Simple activity, context propagation, and message passing samples #20

cretz · 2025-01-21T16:45:22Z

What was changed

Added activity_simple sample based on https://github.com/temporalio/samples-dotnet/tree/main/src/ActivitySimple
Added context_propagation sample based on https://github.com/temporalio/samples-dotnet/tree/main/src/ContextPropagation
Added message_passing_simple sample based on https://github.com/temporalio/samples-python/tree/main/message_passing/introduction

Note, this will not pass CI until the next Ruby SDK release

Checklist

Closes Sample request: Simple activity #5
Closes Sample request: Context propagation #9
Closes Sample request: Signals and queries #16
Closes Sample request: Workflow update #17

dandavison · 2025-01-21T17:04:59Z

activity_simple/my_workflow.rb

+
+module ActivitySimple
+  class MyWorkflow < Temporalio::Workflow::Definition
+    def execute


Please forgive reviewing API in the samples PR.

I would have reached for run instead of execute -- that has consistency with other SDKs, as well as threading APIs such as those of Java and Python etc. Is there a reason to do with the Ruby ecosystem for using execute?

Please forgive reviewing API in the samples PR.

No prob, this is a good place. And I am happy to see others digging in to Ruby.

Based on some ChatGPT ecosystem querying, it did seem execute was more preferred for background-job-like things. There is also perform. It is also what is used in the past Ruby SDK implementation and the Coinbase Ruby SDK implementation with success/familiarity. We use "run" as the attribute/annotation/decorator name, but in those other SDKs you can choose any method name though our samples often choose "run". But for Ruby, this is an actual abstract method and if made sense to match what was already there in ecosystem and existing Temporal Ruby.

dandavison · 2025-01-21T17:08:19Z

activity_simple/worker.rb

+# Use an instance for the stateful DB activity, other activity we will pass
+# in as class meaning it is instantiated each attempt
+db_client = ActivitySimple::MyActivities::MyDatabaseClient.new
+select_from_db_activity = ActivitySimple::MyActivities::SelectFromDatabase.new(db_client)


Isn't .new just shorthand for .new()? But then both would be instances which contradicts what you say above -- my ruby understanding must be failing me.

Oh ignore I see, only one of those is actually an activity.

dandavison · 2025-01-21T17:10:25Z

activity_simple/worker.rb

+
+# Create worker with the activities and workflow
+worker = Temporalio::Worker.new(
+  client:,


Is this syntax shorthand for client: client, a bit like TS/Rust?

activity_simple/worker.rb

dandavison · 2025-01-21T17:17:45Z

context_propagation/interceptor.rb

+        yield
+      ensure
+        # Put them all back, even if they were nil
+        orig_values.each { |key, val| Thread.current[key] = val }


It would be setting a better example to create a single container within the thread-local namespace to hold the application-logic keys, rather than having them all at the the top-level.

The user of the interceptor can do this (single key with a hash of all values needed), this interceptor is just a general purpose key copier. Would actually probably encourage users of this interceptor to not use multiple keys.

I didn't understand your response here.

dandavison · 2025-01-21T17:19:46Z

context_propagation/say_hello_workflow.rb

+      Temporalio::Workflow.logger.info("Workflow called by user: #{Thread.current[:my_user]}")
+
+      # Wait for signal then run activity
+      Temporalio::Workflow.wait_condition { @complete }


Neat. But, won't the logger.info statement be called every time the condition is evaluated? That would be particularly undesirable since it is saying that a user query is being handled.

Oh, no, maybe I don't understand what @complete is. I thought it was a reference to the method which is used as a query hander. What is it? Does @foo just always evaluate to nil for any value of "foo" unless it's been set?

I don't understand what @complete is

@complete is a Ruby attribute. That is class state, akin to self.complete in Python. However, unlike Python, accessing an uninitialized Ruby attribute returns nil instead of errors. Also unlike Python, Ruby attributes are only visible within the class (i.e. they are "private") and you have to use other things to expose them.

