Erik JohnstonandClaude Fable 5.1 63b0aaa6d0 Add a libpq wrapper that resolves libpq's default host ...

Synapse has always connected to Postgres through libpq (via psycopg2),
so a connection string that omits `host=` gets libpq's default: the
compiled-in socket directory (which distributions such as Debian patch)
and environment variables like `PGHOST`. A Rust Postgres client such as
`tokio-postgres` applies its own default (`localhost`) instead. To keep
the existing connection behaviour, the Rust driver will ask the real
libpq what it would do and copy that across.

This adds the asking: `libpq::default_host` calls `PQconnectStart` on an
empty conninfo, which applies libpq's defaults and environment, and
reads the host libpq settled on back with `PQhost`. The connection
attempt that `PQconnectStart` begins is never polled and its outcome is
ignored: `PQhost` reports the resolved default whether or not a server
is listening there.

libpq is an optional runtime dependency, not a build-time one. The
shared library is loaded with `dlopen` (via `libloading`) the first time
`default_host` is called, and the five entry points we use are declared
by hand. Synapse therefore builds and imports without libpq installed;
only a deployment that needs the default host has to have `libpq5`, and
`default_host` returns a clear error if it is missing.

Split out of the Rust Postgres driver branch so the libpq dependency
can be reviewed on its own. Nothing calls `default_host` yet; the
driver's DSN fixup is the consumer.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

2026-10-12 18:15:06 +00:00

..

benches

Add push rules for MSC4075: MatrixRTC invites and notifications (#20227)

2026-09-25 10:40:24 +00:00

src

Add a libpq wrapper that resolves libpq's default host

2026-10-12 18:15:06 +00:00

build.rs

resolves #19403 Report the rust compiler version used in the prometheus metrics (#19643)

2026-04-03 11:21:23 +02:00

Cargo.toml

Add a libpq wrapper that resolves libpq's default host

2026-10-12 18:15:06 +00:00

clippy.toml

Move per-homeserver Rust state into a RustRuntime object on the HomeServer (#20011)

2026-09-21 18:48:37 +01:00