Using Temporal.io inside a Nx Monorepo

Pre-requisites

This article assumes you’re familiar with the following concepts in Nx:

• Nx mental models
• Workspace configuration

And what Temporal.io is

Problem Discovery & Setup

1. Setup workspace

git clone git@github.com:andreasasprou/nx-temporal.git

cd nx-temporal

yarn

2. Build & run worker

yarn nx run temporal-worker:build --prod
node dist/apps/temporal-worker/main.js

At this point, we get an error similar to:

The "path" argument must be of type string or an instance of Buffer or URL. Received type number (872)

This is down to webpack’s optimisation. So let’s disable that for now in apps/temproal-worker/project.json:

Now, if we re-build & get an error similar to:

➜  nx-temporal git:(main) ✗ node dist/apps/temporal-worker/main.js                  
2021-12-18T16:24:23.104Z [INFO] [temporal_sdk_core] Registering worker task_queue="tutorial" 
2021-12-18T16:24:23.624Z [ERROR] asset main.js 387 KiB [emitted] (name: main)
2021-12-18T16:24:23.624Z [ERROR] runtime modules 670 bytes 3 modules
2021-12-18T16:24:23.624Z [ERROR] modules by path ./node_modules/@temporalio/ 91.9 KiB
2021-12-18T16:24:23.624Z [ERROR]   modules by path ./node_modules/@temporalio/common/lib/ 50.8 KiB
2021-12-18T16:24:23.624Z [ERROR]     modules by path ./node_modules/@temporalio/common/lib/*.js 42.3 KiB 14 modules
2021-12-18T16:24:23.624Z [ERROR]     modules by path ./node_modules/@temporalio/common/lib/converter/*.js 8.52 KiB
2021-12-18T16:24:23.624Z [ERROR]       ./node_modules/@temporalio/common/lib/converter/data-converter.js 4.37 KiB [built] [code generated]
2021-12-18T16:24:23.624Z [ERROR]       ./node_modules/@temporalio/common/lib/converter/types.js 1.22 KiB [built] [code generated]
2021-12-18T16:24:23.624Z [ERROR]       ./node_modules/@temporalio/common/lib/converter/payload-converter.js 2.93 KiB [built] [code generated]
2021-12-18T16:24:23.624Z [ERROR]   modules by path ./node_modules/@temporalio/workflow/lib/*.js 41.1 KiB 6 modules
2021-12-18T16:24:23.624Z [ERROR] ../../../../../src/main.js 398 bytes [built] [code generated]
2021-12-18T16:24:23.624Z [ERROR] ./node_modules/long/src/long.js 39.2 KiB [built] [code generated]
2021-12-18T16:24:23.624Z [ERROR] ./node_modules/ms/index.js 2.95 KiB [built] [code generated]
2021-12-18T16:24:23.624Z [ERROR] 
2021-12-18T16:24:23.624Z [ERROR] ERROR in ../../../../../src/main.js 
2021-12-18T16:24:23.624Z [ERROR] Module not found: Error: Can't resolve './apps/temporal-worker/src/workflows.ts' in '/src'
2021-12-18T16:24:23.624Z [ERROR] resolve './apps/temporal-worker/src/workflows.ts' in '/src'
2021-12-18T16:24:23.624Z [ERROR]   No description file found in /src or above
2021-12-18T16:24:23.624Z [ERROR]   No description file found in /src/apps/temporal-worker/src or above
2021-12-18T16:24:23.624Z [ERROR]   no extension
2021-12-18T16:24:23.624Z [ERROR]     /src/apps/temporal-worker/src/workflows.ts doesn't exist
2021-12-18T16:24:23.624Z [ERROR]   .ts
2021-12-18T16:24:23.624Z [ERROR]     /src/apps/temporal-worker/src/workflows.ts.ts doesn't exist
2021-12-18T16:24:23.624Z [ERROR]   .js
2021-12-18T16:24:23.624Z [ERROR]     /src/apps/temporal-worker/src/workflows.ts.js doesn't exist
2021-12-18T16:24:23.624Z [ERROR]   as directory
2021-12-18T16:24:23.624Z [ERROR]     /src/apps/temporal-worker/src/workflows.ts doesn't exist
2021-12-18T16:24:23.624Z [ERROR] 
2021-12-18T16:24:23.624Z [ERROR] webpack 5.65.0 compiled with 1 error in 327 ms

We can investigate by looking at the built worker file where we can find the run function:

function run() {
    return (0, tslib_1.__awaiter)(this, void 0, void 0, function* () {
        const worker = yield worker_1.Worker.create({
            workflowsPath: /*require.resolve*/("./apps/temporal-worker/src/workflows.ts"),
            activities,
            taskQueue: 'tutorial',
        });
        yield worker.run();
    });
}

Webpack is trying to bundle the workflows.ts file and use Webpacks custom require.resolve to retrieve the module id from the locally bundled code.

There are a few ways we can solve this, using Prebuild Workflow Bundles. I’ve explored:

1. Using custom Nx tasks to build workflow.ts separately: PR ❌
2. Using Nx libs to build workflow.ts separately: PR ❌
3. Replacing webpack with ts-node: PR ✅

Solution: Replacing webpack with ts-node

Link to PR

• We can replace the default Nx node build exector with one which uses ts-node.
• ts-config paths (which nx heavily relies on) are not replaced through tsc, so we have to replace them using something like tsc-alias

Conclusions & Improvements

The only solution which seems to work so far is Solution 3.

Esbuild

If you can use esbuild in your project (i.e. you don’t need to run the Typescript compiler for features like emitDecoratorMetadata) then you can use a esbuild nx builder instead of the custom one I wrote in this PR.

