Proposal to add delve debugger commands

[rnagle]

Proposed changes:

• Adds the delve debugger to docker images for api and worker services
• Sets a liberal security_opt in docker-compose.yml to allow the debugger to function properly
• Adds some make commands to start delve: make debug-api and make debug-worker

Requested feedback

• Is this a good idea/would anyone find this useful?

TODO

- [ ] Create and use docker-compose-api-debug.yml (and similar for worker) for a sane way of setting environment variables, volumes and ports EDIT: turns out we don't need this

Change Details

• Running make debug-api or make debug-worker drops you into a (dlv) prompt where you can set breakpoints, examine function arguments, print the results of an expression, etc (see: delve cli docs)

Try it out:

Run docker-compose build to update your local images with delve. Then:

> make debug-api
docker-compose start db queue worker
Starting queue  ... done
Starting db     ... done
Starting worker ... done
docker-compose run -T --rm -p 3000:3000 -v /Users/ryannagle/go/src/github.com/CMSgov/bcda-app:/go/src/github.com/CMSgov/bcda-app api dlv debug -- start-api
Starting bcda-app_queue_1 ... done
Type 'help' for list of commands.
(dlv)

Then:

(dlv) break main.go:54
Breakpoint 1 set at 0xa1b06d for main.main.func1() ./main.go:54
(dlv) continue
> main.main.func1() ./main.go:54 (hits goroutine(1):1 total:1) (PC: 0xa1b06d)
    49:			{
    50:				Name:  "start-api",
    51:				Usage: "Start the API",
    52:				Action: func(c *cli.Context) error {
    53:					// Worker queue connection
=>  54:					queueDatabaseURL := os.Getenv("QUEUE_DATABASE_URL")
    55:					pgxcfg, err := pgx.ParseURI(queueDatabaseURL)
    56:					if err != nil {
    57:						return err
    58:					}
    59:

Examine arguments:

(dlv) args
c = (*github.com/CMSgov/bcda-app/vendor/github.com/urfave/cli.Context)(0xc4200d86e0)
~r1 = error nil

See local variables:

(dlv) locals
queueDatabaseURL = ""

Evaluate an expression:

(dlv) print c.App.Name
"bcda"

[msnook]

Extremely valuable!!

[em1]

Great idea!

[tbellj]

Soooo helpful!

[msnook]

like it!