[Spice-devel] [PATCH vd_agent_linux v2] vdagent: Stop trying to connect to the daemon after a while

[Frediano Ziglio]

> 
> On Mon, 2018-11-19 at 10:23 +0000, Frediano Ziglio wrote:
> > Do not try  indefinitely to connect to the daemon, should not
> > take long to activate.
> > 
> > Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
> > ---
> >  src/vdagent/vdagent.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > Changes since v1:
> > - log error when we reach the limit
> > 
> > diff --git a/src/vdagent/vdagent.c b/src/vdagent/vdagent.c
> > index f7c8b72..7a58150 100644
> > --- a/src/vdagent/vdagent.c
> > +++ b/src/vdagent/vdagent.c
> > @@ -53,6 +53,7 @@ typedef struct VDAgent {
> >      struct vdagent_file_xfers *xfers;
> >      struct udscs_connection *conn;
> >      GIOChannel *x11_channel;
> > +    guint connection_attempts;
> >  
> >      GMainLoop *loop;
> >  } VDAgent;
> > @@ -370,6 +371,11 @@ static gboolean vdagent_init_async_cb(gpointer
> > user_data)
> >                                  daemon_read_complete,
> >                                  daemon_disconnect_cb,
> >                                  debug);
> >      if (agent->conn == NULL) {
> > +        // limit connection attempts, this will try for 5 minutes
> > +        if (++agent->connection_attempts > 5 * 60) {
> > +            syslog(LOG_ERR, "Attempted to contact daemon for 5 minutes,
> > giving up");
> > +            goto err_init;
> > +        }
> 
> (in reference to trying to keep it simple from v1 thread:)
> I think using 60 instead of 1 in g_timeout_add_seconds() wouldn't be
> much of a complication... unless there's something else I'm missing.
> I'm also thinking this is being launched from a .desktop file so AFAIK
> there is no easy way for a user to restart the service, a relogin is
> needed?
> 

It reconnects to the new daemon after detecting the disconnection.
Not sure what will happen if the agent is updated... I think nothing
or possibly the agent will end if not compatible with the new daemon.
If you retry every minute is possible that the user has to wait 1
minute instead of 1 second.
Probably the optimal way would be to use inotify on the socket to
wait for the new daemon, so something like:
- try 10 times with 1 second delay
- setup inotify
- try once to avoid races
- wait inotify
- attempt connection again (repeat from first step)
This way if the daemon is restored after even hours you don't have to
keep polling.

> I also just realized you should reset connection_attempts to 0 after a
> successful connect?
> 

The object is created again so will be 0 again (not that would hurt
to reset on a successful connection).

> Cheers,
> Lukas
> 
> >          g_timeout_add_seconds(1, vdagent_init_async_cb, agent);
> >          return G_SOURCE_REMOVE;
> >      }
>