Docker Component Requirements

Overview

Component developers are required to provide artifacts for the platform to be able to deploy your component including:

  • Component specification <docker-specification>
  • One or more Data Formats <data-formats> *unless they already exist
  • Docker image

In addition, components will have to be enhanced to be compliant with the DCAE platform in order to correctly be deployed and be managed. This page will discuss the changes which are grouped into the following categories:

Additional considerations are:

To help component developers to make and to test the changes needed to have components run on the platform, a command-line tool called dcae-cli is provided by the platform team. (Testing withing the dcae_cli tool is not yet available for Policy).

Service Registration

Every Docker component is registered with the platform’s service discovery layer. Docker components are not expected to make the explicit make registration calls because that is done by through a platform 3rd party registration service. A couple things are needed from component developers in order for this registration to occur successfully:

  1. Docker images must be created from a Dockerfile that has an EXPOSE instruction. This applies to components that listen on a port.
  2. Component healthcheck details must be provided in the Docker auxiliary component specification

Expose port

Components that listen on a specific port must explicitly declare in their Dockerfile that port using the EXPOSE instruction before building the image. Warning! At the current time, you can not expose multiple ports in your Dockerfile or registration will not work correctly. Warning! Be sure to choose a port that is available. This may vary by environment.

Health check

Component developers are required to provide a way for the platform to periodically check the health of their running components. The platform uses Consul to perform these periodic calls. Consul provides different types of check definitions. The details of the definition used by your component is to be provided through the Docker auxiliary specification.

Configuration Management

All configuration for a component is stored in CONSUL under the components uniquely generated name which is provided by the environment variable HOSTNAME as well as SERVICE_NAME. It is then made available to the component via a remote HTTP service call to CONFIG BINDING SERVICE.

The main entry in CONSUL for the component contains its generated application configuration. This is based on the submitted component specification, and consists of the interfaces (streams and services/calls) and parameters sections. Other entries may exist as well, under specific keys, such as :dmaap . Each key represents a specific type of information and is also available to the component by calling CONFIG BINDING SERVICE. More on this below.

Components are required to pull their generated application configuration at application startup. The component must provide an initialization script that retrieves the application configuration and reference that script in its Dockerfile. Other calls can be made to CONFIG BINDING SERVICE to retrieve DMaaP, or Policy Reconfiguration (not yet supported).

You can see more details on the generated application configuration here

Config Binding Service

The config binding service is a platform HTTP service that is responsible for providing clients with its fully resolve configuration JSON at startup, and also other configurations objects when requested.

At runtime, components should make an HTTP GET on:

<config binding service hostname>:<port>/service_component/NAME

For Docker components, NAME should be set to HOSTNAME, which is provided as an ENV variable to the container.

The binding service integrates with the streams and services section of the component specification. For example, if you specify that you call a service:

"services": {
    "calls": [{
        "config_key": "vnf-db",
        "request": {
            "format": "dcae.vnf.meta",
            "version": "1.0.0"
            },
        "response": {
            "format": "dcae.vnf.kpi",
            "version": "1.0.0"
            }
    }],
...
}

Then the config binding service will find all available IP addresses of services meeting the containers needs, and provide them to the container under your config_key:

// your configuration
{
    "vbf-db" :                 // see above
        [IP:Port1, IP:Port2,…] // all of these meet your needs, choose one.
}

Regarding <config binding service hostname>:<port>, there is DNS work going on to make this resolvable in a convenient way inside of your container. However, currently you will be given a name as an ENV variable, CONFIG_BINDING_SERVICE, and you will need to query Consul’s service discovery to get <config binding service hostname>:<port>.

Generated Application Configuration

The DCAE platform uses the component specification to generate the component’s application configuration provided at deployment time. The component developer should expect to use this configuration JSON in the component.

Pro-tip: As you build the component specification, use the dcae-cli dev command to see what the resulting application configuration will look like.

For both Docker and CDAP, when the component is deployed, any streams and services/calls specified, will be injected into the configuration under the following well known structure, along with all parameters. (services/provides is not passed in to the application config). Your component is required to parse this information if it has any DMaaP connections or interfaces with another DCAE component.

This is best served by an example.

The following component spec snippet (from String Matching):

"streams":{
    "subscribes": [{
      "format": "VES_specification",
      "version": "4.27.2",
      "type": "message_router",
      "config_key" : "mr_input"
    }],
    "publishes": [{
      "format": "VES_specification",
      "version": "4.27.2",
      "config_key": "mr_output",
      "type": "message_router"
     }]
  },
  "services":{
    "calls": [{
      "config_key" : "aai_broker_handle",
      "verb": "GET",
      "request": {
        "format": "get_with_query_params",
        "version": "1.0.0"
      },
      "response": {
        "format": "aai_broker_response",
        "version": "3.0.0"
      }
    }],
    "provides": []
  },

Will result in the following top level keys in the configuration (for CDAP, this will be under AppConfig)

