Iter8'sgen-load-and-collect-metrics task enables load test for HTTP services and built on top of Fortio. However, while Fortio has agRPC health check capability, it does not have the ability to load test arbitrary gRPC services. The excellentghz project does have this capability.

This documentation describes the process used to develop thegen-load-and-collect-metrics-grpc task which enables load test for gRPC services and built on top of ghz.

We will create the logic forgen-load-and-collect-metrics-grpc task in the filebase/collect_grpc.go as follows.

package baseimport ("errors")// collectGRPCInputs holds all the inputs for this tasktypecollectGRPCInputsstruct {}const (// CollectGRPCTaskName is the name of this task which performs load generation and metrics collection for gRPC services.CollectGRPCTaskName="gen-load-and-collect-metrics-grpc")// collectGRPCTask enables load testing of gRPC services.typecollectGRPCTaskstruct {TaskMetaWithcollectGRPCInputs`json:"with" yaml:"with"`}// initializeDefaults sets default values for the collect taskfunc (t*collectGRPCTask)initializeDefaults() {}// validate task inputsfunc (t*collectGRPCTask)validateInputs()error {returnnil}// Run executes this taskfunc (t*collectGRPCTask)Run(exp*Experiment)error {// 1. validate inputsvarerrerrorerr=t.validateInputs()iferr!=nil {returnerr}// 2. initialize defaultst.initializeDefaults()// 3. collect raw results from ghz for each version// 4. The inputs for this task determine the number of versions participating in the experiment.// Hence, init insights with num versions// 5. Populate all metrics collected by this taskreturnerrors.New("not implemented")}

At this point, the above file is mostly stubbed, and the collectGRPCTask is unimplemented. However, we have a valid task definition, which we can use to make progress.

TheExperimentSpec struct has a custom unmarshaller in the filebase/experiment.go which we will extend as follows.

// some stuff above// the unmarshaling code we're adding is as follows...case CollectGRPCTaskName:cgt:=&collectGRPCTask{}json.Unmarshal(tBytes,cgt)tsk=cgt// more stuff below

At this point, you have fully defined task. Unfortunately, using this task in an experiment will cause the experiment to fail, since the task is not implemented and its run will result in an error. We will continue with its development as follows.

The struct holding the inputs to this task was stubbed instep 1. It is now time to define the inputs properly. We will define the inputs as follows.

A key thing to remember in this step is to properly document all inputs.

Please refer to thebase/collect-grpc.go file for the inputs (TBD: show marked up code in GitHub)

Time to implement the run method for this task. Please refer to thebase/collect_grpc.go file for the detailed implementation (TBD: show marked up code in GitHub). There are two areas in this file to pay special attention.

This might be the first task to be executed in the experiment. So, initializing insights is necessary in this task, since it populates insights.

// 4. The inputs for this task determine the number of versions participating in the experiment.// Hence, init insights with num versionserr=exp.Result.initInsightsWithNumVersions(len(t.With.VersionInfo))iferr!=nil {returnerr}in:=exp.Result.Insights

m:=iter8BuiltInPrefix+"/"+gRPCRequestCountMetricNamemm:=MetricMeta{Description:"number of gRPC requests sent",Type:CounterMetricType,}in.updateMetric(m,mm,i,float64(gr[i].Count))

Use the above pattern whenever you create/update metrics (single method for both). Refer tobase/collect_grpc.go for more context.

You have two options for testing a task, both of which you will exercise at some stage.

1. Write the unit test that programmatically tests your task (see examples of unit tests for tasks in thebase package)
2. Create anexperiment.yaml file with your task in it. Create a chart with thisexperiment.yaml as the "experiment template". You can do this as follows.

iter8 hub load-testcd load-testecho'{{ define "load-test.experiment" -}}'> templates/_experiment.tplcat<your experiment.yaml>>> templates/_experiment.tplecho'{{ end }}'>> templates/_experiment.tpl

You can now do

iter8 run

This will run the experiment containing your new task.