calldata.md

id	title
calldata	Call Data

Data and metadata can specify template actions that will be parsed and evaluated at every request. Each request gets a new instance of the data. The available variables / actions are:

// CallData represents contextualized data available for templating
type CallData struct {

	// unique worker ID
	WorkerID		   string

	// unique incremented request number for each call
	RequestNumber      int64

	// fully-qualified name of the method call
	FullyQualifiedName string

	// shorter call method name
	MethodName         string

	// the service name
	ServiceName        string

	// name of the input message type
	InputName          string

	// name of the output message type
	OutputName         string

	// whether this call is client streaming
	IsClientStreaming  bool

	// whether this call is server streaming
	IsServerStreaming  bool

	// timestamp of the call in RFC3339 format
	Timestamp          string

	// timestamp of the call as unix time in seconds
	TimestampUnix      int64

	// timestamp of the call as unix time in milliseconds
	TimestampUnixMilli      int64

	// timestamp of the call as unix time in nanoseconds
	TimestampUnixNano      int64

	// UUID v4 for each call
	UUID	string
}

Template Functions

There are also template functions available:

func newUUID() string
Generates a new UUID for each invocation.

func randomString(length int) string
Generates a new random string for each invocation. Accepts a length parameter. If the argument is <= 0 then a random string is generated with a random length between length of 2 and 16.

func randomInt(min, max int) int
Generates a new non-negative pseudo-random number in range [min, max).

You can also use sprig functions within a template.

Examples

This can be useful to inject variable information into the message data JSON or metadata JSON payloads for each request, such as timestamp or unique request number. For example:

-m '{"request-id":"{{.RequestNumber}}", "timestamp":"{{.TimestampUnix}}"}'

Would result in server getting the following metadata map represented here in JSON:

{
  "user-agent": "grpc-go/1.11.1",
  "request-id": "1",
  "timestamp": "1544890252"
}

-d '{"order_id":"{{newUUID}}", "item_id":"{{newUUID}}", "sku":"{{randomString 8 }}", "product_name":"{{randomString 0}}"}'

Would result in data with JSON representation:

{
  "order_id": "3974e7b3-5946-4df5-bed3-8c3dc9a0be19",
  "item_id": "cd9c2604-cd9b-43a8-9cbb-d1ad26ca93a4",
  "sku": "HlFTAxcm",
  "product_name": "xg3NEC"
}

See example calls for some more usage examples.

Data Function API

When using the ghz/runner package programmatically, we can dynamically create data for each request using WithBinaryDataFunc() API:

func dataFunc(mtd *desc.MethodDescriptor, cd *runner.CallData) []byte {
	msg := &helloworld.HelloRequest{}
	msg.Name = cd.WorkerID
	binData, err := proto.Marshal(msg)
	return binData
}

report, err := runner.Run(
	"helloworld.Greeter.SayHello",
	"0.0.0.0:50051",
	runner.WithProtoFile("./testdata/greeter.proto", []string{}),
	runner.WithInsecure(true),
	runner.WithBinaryDataFunc(dataFunc),
)