Observer CLI integration

[michaelklishin]

This introduces a new command, rabbitmq-diagnostics observer, which provides a way to start observer CLI on the target node.

Depends on rabbitmq/rabbitmq-server#2006.

Per discussion with @gerhard.

[gerhard]

This is so cool! Looking forward to QA 💯

[michaelklishin]

What the interface looks like:

It is fully controlled with lettered shortcuts + RET/[Enter] and mimics the GUI Observer Erlang app.

[michaelklishin]

Note: one test is disabled as observer_cli:start/2 currently does not communicate errors correctly.

[zhongwencool]

@michaelklishin 1.4.4 is ready :0

[michaelklishin]

@gerhard this is ready for QA 🙏

[gerhard]

Nice, will check it out shortly!

[gerhard]

observer_cli is failing to install for me:

ls $PWD/.erlang.mk
ls: /Users/gerhard/github.com/rabbitmq/20190501/deps/rabbit/.erlang.mk: No such file or directory

ls $PWD/../observer_cli
ls: /Users/gerhard/github.com/rabbitmq/20190501/deps/rabbit/../observer_cli: No such file or directory

gmake deps
 DEP    observer_cli
tar: Error opening archive: Failed to open '/Users/gerhard/github.com/rabbitmq/20190501/deps/rabbit/.erlang.mk/hex/observer_cli.tar'

ls ../observer_cli
cat ../observer_cli/Makefile
noop:

umbrella is clean, I have the observer_cli branches checked out in both rabbit & rabbitmq_cli. Will continue with this tomorrow.

[gerhard]

observer_cli should be added to rabbitmq-components.mk instead of the Makefile before we merge this. I'm thinking right under dep_recon since these 2 deps are likely to be bumped in lock-step.

I also think that we should add rabbitmqctl observe in the Monitoring, observability and health checks section.

The viewport looks wrong when running scripts/rabbitmq-diagnostic observer (left) vs observer_cli:start() via the gmake run-broker shell (right):

[zhongwencool]

The diff between escript and remsh is because io:rows() can't get row in escript, so use a DEFAULT_ROW(Suppose the screen is only 13 inch).
https://github.com/zhongwencool/observer_cli/blob/master/src/observer_cli_lib.erl#L237-L241

I can't find a better way to solve this problem right now.

[gerhard]

The diff between escript and remsh is because io:rows() can't get row in escript, so use a DEFAULT_ROW(Suppose the screen is only 13 inch).

Thanks! If @dumbbell doesn't have a suggestion, happy to leave this as is.

[michaelklishin]

I also think that we should add rabbitmqctl observe in the Monitoring, observability and health checks section

It already is for rabbitmq-diagnostics. We no longer add new commands to rabbitmqctl unless there are good reason to do so (e.g. it does not clearly fit into any other tool/scope).

[michaelklishin]

@gerhard thank you. This currently will fail in our pipelines as we need zhongwencool/observer_cli#57 to go in before Mix can build it on Concourse (due to a Mix behavior neither @dumbbell nor I can explain at the moment). So we will have to do another rabbitmq-components.mk update.