tink worker command line args

[displague]

Description

This PR makes most constants and environment variables for tink-worker configurable from the command line, environment variables, and falls back to a .tinkerbell.yaml (worker-id: 1234) (or .json) file.

$ ./tink-worker -w 212
Error: required flag(s) "docker-registry", "registry-password", "registry-username" not set
Usage:
  tink-worker [flags]

Flags:
  -r, --docker-registry string     Sets the Docker registry (DOCKER_REGISTRY)
  -h, --help                       help for tink-worker
  -s, --max-file-size int          Maximum file size in bytes (MAX_FILE_SIZE) (default 10485760)
  -m, --max-retry int              Maximum number of retries to attempt (MAX_RETRY) (default 3)
  -p, --registry-password string   Sets the registry-password (REGISTRY_PASSWORD)
  -u, --registry-username string   Sets the registry username (REGISTRY_USERNAME)
  -i, --retry-interval duration    Retry interval in seconds (RETRY_INTERVAL) (default 3ns)
  -v, --version                    version for tink-worker
  -w, --worker-id string           Sets the worker id (WORKER_ID)
  -l, --worker-log-level string    Sets the worker log level (panic, fatal, error, warn, info, debug, trace) (WORKER_LOG_LEVEL) (default "info")
  -t, --worker-timeout duration    Max duration to wait for worker to complete (WORKER_TIMEOUT)

Notably, TINKERBELL_CERT_URL lookups are checked from a client that is defined in a parent package. This variable has not been made configurable in the same way.

This is similar in spirit to #266

Considerable refactoring was done to clean up the use of global variables. The internal pkg contains a Worker and RegistryConnDetails struct which are context bags for the methods that needed these global variables. I imagine we will continue to evolve these types to find a better shape.

Why is this needed

When run from various environments, users may have an easier time manipulating either configuration files, command line arguments, or the environment. Also, by defining these variables with cobra/viper, users can leverage --help and we can eventually use this to generate man pages, shell auto-completions, and markdown docs.

Fixes: #

How Has This Been Tested?

How are existing users impacted? What migration steps/scripts do we need?

Known Bugs

• --help does not include the environment variable hints which are shown when invalid args are supplied 🤔 (these hints are generated at runtime, we could just move them into the text description)

Checklist:

I have:

• updated the documentation and/or roadmap (if required)
• added unit or e2e tests
• provided instructions on how to upgrade

[gianarb]

That's a great effort @displague !! Now we have a page in our documentation for each service. You analyzed the topic well and you know the various ways to configure the tink-worker, do you mind adding a section in the tink-worker doc about this? https://tinkerbell.org/docs/services/tink/ Thanks

[displague]

@gianarb That sounds like a good idea. I'll need to become a little more familiar with tink-worker before I can do that. I need to add tests to this pull request (and actually test it out myself 😅 ) before doing so.

[displague]

@mmlb @detiber I've addressed most of your concerns and commented on the ones that I didn't enact your recommendations.

Do either of you have an environment where you can connect this worker to the service and interact with it as you normally would?

[codecov]

Codecov Report

Merging #287 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #287   +/-   ##
=======================================
  Coverage   22.67%   22.67%           
=======================================
  Files          15       15           
  Lines        1270     1270           
=======================================
  Hits          288      288           
  Misses        963      963           
  Partials       19       19           

Impacted Files	Coverage Δ
http-server/http_handlers.go	6.68% <ø> (ø)

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[detiber]

lgtm, thanks for all the hard work you put into this one @displague!