Re: Your review of pg_receivexlog/pg_basebackup

On Tue, Nov 1, 2011 at 05:53, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
> On Tue, Nov 1, 2011 at 3:08 AM, Magnus Hagander <magnus(at)hagander(dot)net> wrote:
>> On Fri, Oct 28, 2011 at 08:46, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>>> On Thu, Oct 27, 2011 at 11:14 PM, Magnus Hagander <magnus(at)hagander(dot)net> wrote:
>>>> Here's a version that does this. Turns out this requires a lot less
>>>> code than what was previously in there, which is always nice.
>>>>
>>>> We still need to solve the other part which is how to deal with the
>>>> partial files on restore. But this is definitely a cleaner way from a
>>>> pure pg_receivexlog perspective.
>>>>
>>>> Comments/reviews?
>>>
>>> Looks good.
>>>
>>> Minor comment:
>>> the source code comment of FindStreamingStart() seems to need to be updated.
>>
>> Here's an updated patch that both includes this update to the comment,
>> and also the functionality to pre-pad files to 16Mb. This also seems
>> to have simplified the code, which is a nice bonus.
>
> Here are the comments:
>
> In open_walfile(), "zerobuf" needs to be free'd after use of it.

Ooops, yes.

> +       f = open(fn, O_WRONLY | O_CREAT | PG_BINARY, 0666);
>
> We should use "S_IRUSR | S_IWUSR" instead of "0666" as a file access modes?

Agreed, changed.

> +               if (write(f, zerobuf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
> +               {
> +                       fprintf(stderr, _("%s: could not pad WAL segment %s: %s\n"),
> +                                       progname, fn, strerror(errno));
> +                       close(f);
> +                       return -1;
> +               }
>
> When write() fails, we should delete the partial WAL file, like
> XLogFileInit() does?

Yes, that's probably a good idae. Added a simple unlink() call
directly after the close().

> If not, subsequent pg_receivexlog always fails unless a user deletes
> it manually.
> Because open_walfile() always fails when it finds an existing partial WAL file.
>
> When open_walfile() fails, pg_receivexlog exits without closing the connection.
> I don't think this is good error handling. But this issue itself is
> not what we're
> trying to address now. So I think you can commit separately from current patch.

Wow, when looking into that, there was a nice bug in open_walfile -
when the file failed to open, it would write that error message but
not return - then proceed to write a second error message from fstat.
Oops.

Anyway - yes, the return value of ReceiveXLogStream isn't checked at
all. That's certainly not very nice. I'll go fix that too.

I'll apply the patch with the fixes you've mentioned above. Please
check master again in a few minutes. Thanks!

--
 Magnus Hagander
 Me: http://www.hagander.net/
 Work: http://www.redpill-linpro.com/