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From: Andres Freund <[email protected]>
To: Tom Lane <[email protected]>
Cc: Matt Carter <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: BUG #19411: libpq 16.x exhibits a memory leak when connections are repeatedly created and destroyed
Date: Tue, 17 Feb 2026 14:45:17 -0500
Message-ID: <6xylkfh6idnx7ujhfhyoxku3v67ygoeve4yt7z2ytc65vzwvcv@z2sj5jnamhbe> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<BL3PR08MB728301C87997AF17C743633A996DA@BL3PR08MB7283.namprd08.prod.outlook.com>
	<[email protected]>

Hi,

On 2026-02-17 13:47:49 -0500, Tom Lane wrote:
> Matt Carter <[email protected]> writes:
> > Thank you for taking the time to test this and for the feedback.  Your C test showing no leak suggests the issue is specific to how psycopg2 uses libpq, not libpq itself.  I apologize for not including enough environmental details.  I used Kerberos/GSSAPI with SSL (TLS 1.2 connections).  My connection string was: "postgresql://hostname/database" (no password, Kerberos auth).
> > Your mention of "years ago libpq did leak memory while using GSSAPI encryption" is interesting because we ARE using GSSAPI/Kerberos authentication.
> 
> Interesting.  I wondered about GSSAPI, but spinning up such an
> environment is more work than I wanted to do on speculation.

Heh, understandable...

> > I can test with non-GSSAPI authentication to try to isolate that variable.  I can also create a pure psycopg2 reproducer (without SQLAlchemy).  I can also test whether disabling GSSAPI encryption (but keeping GSSAPI auth) changes the behavior.  Would testing with GSSAPI authentication help narrow this down? I can also report this to the psycopg2 project if you think it's their issue.
> 
> Please try varying the connection type and encryption.  I do suspect
> this may be psycopg2's fault, but we lack enough data to pin blame
> as yet.

Matt, you could try analyzing the memory usage with heaptrack, it tends to be
pretty good at finding them even in uninstrumented builds, as long as enough
debug symbols for a backtrace are available.  Often enough it'll pinpoint
where the leak is coming from quite easily (but note that it will report some
constant-sized leaks that are "intentional").

Greetings,

Andres

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  Subject: Re: BUG #19411: libpq 16.x exhibits a memory leak when connections are repeatedly created and destroyed
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