feat(gatsby): enable external jobs with ipc

packages/gatsby/ipc.json

@@ -1,3 +1,3 @@
 {
-  "version": 1
+  "version": 2
 }

packages/gatsby/src/utils/__tests__/jobs-manager.js

@@ -11,6 +11,7 @@ jest.mock(`p-defer`, () =>
 jest.mock(`gatsby-cli/lib/reporter`, () => {
   return {
     phantomActivity: jest.fn(),
+    warn: jest.fn(),
   }
 })
 
@@ -216,7 +217,9 @@ describe(`Jobs manager`, () => {
       try {
         await enqueueJob(jobArgs)
       } catch (err) {
-        expect(err).toMatchInlineSnapshot(`[WorkerError: An error occured]`)
+        expect(err).toMatchInlineSnapshot(
+          `[WorkerError: Error: An error occured]`
+        )
       }
       try {
         await enqueueJob(jobArgs2)
@@ -334,4 +337,150 @@ describe(`Jobs manager`, () => {
       expect(isJobStale({ inputPaths })).toBe(false)
     })
   })
+
+  describe(`IPC jobs`, () => {
+    let listeners = []
+    beforeAll(() => {
+      jest.useFakeTimers()
+    })
+
+    let originalProcessOn
+    let originalSend
+    beforeEach(() => {
+      process.env.ENABLE_GATSBY_EXTERNAL_JOBS = `true`
+      listeners = []
+      originalProcessOn = process.on
+      originalSend = process.send
+      process.on = (type, cb) => {
+        listeners.push(cb)
+      }
+
+      process.send = jest.fn()
+    })
+
+    afterAll(() => {
+      delete process.env.ENABLE_GATSBY_EXTERNAL_JOBS
+      jest.useRealTimers()
+      process.on = originalProcessOn
+      process.send = originalSend
+    })
+
+    it(`should schedule a remote job when ipc and env variable are enabled`, async () => {
+      const { enqueueJob } = jobManager
+      const jobArgs = createInternalMockJob()
+
+      enqueueJob(jobArgs)
+
+      jest.runAllTimers()
+
+      expect(process.send).toHaveBeenCalled()
+      expect(process.send).toHaveBeenCalledWith({
+        type: `JOB_CREATED`,
+        payload: jobArgs,
+      })
+
+      expect(listeners.length).toBe(1)
+      expect(worker.TEST_JOB).not.toHaveBeenCalled()
+    })
+
+    it(`should resolve a job when complete message is received`, async () => {
+      const { enqueueJob } = jobManager
+      const jobArgs = createInternalMockJob()
+
+      const promise = enqueueJob(jobArgs)
+      jest.runAllTimers()
+
+      listeners[0]({
+        type: `JOB_COMPLETED`,
+        payload: {
+          id: jobArgs.id,
+          result: {
+            output: `hello`,
+          },
+        },
+      })
+
+      jest.runAllTimers()
+
+      await expect(promise).resolves.toStrictEqual({
+        output: `hello`,
+      })
+      expect(worker.TEST_JOB).not.toHaveBeenCalled()
+    })
+
+    it(`should reject a job when failed message is received`, async () => {
+      const { enqueueJob } = jobManager
+      const jobArgs = createInternalMockJob()
+
+      const promise = enqueueJob(jobArgs)
+
+      jest.runAllTimers()
+
+      listeners[0]({
+        type: `JOB_FAILED`,
+        payload: {
+          id: jobArgs.id,
+          error: `JOB failed...`,
+        },
+      })
+
+      jest.runAllTimers()
+
+      await expect(promise).rejects.toStrictEqual(
+        new jobManager.WorkerError(`JOB failed...`)
+      )
+      expect(worker.TEST_JOB).not.toHaveBeenCalled()
+    })
+
+    it(`should run the worker locally when it's not available externally`, async () => {
+      worker.TEST_JOB.mockReturnValue({ output: `myresult` })
+      const { enqueueJob } = jobManager
+      const jobArgs = createInternalMockJob()
+
+      const promise = enqueueJob(jobArgs)
+
+      jest.runAllTimers()
+
+      listeners[0]({
+        type: `JOB_NOT_WHITELISTED`,
+        payload: {
+          id: jobArgs.id,
+        },
+      })
+
+      jest.runAllTimers()
+
+      await expect(promise).resolves.toStrictEqual({ output: `myresult` })
+      expect(worker.TEST_JOB).toHaveBeenCalledTimes(1)
+    })
+
+    it(`shouldn't schedule a remote job when ipc is enabled and env variable is false`, async () => {
+      process.env.ENABLE_GATSBY_EXTERNAL_JOBS = `false`
+      jest.useRealTimers()
+      const { enqueueJob } = jobManager
+      const jobArgs = createInternalMockJob()
+
+      await enqueueJob(jobArgs)
+
+      expect(process.send).not.toHaveBeenCalled()
+      expect(worker.TEST_JOB).toHaveBeenCalled()
+    })
+
+    it(`should warn when external jobs are enabled but ipc isn't used`, async () => {
+      process.env.ENABLE_GATSBY_EXTERNAL_JOBS = `true`
+      process.send = null
+      jest.useRealTimers()
+      const { enqueueJob } = jobManager
+      const jobArgs = createInternalMockJob()
+      const jobArgs2 = createInternalMockJob({
+        args: { key: `val` },
+      })
+
+      await enqueueJob(jobArgs)
+      await enqueueJob(jobArgs2)
+
+      expect(reporter.warn).toHaveBeenCalledTimes(1)
+      expect(worker.TEST_JOB).toHaveBeenCalled()
+    })
+  })
 })

