* Fixed fdbcli to be more idiomatic.
* Removed is_binary_serializable in favor of std::is_pod<>
* Removed custom enable_if<> in favor of std::enable_if<>
* Removed HEY REVIEWER comments
* Removed print from prof.py
* Added FLOW_PROFILER_ENABLED=yes to circus components that wished to enable the flow profiler.
backtrace() gives a list of return addresses, which means that addr2line will
print out the line after the caller. GetStackTrace returns the list of caller
addresses, so the addr2line results should be accurate. The flow profiler was
also changed to use the new backtracing code, so flow profiles will now be
accurate as well. Unfortunately, the abseil code doesn't work on MacOS, so we
still fall back to backtrace() in this case.
For the stack unwinder to work, we must disable -fomit-frame-pointer. This can
result in a small performance penalty, as it effectively reduces the number of
general purpose registers available by one. (I'm also curious if this has
anything to do with the overly frequent "<value optimized out>" messages from
gdb.) If this shows up as a problem, we can make release builds still have
-fomit-frame-pointer, and fall back to backtrace when it's enabled then as
well.
This code is all Apache 2 licensed, and all headers were maintained when
concatinated, so we should be completely fine from a legal standpoint.
I've scriptified the steps that I took so that if we need to update this code
in the future, it hopefully shouldn't be too much of a hassle.
This is the combination of two small changes.
1. Add support for a string knob type.
2. Change profiles to be written to the log directory instead of the working
directory.
We have three options of where to write files: the working directory, the data
directory, and the log directory.
The working directory may be set to a non-writable location, and likely
contains the fdb binaries. Allowing these files to be overwritten would likely
not be a wise idea.
The data directory hosts our sqlite b-trees. It would also be very unfortunate
if these were ever overwritten by an unfortunate profile name.
The log directory contains logs. Out of the three, these matter the least if
they disappear or become corrupted.
Thus, we write to the log directory.
Previously, one could request profiles to be stored at
"../../../../../../etc/passwd". Now we expand the paths, including symlinks,
and ensure that the target is a child of the targetted subdirectory. This was
the least convoluted way I could figure out to handle paths.
This adds the fdbcli commands:
* profile list -- Lists all workers in a way that doesn't fill `kill`'s list.
* profile flow run -- Allows starting flow profiling on a set of hosts for a specified interval.
And threads through all the support for enabling and disabling profiling as an RPC.
Yichi Chiang