Mwp-consumer NPM

Mock MWP consumer app for platform testing

Setup

Go to the meetup-web-platform repo root and run lerna bootstrap. You may need to first install lerna if you haven't already npm install --global lerna
Go to the meetup-web-platform/packages/mwp-consumer/ directory and run lerna run build && yarn start | grep "GC HAPPENED"

In a new terminal window, run Apache Bench with a valid member cookie env variable, e.g.

$ COOKIE='MEETUP_MEMBER_DEV="id=..."'
$ ab -H Cookie:$COOKIE -l -c 10 -n 3000 https://beta2.dev.meetup.com:8000/

Watch the server logs - you should see periodic "GC HAPPENED" output, and eventually something that looks like

GC HAPPENED Memory leak detected:
{ growth: 8509368,
 reason: 'heap growth over 5 consecutive GCs (33s) - 885.29 mb/hr' }

Important If you are making changes to files, you must re-build and restart the dev server with lerna run build && yarn start | grep "GC HAPPENED"

Performance monitoring strategies

The early-return

Requests to the app-rendering endpoint primarily go through the following modules:

mwp-app-server/src/util/index.js - Starting and configuring the Node server
mwp-app-route-plugin/src/handler.js - Node route handler
mwp-core/src/renderers/server-render.jsx - Application setup, including Redux store
mwp-app-render/src/components/ServerApp.jsx - React app mounting

There are many other modules involved, but these are the best-defined entry points for testing how the server behaves when each function returns early, i.e. checking the performance impact of skipping some rendering steps.

For the most part, every part of the server startup routine is required.
The route handler just needs to call reply('<SOME RESPONSE STRING>') - adding that and a return before the renderer is called will show the the theoretical performance of a fully-configured server that executes no rendering logic
The main rendering function in server-render.jsx is makeRenderer, which returns a function that is called with each incoming request object and returns an Observable that emits a { statusCode: int, result: string } object. You can return the following to short-circuit the function at any point:
```
return Observable.of({ statusCode: 200, result: 'whatever' });
```
ServerApp is just the top-level React component wrapper for the consumer app that is defined statically routes object. You can return plain HTML JSX elements anywhere in the app tree to determine the performance impact of particular branches of the application tree.

The plugin switcheroo

Testing the effect of particular plugins on server performance is a bit trickier because they have cross dependencies. For example, mwp-app-route-plugin depends on mwp-logger-plugin, so in order to test the server without mwp-logger-plugin, mwp-app-route-plugin has to be refactored to use something else, or mwp-logger-plugin must be refactored to supply the same API through dummy functions, e.g. { log() {}, error() {}, warn() {} }. The latter approach is preferable because you won't have to refactor all dependent packages.

Over time, we hope to update all plugins to have fewer cross dependencies - e.g. by making mwp-logger-plugin optional using a fallback interface that is internally defined within each plugin that uses it. This is a long-term goal and is unlikely to be done until well into 2018.