libflux: refactor reactor/watcher implementation #6494
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garlick
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Problem: some older code violates RFC 7 whitespace guidelines. Break long parameter lists to one per line.
Problem: watcher implementations are derefencing w->fn() but otherwise use accessors for struct watcher internals. Add watcher_call() to replace direct access to structure member.
Problem: the zmq watcher is implemented in an ambigously named source file. Use zwatcher.[ch] instead of reactor.[ch] Rename unit test too. Update include directives.
Problem: the zmq watcher is implemeted directly on libev which complicates changing the Flux reactor implementation to something else. Reimplement watcher using the Flux API.
Problem: the flux_t handle watcher is implemeted directly on libev which complicates changing the Flux reactor implementation to something else. Reimplement watcher using the Flux API. Move it to a new source file since it is now fairly standalone.
Problem: the subprocess internal "buffer watchers" are implemeted directly on libev which complicates changing the Flux reactor implementation to something else. Reimplement watcher using the Flux API.
Problem: the internal sdbus watcher is_active() callback calls ev_is_active() on a flux_watcher_t, which is accepted because ev_is_active() is a macro that casts its pointer argument. Although flux_watcher_is_active() is not currently used in the sdbus module (the only user of the watcher), fix the code in case it ever is.
Problem: the reactor and watcher implementations are unnecessarily exposed and co-mingled. Split up reactor.c, reactor.h (public), reactor_private.h into: reactor.c, reactor_private.h Only the reactor struct and implementation. Add an accessor for the ev_loop, to be used only in watcher_wrap.c watcher.c, watcher_private.h Only the watcher struct and generic "class" implementation. Add accessors to avoid exposing watcher struct details to watcher implementations. watcher_wrap.c Wrapped libev watcher implementations. These now use watcher accessors rather than directly accessing the watcher struct. A public watcher.h header is added to split out the public watcher interfaces from reactor.h. This was not strictly necessary, but reactor.h was a little busy. Users are still expected to just include <flux/core.h>. Update the zmq watcher, flux_t handle watcher, fbuf watchers, and sdbus watcher to include watcher_private.h and use watcher accessors. Replacing the inlines in reactor_private.h with actual functions in watcher.c necessitated linking some executables with src/common/libflux/watcher.lo. libev use is now localized to reactor.c and watcher_wrap.c, which should make transitioning to a new implementation somewhat easier than before. The code should also be easier to read and navigate.
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Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #6494 +/- ##
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- Coverage 83.63% 83.62% -0.02%
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Files 525 522 -3
Lines 87682 87669 -13
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- Hits 73334 73309 -25
- Misses 14348 14360 +12
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This was split off of an (aborted for now) effort to convert flux to libuv, mentioned in #6492.
This isolates the reactor and watcher implementations from each other somewhat, and also localizes libev calls to two source files.
Full disclosure: several watchers including the ones for zmq sockets,
flux_thandles, and subprocess buffers are reimplemented in terms of the Flux API, which might introduce a few extra small mallocs per instance. This is because libev watchers are just structs that you initialize instead of opaque objects that you allocate, and each of these high level "composite watchers" contains three or four internal watchers that are nowflux_watcher_t's. I can't imagine this is a big deal.