Temporal vm issues

Solution 1 & 2 both have issues when running the built application and starting a workflow:

-> node dist/apps/temporal-worker/main.js

2021-12-18T16:57:17.758Z [INFO] [temporal_sdk_core] Registering worker task_queue="tutorial" 
2021-12-18T16:57:17.858Z [INFO] Worker state changed { state: 'RUNNING' }
2021-12-18T16:57:42.006Z [ERROR] Failed to activate workflow {
  runId: '102e52a3-12e9-47fc-b048-0349ace119e0',
  error: workflow-isolate:15
  module.exports = require("tslib");
  ^
  
  ReferenceError: require is not defined
      at Object.tslib (workflow-isolate:15:1)
      at __webpack_require__ (workflow-isolate:39:41)
      at workflow-isolate:53:17
      at workflow-isolate:66:3
      at workflow-isolate:71:12
      at Script.runInContext (vm.js:143:18)

Reproduction steps

git clone git@github.com:andreasasprou/nx-temporal.git
cd nx-temporal && yarn

git checkout workflows-build-step

yarn nx run temporal-worker:build --prod
node dist/apps/temporal-worker/main.js

# In another shell
ts-node apps/temporal-worker/src/client.ts

Development issues

Solution 1 & 2 also have issues with the development server:

> nx run temporal-worker:serve 
chunk (runtime: main) main.js (main) 2.05 KiB [entry] [rendered]
webpack compiled successfully (404e652e986324f3)
Debugger listening on ws://localhost:9229/1338b338-24f1-4e88-b6d8-abfa7faaa813
Debugger listening on ws://localhost:9229/1338b338-24f1-4e88-b6d8-abfa7faaa813
For help, see: https://nodejs.org/en/docs/inspector
Issues checking in progress...
2021-12-18T16:44:03.263Z [INFO] [temporal_sdk_core] Registering worker task_queue="tutorial" 
2021-12-18T16:44:03.803Z [ERROR] asset main.js 387 KiB [emitted] (name: main)
2021-12-18T16:44:03.803Z [ERROR] runtime modules 670 bytes 3 modules
2021-12-18T16:44:03.803Z [ERROR] modules by path ./node_modules/@temporalio/ 91.9 KiB
2021-12-18T16:44:03.803Z [ERROR]   modules by path ./node_modules/@temporalio/common/lib/ 50.8 KiB
2021-12-18T16:44:03.803Z [ERROR]     modules by path ./node_modules/@temporalio/common/lib/*.js 42.3 KiB 14 modules
2021-12-18T16:44:03.803Z [ERROR]     modules by path ./node_modules/@temporalio/common/lib/converter/*.js 8.52 KiB
2021-12-18T16:44:03.803Z [ERROR]       ./node_modules/@temporalio/common/lib/converter/data-converter.js 4.37 KiB [built] [code generated]
2021-12-18T16:44:03.803Z [ERROR]       ./node_modules/@temporalio/common/lib/converter/types.js 1.22 KiB [built] [code generated]
2021-12-18T16:44:03.803Z [ERROR]       ./node_modules/@temporalio/common/lib/converter/payload-converter.js 2.93 KiB [built] [code generated]
2021-12-18T16:44:03.803Z [ERROR]   modules by path ./node_modules/@temporalio/workflow/lib/*.js 41.1 KiB 6 modules
2021-12-18T16:44:03.803Z [ERROR] ../../../../../src/main.js 398 bytes [built] [code generated]
2021-12-18T16:44:03.803Z [ERROR] ./node_modules/long/src/long.js 39.2 KiB [built] [code generated]
2021-12-18T16:44:03.803Z [ERROR] ./node_modules/ms/index.js 2.95 KiB [built] [code generated]
2021-12-18T16:44:03.803Z [ERROR] 
2021-12-18T16:44:03.803Z [ERROR] ERROR in ../../../../../src/main.js 
2021-12-18T16:44:03.803Z [ERROR] Module not found: Error: Can't resolve './apps/temporal-worker/src/workflows.ts' in '/src'
2021-12-18T16:44:03.803Z [ERROR] resolve './apps/temporal-worker/src/workflows.ts' in '/src'
2021-12-18T16:44:03.803Z [ERROR]   No description file found in /src or above
2021-12-18T16:44:03.803Z [ERROR]   No description file found in /src/apps/temporal-worker/src or above
2021-12-18T16:44:03.803Z [ERROR]   no extension
2021-12-18T16:44:03.803Z [ERROR]     /src/apps/temporal-worker/src/workflows.ts doesn't exist
2021-12-18T16:44:03.803Z [ERROR]   .ts
2021-12-18T16:44:03.803Z [ERROR]     /src/apps/temporal-worker/src/workflows.ts.ts doesn't exist
2021-12-18T16:44:03.803Z [ERROR]   .js
2021-12-18T16:44:03.803Z [ERROR]     /src/apps/temporal-worker/src/workflows.ts.js doesn't exist
2021-12-18T16:44:03.803Z [ERROR]   as directory
2021-12-18T16:44:03.803Z [ERROR]     /src/apps/temporal-worker/src/workflows.ts doesn't exist
2021-12-18T16:44:03.803Z [ERROR] 
2021-12-18T16:44:03.803Z [ERROR] webpack 5.65.0 compiled with 1 error in 329 ms

Reproduction steps

git clone git@github.com:andreasasprou/nx-temporal.git
cd nx-temporal && yarn

git checkout workflows-build-step

yarn nx run temporal-worker:serve