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DescriptionMichele Baldessari
2019-06-12 08:36:37 UTC
Description of problem:
Currently podman exec returns 125 in both these cases:
A) Non-existing container
[root@controller-0 ~]# podman exec nonexistingcontainer /bin/true; echo $?
unable to exec into nonexistingcontainer: no container with name or ID nonexistingcontainer found: no such container
125
B) Stopped container
[root@controller-0 ~]# podman exec memcached /bin/true; echo $?
cannot exec into container that is not running
125
So in order to work around the I/O perf issues reported via https://bugzilla.redhat.com/show_bug.cgi?id=1718230, in the pacemaker podman resource agent, we're trying to avoid any "podman inspect" calls.
Currently in order to know if a container exists (running or not) at all we do:
podman inspect --format {{.State.Running}} $CONTAINER | egrep '(true|false)'
Since the above call is problematic when the system is I/O loaded, we are looking for alternatives to answer the question "does a container exist (be it running or stopped)". I tried to see if I could get that info via 'podman ps -a -l --format {{.State}} --filter name=nova_api >/dev/null 2>&1' but it seems that performance wise that is still quite expensive. On an unloaded system I get 7s for 200 podman exec calls and 40s for 200 podman ps -a -l calls.
TLDR; If I could get a separate return code from podman exec when the container does not exist (or a cheap call that tells me if the container exists [stopped or running]) that would somewhat alleviate the perf issues mentioned in bz#1718230 in the pacemaker context
Here are the documented return codes for podman run, we need to document these for podman exec as well
125 if the error is with podman itself
$ podman run --foo busybox; echo $?
# flag provided but not defined: --foo
See 'podman run --help'.
125
126 if the contained command cannot be invoked
$ podman run busybox /etc; echo $?
# exec: "/etc": permission denied
podman: Error response from daemon: Contained command could not be invoked
126
127 if the contained command cannot be found
$ podman run busybox foo; echo $?
# exec: "foo": executable file not found in $PATH
podman: Error response from daemon: Contained command not found or does not exist
127
It would seem that 126 might be the correct code to return for podman exec if the container is stopped.
Comment 2Michele Baldessari
2019-06-12 09:14:54 UTC
(In reply to Daniel Walsh from comment #1)
> It would seem that 126 might be the correct code to return for podman exec
> if the container is stopped.
Ack, that should work to cover this case
Test with podman-1.4.2-5.module+el8.1.0+4240+893c1ab8.x86_64 and it works as expect:
Fri Sep 27 15:24:36 UTC 2019
$podman exec nonexistingcontainer /bin/true; echo $?
Error: unable to exec into nonexistingcontainer: no container with name or ID nonexistingcontainer found: no such container
125
$ podman run -it busybox
/ # exit
$ podman ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
67f868be0f97 docker.io/library/busybox:latest sh 4 seconds ago Exited (0) 2 seconds ago mystifying_shaw
$ podman exec 67f868be0f97 /bin/true; echo $?
Error: cannot exec into container that is not running: container state improper
126
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2019:3403