Re: [Postgres-xc-general] Unable to create sequences

[Masataka S. <pg...@gm...>]

Hi, Aaron

I think you've done right analysis.

The order of evaluation of sub-expressions and the order in which side
effects take place are frequently defined as unspecified behavior by
the C Standard. As you saw, it's one of the such case that the order
in which the arguments to a function are evaluated.

The patch looks good, and I think we must back-patch it to all the
versions after 1.0.

Regards.

On 3 June 2014 16:20, Aaron Jackson <aja...@re...> wrote:
> I've been able to work my way backwards through the problem and have
> discovered the underlying problem.  When a data coordinator is paired with a
> GTM proxy, it forwards its message to the GTM proxy who adds some data to
> the payload and forwards it to the GTM.  Here is what I saw when looking at
> the wire.
>
> The message captured between the data coordinator and the GTM proxy was as
> follows:
>
> 430000003d000000270000001064656d6f2e7075626c69632e666f6f0001000000000000000100000000000000ffffffffffffff7f010000000000000000
>
> The message captured between the GTM proxy and the GTM was as follows:
>
> 430000000a00000000002746000000080000003b
>
>
> Definitely a horrible truncation of the payload.  The problem is in
> GTMProxy_ProxyCommand, specifically, the two calls to pq_getmsgunreadlen().
> The assumption is that these are called before anything else.
> Unfortunately, the intel compiler calls pq_getmsgbytes() and subsequently
> calls the second instance of pq_getmsgunreadlen().  The second time it is
> called, the value returns zero and we end up with all kinds of byte
> truncation.  I've attached a patch to fix the issue.
>
> --- postgres-xc-1.2.1-orig/src/gtm/proxy/proxy_main.c   2014-04-03
> 05:18:38.000000000 +0000
> +++ postgres-xc-1.2.1/src/gtm/proxy/proxy_main.c        2014-06-03
> 07:14:58.451411000 +0000
> @@ -2390,6 +2390,7 @@
>         GTMProxy_CommandInfo *cmdinfo;
>         GTMProxy_ThreadInfo *thrinfo = GetMyThreadInfo;
>         GTM_ProxyMsgHeader proxyhdr;
> +       size_t msgunreadlen = pq_getmsgunreadlen(message);
>
>         proxyhdr.ph_conid = conninfo->con_id;
>
> @@ -2397,8 +2398,8 @@
>         if (gtmpqPutMsgStart('C', true, gtm_conn) ||
>                 gtmpqPutnchar((char *)&proxyhdr, sizeof
> (GTM_ProxyMsgHeader), gtm_conn) ||
>                 gtmpqPutInt(mtype, sizeof (GTM_MessageType), gtm_conn) ||
> -               gtmpqPutnchar(pq_getmsgbytes(message,
> pq_getmsgunreadlen(message)),
> -                                         pq_getmsgunreadlen(message),
> gtm_conn))
> +               gtmpqPutnchar(pq_getmsgbytes(message, msgunreadlen),
> +                                         msgunreadlen, gtm_conn))
>                 elog(ERROR, "Error proxing data");
>
>         /*
>
>
>
> Aaron
> ________________________________
> From: Aaron Jackson [aja...@re...]
> Sent: Monday, June 02, 2014 4:11 PM
> To: pos...@li...
> Subject: [Postgres-xc-general] Unable to create sequences
>
> I tried to create a database as follows ...
>
> CREATE TABLE Schema.TableFoo(
>     SomeId serial NOT NULL,
>     ForeignId int NOT NULL,
>     ...
> ) WITH (OIDS = FALSE);
>
>
> The server returned the following...
>
> ERROR:  GTM error, could not create sequence
>
>
> Looked at the server logs for the gtm_proxy, nothing so I went to the gtm.
>
> LOCATION:  pq_copymsgbytes, pqformat.c:554
> 1:140488486782720:2014-06-02 21:10:58.870 UTC -WARNING:  No transaction
> handle for gxid: 0
> LOCATION:  GTM_GXIDToHandle, gtm_txn.c:163
> 1:140488486782720:2014-06-02 21:10:58.870 UTC -WARNING:  Invalid transaction
> handle: -1
> LOCATION:  GTM_HandleToTransactionInfo, gtm_txn.c:213
> 1:140488486782720:2014-06-02 21:10:58.870 UTC -ERROR:  Failed to get a
> snapshot
> LOCATION:  ProcessGetSnapshotCommandMulti, gtm_snap.c:420
> 1:140488478390016:2014-06-02 21:10:58.871 UTC -ERROR:  insufficient data
> left in message
> LOCATION:  pq_copymsgbytes, pqformat.c:554
> 1:140488486782720:2014-06-02 21:10:58.871 UTC -ERROR:  insufficient data
> left in message
> LOCATION:  pq_copymsgbytes, pqformat.c:554
>
>
> I'm definitely confused here.  This cluster has been running fine for
> several days now.  And now the GTM is failing. I performed a restart of the
> gtm and proxies (each using gtm_ctl to stop and restart the instance).
> Nothing has changed, the GTM continues to fail and will not create the
> sequence.
>
> Any ideas?
>
> Aaron
>
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