Remove EventMachine from Health Monitor and the Director #2502
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The eventmachine gem is no longer receiving updates. This commit moves asynchronous functionality of bosh-monitor / Health Monitor to use the async gem (and associated ecosystem) instead. * em-http-request gem is replaced by async-http gem * EventMachine connections are replaced with async-io gem * EventMachine's SMTP functionality has been replaced with net-smtp gem wrapped in async blocks. * EventMachine.popen is replaced with Open3 wrapped in async blocks * The em_threadpool_size config has been removed as there does not appear to be an analog in the async gem
With the remove from bosh-monitor, no subcomponents in the BOSH Director rely on the eventmachine gem. 🌋
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aramprice
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What is this change about?
The eventmachine gem is no longer receiving updates. This commit moves
asynchronous functionality of bosh-monitor / Health Monitor to use the
async gem (and associated ecosystem) instead.
wrapped in async blocks.
appear to be an analog in the async gem
Please provide contextual information.
Previous PRs removing other instances of EventMachine: #2497, #2499, #2500
What tests have you run against this PR?
Overall tests:
Plugins:
Very notably, several individual Health Monitor plugins have not been verified to work. The biggest risk plugins seem to be Email, Graphite, and TSDB, as they required the most rewrites due to high coupling with EventMachine. Email and Graphite have received some very basic manual tests.
Does this PR introduce a breaking change?
Not necessarily a breaking change, but the
em_threadpool_sizeconfig option for Health Monitor has been removed with no analogous configuration option added. EventMachine seems to have created a fixed-size thread pool to run its event loop whereas the async gem uses Ruby fibers.This does mean there may be a slight risk in certain places in the code of spawning many async tasks simultaneously that would have been previously limited by the size of the EventMachine thread pool; in those places, I've added a semaphore to limit the number of simultaneous tasks.