Can't ^C when using the daemon, during connection to pailgun

[illicitonion]

There are a bunch of ^Cs in the middle of this log which were ignored (see that the process fully resolved and gave a list of changed targets)

pants$ ./pants -ldebug --changed-parent=master list
DEBUG] Selected watchman binary bootstrapped to: /Users/dwagnerhall/.cache/pants/bin/watchman/mac/10.13/4.5.0/watchman
DEBUG] Executing: git --git-dir=/Users/dwagnerhall/src/github.com/pantsbuild/pants/.git --work-tree=/Users/dwagnerhall/src/github.com/pantsbuild/pants rev-parse --abbrev-ref HEAD
DEBUG] Detected git repository at /Users/dwagnerhall/src/github.com/pantsbuild/pants on branch dwagnerhall/options/targetroots
DEBUG] Target alias resources has already been registered. Overwriting!
DEBUG] ProjectTree ignore_patterns: ['.*/', '/dist/', '/build-support/*.venv/']
DEBUG] loading native engine python module from: /var/folders/1j/jzw90nc51nn_358mmhnwc_fh0000gn/T/tmpsUEMGN
DEBUG] Selected watchman binary bootstrapped to: /Users/dwagnerhall/.cache/pants/bin/watchman/mac/10.13/4.5.0/watchman
DEBUG] watchman is running, pid=80339 socket=/Users/dwagnerhall/src/github.com/pantsbuild/pants/.pids/watchman/watchman.sock
DEBUG] acquiring lock: <pants.process.lock.OwnerPrintingInterProcessFileLock object at 0x103a591d0>
DEBUG] pantsd: is_alive=True new_fingerprint=fddd842df3ffcde738721674a3c1c0cbea94aa3a current_fingerprint=cf404e17a8a81843b45dd2283b2d9b81ab7f448b
DEBUG] terminating pantsd
DEBUG] sending signal 15 to pid 80341
DEBUG] successfully terminated pid 80341
DEBUG] purging metadata directory: /Users/dwagnerhall/src/github.com/pantsbuild/pants/.pids/pantsd
DEBUG] launching pantsd
DEBUG] purging metadata directory: /Users/dwagnerhall/src/github.com/pantsbuild/pants/.pids/pantsd
DEBUG] cmd is: PANTS_ENTRYPOINT=pants.pantsd.pants_daemon:launch /Users/dwagnerhall/src/github.com/pantsbuild/pants/build-support/pants_dev_deps.venv/bin/python /Users/dwagnerhall/src/github.com/pantsbuild/pants/src/python/pants/bin/pants_loader.py -ldebug --changed-parent=master list
DEBUG] released lock: <pants.process.lock.OwnerPrintingInterProcessFileLock object at 0x103a591d0>
DEBUG] pantsd is running at pid 80654, pailgun port is 55209
DEBUG] connecting to pailgun on port 55209
^C^C^C^CDEBUG] Target alias resources has already been registered. Overwriting!
DEBUG] spec_roots are: OrderedSet()
DEBUG] changed_request is: ChangedRequest(changes_since='master', diffspec=None, include_dependees='none', fast=False)
DEBUG] Executing: git --git-dir=/Users/dwagnerhall/src/github.com/pantsbuild/pants/.git --work-tree=/Users/dwagnerhall/src/github.com/pantsbuild/pants diff --name-only HEAD -- /Users/dwagnerhall/src/github.com/pantsbuild/pants
DEBUG] Executing: git --git-dir=/Users/dwagnerhall/src/github.com/pantsbuild/pants/.git --work-tree=/Users/dwagnerhall/src/github.com/pantsbuild/pants diff --name-only master...HEAD -- /Users/dwagnerhall/src/github.com/pantsbuild/pants
DEBUG] Executing: git --git-dir=/Users/dwagnerhall/src/github.com/pantsbuild/pants/.git --work-tree=/Users/dwagnerhall/src/github.com/pantsbuild/pants ls-files --other --exclude-standard -- /Users/dwagnerhall/src/github.com/pantsbuild/pants
DEBUG] changed files: set([u'src/python/pants/init/target_roots.py', u'pants.ini', u'tests/python/pants_test/engine/legacy/test_graph.py', u'src/python/pants/pantsd/service/pailgun_service.py'])
DEBUG] Launching 4 roots.
DEBUG] Root Select(AscendantAddresses(directory=u'src/python/pants/init'), =Collection.of(HydratedTarget)) completed.
DEBUG] Root Select(AscendantAddresses(directory=u'tests/python/pants_test/engine/legacy'), =Collection.of(HydratedTarget)) completed.
DEBUG] Root Select(AscendantAddresses(directory=u'src/python/pants/pantsd/service'), =Collection.of(HydratedTarget)) completed.
DEBUG] Root Select(AscendantAddresses(directory=u''), =Collection.of(HydratedTarget)) completed.
DEBUG] computed 4 nodes in 0.003063 seconds. there are 2932 total nodes.
DEBUG] changed addresses: [BuildFileAddress(src/python/pants/init/BUILD, init), BuildFileAddress(tests/python/pants_test/engine/legacy/BUILD, graph), BuildFileAddress(src/python/pants/pantsd/service/BUILD, pailgun_service)]
DEBUG] target_roots are: ChangedTargetRoots((SingleAddress(directory='src/python/pants/init', name='init'), SingleAddress(directory='tests/python/pants_test/engine/legacy', name='graph'), SingleAddress(directory='src/python/pants/pantsd/service', name='pailgun_service')))
