Hi everybody, Currently if you do
juju debug-hooks <unit-name> # no event (hook) in particular each time there is a new event you will get a new tmux window open and this will be done serially as there is no parallelism in hook execution on a given logical machine. This is all good and intentional but when you've observed the charm behavior and want to let it work without your interference again, you need to end your tmux session. This can be hard via `exit [status]` shell builtin when you get a lot of events (think of an OpenStack HA deployment) - each time you do ./hooks/$JUJU_HOOK_NAME && exit you are dropped into a session '0' and a new session is created for a queued event for which you have to manually execute a hook and exit again until you process the backlog. tmux list-windows 0: bash- (1 panes) [239x62] [layout bbde,239x62,0,0,1] @1 # <--- dropping here after `exit` 1: update-status* (1 panes) [239x62] [layout bbe0,239x62,0,0,3] @3 (active) https://jujucharms.com/docs/stable/authors-hook-debug#running-a-debug-session "Note: To allow Juju to continue processing events normally, you must exit the hook execution with a zero return code (using the exit command), otherwise all further events on that unit may be blocked indefinitely." My initial thought was something like this - send SIGTERM to a child of sshd which will terminate your ssh session: unset n ; p=`pgrep -f 'tmux attach-session.*'$JUJU_UNIT_NAME` ; while [ "$n" != "sshd" ] ; do pc=$p ; p=$(ps -o ppid= $p | tr -d ' ') ; echo $p ; n=`basename $(readlink /proc/$p/exe || echo -n none)` ; done && kill $pc as an agent waits for an SSH client to exit: https://github.com/juju/juju/blob/develop/worker/uniter/runner/debug/server.go#L53 After thinking about it some more, I thought it would be cleaner to just kill a specific tmux session: tmux list-sessions gluster/0: 2 windows (created Fri Jun 2 20:22:30 2017) [239x62] (attached) ./hooks/$JUJU_HOOK_NAME && tmux kill-session -t $JUJU_UNIT_NAME [exited] Cleaning up the debug session no server running on /tmp/tmux-0/default Connection to 10.10.101.77 closed. The cleanup message comes from debugHooksClientScript that simply sets up a bash trap on EXIT: https://github.com/juju/juju/blob/develop/worker/uniter/runner/debug/client.go#L51 Judging by the code, it should be pretty safe to do so - unless there is a debug session in a debug context for a particular unit, other hooks will be executed regularly by an agent instead of creating a new tmux window: https://github.com/juju/juju/blob/develop/worker/uniter/runner/runner.go#L225 debugctx := debug.NewHooksContext(runner.context.UnitName()) if session, _ := debugctx.FindSession(); session != nil && session.MatchHook(hookName) { logger.Infof("executing %s via debug-hooks", hookName) err = session.RunHook(hookName, runner.paths.GetCharmDir(), env) } else { err = runner.runCharmHook(hookName, env, charmLocation) } return runner.context.Flush(hookName, err) There are two scripts: - a client script executed via an ssh client when you run juju debug-hooks - a server script which is executed in the `RunHook` function by an agent and creates a new window for an existing tmux session. client side: https://github.com/juju/juju/blob/develop/cmd/juju/commands/debughooks.go#L137 script := base64.StdEncoding.EncodeToString([]byte(unitdebug.ClientScript(debugctx, c.hooks))) innercmd := fmt.Sprintf(`F=$(mktemp); echo %s | base64 -d > $F; . $F`, script) args := []string{fmt.Sprintf("sudo /bin/bash -c '%s'", innercmd)} c.Args = args return c.sshCommand.Run(ctx) Server script: https://github.com/juju/juju/blob/develop/worker/uniter/runner/debug/server.go#L90 Client script: https://github.com/juju/juju/blob/develop/worker/uniter/runner/debug/client.go#L49 A worker waits until a client exists by monitoring a file lock at ClientExitFileLock: https://github.com/juju/juju/blob/develop/worker/uniter/runner/debug/server.go#L34 https://github.com/juju/juju/blob/develop/worker/uniter/runner/debug/server.go#L53 A path of a lock itself for a particular session: https://github.com/juju/juju/blob/develop/worker/uniter/runner/debug/common.go#L24 --- If this approach with killing a tmux session is fine then I could create a PR for the doc repo and for the description in the debugHooksServerScript to explicitly mention it. I doubt it deserves a helper command but rather a more verbose explanation. Have anybody else encountered the need to do the same? Best Regards, Dmitrii Shcherbakov Field Software Engineer IRC (freenode): Dmitrii-Sh -- Juju-dev mailing list Juju-dev@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/juju-dev
