Reduce CPU overhead associated with server service in development

[hectcastro]

Description

With the changes introduced in https://github.com/PublicMapping/district-builder-2/pull/40, the server service causes the CPU to spike (100% utilization on all virtual machine available CPUs).

Steps To Reproduce

1. Use Docker for Mac/Docker Desktop on a Mac
2. Follow the README to setup a local development environment
3. Wait for the NestJS watcher to finalize loading
4. Observe CPU utilization

Expected behavior

CPU allocated to Docker are not saturated.

Actual behavior

CPUs allocated to Docker are saturated.

Your environment

[rbreslow]

I was able to determine that this CPU overhead is only associated with the initial compilation when tsc --watch is ran for the NestJS service.

I tried configuring the /home/node/app/server volume mount with each type of performance tuning configuration, but the numbers didn't change.

I tried each available configuration for watching using the environment variable TSC_WATCHFILE. I also increased each of the TSC_WATCH_POLLINGINTERVAL levels to 5000ms.

Through the help of folks in https://github.com/microsoft/TypeScript/issues/34119, I ran tsc --watch with the --extendedDiagnostics flag. Things appear to get stuck on the initial directory watching of node_modules:

yarn run v1.22.0
$ /home/node/app/server/node_modules/.bin/tsc --watch --extendedDiagnostics -p tsconfig.build.json
[4:55:32 PM] Starting compilation in watch mode...

Current directory: /home/node/app/server CaseSensitiveFileNames: true
FileWatcher:: Added:: WatchInfo: /home/node/app/server/tsconfig.build.json 2000 undefined Config file
Synchronizing program
CreatingProgramWith::
  roots: ["/home/node/app/server/migrations/1580263521268-CreateUserTable.ts","/home/node/app/server/src/app.controller.ts","/home/node/app/server/src/app.module.ts","/home/node/app/server/src/app.service.ts","/home/node/app/server/src/main.ts","/home/node/app/server/src/healthcheck/healthcheck.service.ts","/home/node/app/server/src/users/users.module.ts","/home/node/app/server/src/users/controllers/users.controller.ts","/home/node/app/server/src/users/entities/user.entity.ts","/home/node/app/server/src/users/services/users.service.ts"]
  options: {"module":1,"declaration":true,"removeComments":true,"emitDecoratorMetadata":true,"experimentalDecorators":true,"target":4,"sourceMap":true,"outDir":"/home/node/app/server/dist","baseUrl":"/home/node/app/server","incremental":true,"watch":true,"extendedDiagnostics":true,"project":"/home/node/app/server/tsconfig.build.json","configFilePath":"/home/node/app/server/tsconfig.build.json"}
FileWatcher:: Added:: WatchInfo: /home/node/app/server/migrations/1580263521268-CreateUserTable.ts 250 undefined Source file
FileWatcher:: Added:: WatchInfo: /home/node/app/server/node_modules/typeorm/index.d.ts 250 undefined Source file
DirectoryWatcher:: Added:: WatchInfo: /home/node/app/server/node_modules 1 undefined Failed Lookup Locations
Elapsed:: 52683ms DirectoryWatcher:: Added:: WatchInfo: /home/node/app/server/node_modules 1 undefined Failed Lookup Locations
FileWatcher:: Added:: WatchInfo: /home/node/app/server/node_modules/reflect-metadata/index.d.ts 250 undefined Source file
FileWatcher:: Added:: WatchInfo: /home/node/app/server/node_modules/typeorm/connection/ConnectionManager.d.ts 250 undefined Source file
FileWatcher:: Added:: WatchInfo: /home/node/app/server/node_modules/typeorm/connection/Connection.d.ts 250 undefined Source file
FileWatcher:: Added:: WatchInfo: /home/node/app/server/node_modules/typeorm/driver/Driver.d.ts 250 undefined Source file
. . .

According to https://github.com/microsoft/TypeScript/issues/33338, we can't ignore the node_modules directory because the TypeScript compiler will watch all included source files.

There was another issue, https://github.com/microsoft/TypeScript/issues/25018, to investigate poor initial performance with --watch that was closed:

Closing this now since we have handled the optimization as best as we can for recursive directory watching where node doesnt support file system level events for recursive watching

[aaronxsu]

Had a discussion with @maurizi about this issue:

Using Docker-on-host instead of Vagrant is implied by this issue. After we determine the cause and fix this CPU overhead on MacOS, we could remove Vagrant + Ansible, which is good since it reduces the technical components and upgrades we will need to maintain in the long term.

[rbreslow]

@aaronxsu Have you looked into Docker for Mac's new experimental file system?

I tried it out and achieved performance much closer to native on an I/O intensive application at @d3b-center. Here's an analysis (from a private repo) where I compared the same data analysis running in the Docker VM vs. using a native solution:

[aaronxsu]

@rbreslow thanks for providing the analysis. I have not gotten a chance to look into this new file system yet, but this sounds familiar to something that the team member have recently dabbled on another client project (maybe).

This looks like a good hint to experiment when we get to this issue, hopefully, soon!