Import from internal

.gitignore

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+
+node_modules
+package-lock.json
+dist
+samconfig.toml

.vscode/settings.json

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+{
+  "editor.defaultFormatter": "esbenp.prettier-vscode",
+  "editor.formatOnSave": true,
+  "eslint.validate": ["javascript"],
+  "editor.codeActionsOnSave": {
+    "source.fixAll.eslint": true
+  },
+  "typescript.tsdk": "node_modules/typescript/lib"
+}

LICENSE

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+MIT License
+
+Copyright (c) 2020 Michael Hart
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# sync-threads
+
+Make asynchronous calls in Node.js synchronously using [worker threads](https://nodejs.org/api/worker_threads.html) and [Atomics mutexes](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Atomics).
+
+Especially useful when you need to resolve promises at require-time,
+for example in an AWS Lambda function when using [provisioned concurrency](https://docs.aws.amazon.com/lambda/latest/dg/configuration-concurrency.html#configuration-concurrency-provisioned).
+
+NOTE: you don't need this library if you're happy with the overhead of creating a Node.js subprocess,
+see the [Appendix](#appendix) for details.
+
+# Example
+
+This example shows how we can synchronously retrieve secrets from [AWS SSM](https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-parameter-store.html)
+at require-time – that is, before the init stage of Lambda has finished.
+
+`index.js`:
+
+```js
+const { createSyncFn } = require('sync-threads')
+
+// Create our synchronous function
+const getSsmSecretSync = createSyncFn('./worker.js')
+
+// Call it at init (require) time, no async needed!
+const secret = getSsmSecretSync('/my-secret')
+
+// Logged at init time
+console.log({ secret, source: 'init' })
+
+exports.handler = async () => {
+  // This value can be used in our handler without needing to resolve anything async
+  console.log({ secret, source: 'handler' })
+}
+```
+
+`worker.js`:
+
+```js
+const SSM = require('aws-sdk/clients/ssm')
+const { runAsWorker } = require('sync-threads')
+
+const ssm = new SSM()
+
+runAsWorker(async (ssmParamName) => {
+  const {
+    Parameter: { Value },
+  } = await ssm.getParameter({ Name: ssmParamName, WithDecryption: true }).promise()
+  return Value
+})
+```
+
+You can see this example, as well as how you'd bundle it if you're using webpack or similar, in the [`examples`](./examples) directory.
+
+# API
+
+`sync-threads` exports two main functions: `createSyncFn` and `runAsWorker`
+
+## `createSyncFn(filename[, bufferSize])`
+
+Returns a synchronous function that will run the specified file as a worker, pass in any arguments you give it, and wait for the result.
+
+### `runAsWorker(workerAsyncFn)`
+
+To be called from inside your worker code. It will run the given asynchronous function with the given arguments from the parent and share the result.
+
+# Installation
+
+With [npm](http://npmjs.org/) do:
+
+```
+npm install sync-threads
+```
+
+# Appendix
+
+You can achieve something very similar to this library using the
+`spawnSync`/`execSync` functions from the `child_process` module in Node.js.
+
+The main difference is that this library performs the async work in a thread, without creating a separate `node` process,
+which makes it a little faster.
+
+Here's a simple example of how you'd do it without needing this library:
+
+`index.js`:
+
+```js
+const { execSync } = require('child_process')
+
+const { secret } = JSON.parse(execSync('node worker.js /my-secret', 'utf8').trim().split('\n').pop())
+
+console.log({ secret, source: 'init' })
+
+exports.handler = async () => {
+  console.log({ secret, source: 'handler' })
+}
+```
+
+`worker.js`:
+
+```js
+const SSM = require('aws-sdk/clients/ssm')
+
+const ssm = new SSM()
+
+;(async () => {
+  const {
+    Parameter: { Value },
+  } = await ssm.getParameter({ Name: process.argv[2], WithDecryption: true }).promise()
+  console.log('%j', { secret: Value })
+})()
+```

declaration.tsconfig.json

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+{
+  "extends": "./tsconfig",
+  "compilerOptions": {
+    "outDir": "types",
+    "declaration": true,
+    "noEmit": false,
+    "emitDeclarationOnly": true,
+    "removeComments": true
+  }
+}

examples/bare/index.js

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+const { createSyncFn } = require('sync-threads')
+
+const getSsmSecretSync = createSyncFn('./worker.js')
+
+// Happens at init (require) time
+const secret = getSsmSecretSync('/my-secret')
+
+console.log({ secret, source: 'init' })
+
+exports.handler = async () => {
+  // Happens every invoke
+  const secret = getSsmSecretSync('/my-secret')
+
+  console.log({ secret, source: 'handler' })
+}

examples/bare/package.json

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+{
+  "name": "syncworker-bare-example",
+  "version": "1.0.0",
+  "dependencies": {
+    "aws-sdk": "^2.783.0",
+    "sync-threads": "^1.0.0"
+  },
+  "scripts": {
+    "deploy": "sam deploy"
+  }
+}

