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Re: FSFS error in DAV MERGE - Can't open file 'db/transactions/props'

From: C. Michael Pilato <cmpilato_at_collab.net>
Date: Thu, 15 Jul 2010 11:06:16 -0400

On 06/22/2010 08:57 AM, Julian Foad wrote:
> Here are some Apache access log entries from one occurrence, with paths
> anonymized and the client Id string (always "SVN/1.6.6 (r40053)
> neon/0.28.3") omitted for brevity:
> [[[
> 127.0.0.1 - UserK [16/Dec/2009:20:25:17 -0800]
> "MKACTIVITY /svn/RepoJ/!svn/act/ActivityA HTTP/1.1" 201 312 "-"
> 127.0.0.1 - UserK [16/Dec/2009:23:20:45 -0800]
> "PROPPATCH /svn/RepoJ/!svn/wrk/ActivityA/branches/BranchD/PathG HTTP/1.1" 207 582 "-"
> 127.0.0.1 - UserM [17/Dec/2009:00:12:45 -0800]
> "MERGE /svn/RepoJ/branches/BranchH/PathC HTTP/1.1" 200 953 "-"
> 127.0.0.1 - UserM [17/Dec/2009:00:12:59 -0800]
> "MERGE /svn/RepoJ/branches/BranchP/PathC HTTP/1.1" 200 965 "-"
> 127.0.0.1 - UserK [17/Dec/2009:00:21:19 -0800]
> "DELETE /svn/RepoJ/!svn/act/ActivityA HTTP/1.1" 204 - "-"
> 127.0.0.1 - UserK [17/Dec/2009:00:32:45 -0800]
> "MKACTIVITY /svn/RepoJ/!svn/act/ActivityB HTTP/1.1" 201 312 "-"
> 127.0.0.1 - UserK [17/Dec/2009:00:39:58 -0800]
> "MERGE /svn/RepoJ/branches/BranchD/PathJ HTTP/1.1" 500 279 "-"
> 127.0.0.1 - UserK [17/Dec/2009:00:39:59 -0800]
> "PROPPATCH /svn/RepoJ/!svn/wrk/ActivityB/branches/BranchD/PathE HTTP/1.1" 207 569 "-"
> 127.0.0.1 - UserK [17/Dec/2009:00:39:59 -0800]
> "MERGE /svn/RepoJ/branches/BranchD/PathJ HTTP/1.1" 500 279 "-"
> ]]]

This sequence looks weird to me. In Subversion, there's always exactly one
MERGE -- the next-to-last step in a commit (which is begun by a MKACTIVITY
in HTTPv1, a POST in HTTPv2). You've got two MKACTIVITYs, and four MERGEs.
 Unless there are more operations that occurred but are just missing from
your report there, that's just weird.

> and the corresponding error log:
> [[[
> [Thu Dec 17 00:39:58 2009] [error] [client 127.0.0.1]
> Could not MERGE resource "/svn/RepoJ/!svn/act/ActivityA" into "/svn/RepoJ/branches/BranchD/PathJ". [500, #0]
> [Thu Dec 17 00:39:58 2009] [error] [client 127.0.0.1]
> There was a problem opening the transaction specified by this activity. [500, #2]
> [Thu Dec 17 00:39:58 2009] [error] [client 127.0.0.1]
> Can't open file '/svn/repos/RepoJ/db/transactions/props': No such file or directory [500, #2]
> ]]]
>
> The error appears to match the second-last MERGE in the access log. I
> don't have a copy of the body of the MERGE request in this case.
>
> The error refers to an activity Id that was the subject of the DELETE
> that was logged 18 minutes earlier. A comment from one of our guys
> looking at the logs: "We are seeing 22,600 changes for Activity A and no
> merge at the end (just a DELETE). Then we see about 931 commands for
> Activity B and a MERGE that fails for Activity A."
>
> Is this a case where the client side shouldn't be sending a MERGE at
> this point? Even if that is the primary problem, I'm still interested
> in Subversion's response to this MERGE request.

Our codebase should definitely not allow a bogus (NULL) txn-id to be
casually transformed in a path. You can commit assertions around those
parts *right now*.

If no MERGE occurs at the end of a stream of activity modifications, that's
usually means that one of those modifications failed and the client has
bailed on the commit (it then issues the DELETE of the activity as a cleanup
step). Weird that something would then try to MERGE the activity that was
already DELETEd.

This is not behavior I've seen in Subversion's own codebase -- so maybe just
a rare WANdisco software bug?

-- 
C. Michael Pilato <cmpilato_at_collab.net>
CollabNet   <>   www.collab.net   <>   Distributed Development On Demand

Received on 2010-07-15 17:06:59 CEST

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