On Mon, Jan 9, 2012 at 11:09, Magnus Hagander <mag...@hagander.net> wrote:
> On Mon, Jan 9, 2012 at 07:34, Jaime Casanova <ja...@2ndquadrant.com> wrote:
>> Hi,
>>
>> I was trying pg_basebackup on head, i used this command:
>> """
>> postgres@jaime:/usr/local/pgsql/9.2$ bin/pg_basebackup -D $PWD/data2
>> -x stream -P -p 54392
>> """
>>
>> i got this error
>> """
>> 19093/19093 kB (100%), 1/1 tablespace
>> pg_basebackup: streaming header too small: 17
>> pg_basebackup: child process exited with error 1
>> """
>>
>> now, this streaming header size is defined in
>> src/bin/pg_basebackup/receivelog.c as "#define STREAMING_HEADER_SIZE
>> (1+8+8+8)", so WTF is this?
>> what are these numbers? shouldn't be at least a comment explaining
>> those? more important it's seems obvious something broke that, unless
>
> Those numbers are the size of WalDataMessageHeader - a struct which is
> not available in the frontend, or at least wasn't at the time.
>
>> i misunderstood something which is completely possible, and that the
>> way is do it it will broke again in the future if the header change
>
> Without looking at the details, I'm pretty sure it's the keepalive
> message patch (64233902d22ba42846397cb7551894217522fad4).That one does
> introduce a new message that's exactly that size.
>
> pg_basebackup assumes the only kind of messages that can arrive are
> the data messages, and this is no longer true. But if you check the
> code for pg_basebackup, you'll see it checks the size of the message
> *before* it checks the type of the message, which is why you get a
> misleading error.
>
> I'll dig into the details later - but you could try backing out that
> patch to confirm if that's the problem.
Confirmed that is it, and attached are two patches to fix it. The
first one I intend to backport to 9.1, since it just fixes the error
message. The other one is for 9.2. I'll also look at a better way to
get that structure size. comments?
--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/
From 99764c7132019c870e36ac56385500b8d5b454ed Mon Sep 17 00:00:00 2001
From: Magnus Hagander <mag...@hagander.net>
Date: Mon, 9 Jan 2012 11:53:38 +0100
Subject: [PATCH 1/2] Reorder check for streaming message and header size
This produces a more relevant error message when talking to a 9.2
server that sends keepalive messages.
---
src/bin/pg_basebackup/receivelog.c | 12 ++++++------
1 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/src/bin/pg_basebackup/receivelog.c b/src/bin/pg_basebackup/receivelog.c
index c18db4f..d76eed6 100644
--- a/src/bin/pg_basebackup/receivelog.c
+++ b/src/bin/pg_basebackup/receivelog.c
@@ -374,18 +374,18 @@ ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline, char *sysi
progname, PQerrorMessage(conn));
return false;
}
- if (r < STREAMING_HEADER_SIZE + 1)
- {
- fprintf(stderr, _("%s: streaming header too small: %i\n"),
- progname, r);
- return false;
- }
if (copybuf[0] != 'w')
{
fprintf(stderr, _("%s: unrecognized streaming header: \"%c\"\n"),
progname, copybuf[0]);
return false;
}
+ if (r < STREAMING_HEADER_SIZE + 1)
+ {
+ fprintf(stderr, _("%s: streaming header too small: %i\n"),
+ progname, r);
+ return false;
+ }
/* Extract WAL location for this block */
memcpy(&blockpos, copybuf + 1, 8);
--
1.7.5.4
From 0c590630575014c1bc5a2ed700b802000d6a24ac Mon Sep 17 00:00:00 2001
From: Magnus Hagander <mag...@hagander.net>
Date: Mon, 9 Jan 2012 11:57:56 +0100
Subject: [PATCH 2/2] Accept (and ignore) keepalive messages in pg_basebackup
---
src/bin/pg_basebackup/receivelog.c | 18 +++++++++++++++++-
1 files changed, 17 insertions(+), 1 deletions(-)
diff --git a/src/bin/pg_basebackup/receivelog.c b/src/bin/pg_basebackup/receivelog.c
index d76eed6..c5579ee 100644
--- a/src/bin/pg_basebackup/receivelog.c
+++ b/src/bin/pg_basebackup/receivelog.c
@@ -35,6 +35,7 @@
/* Size of the streaming replication protocol header */
#define STREAMING_HEADER_SIZE (1+8+8+8)
+#define STREAMING_KEEPALIVE_SIZE (1+8+8)
const XLogRecPtr InvalidXLogRecPtr = {0, 0};
@@ -374,7 +375,22 @@ ReceiveXlogStream(PGconn *conn, XLogRecPtr startpos, uint32 timeline, char *sysi
progname, PQerrorMessage(conn));
return false;
}
- if (copybuf[0] != 'w')
+ if (copybuf[0] == 'k')
+ {
+ /*
+ * keepalive message, sent in 9.2 and newer. We just ignore
+ * this message completely, but need to forward past it
+ * in our reading.
+ */
+ if (r != STREAMING_KEEPALIVE_SIZE)
+ {
+ fprintf(stderr, _("%s: keepalive message is incorrect size: %i\n"),
+ progname, r);
+ return false;
+ }
+ continue;
+ }
+ else if (copybuf[0] != 'w')
{
fprintf(stderr, _("%s: unrecognized streaming header: \"%c\"\n"),
progname, copybuf[0]);
--
1.7.5.4
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