[svn.haxx.se] · SVN Dev · SVN Users · SVN Org · TSVN Dev · TSVN Users · Subclipse Dev · Subclipse Users · this month's index

Re: Making fsfs generate unique transaction names

From: Blair Zajac <blair_at_orcaware.com>
Date: 2007-06-18 18:38:51 CEST

On Jun 18, 2007, at 6:57 AM, C. Michael Pilato wrote:

> Blair Zajac wrote:
>> On Jun 16, 2007, at 2:28 PM, Blair Zajac wrote:
>>> Daniel Berlin wrote:
>>>> On 6/13/07, Blair Zajac <blair@orcaware.com> wrote:
>>>>> I'm making a svn filesystem network aware using Ice RPC and one
>>>>> of the
>>>>> things I'm running into is that FSFS transactions are not
>>>>> unique. BDB
>>>>> seems to generate transaction names via a sequence, so this
>>>>> isn't an
>>>>> issue.
>>>>> I have the ability for a client to begin a transaction remotely
>>>>> and
>>>>> then
>>>>> refer to that transaction to do work. In FSFS, if a client
>>>>> begins a
>>>>> transaction, gives the transaction name to another process,
>>>>> which then
>>>>> closes it, and a third process begins a new transaction based
>>>>> on the
>>>>> same revision, then it will get the same transaction name and
>>>>> the owner
>>>>> of the original transaction will be operating inside a different
>>>>> transaction and will be able to abort the transaction, which it
>>>>> should
>>>>> not be able to do.
>>>>> So I'd like to make the transaction names unique, using
>>>>> something like
>>>>> "%s-%05ds-%s-%05d" % (apr_gethostname(),
>>>>> apr_uid_current(),
>>>>> apr_time_now(),
>>>>> i)
>>>>> where i is incremented until it finds a non-existent directory
>>>>> name.
>>>> apr-util has apr_uuid_get to get new UUID's, and apr_uuid_format to
>>>> turn them into strings.
>>>> Is there some reason you can't use it?
>>>> Otherwise, I was going to suggest this myself as part of a
>>>> design i'm
>>>> working on for 2.0's merge tracking.
>>> No, wasn't aware that apr had a uuid method. We could switch over.
>>> In fact, making BDB and FSFS use uuid's would be nice.
>> BTW, if we do switch BDB over to use uuid's, then I believe code will
>> have to be written to check if a BDB transaction name is already
>> used.
>> Now, since there's a sequence, it can assume that the transaction
>> name
>> will be fresh.
> We have no compelling reason to change BDB at all, so I'm -1 on
> doing so.
> As transaction names wind up being stored as part of the node-
> revision-id
> triplet, I wouldn't want to start seeing nodes like
> '4uv.3e.22006a41-a1fb-0310-bd7e-c51a55d5d677'. That BDB
> transaction IDs are
> sequential base-36 numbers has, on more than one occasion, assisted
> me in
> debugging a BDB-backed repository.

How is having a short name any different than a long name in debugging?

I've seen the long transaction names in the transaction fsfs files,
but you're saying they also end up in revisions? If so, would you
rather see uuids or the new transaction names I put in 1.5

Personally, I like seeing a hostname and pid in the transaction name
for my project, it'll make it easier to debug my new RPC framework.


To unsubscribe, e-mail: dev-unsubscribe@subversion.tigris.org
For additional commands, e-mail: dev-help@subversion.tigris.org
Received on Mon Jun 18 18:38:57 2007

This is an archived mail posted to the Subversion Dev mailing list.

This site is subject to the Apache Privacy Policy and the Apache Public Forum Archive Policy.