dependencies

Dependencies

after: and before: control startup ordering. A service listed in another's after is started first; before is the same edge written from the other side. gopherd computes the order with a topological sort.

Config

# Order startup with `after` and `before`: zeroth -> first -> second.
processes:
  - name: second
    command: /bin/sh
    args: ["-c", "echo second >> ORDERLOG && sleep 300"]
    after: [first]
    on-failure: shutdown
  - name: first
    command: /bin/sh
    args: ["-c", "echo first >> ORDERLOG && sleep 300"]
    on-failure: shutdown
  - name: zeroth
    command: /bin/sh
    args: ["-c", "echo zeroth >> ORDERLOG && sleep 300"]
    before: [first]
    on-failure: shutdown

• second declares after: [first], so gopherd starts first first.
• zeroth declares before: [first] — the mirror form, useful when the inserted service is the one being added and the existing configs should stay untouched.
• Declaration order in the file does not matter — the dependency graph does.
• after/before order startup only; use requires if a dependency failure should also fail the dependent.

Expected behavior

• zeroth starts first, then first, then second; the log reads zeroth, first, second.

Test

ORDERLOG is replaced with a temp path via RunConfig. The test asserts gopherd's started lines appear in zeroth, first, second order. Note after/before order gopherd's start calls; the echoes themselves run in separate shells, so use a ready-check when the dependent needs the dependency's work completed.

go test ./documentation/dependencies/ -v