Re: abstract Unix-domain sockets

Updated patch set after some conflicts had emerged.

On 2020-10-09 09:28, Peter Eisentraut wrote:
> During the discussion on Unix-domain sockets on Windows, someone pointed
> out[0] abstract Unix-domain sockets.  This is a variant of the normal
> Unix-domain sockets that don't use the file system but a separate
> "abstract" namespace.  At the user interface, such sockets are
> represented by names starting with "@".  I took a look at this and it
> wasn't hard to get working, so here is a patch.  It's supposed to be
> supported on Linux and Windows right now, but I haven't tested on Windows.
> 
> I figure, there are so many different deployment options nowadays, this
> could be useful somewhere.  It relieves you from dealing with the file
> system, you don't have to set up /tmp or something under /var/run, you
> don't need to make sure file system permissions are right.  Also, there
> is no need for a lock file or file cleanup.  (Unlike file-system
> namespace sockets, abstract namespace sockets give an EADDRINUSE when
> trying to bind to a name already in use.)  Conversely, of course, you
> don't get to use file-system permissions to manage access to the socket,
> but that isn't essential functionality, so it's a trade-off users can
> make on their own.
> 
> And then some extra patches for surrounding cleanup.  During testing I
> noticed that the bind() failure hint "Is another postmaster already
> running ..." was shown in inappropriate situations, so I changed that to
> only show for EADDRINUSE errors.  (Maybe other error codes could be
> appropriate, but I couldn't find any more.)
> 
> And then looking for other uses of EADDRINUSE I found some dead
> Windows-related code that can be cleaned up.

This last piece has been committed.

> 
> 
> [0]:
> https://www.postgresql.org/message-id/20191218142419.fvv4ikm4wq4gnkco@isc.upenn.edu

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
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