@appland/appmap-agent-js

Getting started with appmap-agent-js

appmap-agent-js is a JavaScript recording agent for the AppMap framework.

Introduction

appmap-agent-js records AppMaps from Node.js processes when they run. There are two recommended strategies for recording AppMaps when getting started:

1. Record mocha test cases when they run.
2. Record Node.js processes using start/stop controls via http calls to web endpoints. These are implemented by the AppMap agent to let users control the recording remotely.

appmap-agent-js starts the test and application processes that will be recorded.

Installation and setup

Requirements

Supported platforms:

• Unix-like os, tested on Linux and macOS; Windows is currently not supported
• Node.js 14, 16, 17
• Express.js
• git is highly recommended
• mocha >= 8.0.0 is requried for recording AppMaps from test cases (earlier versions do not support required root hooks)

Please open a new GitHub ticket if your application does not satisfy the criteria or if you experience any problems with the agent.

Installation

Run this command in your Node.js project folder (where package.json is located):

npx @appland/appmap install

You will be guided through a series of steps for installing and configuring the agent.

To use remote recording, and view and interact with recorded AppMaps, we recommend installing the AppMap extension for popular code editors:

• AppMap in VS Code Marketplace
• AppMap in JetBrains Marketplace

Initial configuration

The agent requires a valid configuration in appmap.yml file. The install command creates a default appmap.yml file by scanning the project directories. We recommend that you review the generated appmap.yml file and confirm your application name and a list of directories that will be recorded.

For projects with JavaScript source maps: add paths to sources to be recorded. For example:

name: MyApp
packages:
  - path: src/server/controllers
  - path: src/server/data
  - path: src/server/lib
  - path: src/server/models
  - path: src/server/routes

For projects without JavaScript source maps: include build folders. For example:

name: MyApp
packages:
  - path: dist/controllers
  - path: dist/data
  - path: dist/lib
  - path: dist/models
  - path: dist/routes

If you aren't sure which option to take, start with both source and build folders and optimize the appmap.yml file later.

Recording AppMaps

Once appmap.yml is configured for your project, you're ready to record AppMaps.

Recording mocha test cases:

1. Validate that the tests run prior to recording AppMaps.
2. Run appmap-agent-js with the mocha command and its parameters following the -- delimiter. For example:

npx appmap-agent-js -- mocha test/**/*.ts

1. appmap-agent-js will run the tests. When the tests are complete, the AppMaps will be stored in the default output directory tmp/appmap/mocha.

Recording Node.js processes with remote recording:

1. Run appmap-agent-js with the application-starting command and its parameters following the -- delimiter. For example:

npx appmap-agent-js -- node app/main.js --param1 hello --param2=world

1. appmap-agent-js will start the app and inject itself in its http stack. It will listen for remote recording requests on all http ports of the application.
2. Start the remote recording:
   • in VS Code
   • in JetBrains IDEs
   • with curl
3. Interact with your application or service to exercise code included in appmap.yml
4. Stop the recording and save the new AppMap to disk.

Viewing AppMaps

Recorded AppMap are saved as .appmap.json files in the project folders (default location: tmp/appmap.)

Follow the documentation for your IDE to open the recorded .appmap.json files:

• in VS Code
• in JetBrains IDEs

Frequently used parameters

The most frequently used appmap-agent-js parameters are:

• --recorder=[mocha|remote|process] : process recorder
  • default recorder is inferred from the starting command:
    • mocha if the the command contains mocha
    • remote in all other cases
  • mocha recorder records AppMaps from test cases automatically
  • remote recorder has to be started and stopped manually with http requests
  • process recorder records entire processes automatically, from start to finish
    • Warning: AppMaps recorded with the process recorder can be excessively large and noisy.
• --command="_start command_" : alternate method of specifying the app- or tests-starting command, wrapped in quotes
• --log-level=[debug|info|warning|error] : defaults to info
• --output-dir=_directory_ : location of recorded AppMap files, default is tmp/appmap or tmp/appmap/mocha

Example

npx appmap-agent-js --recorder=mocha --command="mocha test/**/*.ts" --log-level=error

Next steps

• View apppmap-agent-js reference guide
• Open AppMap documentation

Changelog

9.4.2 (2022-01-21)

Bug Fixes

• Improved node version compatibility (646692e)