libtest: ports obtained via get_free_port() for secondary/auxiliary uses are never released

[p-alik]

Background

#471 / #472 fixed the primary port-reservation race in libtest::Server::start(): get_free_port() now keeps its reservation socket bound until the caller explicitly calls release_port(), and Server::start() releases its own _port once the server is confirmed up (or definitively failed) via an RAII guard.

That fix only releases the Server object's own _port. Several call sites use get_free_port() to reserve a port for something other than the Server's primary port — e.g.:

• tests/httpd_test.cc:149 — http_port is reserved and passed as --http-port= to a gearmand instance whose Server::_port is actually default_port(). The Server never knows about http_port, so its reservation is never released.
• tests/gearmand.cc:190,549 (long_keepalive_start_TEST, config_file_SIMPLE_TEST) — ports reserved via get_free_port() for --check-args runs that don't go through a Server object at all.

In all of these, the reservation socket now stays open (bound, unreleased) for the remaining lifetime of the test process instead of being freed once it's no longer needed.

Impact

Low severity — this does not reintroduce the original race (holding a reservation longer than necessary is safe, just wasteful). The practical effect is a growing number of open file descriptors / permanently-occupied ephemeral ports for the rest of a given test binary's run. Unlikely to cause failures on its own, but wastes resources and could compound in long-running or -j-parallel test invocations.

Suggested fix

Give these call sites an explicit release_port(port) once the port is no longer needed (e.g. after the associated server/process is confirmed started, or via a scoped RAII guard similar to the one added in Server::start()). Would need to audit all get_free_port() call sites under tests/ to find which ones aren't already covered by a Server::start()/release_port() pair.

References

• Introduced as a side effect of Fix port-reservation race in libtest::Server::start() #472 (fix for Intermittent CI test failures due to port-reservation race in libtest::Server::start() #471).
• Flagged during code review of Fix port-reservation race in libtest::Server::start() #472.

🤖 Generated with Claude Code

[esabol]

WIth the merger of PR #472, this issue can be closed, right, @p-alik?

[p-alik]

Not quite — #472 fixed the primary port-reservation race, but it's actually what introduced this issue as a side effect: get_free_port() now holds its reservation socket open until release_port() is called, and Server::start() only releases its own primary _port. Several other call sites reserve a port for something other than a Server's primary port (e.g. httpd_test.cc's http_port, the --check-args ports in gearmand.cc, the Context/cycle_context_st reset() patterns) and never released it, so those reservations now leak for the rest of the test process.

I've opened #475 to fix this — it's passing CI now. Once that merges, this can be closed.