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From: Cyrill Gorcunov via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: Serge Petrenko <sergepetrenko@tarantool.org>
Cc: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>,
	tml <tarantool-patches@dev.tarantool.org>
Subject: Re: [Tarantool-patches] [PATCH v8 1/2] applier: send transaction's first row WAL time in the applier_writer_f
Date: Wed, 16 Jun 2021 16:32:38 +0300
Message-ID: <YMn9dg8JNQm5Xl0p@grain> (raw)
In-Reply-To: <22738ee6-74e1-0090-4eb0-c08183bb16e8@tarantool.org>

On Tue, Jun 15, 2021 at 12:36:02PM +0300, Serge Petrenko wrote:
> > @@ -193,6 +196,16 @@ applier_writer_f(va_list ap)
> >   			applier->has_acks_to_send = false;
> >   			struct xrow_header xrow;
> >   			xrow_encode_vclock(&xrow, &replicaset.vclock);
> > +			/*
> > +			 * For relay lag statistics we report last
> > +			 * written transaction timestamp in tm field.
> > +			 *
> > +			 * Replica might be dead already so we have to
> > +			 * test on each iteration.
> > +			 */
> > +			struct replica *r = replica_by_id(replica_id);
> > +			if (likely(r != NULL))
> > +				xrow.tm = r->applier_txn_start_tm;
> 
> How could a replica be dead here?
> AFAIR we delete a replica only when it's deleted from _cluster. Shouldn't
> the applier writer be dead as well by that time?

Before accessing replica_by_id we're sitting in event loop trying to
fetch data from the network. Which means an admin may cleanup the
entry manually before we get back to this code in result we will
get a nil dereference (if only I'm not missing something).

  reply	other threads:[~2021-06-16 13:32 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-07 15:55 [Tarantool-patches] [PATCH v8 0/2] relay: provide downstream lag information Cyrill Gorcunov via Tarantool-patches
2021-06-07 15:55 ` [Tarantool-patches] [PATCH v8 1/2] applier: send transaction's first row WAL time in the applier_writer_f Cyrill Gorcunov via Tarantool-patches
2021-06-07 19:20   ` Vladislav Shpilevoy via Tarantool-patches
2021-06-15  9:36   ` Serge Petrenko via Tarantool-patches
2021-06-16 13:32     ` Cyrill Gorcunov via Tarantool-patches [this message]
2021-06-17  9:16       ` Serge Petrenko via Tarantool-patches
2021-06-07 15:55 ` [Tarantool-patches] [PATCH v8 2/2] relay: provide information about downstream lag Cyrill Gorcunov via Tarantool-patches
2021-06-07 19:21   ` Vladislav Shpilevoy via Tarantool-patches
2021-06-08  8:40     ` Cyrill Gorcunov via Tarantool-patches
2021-06-08  9:58       ` Cyrill Gorcunov via Tarantool-patches
2021-06-08 18:15       ` Vladislav Shpilevoy via Tarantool-patches
2021-06-15 10:03   ` Serge Petrenko via Tarantool-patches
2021-06-17  6:55     ` Cyrill Gorcunov via Tarantool-patches
2021-06-17  9:01       ` Serge Petrenko via Tarantool-patches
2021-06-17  9:58         ` Cyrill Gorcunov via Tarantool-patches
2021-06-07 19:20 ` [Tarantool-patches] [PATCH v8 0/2] relay: provide downstream lag information Vladislav Shpilevoy via Tarantool-patches
2021-06-07 20:00   ` Cyrill Gorcunov via Tarantool-patches

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