examples/bare/template.yml

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+AWSTemplateFormatVersion: 2010-09-09
+Transform: AWS::Serverless-2016-10-31
+Resources:
+  WorkerTestFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      Runtime: nodejs12.x
+      CodeUri: .
+      Handler: index.handler
+      MemorySize: 1024
+      AutoPublishAlias: live
+      ProvisionedConcurrencyConfig:
+        ProvisionedConcurrentExecutions: 1
+      DeploymentPreference:
+        Type: AllAtOnce
+      Policies:
+        - SSMParameterReadPolicy:
+            ParameterName: my-secret

examples/bare/worker.js

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+const SSM = require('aws-sdk/clients/ssm')
+const { runAsWorker } = require('sync-threads')
+
+const ssm = new SSM()
+
+runAsWorker(async (ssmParamName) => {
+  const {
+    Parameter: { Value },
+  } = await ssm.getParameter({ Name: ssmParamName, WithDecryption: true }).promise()
+  return Value
+})

examples/webpack/package.json

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+{
+  "name": "syncworker-webpack-example",
+  "version": "1.0.0",
+  "dependencies": {
+    "aws-sdk": "^2.783.0",
+    "sync-threads": "^1.0.0"
+  },
+  "devDependencies": {
+    "webpack": "^4.44.2",
+    "webpack-cli": "^4.1.0"
+  },
+  "scripts": {
+    "build": "webpack",
+    "deploy": "npm run build && sam deploy"
+  }
+}

examples/webpack/src/index.js

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+const { createSyncFn } = require('sync-threads')
+
+const getSsmSecretSync = createSyncFn('./worker.js')
+
+// Happens at init (require) time
+const secret = getSsmSecretSync('/my-secret')
+
+console.log({ secret, source: 'init' })
+
+exports.handler = async () => {
+  // Happens every invoke
+  const secret = getSsmSecretSync('/my-secret')
+
+  console.log({ secret, source: 'handler' })
+}

examples/webpack/src/worker.js

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+const SSM = require('aws-sdk/clients/ssm')
+const { runAsWorker } = require('sync-threads')
+
+const ssm = new SSM()
+
+runAsWorker(async (ssmParamName) => {
+  const {
+    Parameter: { Value },
+  } = await ssm.getParameter({ Name: ssmParamName, WithDecryption: true }).promise()
+  return Value
+})

examples/webpack/template.yml

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+AWSTemplateFormatVersion: 2010-09-09
+Transform: AWS::Serverless-2016-10-31
+Resources:
+  WorkerTestFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      Runtime: nodejs12.x
+      CodeUri: dist
+      Handler: index.handler
+      MemorySize: 1024
+      AutoPublishAlias: live
+      ProvisionedConcurrencyConfig:
+        ProvisionedConcurrentExecutions: 1
+      DeploymentPreference:
+        Type: AllAtOnce
+      Policies:
+        - SSMParameterReadPolicy:
+            ParameterName: my-secret

examples/webpack/webpack.config.js

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+const path = require('path')
+
+module.exports = {
+  mode: 'production',
+  target: 'node',
+  node: { __filename: false }, // false, // counterintuitively, this turns off any messing with __dirname, __filename, etc
+  entry: {
+    index: './src/index.js',
+    worker: './src/worker.js',
+  },
+  output: {
+    path: path.resolve(__dirname, 'dist'),
+    filename: '[name].js',
+    libraryTarget: 'commonjs2',
+  },
+  externals: {
+    './worker': 'commonjs2 ./worker',
+  },
+  // These are only to make the output easier to read
+  optimization: { minimize: false, namedModules: true },
+}

package.json

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+{
+  "name": "sync-threads",
+  "version": "1.0.0",
+  "description": "Perform asynchronous work synchronously using worker threads",
+  "author": "Michael Hart <[email protected]> (https://github.com/mhart)",
+  "license": "MIT",
+  "repository": "github:lambci/sync-threads",
+  "main": "src/index.js",
+  "types": "types/index.d.ts",
+  "files": [
+    "src",
+    "types"
+  ],
+  "devDependencies": {
+    "@types/node": "^12.19.3",
+    "eslint": "^7.12.1",
+    "eslint-config-prettier": "^6.15.0",
+    "prettier": "^2.1.2",
+    "typescript": "^4.0.5"
+  },
+  "scripts": {
+    "declaration": "tsc -p declaration.tsconfig.json",
+    "build": "npm run declaration",
+    "prepare": "npm run build",
+    "lint": "prettier -c . && eslint ."
+  },
+  "prettier": {
+    "semi": false,
+    "singleQuote": true,
+    "printWidth": 120
+  },
+  "eslintConfig": {
+    "extends": [
+      "eslint:recommended",
+      "prettier"
+    ],
+    "env": {
+      "node": true,
+      "es2017": true
+    },
+    "parserOptions": {
+      "ecmaVersion": 2019,
+      "sourceType": "module"
+    }
+  }
+}