On Fri, Sep 04, 2015 at 01:11:14PM -0400, Stéphane Graber wrote: > On Fri, Sep 04, 2015 at 04:21:42PM +0200, Christian Brauner wrote: > > On Fri, Sep 04, 2015 at 02:04:29PM +0000, Serge Hallyn wrote: > > > Quoting Christian Brauner (christianvanbrau...@gmail.com): > > > > On Mon, Aug 31, 2015 at 09:53:03PM +0200, Christian Brauner wrote: > > > > > On Mon Aug 31, 2015 at 04:08:33PM +0000, Serge Hallyn wrote: > > > > > > Quoting Stéphane Graber (stgraber at ubuntu.com): > > > > > > > On Mon, Aug 31, 2015 at 01:43:07PM +0000, Serge Hallyn wrote: > > > > > > > > Quoting Christian Brauner (christianvanbrauner at gmail.com): > > > > > > > > > On Fri, Aug 28, 2015 at 12:46:17AM +0200, Christian Brauner > > > > > > > > > wrote: > > > > > > > > > > On Thu, Aug 27, 2015 at 03:41:03PM -0400, Stéphane Graber > > > > > > > > > > wrote: > > > > > > > > > > > On Sun, Aug 16, 2015 at 04:46:31PM +0000, Serge Hallyn > > > > > > > > > > > wrote: > > > > > > > > > > > > Quoting Christian Brauner (christianvanbrauner at > > > > > > > > > > > > gmail.com): > > > > > > > > > > > > Hey, > > > > > > > > > > > > > > > > > > > > > > > > I'll leave this to Stéphane, as he's pretty keen on > > > > > > > > > > > > leaving the # > > > > > > > > > > > > commands > > > > > > > > > > > > low. As you say we might eventually be able to > > > > > > > > > > > > deprecate > > > > > > > > > > > > lxc-clone, > > > > > > > > > > > > and > > > > > > > > > > > > lxc-copy might eventually be a nice hook for migration. > > > > > > > > > > > > > > > > > > > > > > That'd be fine with me I think, bonus point if we can > > > > > > > > > > > somehow merge > > > > > > > > > > > lxc-start-ephemeral in there and kill two birds with one > > > > > > > > > > > stone > > > > > > > > > > > (lxc-clone & lxc-start-ephemeral). > > > > > > > > > > > > > > > > > > > > > > The timeline for this would be having lxc-copy in 1.2 > > > > > > > > > > > with both > > > > > > > > > > > lxc-clone and lxc-start-ephemeral doing arg swapping + > > > > > > > > > > > re-exec > > > > > > > > > > > tricks > > > > > > > > > > > with a warning that they'll go away for good in 2.0. > > > > > > > > > > > > > > > > > > > > > > How does that sound? > > > > > > > > > > > > > > > > > > > > Sounds good! I'm on it! > > > > > > > > > > > > > > > > > > > > Christian > > > > > > > > > > > > > > > > > > In the current python implementation of lxc-start-ephemeral > > > > > > > > > we generate > > > > > > > > > a > > > > > > > > > pre-mount and post-stop script. The post-stop script seems to > > > > > > > > > be used to > > > > > > > > > destroy > > > > > > > > > the container. For the rewrite in C and the merge with > > > > > > > > > lxc-clone I > > > > > > > > > thought > > > > > > > > > about > > > > > > > > > using a simple snapshot-clone with c->clone() with a random > > > > > > > > > name, start > > > > > > > > > it > > > > > > > > > c->start() and when the container is shutdown destroy it with > > > > > > > > > c->destroy(). > > > > > > > > > This seems cleaner to me then generating scripts. Are there > > > > > > > > > any reasons > > > > > > > > > to > > > > > > > > > not > > > > > > > > > do it this way? And if so what would you prefer? > > > > > > > > > > > > > > > > If you can do this robustly and cleanly then I prefer this. > > > > > > > > > > > > > > The reason was that the container could be started backgrounded > > > > > > > (-d) in > > > > > > > which case lxc-start-ephemeral wasn't around anymore to clean > > > > > > > things up > > > > > > > when the container exits. > > > > > > > > > > > > > > The post-stop method ensured that the container would be destroyed > > > > > > > whenever it finally dies and regardless of how it was killed > > > > > > > (either > > > > > > > shutdown from inside the container or lxc-stop/lxc-destroy). > > > > > > > > > > > > Right, so to do this without post-stop we'd probably have to hack a > > > > > > special > > > > > > case into the reboot: loop around container-start. Maybe even > > > > > > hardcode the > > > > > > 'transient' case into the lxc_handler struct. Or just have a > > > > > > 'special' > > > > > > post-stop hook (doesn't even have to be a script, just a hard-code > > > > > > value > > > > > > checked for before we run the script) telling us 'delete this > > > > > > thing'. > > > > > > > > > > > > It could end up looking nice, or could end up a mess. I reserve > > > > > > final > > > > > > judgement until there's code :) > > > > > Agreed. Let's see how mess-less I can code this. > > > > > > > > > > As long as the container is started in foreground mode the container > > > > > will be > > > > > destroyed regardless of whether it was killed by lxc-stop or shutdown > > > > > from > > > > > inside. The only problematic case is when the container is started > > > > > daemonized. > > > > > > > > > > I need to think about how to handle that case for a bit. I'd like to > > > > > code more > > > > > than one option I think. Unless there's need for rush. :) Suggestions > > > > > of course > > > > > welcome. > > > > I'm currently in favour of the lxc.hook.post-stop version for daemonized > > > > containers. The rest means fiddling with a lot of the api-functions for > > > > the > > > > a rather special case. But there are two things I would like to have > > > > input > > > > about: > > > > > > > > 1) Should we register ephemeral clone-snapshots in the lxc_snapshots > > > > file of the > > > > original container? (I would think not.) > > > > > > If for instance it is a overlayfs based snapshot, and you allow the parent > > > to be deleted, then the ephemeral container will misbehave. I'm pretty > > > sure that's the case now and I haven't heard any complaints, but it is > > > non-ideal. > > > > > > > 2) Should we have an additional state TRANSIENT in addition to RUNNING, > > > > STARTING, etc.? > > > > > > What exactly would it mean? STARTING is already inherently TRANSIENT. > > > Would > > > TRANSIENT mean 'building but not yet starting'? > > I was unclear. TRANSIENT or EPHEMERAL in the sense of "this is a running > > container but it will be deleted once it is shutdown". So when you do work > > on a > > container and you're unsure whether it is an ephemeral container you could > > check > > with lxc-info -n NAME and see TRANSIENT or EPHEMERAL and know "this thing is > > going to be deleted when I shut it down." > > It seems to me like this has the potential to break a fair amount of > existing tools which wait for "RUNNING" before interacting with a > container. If we were to have multiple "RUNNING" equivalent state, we > ought to add a new exported function that'd check whether the container > is running regardless of the state's name but requiring the use of this > would only be possible when we break backward compatibility (so LXC > 2.0).
