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.
A way to access this stream is required if we wish to be able to toggle
profiling from fdbcli. There's two ways to do this:
1. Use `monitorLeader()` to get a `ClusterControllerFullInterface`, and use
`getWorkers` from there to get a list of `WorkerInterface`s, from which we can
access cpuProfilerRequest.
2. Move cpuProfilerRequest to ClientWorkerInterface and use the existing code
in the client that can fetch a list of all `ClientWorkerInterface`s.
The split between WorkerInterface and ClientWorkerInterface appears to be
what a client might have a need to call versus what is fdbserver-internal (and
thus no client should even want to call). Thus, it seems to make more sense to
acknowledge that profiling is useful to be able to toggle from a client, and go
with option (2).
Alec Grieser