DEBUG] build_graph is: <pants.engine.legacy.graph.LegacyBuildGraph object at 0x110d83150>
DEBUG] Injecting to <pants.engine.legacy.graph.LegacyBuildGraph object at 0x110d83150>: (SingleAddress(directory='src/python/pants/init', name='init'), SingleAddress(directory='tests/python/pants_test/engine/legacy', name='graph'), SingleAddress(directory='src/python/pants/pantsd/service', name='pailgun_service'))
DEBUG] Launching 6 roots.
DEBUG] Root Select(SingleAddress(directory='src/python/pants/init', name='init'), =Collection.of(HydratedTarget)) completed.
DEBUG] Root Select(SingleAddress(directory='src/python/pants/init', name='init'), =BuildFileAddresses) completed.
DEBUG] Root Select(SingleAddress(directory='tests/python/pants_test/engine/legacy', name='graph'), =Collection.of(HydratedTarget)) completed.
DEBUG] Root Select(SingleAddress(directory='tests/python/pants_test/engine/legacy', name='graph'), =BuildFileAddresses) completed.
DEBUG] Root Select(SingleAddress(directory='src/python/pants/pantsd/service', name='pailgun_service'), =Collection.of(HydratedTarget)) completed.
DEBUG] Root Select(SingleAddress(directory='src/python/pants/pantsd/service', name='pailgun_service'), =BuildFileAddresses) completed.
DEBUG] computed 6 nodes in 0.004505 seconds. there are 2935 total nodes.
DEBUG] address_mapper is: <pants.engine.legacy.address_mapper.LegacyAddressMapper object at 0x110d83390>
DEBUG] Launching 1 roots.
DEBUG] Root Select(SingleAddress(directory=u'list', name=u'list'), =BuildFileAddresses) completed.
DEBUG] computed 1 nodes in 0.009143 seconds. there are 2940 total nodes.
DEBUG] Injecting to <pants.engine.legacy.graph.LegacyBuildGraph object at 0x110d83150>: (SingleAddress(directory='src/python/pants/init', name='init'), SingleAddress(directory='tests/python/pants_test/engine/legacy', name='graph'), SingleAddress(directory='src/python/pants/pantsd/service', name='pailgun_service'))
DEBUG] Launching 6 roots.
DEBUG] Root Select(SingleAddress(directory='src/python/pants/init', name='init'), =Collection.of(HydratedTarget)) completed.
DEBUG] Root Select(SingleAddress(directory='src/python/pants/init', name='init'), =BuildFileAddresses) completed.
DEBUG] Root Select(SingleAddress(directory='tests/python/pants_test/engine/legacy', name='graph'), =Collection.of(HydratedTarget)) completed.
DEBUG] Root Select(SingleAddress(directory='tests/python/pants_test/engine/legacy', name='graph'), =BuildFileAddresses) completed.
DEBUG] Root Select(SingleAddress(directory='src/python/pants/pantsd/service', name='pailgun_service'), =Collection.of(HydratedTarget)) completed.
DEBUG] Root Select(SingleAddress(directory='src/python/pants/pantsd/service', name='pailgun_service'), =BuildFileAddresses) completed.
DEBUG] computed 6 nodes in 0.001575 seconds. there are 2940 total nodes.
DEBUG] Executing: git --git-dir=/Users/dwagnerhall/src/github.com/pantsbuild/pants/.git --work-tree=/Users/dwagnerhall/src/github.com/pantsbuild/pants rev-parse HEAD
DEBUG] Executing: git --git-dir=/Users/dwagnerhall/src/github.com/pantsbuild/pants/.git --work-tree=/Users/dwagnerhall/src/github.com/pantsbuild/pants rev-parse --abbrev-ref HEAD
src/python/pants/init:init
tests/python/pants_test/engine/legacy:graph
src/python/pants/pantsd/service:pailgun_service

[kwlzn]

I'm able to repro this too. I also see a strange delay in handling the ^C without the daemon enabled, but that eventually results in a segv.

I believe whats happening here in the daemon context is roughly along the lines of:

1. the thin client launches the daemon and connects to it, issuing an execution request to the captive engine/scheduler
2. the way the thin client handles control-C is by storing the PID of the pantsd-runner and then sending a signal to it via os.kill().
3. the PID is not sent to the thin client until the pantsd-runner forks, to avoid the signal hitting pantsd directly (which will presumably crash and lose all daemon state), so until the fork happens, control-C is effectively an un-retried no-op

so to fix, I think we'll have to:

(1) instruct the thin client to target the daemon process for control-c signals in addition to the pantsd-runner
and
(2A) be ok with crashing the daemon if a user hits control-C during the sync phase (based on presumed default signal handling)
or
(2B) figure out how to plumb a smarter signal handler into the daemon that would be able to gracefully interrupt engine execution without crashing

[blorente]

Closed in #7924