Add --graph-only option for the orca serve entry point

[jonmmease]

Overview

Added a --graph-only boolean command line option to the orca serve entry point. When this option is present, only the plotly-graph component is run (not thumbnail, dash, etc.).

When graph conversion is the only service needed, this option reduces the number of electron processes, the memory usage, and startup time.

Past Discussion

See #110

Resource usage comparison

Here's a comparison of the baseline resource usage on OSX

Without --graph-only (legacy behavior)

There are 8 processes running, consuming ~390MB of memory.

Based on my testing from Python, from launching the server to receiving the first image conversion takes about 2.2 seconds.

With `--graph-only

There are 3 processes running, consuming ~120MB of memory.

Based on my testing from Python, from launching the server to receiving the first image conversion takes about 1.7 seconds.

Resource Summary

If all you need is graph conversion, this flag saves 5 processes, 270MB of memory, and a half second of startup time.

Testing

I added a new integration testing file at test/integration/orca_serve_graph-only_test.js. This file is based on a subset of the testing in test/integration/orca_serve_test.js. But it checks to make sure there is only 1 window running, that the graph-component is running, and that the thumbnail component is not running.

[etpinard]

Brilliant PR @jonmmease ! Thanks very much!

Now, that docker-build-and-push job is failing again, and but the looks of it it never ran successfully off one of your branches.

Digging deeper, the environment variable $DOCKER_USER and $DOCKER_PASS are blank on runs off your branches whereas they are correctly filled otherwise.

So, I think we should probably disable docker-build-and-push off forks. I hope there's a way to do that in the circle config. I doubt we want to pass environment variable to all open-source contributors. Alternatively, @jonmmease you could start branching off the official repo (I invited you to join as collaborator) instead of off your fork.

[jonmmease]

Sure thing!

Yeah, it would be nice to disable the docker-build-and-push CI job for forks if there's a way. But in the meantime I'll go ahead and move my two current PRs to the main repo and see if that takes care of it.

[etpinard]

But in the meantime I'll go ahead and move my two current PRs to the main repo and see if that takes care of it.

Thanks 🎉

[etpinard]

🐄 . at the end.

[jonmmease]

Done in #114 🙂

[jonmmease]

Replaced by #114