Privatae
38 lines
1.3 KiB
Go
38 lines
1.3 KiB
Go
//go:build linux
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package main
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import (
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"os"
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"syscall"
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"golang.org/x/sys/unix"
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)
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// stdinIsTerminal distinguishes a person at a shell from the service. It decides
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// which way the machine lock waits: a human who typed `run` wants "already
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// running" immediately, while the unit must BLOCK so a restart queues behind the
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// dying primary instead of exiting and being restarted every two seconds — the
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// crash-loop the lock exists to end.
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//
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// It is a real isatty (TCGETS), not a character-device test. os.ModeCharDevice —
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// which the first draft used — is TRUE for /dev/null, and every installed daemon
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// has stdin on /dev/null: the installed unit sets no StandardInput, so systemd's
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// default (null) applies. The daemon therefore took the fail-fast branch in the
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// only deployment shape that exists, and the blocking standby the design asks
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// for was unreachable. Measured on 18 of 18 reachable boxes in one deployment.
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func stdinIsTerminal() bool {
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_, err := unix.IoctlGetTermios(int(os.Stdin.Fd()), unix.TCGETS)
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return err == nil
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}
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// ownerUID reports the owning uid of a stat result. Used to refuse locking inside
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// a runtime directory root does not own.
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func ownerUID(fi os.FileInfo) (uint32, bool) {
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st, ok := fi.Sys().(*syscall.Stat_t)
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if !ok {
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return 0, false
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}
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return st.Uid, true
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}
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