Eager workflow start sample (#55)

Author: THardy98

README.md

@@ -23,6 +23,7 @@ Prerequisites:
 * [context_propagation](context_propagation) - Use interceptors to propagate thread/fiber local data from clients
   through workflows/activities.
 * [dsl](dsl) - Demonstrates having a workflow interpret/invoke arbitrary steps defined in a DSL.
+* [eager_wf_start](eager_wf_start) - Demonstrates Eager Workflow Start to reduce latency for workflows that start with a local activity.
 * [encryption](encryption) - Demonstrates how to make a codec for end-to-end encryption.
 * [env_config](env_config) - Load client configuration from TOML files with programmatic overrides.
 * [message_passing_simple](message_passing_simple) - Simple workflow that accepts signals, queries, and updates.

eager_wf_start/README.md

@@ -0,0 +1,14 @@
+# Eager Workflow Start
+
+This sample shows how to create a workflow that uses Eager Workflow Start.
+
+The target use case is workflows whose first task needs to execute quickly (ex: payment verification in an online checkout workflow). That work typically can't be done directly in the workflow (ex: using web APIs, databases, etc.), and also needs to avoid the overhead of dispatching another task. Using a Local Activity suffices both needs, which this sample demonstrates.
+
+You can read more about Eager Workflow Start in our:
+
+- [Eager Workflow Start blog](https://temporal.io/blog/improving-latency-with-eager-workflow-start)
+- [Worker Performance Docs](https://docs.temporal.io/develop/worker-performance#eager-workflow-start)
+
+To run, first see [README.md](../README.md) for prerequisites. Then run the sample via:
+
+    bundle exec ruby eager_wf_start/run.rb

eager_wf_start/eager_workflow.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+require 'temporalio/workflow'
+require_relative 'greeting_activity'
+
+module EagerWfStart
+  class EagerWorkflow < Temporalio::Workflow::Definition
+    def execute(name)
+      Temporalio::Workflow.execute_local_activity(
+        GreetingActivity,
+        name,
+        schedule_to_close_timeout: 5
+      )
+    end
+  end
+end

eager_wf_start/greeting_activity.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require 'temporalio/activity'
+
+module EagerWfStart
+  class GreetingActivity < Temporalio::Activity::Definition
+    def execute(name)
+      "Hello, #{name}!"
+    end
+  end
+end

eager_wf_start/run.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+require 'securerandom'
+require 'temporalio/client'
+require 'temporalio/worker'
+require_relative 'eager_workflow'
+require_relative 'greeting_activity'
+
+TASK_QUEUE = 'eager-wf-start-task-queue'
+
+# Note that the worker and client run in the same process and share the same client connection
+client = Temporalio::Client.connect('localhost:7233', 'default')
+
+worker = Temporalio::Worker.new(
+  client:,
+  task_queue: TASK_QUEUE,
+  workflows: [EagerWfStart::EagerWorkflow],
+  activities: [EagerWfStart::GreetingActivity]
+)
+
+# Run worker in the background while we start the workflow
+worker.run do
+  handle = client.start_workflow(
+    EagerWfStart::EagerWorkflow,
+    'Temporal',
+    id: "eager-workflow-id-#{SecureRandom.uuid}",
+    task_queue: TASK_QUEUE,
+    request_eager_start: true
+  )
+
+  puts handle.result
+end