packages/gatsby/src/utils/jobs-manager.js

@@ -7,11 +7,22 @@ const _ = require(`lodash`)
 const { createContentDigest, slash } = require(`gatsby-core-utils`)
 const reporter = require(`gatsby-cli/lib/reporter`)
 
+const MESSAGE_TYPES = {
+  JOB_CREATED: `JOB_CREATED`,
+  JOB_COMPLETED: `JOB_COMPLETED`,
+  JOB_FAILED: `JOB_FAILED`,
+  JOB_NOT_WHITELISTED: `JOB_NOT_WHITELISTED`,
+}
+
 let activityForJobs = null
 let activeJobs = 0
+let isListeningForMessages = false
+let hasShownIPCDisabledWarning = false
 
 /** @type {Map<string, {id: string, deferred: pDefer.DeferredPromise<any>}>} */
 const jobsInProcess = new Map()
+/** @type {Map<string, {job: InternalJob, deferred: pDefer.DeferredPromise<any>}>} */
+const externalJobsMap = new Map()
 
 /**
  * We want to use absolute paths to make sure they are on the filesystem
@@ -57,6 +68,10 @@ const createFileHash = path => hasha.fromFileSync(path, { algorithm: `sha1` })
 /** @type {pDefer.DeferredPromise<void>|null} */
 let hasActiveJobs = null
 
+const hasExternalJobsEnabled = () =>
+  process.env.ENABLE_GATSBY_EXTERNAL_JOBS === `true` ||
+  process.env.ENABLE_GATSBY_EXTERNAL_JOBS === `1`
+
 /**
  * Get the local worker function and execute it on the user's machine
  *
@@ -81,12 +96,60 @@ const runLocalWorker = async (workerFn, job) => {
           })
         )
       } catch (err) {
-        reject(err)
+        reject(new WorkerError(err))
       }
     })
   })
 }
 
+const listenForJobMessages = () => {
+  process.on(`message`, msg => {
+    if (
+      msg &&
+      msg.type &&
+      msg.payload &&
+      msg.payload.id &&
+      externalJobsMap.has(msg.payload.id)
+    ) {
+      const { job, deferred } = externalJobsMap.get(msg.payload.id)
+      switch (msg.type) {
+        case MESSAGE_TYPES.JOB_COMPLETED: {
+          deferred.resolve(msg.payload.result)
+          break
+        }
+        case MESSAGE_TYPES.JOB_FAILED: {
+          deferred.reject(new WorkerError(msg.payload.error))
+          break
+        }
+        case MESSAGE_TYPES.JOB_NOT_WHITELISTED: {
+          deferred.resolve(runJob(job, true))
+          break
+        }
+      }
+
+      externalJobsMap.delete(msg.payload.id)
+    }
+  })
+}
+
+/**
+ * @param {InternalJob} job
+ */
+const runExternalWorker = job => {
+  const deferred = pDefer()
+  externalJobsMap.set(job.id, {
+    job,
+    deferred,
+  })
+
+  process.send({
+    type: MESSAGE_TYPES.JOB_CREATED,
+    payload: job,
+  })
+
+  return deferred.promise
+}
+
 /**
  * Make sure we have everything we need to run a job
  * If we do, run it locally.
@@ -95,14 +158,32 @@ const runLocalWorker = async (workerFn, job) => {
  * @param {InternalJob} job
  * @return {Promise<object>}
  */
-const runJob = job => {
+const runJob = (job, forceLocal = false) => {
   const { plugin } = job
   try {
     const worker = require(path.posix.join(plugin.resolve, `gatsby-worker.js`))
     if (!worker[job.name]) {
       throw new Error(`No worker function found for ${job.name}`)
     }
 
+    if (!forceLocal && hasExternalJobsEnabled()) {
+      if (process.send) {
+        if (!isListeningForMessages) {
+          isListeningForMessages = true
+          listenForJobMessages()
+        }
+
+        return runExternalWorker(job)
+      } else {
+        // only show the offloading warning once
+        if (!hasShownIPCDisabledWarning) {
+          hasShownIPCDisabledWarning = true
+          reporter.warn(
+            `Offloading of a job failed as IPC could not be detected. Running job locally.`
+          )
+        }
+      }
+    }
     return runLocalWorker(worker[job.name], job)
   } catch (err) {
     throw new Error(