Re: Cannot shutdown subscriber after DROP SUBSCRIPTION

On Thu, Feb 2, 2017 at 2:13 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> writes:
>> Then, the reason for the TRY-CATCH cluase is that I found that
>> some functions called from there can throw exceptions.
>
> Yes, but all LWLocks should be released by normal error recovery.
> It should not be necessary for this code to clean that up by hand.
> If it were necessary, there would be TRY-CATCH around every single
> LWLockAcquire in the backend, and we'd have an unreadable and
> unmaintainable system.  Please don't add a TRY-CATCH unless it's
> *necessary* -- and you haven't explained why this one is.

Putting hands into the code and at the problem, I can see that
dropping a subscription on a node makes it unresponsive in case of a
stop. And that's just because calls to LWLockRelease are missing as in
the patch attached. A try/catch problem should not be necessary.
-- 
Michael