ${SMUGGLER_DESTINATION_DIR}
    fi

  out: /opt/resource/wrapped/s3/out ${SMUGGLER_SOURCES_DIR}

Complex commands and inline scripts

Commands can be defined using these two syntaxes:

1. a bash/sh script using multiline literal strings in yaml

   This is great for simple bash scripts.

2. A hash with path: <string> and args: [<string>, ...]

   This would allow you to use any embedded scripting language in your definition, like bash, python, perl, ruby...

Supported tags and Dockerfiles

• alpine or x.x.x-alpine Dockerfile.alpine
• ubuntu or x.x.x-ubuntu Dockerfile.ubuntu

Contributions

Smuggling is fun! Share it! Send over or comment us your hacks and implementations.

See the AUTHORS file for contributions.

Credits

I stoled a lot of code around in github, specially from other resources like s3-resource. Thanks to all of you!