Re: [libvirt] [dbus RFC 06/11] connect: implement reconnect functionality to libvirt

On Mon, Jan 22, 2018 at 06:16:04PM +0100, Pavel Hrdina wrote: > If the connection dies for some reason between D-Bus calls we need > to properly reconnect because the current connection is not usable > anymore. Without this the only solution would be to restart the > libvirt-dbus daemon. > > Signed-off-by: Pavel Hrdina <phrdina(a)redhat.com&gt; > --- > src/connect.c | 37 +++++++++++++++++++++++++++---------- > 1 file changed, 27 insertions(+), 10 deletions(-) > > diff --git a/src/connect.c b/src/connect.c > index 9de764c..10183f3 100644 > --- a/src/connect.c > +++ b/src/connect.c > @@ -4,6 +4,7 @@ > #include "util.h" > > #include <errno.h> > +#include <stdbool.h> > #include <stdlib.h> > > static int virtDBusConnectCredType[] = { > @@ -34,12 +35,34 @@ static virConnectAuth virtDBusConnectAuth = { > NULL, > }; > > +static void > +virtDBusConnectClose(virtDBusConnect *connect, > + bool deregisterEvents) > +{ > + > + for (int i = 0; i < VIR_DOMAIN_EVENT_ID_LAST; i += 1) { > + if (connect->callback_ids[i] >= 0) { > + if (deregisterEvents) { > + virConnectDomainEventDeregisterAny(connect->connection, > + connect->callback_ids[i]); > + } > + connect->callback_ids[i] = -1; > + } > + } > + > + virConnectClose(connect->connection); I think it is prudent to set connect->connection = NULL at this point.

> static int > virtDBusConnectOpen(virtDBusConnect *connect, > sd_bus_error *error) > { > - if (connect->connection) > - return 0; > + if (connect->connection) { > + if (virConnectIsAlive(connect->connection)) This means that every single dbus call runs an extra RPC call to ping the server for liveliness. That's not a huge problem, but at some point I'd recommend that just use the close callback to immediately detect connection failure and close the connection & run background job to re-open it. Presumably you're going to issue dbus signals for domain lifecycle events. Using the close callback & job to re-open means your lifecycle events will start working again in the shortest amount of time, instead of waiting for the next methd call to detect the failure.