`poetry install` over a running instance causes processes to segfault

[DMRobertson]

When we looking into this, we saw that poetry install is "editing" the shared object file rather than replacing it.

3510767 stat("/home/erikj/synapse/target/debug/libsynapse.so", {st_mode=S_IFREG|0755, st_size=35088552, ...}) = 0
3510767 stat("/home/erikj/synapse/synapse/synapse_rust.abi3.so", {st_mode=S_IFREG|0755, st_size=35088552, ...}) = 0
3510767 stat("/home/erikj/synapse/target/debug/libsynapse.so", {st_mode=S_IFREG|0755, st_size=35088552, ...}) = 0
3510767 stat("/home/erikj/synapse/synapse/synapse_rust.abi3.so", {st_mode=S_IFREG|0755, st_size=35088552, ...}) = 0
3510767 openat(AT_FDCWD, "/home/erikj/synapse/target/debug/libsynapse.so", O_RDONLY|O_CLOEXEC) = 3
3510767 fstat(3, {st_mode=S_IFREG|0755, st_size=35088552, ...}) = 0
3510767 ioctl(3, TCGETS, 0x7ffd23d7be30) = -1 ENOTTY (Inappropriate ioctl for device)
3510767 lseek(3, 0, SEEK_CUR)           = 0
3510767 openat(AT_FDCWD, "/home/erikj/synapse/synapse/synapse_rust.abi3.so", O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = 4
3510767 fstat(4, {st_mode=S_IFREG|0755, st_size=0, ...}) = 0
3510767 ioctl(4, TCGETS, 0x7ffd23d7be30) = -1 ENOTTY (Inappropriate ioctl for device)
3510767 lseek(4, 0, SEEK_CUR)           = 0
3510767 fstat(3, {st_mode=S_IFREG|0755, st_size=35088552, ...}) = 0
3510767 sendfile(4, 3, [0] => [35088552], 35088552) = 35088552
3510767 sendfile(4, 3, [35088552], 35088552) = 0
3510767 close(4)                        = 0
3510767 close(3)                        = 0
3510767 stat("/home/erikj/synapse/synapse/synapse_rust.abi3.so", {st_mode=S_IFREG|0755, st_size=35088552, ...}) = 0
3510767 chmod("/home/erikj/synapse/synapse/synapse_rust.abi3.so", 0100755) = 0

Erik investigated further and ultimately submitted a patch to setuptools-rust: PyO3/setuptools-rust#295. This was accepted, but has yet to be released.

---

Once a newer setuptools-rust release is available, we should take advantage of this to ensure that we don't accidentally segfault running processes when we actually want to do a rolling restart.

At the moment, setuptools_rust is currently upper-bounded at the current release version:

synapse/pyproject.toml

Lines 366 to 371 in ae69d69

	# The upper bounds here are defensive, intended to prevent situations like
	# #13849 and #14079 where we see buildtime or runtime errors caused by build
	# system changes.
	# We are happy to raise these upper bounds upon request,
	# provided we check that it's safe to do so (i.e. that CI passes).
	requires = ["poetry-core>=1.0.0,<=1.5.0", "setuptools_rust>=1.3,<=1.5.2"]

which will presumably need bumping; confusingly we also have a lower bound here:

synapse/pyproject.toml

Lines 212 to 220 in ae69d69

	# This is for building the rust components during "poetry install", which
	# currently ignores the `build-system.requires` directive (c.f.
	# https://github.com/python-poetry/poetry/issues/6154). Both `pip install` and
	# `poetry build` do the right thing without this explicit dependency.
	#
	# This isn't really a dev-dependency, as `poetry install --no-dev` will fail,
	# but the alternative is to add it to the main list of deps where it isn't
	# needed.
	setuptools_rust = ">=1.3"

[DMRobertson]

Once a newer setuptools-rust release is available

Until then, the current workaround is to

• mv synapse_rust_abi.so synapse_rust_abi.so.backup
• and then poetry install

which should keep currently active processes running.

[DMRobertson]

#15512 means that anything using the poetry environment should now include the fix.

[landryb]

#15512 means that anything using the poetry environment should now include the fix.

shouldnt the dependency in https://github.com/matrix-org/synapse/blame/develop/pyproject.toml#L371 be relaxed to accept 1.6.0 now ?

[DMRobertson]

Urgh, yes it should. Thank you for spotting.