"streams_publishes":{
   "mr_output":{                // notice the config key above
      "aaf_password":"XXX",
      "type":"message_router",
      "dmaap_info":{
         "client_role": null,
         "client_id": null,
         "location": null,
         "topic_url":"https://YOUR_HOST:3905/events/com.att.dcae.dmaap.FTL2.DCAE-CL-EVENT" // just an example
      },
      "aaf_username":"XXX"
   }
},
"streams_subscribes":{
   "mr_input":{                 // notice the config key above
      "aaf_password":"XXX",
      "type":"message_router",
      "dmaap_info":{
         "client_role": null,
         "client_id": null,
         "location": null,
         "topic_url":"https://YOUR_HOST:3905/events/com.att.dcae.dmaap.FTL2.TerrysStringMatchingTest" // just an example
      },
      "aaf_username":"XXX"
   }
},
"services_calls":{
   "aai_broker_handle":[        // notice the config key above
      "135.205.226.128:32768"   // based on deployment time, just an example
   ]
}

These keys will always be populated whether they are empty or not. So the minimum configuration you will get, (in the case of a component that provides an HTTP service, doesn’t call any services, and has no streams, is:

"streams_publishes":{},
"streams_subscribes":{},
"services_calls":{}

Thus your component should expect these well-known top level keys.

DMaaP

Components can be publishers or subscribers to either message router topics or data router feeds. This is defined in the component specification under the streams section where you can specify whether your component is expected to subscribe or to publish to a message router topic or to a data router feed. Given a composition with components that use DMaaP, the platform will provision the topic or feed and provide the necessary connection details at runtime for each DMaaP dependent component. These connection details are provided through your application’s generated configuration.

In order to test DMaaP connections in onboarding, the developer (currently) must provision all test topics and feeds manually and provide the dcae-cli with the connection details when deploying your application.

Even thought the DMaaP connection information is included in the generated application configuration, it may be obtained by doing a call as in this example:

curl http://<config binding service>:<port>/dmaap/jm416b.d345ada1-cc31-4121-a741-9007b9f64808.1-0-1.dcae-collectors-cli-pm

This would return the following:

{"cli_gamma_cisco_pm_config_stat":
    {
    "publish_url": "https://YOUR_HOST/publish/1362",
    "username": "mtl5-0",
    "log_url": null,
    "location": "mtl5-0",
    "password": "i5qji048hdm2e38f0bg872tnqd",
    "publisher_id": "1234"
    }
}

Policy Reconfiguration

(not yet supported)

Components must provide a way to receive policy reconfiguration, that is, configuration parameters that have been updated via the Policy UI. The component developer provides a docker script (defined in the Docker auxiliary specification) that will be triggered when this occurs.

Docker on the platform

Images

Docker images must be pushed to the environment specific Nexus repository. This requires tagging your build with the full name of you image which includes the Nexus repository name.

Use the Docker command-line to tag your Docker image where the target image must contain the registry host name and port.

For example, an application called yourapp has been tagged for an example Nexus registry:

YOUR_NEXUS_DOCKER_REGISTRY/yourapp                                                 0.4.0               154cc382df61        7 weeks ago         710.5 MB
yourapp                                                                                    0.4.0               154cc382df61        7 weeks ago         710.5 MB

The solutioning environment’s Nexus host for the Docker registry is YOUR_NEXSUS_HOST:18443. You must run docker login YOUR_NEXSUS_HOST:18443 to access the registry. Please contact the DCAE platform team to provide you with the credentials.

docker login YOUR_NEXSUS_HOST:18443

Tag your image:

docker tag yourapp:0.4.0 YOUR_NEXSUS_HOST:18443/dcae-platform/yourapp:0.4.0

Or build and tag:

docker build -t YOUR_NEXSUS_HOST:18443/dcae-platform/yourapp:0.4.0 .

After tagging, upload your image to the remote registry using the Docker push command. Note that the registry may require a login. Use the Docker login command before pushing in that case.

docker push YOUR_NEXSUS_HOST:18443/dcae-platform/yourapp:0.4.0

NOTE Replace dcae-platform with the group directory that is applicable to your image. Replace yourapp with your application’s name. Replace the 0.4.0 version with your application’s version.

Dockerfile

The Dockerfile must contain the name of the container’s initialization script. This will be called when the container is deployed, and must call Config Binding Service as described in Config Binding Service

Ports

On the DCAE platform, Docker components are run with the --publish-all or -P argument. This means the Docker container for your component will be listening on a random port and that random port will be mapped to the port you exposed.

Envs

The platform provides a set of environment variables into each Docker container:

Name Type Description
HOSTNAME string Unique name of the component instance that is generated
CONSUL_HOST string Hostname of the platform’s Consul instance
CONFIG_BINDING_SERVICE string Hostname of the platform’s config binding service instance
DOCKER_HOST string Host of the target platform Docker host to run the container on

Operational Concerns

Logging

Currently the platform uses the default json-file logging driver for Docker. For onboarding testing, component developers can access their logs from their Docker containers either by running their component using the --attached flag or by using the docker logs command. The requirement is that applications must write to stdout and/or stderr.

To use the docker logs command for your deployed running Docker container,

  • You must have Docker installed on your local machine
  • Have the generated name of your component. This is generated for you when you execute dcae_cli component dev or dcae_cli component run.
  • Find the target Docker host using the dcae_cli profiles show command:
$ dcae_cli profiles show solutioning
{
    "cdap_broker": "cdap_broker",
    "config_binding_service": "config_binding_service",
    "consul_host": "YOUR_CONSUL_HOST",
    "docker_host": "YOUR_DOCKER_HOST:2376"
}
  • Set your Docker client to point to the target Docker host:
$ export DOCKER_HOST="tcp://YOUR_DOCKER_HOST:2376"
  • Use the docker logs command:
$ docker logs <generated component name>