Triggered by investigating
xmon: could not read message type: unexpected EOF, will reconnect
xmon: connected to xmon REDACTED
Undertaker: hard abort - running abort handlers
Uncaught exception thrown: SyscallException(Xmon.cpp@186, 9/EBADF=Bad file descriptor in void Xmon::run()): setsockopt
which caused crashes in shards/CDC.
And hopefully reduce the likelihood of bugs. On the write end, given
that we do things less asynchronously, things might be a bit slower,
but I think the simplification is worth it for now.
Also, fix/improve a bunch of other stuff.
This is one of the two data model/protocol changes I want to perform
before going into production, the other being file atime.
Right now the kernel module does not take advantage of this, but
it's OK since I tested the rest of the code reasonably and the goal
here is to perform the protocol/data changes.
...most notably we now produce fully static binaries in an alpine
image.
A few assorted thoughts:
* I really like static binaries, ideally I'd like to run EggsFS
deployments with just systemd scripts and a few binaries.
* Go already does this, which is great.
* C++ does not, which is less great.
* Linking statically against `glibc` works, but is unsupported.
Not only stuff like NSS (which `gethostbyname` requires)
straight up does not work, unless you build `glibc` with
unsupported and currently apparently broken flags
(`--enable-static-nss`), but also other stuff is subtly
broken (I couldn't remember exactly what was broken,
but see comments such as
<https://github.com/haskell/haskell-language-server/issues/2431#issuecomment-985880838>).
* So we're left with alternative libcs -- the most popular being
musl.
* The simplest way to build a C++ application using musl is to just
build on a system where musl is already the default libc -- such
as alpine linux.
The backtrace support is in a bit of a bad state. Exception stacktraces
work on musl, but DWARF seems to be broken on the normal release build.
Moreover, libunwind doesn't play well with musl's signal handler:
<https://maskray.me/blog/2022-04-10-unwinding-through-signal-handler>.
Keeping it working seems to be a bit of a chore, and I'm going to revisit
it later.
In the meantime, gdb stack traces do work fine.
Also, produce fully static binaries. This means that `gethostname`
does not work (doesn't work with static glibc unless you build it
with `--enable-static-nss`, which no distro builds glibc with).
