Error generating merge proposal diff when "source branch has pending writes"

It would help to know what the merge proposal was. This could be a dupe of bug #610713

BranchMergeProposalJobSource.iterReady() calls checkReady(), and catches
exceptions that the job isn't ready and waits.

UpdatePreviewDiffJob.run() calls checkReady() but lets the exception
bubble up, which ends up sending an email.

If the state of the branch changes between the two events then this
behaviour will happen.

I think run() needs a way to signal that the job should be deferred for some
time to handle this.

There are other issues too, such as the email not having much
information.

The cases that the user would be mailed about would be:

        if bmp.source_branch.last_scanned_id is None:
            raise UpdatePreviewDiffNotReady(
                'The source branch has no revisions.')
        if bmp.target_branch.last_scanned_id is None:
            raise UpdatePreviewDiffNotReady(
                'The target branch has no revisions.')
        if bmp.source_branch.pending_writes:
            raise UpdatePreviewDiffNotReady(
                'The source branch has pending writes.')

where I'm not sure any of them are useful.

The first two should give an empty diff on the merge proposal or
something. The latter should just delay, and then oops if it has been
delayed multiple times, as there is something wrong.

Thanks,

James

I just got this again on

  https://code.edge.launchpad.net/~james-w/launchpad/soyuz-factory-improvements/+merge/31890

you can see that I pushed two revisions in quick succession.

Thanks,

James

I got this as well, but in my case there was only one revision recently pushed, and it was pushed long before the merge proposal was created. https://code.edge.launchpad.net/~salgado/launchpad/layer-specific-navigation/+merge/32119

And I got another email like that after resubmitting my proposal. (the submitted one: https://code.edge.launchpad.net/~salgado/launchpad/layer-specific-navigation/+merge/32124)

In my case it seems to be a different problem -- Aaron told me it wasn't generating the diff because of a bug (which is fixed in devel) that is triggered when you use a merge directive. I've deleted that branch, created a new one and then the new mp got a diff.

I've just hit this.

I think we should raise this to high - its a very opaque error that will leave a poor impression on users.

@lifeless: I respect de-duplicating this bug from Bug #640882 and bug #702411 but fixing one should be easier for someone already fixing the other no ? Or may give some hint...

There are two separate bugs: fixing the error could be done without improving the error message. And somone fixing the error message can do so without looking into the cause of the error at all.

bug 640882 is probably a dupe of this.

I think there is no point sending this to users and we might as well just suppress the mail and log it internally. Separately, we can deal with any merge proposals that are getting permanently stuck - there may already be separate bugs for them. When I've seen this message, the actual mp has generally looked fine _or_ there has been another more obvious bug.

Fixed in stable r14238 <http://bazaar.launchpad.net/~launchpad-pqm/launchpad/stable/revision/14238>.

untestable: the race is a bit hard to hit and qas's code hosting and mail setup is unrealistic

(Looks like I'm getting another occurrence of this in bug #1231589.)