Integrating C++ singletons into postgresql extensions???

From: Stephen Woodbridge <woodbri(at)swoodbridge(dot)com>
To: PostgreSQL General <pgsql-general(at)postgresql(dot)org>
Subject: Integrating C++ singletons into postgresql extensions???
Date: 2014-10-17 23:59:54
Message-ID: 5441AD7A.3070809@swoodbridge.com
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Hi,

I've been writing C++ code that needs to get wrapped into a postgresql
extension and it has a few singleton classes like:

1. Config object that holds some general configuration information.
2. Stats object for global stats collection.
3. Logger object for enabling/disabling debug logging to a file.
4. curlpp class for making outbound calls to an OSRM web service from
the c++ code

I can probably do without 1-3 if I had to when the code is integrated,
but they are handy to keep around in the code for when we are developing
and working outside the postgresql database. I could #ifdef then all,
but I would like to avoid cluttering the code with tons of #ifdef.

Item 4 is a little more problematic and needs to be kept around or
something else implemented to take its place. I have looked at the curl
extension and actual built another module in C that uses those ideas.,
but the curlpp is a nice OO class that encapsules and hides all the curl
stuff from the C++ code.

So my question(s) are:

1. Any insights into singletons working/not working within the
postgresql server extensions? My understanding is that these are
implemented as global static classes with a lifetime of the process and
they have no destructor, so I'm a little worried about memory leaks or
multiple queries sharing the singleton.

2. Is there another way implement the equivalent of a singleton for C++
code that has a lifetime of the query in the server?

3. What do for logging classes when integrating C++ code into postgresql?

Any help or ideas would be appreciated.

Thanks,
-Steve

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