Protobuf

ZIO-Temporal provides with the zio-temporal-protobuf module allowing to use Protobuf transport. To use Protobuf, you must properly install Scalapb

Defining protobuf files

When using Protobuf, it's first required to write protobuf message definition:

syntax = "proto2";

package com.example.workflow;

message WorkflowParams {
  required string message = 1;
  // Unix time
  required int64 processingTime = 2;
}

// ZIO Temporal ships some non-standard data types, such as UUID
import "zio-temporal.proto";

message WorkflowResult {
  required zio.temporal.protobuf.UUID processId = 1;
}

Scalapb compiles such a message into a case class similar to this one:

case class WorkflowParams(message: String, processingTime: Long)

case class WorkflowResult(processId: zio.temporal.protobuf.UUID)

It can be then used in workflow interface definitions:

import zio._
import zio.temporal._
import zio.temporal.workflow._

@workflowInterface
trait SampleWorkflow {
  @workflowMethod
  def process(params: WorkflowParams): WorkflowResult
}

When implementing the workflow, you might need to convert from protobuf representation to your own.
For instance, it's much easier operating with java.time types rather than Unix time represented as Long.
Here zio.temporal.protobuf.syntax comes to the rescue!

import zio.temporal.protobuf.syntax._
import java.time.LocalDateTime

class SampleWorkflowImpl extends SampleWorkflow {
  private val logger = ZWorkflow.makeLogger
  
  override def process(params: WorkflowParams): WorkflowResult = {
    // Converts from Protobuf representation
    val processingTime = params.processingTime.fromProto[LocalDateTime]
    // Always use this method to get the current time
    // Otherwise, the workflow won't be deterministic
    val now = ZWorkflow.currentTimeMillis.toLocalDateTime()
    
    val lag = java.time.Duration.between(processingTime, now)
    logger.info(s"The lag is $lag")
    // Do stuff
    // ...
    val processId = ZWorkflow.randomUUID
    // Converts into Protobuf representation
    WorkflowResult(processId.toProto)
  }
}

Notes

• import zio.temporal.protobuf.syntax._ is required
• fromProto extension method converts the data type from the Protobuf representation
• toProto extension method converts the data type into the Protobuf representation

In order to use Protobuf serializer, it's required to override the default DataConverter:

import zio.temporal.workflow.ZWorkflowClientOptions
import zio.temporal.protobuf.ProtobufDataConverter

val optionsLayer =
  ZWorkflowClientOptions.make @@
    ZWorkflowClientOptions.withDataConverter(ProtobufDataConverter.make())
// optionsLayer: ZLayer[Any, Config.Error, ZWorkflowClientOptions] = Suspend(
//   self = zio.ZLayer$$Lambda$8955/0x00007fea09a20580@40c24e51
// )