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

[Lukáš Hrázký]

On Mon, 2018-11-19 at 11:42 -0500, Frediano Ziglio wrote:
> > 
> > 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.

Well, you wanted a simple solution and I agree with that. I suggested
something that keeps the agent running and doesn't really make it more
complicated. Now you're suggesting a much more complex solution... :)

> > 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).

Right, didn't notice that...

Cheers,
Lukas

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