libstore: skip Spotlight processes when finding GC roots #13051
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Despite installations of Nix explicitly setting the `nobrowse` mount option on the store, `mdworker` processes continue to run on newly created files within it, which can result in spurious GC/path deletion failures if the stars are aligned right. IMO, the best way to fix this is to simply ignore any processes started by the Spotlight user, so that's exactly what we do here. Fixes: NixOS#6141 Change-Id: I6a6a636c70f3f443f07ba9280d5f1e04b2ed2985
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| auto lsofLines = | ||
| tokenizeString<std::vector<std::string>>(runProgram(LSOF, true, { "-n", "-w", "-F", "n" }), "\n"); | ||
| tokenizeString<std::vector<std::string>>(runProgram(LSOF, true, { "-n", "-w", "-F", "n", "-u", "^89", "-g", "^89" }), "\n"); |
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Echoing what @Qyriad said in https://gerrit.lix.systems/c/lix/+/3011/1/lix/libstore/platform/darwin.cc#53, the 89 should be pulled out into constant, with a name, and with (lots of!) docs.
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I still don't fully understand why excluding this user+processes from being GC roots makes GC more reliable.
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I assume that uid/gid 89 is related to the mdworker? We should not check this process for live gcroots because that process shouldn't create a lock.
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Also, this should only be done on macOS, since the uid 89 may refer to something else on other systems.
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It looks like lsof -u and -g supports taking names which I think would be better:
-u ^_spotlight -g ^_spotlight
grahamc@Grahams-MacBook-Pro detsys-ids-client % cat /etc/passwd | grep 89
_spotlight:*:89:89:Spotlight:/var/empty:/usr/bin/false
_biome:*:289:289:Biome:/var/db/biome:/usr/bin/false
grahamc@Grahams-MacBook-Pro detsys-ids-client % cat /etc/group | grep 89
_spotlight:*:89:
_biome:*:289:_biome
ref:
1) the `^' (negated) login name or user ID (UID), specified with the -u option;
2) the `^' (negated) process ID (PID), specified with the -p option;
3) the `^' (negated) process group ID (PGID), specified with the -g option;
4) the `^' (negated) command, specified with the -c option;
5) the (`^') negated TCP or UDP protocol state names, specified with the -s [p:s] option.
Modified from @winterqt 's patch:
Despite installations of Nix explicitly setting the
nobrowsemount option on the store,mdworkerprocesses continue to run on newly created files within it, which can result in spurious GC/path deletion failures if the stars are aligned right.IMO, the best way to fix this is to simply ignore any processes started by the Spotlight user, so that's exactly what we do here.
Fixes: #6141
Makes an assumption of the Spotlight uid/gid.