introduce enabled/recording settings

[beniwohli]

What does this pull request do?

Introduce recording/enabled as per elastic/apm#92 (comment)

[basepi]

I may be missing something, but I'm not sure I can see code paths for stopping the agent when enabled is set to False via remote config. It appears that all enabled code paths are only hit on startup, around starting threads and instrumenting code. We need to be able to disable the agent in mid-run as well via remote config, right?

[beniwohli]

@basepi the "spec" (a.k.a. random comment amidst lengthy discussion) says

Introduce enabled config: true by default, setting to false will completely disable the agent, including instrumentation and remote config polling. This can only be set locally to the agent (e.g. in code, config file, environment variable), and is interpreted once at agent initialisation time; once disabled, disabled for the process's lifetime.

That's the only place I'm aware of that defines behavior of these new settings. Is there any other place I missed?

[basepi]

Oh! I missed that. I thought enabled was a remote config option as well. We always talk about enabled/recording together in the remote config issue: elastic/apm#213

That certainly makes things easier, thanks for the explanation.

[basepi]

Great work on this! Definitely simpler and cleaner without having to deal with enabled from remote config, that was the piece that I was planning to spend the most time one. Probably good you got to this one since you had internalized the requirements better than I had. 👍

[apmmachine]

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Build stats

• Build Cause: [Pull request introduce enabled/recording settings #790 updated]

• Start Time: 2020-05-01T09:26:44.644+0000

• Duration: 27 min 51 sec (1610614)

• Commit: 56f8df9

Test stats 🧪

Test	Results
Failed	0
Passed	9193
Skipped	6667
Total	15860

[basepi]

@beniwohli if this is ready let's get it merged on Monday and cut a new release early next week.