On Tue, Jan 23, 2018 at 10:02:24AM +0000, Daniel P. Berrange wrote:
> 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@xxxxxxxxxx>
> > ---
> > 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.
Right, I'll fix that.
> > 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.
I knew that this implementation was too easy. I'll prepare a followup
patch to use close callback instead.
Pavel
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