Agreed!.
>
> I suspect a cleaner way would be to have a config option for ephemeral
> containers, something like lxc.ephemeral=1 that will cause LXC to
> destroy the container when it dies and can be used by API clients to
> query whether a container is ephemeral.
I actually already done that. I just need to bring it in final shape. But here
is a sneak-preview so you can stop me if you'd rather have it a different way.
And thanks for all the feedback and quick answers!
PRELIMINARY: Destroy ephemeral overlayfs container
---
src/lxc/conf.h | 3 +++
src/lxc/confile.c | 16 ++++++++++++++++
src/lxc/start.c | 14 ++++++++++++++
3 files changed, 33 insertions(+)
diff --git a/src/lxc/conf.h b/src/lxc/conf.h
index dc5328a..6e75713 100644
--- a/src/lxc/conf.h
+++ b/src/lxc/conf.h
@@ -370,6 +370,9 @@ struct lxc_conf {
* should run under when using lxc-execute */
uid_t init_uid;
gid_t init_gid;
+
+ /* transient */
+ int transient;
};
#ifdef HAVE_TLS
diff --git a/src/lxc/confile.c b/src/lxc/confile.c
index ca3b8d8..356d85f 100644
--- a/src/lxc/confile.c
+++ b/src/lxc/confile.c
@@ -108,6 +108,8 @@ static int config_environment(const char *, const char *,
struct lxc_conf *);
static int config_init_cmd(const char *, const char *, struct lxc_conf *);
static int config_init_uid(const char *, const char *, struct lxc_conf *);
static int config_init_gid(const char *, const char *, struct lxc_conf *);
+static int config_transient(const char *key, const char *value,
+ struct lxc_conf *lxc_conf);
static struct lxc_config_t config[] = {
@@ -176,6 +178,7 @@ static struct lxc_config_t config[] = {
{ "lxc.init_cmd", config_init_cmd },
{ "lxc.init_uid", config_init_uid },
{ "lxc.init_gid", config_init_gid },
+ { "lxc.transient", config_transient },
};
struct signame {
@@ -2490,6 +2493,8 @@ int lxc_get_config_item(struct lxc_conf *c, const char
*key, char *retv,
return lxc_get_conf_int(c, retv, inlen, c->init_uid);
else if (strcmp(key, "lxc.init_gid") == 0)
return lxc_get_conf_int(c, retv, inlen, c->init_gid);
+ else if (strcmp(key, "lxc.transient") == 0)
+ return lxc_get_conf_int(c, retv, inlen, c->transient);
else return -1;
if (!v)
@@ -2759,3 +2764,14 @@ bool network_new_hwaddrs(struct lxc_conf *conf)
}
return true;
}
+
+static int config_transient(const char *key, const char *value,
+ struct lxc_conf *lxc_conf)
+{
+ int v = atoi(value);
+
+ lxc_conf->transient = v;
+
+ return 0;
+}
+
diff --git a/src/lxc/start.c b/src/lxc/start.c
index ffb8d12..e551ca4 100644
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -495,6 +495,20 @@ void lxc_fini(const char *name, struct lxc_handler
*handler)
close(handler->ttysock[0]);
close(handler->ttysock[1]);
}
+ if (handler->conf->transient > 0) {
+ char *check_rootfs = handler->conf->rootfs.path;
+ if (strncmp(check_rootfs, "overlayfs:", 10) == 0) {
+ int ret;
+ char destroy[MAXPATHLEN];
+ ret = snprintf(destroy, MAXPATHLEN, "%s/%s",
handler->lxcpath, name);
+ if (ret < 0)
+ ERROR("Error creating string");
+ INFO(destroy);
+ ret = lxc_rmdir_onedev(destroy, NULL);
+ if (ret < 0)
+ ERROR("Destroying container failed");
+ }
+ }
cgroup_destroy(handler);
free(handler);
}
--
2.5.1
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