OpenWhisk Trace Collector

The OpenWhisk Trace Collector is a microservice based on the OpenTelemetry Collector Library to post-process FaaS-function invocation spans in TppFaaS. For this, the service receives spans generated by the OpenTelemetry Library, which instruments the FaaS-functions. Each span represents a function invocation and is marked with a unique activationId generated by OpenWhisk, which associates the span with its respective invocation. The Collector uses the Id to retrieve meta-information about the span's invocation from the OpenWhisk API. The meta-information includes:

• Timestamps recording the start and end of the invocation
• The function initialization time (initTime in OpenWhisk terminology) in case of a cold start
• The waitTime capturing the delay of the invocation in the internal OpenWhisk system

Inside the Collector the span traverses a pipeline including the two configurable processors owspanprocessor and owspanattacher which transform the span using the retrieved meta-information:

• owspanprocessor receives spans in the OpenTelemetry data format. Each span represents a function invocation and must contain the respective activationId as an attribute. The processor retrieves the invocation's meta-information from the OpenWhisk API, which contains the waitTime and initTime. Both values are added to the span as attributes. Furthermore, the start and end time of the span is adjusted to conform with the retrieved information.

• owspanattacher is optional and must be located in the pipeline after the owspanprocessor as it extracts the waitTime and initTime attributes from the span to create corresponding child spans. The processor generates a child span for the code execution, the waitTime, and the initTime.

In the pipeline's last step, the span is exported to Zipkin. Here, the span is aggregated to a trace with other spans of the FaaS-application. One example of such a trace representing an execution of a tree-shaped FaaS-application is depicted below:

Configuration and Deployment

Configure the processors and the exporter in k8s/config.yaml, a k8s manifest for deploying the Collector in your cluster.

...
processors:
    ...
    owspanprocessor:
        ow_host: http://owdev-nginx.openwhisk.svc.cluster.local:80
        ow_auth_token: 23bc46b1-71f6-4ed5-8c54-816aa4f8c502:123zO3xZCLrMN6v2BKK1dXYFpXlPkccOFqm12CdAsMgRU4VrNZ9lyGVCGuMDGIwP
        logging: true
    owspanattacher:
        logging: true
exporters:
    zipkin:
        endpoint: "http://zipkinot.default.svc.cluster.local:9411/api/v2/spans"
...

Build a Docker Image of the Collector

docker build -t koelschkellerkind/owtracecollector:tag .

Releases

• 1.0.0 initial release
• 1.0.1 refactoring: owtracecollector is separated in owspanprocessor and owspanattacher (24th March 2021)
• 1.0.2 changed unit of wait and initTime attributes to milliseconds (29th March 2021)
• 1.0.3 renamed child spans of attacher (31st March 2021)
• 1.0.4 bugfix: start from OpenWhisk activation record represents beginning of initialization (7th April 2021)

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Build a Collector Executable via Opentelemetry-Collector-Builder (DEPRECATED)

Opentelemetry-collector-builder can be used to build a executable of the collector.

1. Clone https://github.com/koelschkellerkind/opentelemetry-collector-builder

2. Create the binary of the builder with

   go build

3. Add the binary to your your PATH

4. Create the binary of the collector with

   opentelemetry-collector-builder --config builder.yaml

5. Then

   cd owtracecollector-dist

6. Start the collector with

   ./owtracecollector --config ../otel-collector-config.yaml  

Pitfalls

Using tabs in the builder.yaml results in an error