Unfortunately, these values aren't available from getrusage(2), or any other
builtin Go API. Go itself doesn't provide a mechanism (like on Windows) to call
into system libraries. Using a 3rd party package[1] to dynamically call system
libraries was proposed and rejected, to avoid adding to the number of
dependencies. That leaves using cgo, which is used here when available. When
not available (either because of cross compiling or explicitly disabling it), a
stub function is linked instead, and the metrics are not exported. That way,
cross compiling of other platforms is unaffected (and can also still be done
with Darwin too, but at the cost of not exporting these metrics).
Note that building an amd64 image on an arm64 mac or vice-versa is cross
compiling, and will use the stub method by default. This can be avoided by
setting `CGO_ENABLED=1` in the environment to force the use of cgo for both
architectures.
I'm unsure of the usefulness of the potential adjustment made to the virtual
memory value after calling `mach_vm_region()`. I've not seen that code get run
with a native amd64 or arm64 image, or with an amd64 image running under
Rosetta. But that's what the `ps(1)` command does, and I think we should report
what the system tools do.
When I was testing this on a beta of macOS 15 with Go 1.21.13 (the current
minimum support for this module), the amd64 image ran fine under Rosetta, but
the arm64 image immediately printed a message that it was killed, even prior to
the cgo call. This seems to be a recurring issue on macOS[2][3], and passing
`-ldflags -s` to `go build` avoided the issue. Go 1.23.1 worked out of the box,
without fiddling with linker flags, so I don't think this is an issue- Go 1.21
is simply too old to support macOS 15, but I thought it was worth noting. I
supposed we could gate the cgo code with an additional build flag, if anyone is
concerned about this.
[1] https://github.com/ebitengine/purego
[2] https://github.com/golang/go/issues/19841#issuecomment-293334802
[3] https://github.com/golang/go/issues/11887#issuecomment-125694604
Signed-off-by: Matt Harbison <mharbison72@gmail.com>
* process_collector: fill in most statistics on macOS
Unfortunately, the virtual memory, resident memory, and network stats will
require access to undocumented C functions. I was warned off of cgo in IRC
because it would then have to be enabled in a bunch of different projects that
use this module, but I already was against it because that would break the
ability to cross-compile. There is no interface to `dlopen` built into golang.
The `github.com/ebitengine/purego` module looks promising (I can cross-compile
and call these methods), but I'm currently getting unexpected results. I'll
follow up with that separately if I can get it working, but hopefully this stuff
is pretty uncontroversial.
Tested on macOS 10.14.6 (amd64), macOS 14.6.1 (amd64), and macOS 15.0 (arm64)
by spawning `/usr/bin/ulimit -a -S` and `/usr/sbin/lsof -c $my_process` from
the test exporter process, and `ps -o lstart,vsize,rss,utime,stime,command` from
the shell, and comparing results with the exported metrics.
I can't find documentation for `RLIMIT_AS` on macOS (specifically if it's in
bytes or pages). It's currently being reported back as `RLIM_INFINITY`, which
seems reasonable, because I've come across reports that the value is ignored
anyway[1]. The bash 3.2 code for the built-in `ulimit` divides the value
reported by `getrusage(2)` by 1024 when printing, as it does for `RLIMIT_DATA`,
which is documented as being bytes in `getrusage(2)`. The help for `ulimit`
indicates it prints both in kbytes, so it's reasonable to assume this is already
in bytes.
[1] https://issues.chromium.org/issues/40581251#comment3
Signed-off-by: Matt Harbison <mharbison72@gmail.com>
* Update prometheus/process_collector_darwin.go
Co-authored-by: Ben Kochie <superq@gmail.com>
Signed-off-by: Matt Harbison <57785103+mharbison72@users.noreply.github.com>
---------
Signed-off-by: Matt Harbison <mharbison72@gmail.com>
Signed-off-by: Matt Harbison <57785103+mharbison72@users.noreply.github.com>
Co-authored-by: Ben Kochie <superq@gmail.com>
Co-authored-by: Bartlomiej Plotka <bwplotka@gmail.com>
Matt Harbison