If a thread command fails (like the input framework not finding a
file), that now (1) no longer hangs Bro, and (2) even allows for
propagating error messages back before the thread is stops.
(Actually, the thread doesn't really "stop"; the thread manager keeps
threads around independent of their success; but it no longer polls
them for input.)
Closes#858.
Sending SIGTERM triggers a normal shutdown of all threads that waits
until they have processed their remaining data. However, sending a 2nd
SIGTERM while waiting for them to finish will immediately kill them
all.
This is based on Gilbert's code but I ended up refactoring it quite a
bit. That's why I didn't do a direct merge but started with a new
branch and copied things over to adapt. It looks quite a bit different
now as I tried to generalize things a bit more to also support the
Input Framework.
The larger changes code are:
- Moved all logging code into subdirectory src/logging/. Code
here is in namespace "logging".
- Moved all threading code into subdirectory src/threading/. Code
here is in namespace "threading".
- Introduced a central thread manager that tracks threads and is
in charge of termination and (eventually) statistics.
- Refactored logging independent threading code into base classes
BasicThread and MsgThread. The former encapsulates all the
pthread code with simple start/stop methods and provides a
single Run() method to override.
The latter is derived from BasicThread and adds bi-directional
message passing between main and child threads. The hope is that
the Input Framework can reuse this part quite directly.
- A log writer is now split into a general WriterFrontend
(LogEmissary in Gilbert's code) and a type-specific
WriterBackend. Specific writers are implemented by deriving from
the latter. (The plugin interface is almost unchanged compared
to the 2.0 version.).
Frontend and backend communicate via MsgThread's message
passing.
- MsgThread (and thus WriterBackend) has a Heartbeat() method that
a thread can override to execute code on a regular basis. It's
triggered roughly once a second by the main thread.
- Integration into "the rest of Bro". Threads can send messages to
the reporter and do debugging output; they are hooked into the
I/O loop for sending messages back; and there's a new debugging
stream "threading" that logs, well, threading activity.
This all seems to work for the most part, but it's not done yet.
TODO list:
- Not all tests pass yet. In particular, diffs for the external
tests seem to indicate some memory problem (no crashes, just an
occasional weird character).
- Only tested in --enable-debug mode.
- Only tested on Linux.
- Needs leak check.
- Each log write is currently a single inter-thread message. Bring
Gilbert's bulk writes back.
- Code needs further cleanup.
- Document the class API.
- Document the internal structure of the logging framework.
- Check for robustness: live traffic, aborting, signals, etc.
- Add thread statistics to profile.log (most of the code is there).
- Customize the OS-visible thread names on platforms that support it.