Does @foo just always evaluate to nil for any value of "foo" unless it's been set?

Yup, which makes Ruby workflows so nice and easy to write and really Ruby is a very pretty language altogether, so much so that in my biased opinion, workflows written in Ruby will be the most dev friendly to read/write of all.

I agree they're very nice to read. I don't think that having a poor typing story is the most dev-friendly for writing.

dandavison · 2025-01-21T17:22:08Z

context_propagation/starter.rb

+puts 'Executing workflow with user "Alice"'
+handle = client.start_workflow(
+  ContextPropagation::SayHelloWorkflow,
+  'Bob',


Are we restricting to 0- or 1-arity in Ruby as we wish we had done for others?

No, and we didn't wish to do this for the others, we just discourage multi-param. Every SDK needs to support multiple parameters, even if we encourage a single one.

Not sure about that

dandavison · 2025-01-21T17:23:46Z

activity_simple/my_activities.rb

+  module MyActivities
+    # Fake database client
+    class MyDatabaseClient
+      def select_value(table)


probably worth adding a short sleep here to emphasize that we're faking I/O (as you do below in the message-passing sample)

Meh, not really needed that much (the async concepts of whether a sleep is present or not is different in Ruby and doesn't really mean anything) and wasn't done at https://github.com/temporalio/samples-dotnet/blob/main/src/ActivitySimple/MyActivities.cs either where it doesn't matter there either. But I may add this.

dandavison · 2025-01-21T17:25:33Z

message_passing_simple/greeting_workflow.rb

+    #    workflow_query
+    #    def language
+    #        @language
+    #    end


dandavison · 2025-01-21T17:29:34Z

message_passing_simple/greeting_workflow.rb

+    def approve(input)
+      # A signal handler mutates the workflow state but cannot return a value.
+      @approved_for_release = true
+      @approver_name = input['name']


Out of interest is assignment an expression in ruby?

Yes, so technically this method does return a value. The last statement of every method is the return value of the method. But whether that's meaningful or not depends on docs and context (so you know a workflow signal handler's return value is discarded).

OK good to know. So I guess there's nothing stopping a user from writing a signal handler that returns a value and using it as a normal method, in addition to as a signal handler.

message_passing_simple/greeting_workflow.rb

dandavison · 2025-01-21T17:33:35Z

message_passing_simple/greeting_workflow.rb

+          # will fail the update. The WorkflowExecutionUpdateAccepted event will still be added to history. (Update
+          # validators can be used to reject updates before any event is written to history, but they cannot be async,
+          # and so we cannot use an update validator for this purpose.)
+          raise Temporalio::Error::ApplicationError, "Greeting service does not support #{new_language}" unless greeting


Can't say I immediately love the style of

raise ErrorThatProbablyDidntHappen unless something_which_is_probably_true

Is it unquestioned Ruby idiom or is it acceptable to use an if statement in this situation?

It is an unquestioned Ruby idiom. So much so that if you tried to use if ! instead of unless here or you tried to use a block instead this suffixed inline conditional, the style detector (Rubocop) would ding you. And in most cases the plugins in the IDE including the one I use, would auto-correct it to this if it'll fit on the line.

dandavison

Nice! Did a pass -- my first real pass at Ruby SDK -- and asked some questions.

Simple activity, context propagation, and message passing samples

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cretz requested a review from a team January 21, 2025 16:45

dandavison reviewed Jan 21, 2025

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message_passing_simple/greeting_workflow.rb

# workflow_query

# def language

# @language

# end

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cretz added 2 commits January 21, 2025 15:24

Remove workflow_executor default and other minor change

36af3a9

Remove specific dependency path

6a6974f

cretz merged commit ebaa2fa into temporalio:main Jan 22, 2025
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cretz deleted the activity-simple branch January 22, 2025 14:08

Simple activity, context propagation, and message passing samples #20

Simple activity, context propagation, and message passing samples #20

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cretz commented Jan 21, 2025

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