CI: Postgres on 127.0.0.1, because the runner uses host networking

The runner is configured with `container.network: host`. That one setting
explains all three earlier failures, and the workflow now records them so
nobody repeats the sequence:

  services:                     not resolvable by name from a host-networked
                                job — "getaddrinfo EAI_AGAIN postgres"
  --network container:$HOSTNAME /etc/hostname is the HOST's name, not a
                                container id, so the join finds nothing
  default-gateway addressing    wrong idea outright: with host networking the
                                default route is the real router, not a bridge

Sharing the host's network namespace means a published port is just on
127.0.0.1. Readiness is now checked over TCP from the job itself rather than
with pg_isready inside the container — the latter proves the server started,
not that this job can reach it, which is the thing that actually failed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -30,21 +30,25 @@ jobs:
   verify:
     runs-on: ubuntu-latest
 
-    # Postgres is started as a step rather than through `services:`.
+    # Postgres is started as a step rather than through `services:`, because
+    # this runner is configured with `container.network: host`.
     #
-    # Two approaches were tried and rejected before this one:
+    # That single setting explains three failed attempts, and is worth writing
+    # down so nobody repeats them:
     #
-    #   `services:`                    — this runner does not attach service
-    #                                    containers to the job network, giving
-    #                                    "getaddrinfo EAI_AGAIN postgres".
-    #   `--network container:$HOSTNAME` — /etc/hostname inside the job reports
-    #                                    the HOST's name, not the container id,
-    #                                    so the namespace join finds no such
-    #                                    container.
+    #   `services:`                     Service containers are not resolvable by
+    #                                   name from a host-networked job, giving
+    #                                   "getaddrinfo EAI_AGAIN postgres".
+    #   `--network container:$HOSTNAME` /etc/hostname reports the HOST's name,
+    #                                   not a container id, so the namespace
+    #                                   join finds no such container.
+    #   default-gateway addressing      The wrong idea entirely: with host
+    #                                   networking the default route is the
+    #                                   real router, not a docker bridge.
     #
-    # What works without needing to know our own container id: publish the port
-    # on the host and reach it through the job container's default gateway. The
-    # port is derived from the run id so concurrent runs cannot collide.
+    # Because the job shares the host's network namespace, a published port is
+    # simply on 127.0.0.1. The port is derived from the run id so concurrent
+    # runs cannot collide.
     env:
       PG_CONTAINER: pig-ci-pg-${{ github.run_id }}
 
@@ -57,29 +61,33 @@ jobs:
 
       - name: Start Postgres
         run: |
-          # A per-run port in the ephemeral range, so two runs never collide.
           PG_PORT=$(( 45000 + (${{ github.run_id }} % 15000) ))
-          GATEWAY=$(ip route | awk '/^default/ {print $3; exit}')
-          if [ -z "$GATEWAY" ]; then echo "Could not determine the gateway"; exit 1; fi
-          echo "Postgres will be published on ${GATEWAY}:${PG_PORT}"
+          echo "Publishing Postgres on 127.0.0.1:${PG_PORT}"
 
           docker rm -f "$PG_CONTAINER" 2>/dev/null || true
           docker run -d --name "$PG_CONTAINER" \
-            -p "${PG_PORT}:5432" \
+            -p "127.0.0.1:${PG_PORT}:5432" \
             -e POSTGRES_USER=pig -e POSTGRES_PASSWORD=pig -e POSTGRES_DB=pig \
             postgres:16-alpine
 
+          # pg_isready inside the container only proves the server started.
+          # What matters is that THIS job can reach it through the published
+          # port, so the readiness check is made from here, over TCP.
           for i in $(seq 1 60); do
-            if docker exec "$PG_CONTAINER" pg_isready -U pig -q; then
-              echo "Postgres ready after ${i}s"
-              # Export for every later step.
-              echo "DATABASE_URL=postgres://pig:pig@${GATEWAY}:${PG_PORT}/pig" >> "$GITHUB_ENV"
+            if node -e "
+              const net=require('net');
+              const s=net.connect(${PG_PORT},'127.0.0.1');
+              s.on('connect',()=>{s.end();process.exit(0)});
+              s.on('error',()=>process.exit(1));
+            " 2>/dev/null; then
+              echo "Reachable after ${i}s"
+              echo "DATABASE_URL=postgres://pig:pig@127.0.0.1:${PG_PORT}/pig" >> "$GITHUB_ENV"
               exit 0
             fi
             sleep 1
           done
-          echo "Postgres did not become ready"
-          docker logs "$PG_CONTAINER" | tail -30
+          echo "Postgres never became reachable on 127.0.0.1:${PG_PORT}"
+          docker logs "$PG_CONTAINER" 2>&1 | tail -30
           exit 1
 
       - name: Install