fix: the web service starts once libpq can be found.

ADR.md

@@ -359,11 +359,22 @@ missing. PostgreSQL may also start after the services at boot.
 Decision: The web service makes its signing key and creates the refresh tokens' database itself,
 and the Router Manager its sessions database; neither `vpn-router-setup` nor a maintainer script
 creates them. Each service does it before it listens, retrying every 15 seconds and logging each
-failure, then listens.
+failure, then listens. `vpnrouter_auth` turns every failure of the database into
+`DatabaseError`, the only database exception the web service and `vpn-router-user` handle.
 
-Consequences: The order of installation and of the start of PostgreSQL does not matter; a
-database that cannot be created is created once the cause is gone, and the reason is in the
-service's log. The web unit may write `/etc/vpn-router` for the key and the database password.
+psycopg (Ubuntu ships only its pure-Python implementation) finds libpq through the dynamic linker
+cache, which dpkg refreshes with its deferred `ldconfig` only at the end of an installation, so a
+service started during the installation cannot import it yet; a failed import cannot be repeated
+in the same process either, as psycopg caches the lookup. The services therefore import psycopg
+plainly, and their units wait instead: `ExecStartPre=wait-for-libpq`, a shell script of each
+package, waits until `ldconfig -p` lists `libpq.so.5`, within `TimeoutStartSec=5min`. The
+maintainer scripts start the units with `systemctl --no-block` (debhelper's start is turned off),
+because a start that waited would hold dpkg before its `ldconfig`.
+
+Consequences: The order of installation and of the start of PostgreSQL and of the linker cache
+does not matter; a database that cannot be created is retried until the cause is gone, and the
+reason is in the service's log. Outside an installation the wait ends at once. The web unit may
+write `/etc/vpn-router` for the key and the database password.
 
 ## ADR-17: Bootstrap diagnostics run only until the first setup succeeds
 

debian-package/debian/changelog

@@ -1,3 +1,27 @@
+vpn-router (0.9.2-1) unstable; urgency=medium
+
+  fix: the web service starts once libpq can be found.
+
+  * The web service unit waits, with wait-for-libpq, until libpq is in the
+    linker cache before it starts the service, for at most 5 minutes; the
+    service imports psycopg at start again.
+  * The package starts the web service without waiting for it.
+
+ -- Slawomir Koszewski <slawek@koszewscy.waw.pl>  Sun, 25 Oct 2026 06:00:00 +0200
+
+vpn-router (0.9.1-1) unstable; urgency=medium
+
+  fix: the web service waits for the PostgreSQL driver instead of failing at start.
+
+  * The web service imports psycopg as the first step of its
+    initialization, retrying every 15 seconds and logging the failure while
+    libpq cannot be found yet during an installation.
+  * vpn-router-user and vpn-router-token load without psycopg; a command
+    that needs the token database then reports that the driver cannot be
+    loaded, as it reports every failure of that database.
+
+ -- Slawomir Koszewski <slawek@koszewscy.waw.pl>  Sun, 25 Oct 2026 05:00:00 +0200
+
 vpn-router (0.9.0-1) unstable; urgency=medium
 
   feature: bootstrap diagnostics on port 17081 during the first setup.

debian-package/debian/install

@@ -15,6 +15,7 @@ src/usr/lib/vpn-router/docker-rules                   usr/lib/vpn-router/
 src/usr/lib/vpn-router/setup                          usr/lib/vpn-router/
 src/usr/lib/vpn-router/web                            usr/lib/vpn-router/
 src/usr/lib/vpn-router/bootstrap                      usr/lib/vpn-router/
+src/usr/lib/vpn-router/wait-for-libpq                 usr/lib/vpn-router/
 src/usr/lib/vpn-router/generate-config                usr/lib/vpn-router/
 src/usr/lib/vpn-router/vpnrouter_platforms/*.py       usr/lib/vpn-router/vpnrouter_platforms/
 src/usr/share/vpn-router/templates/*                  usr/share/vpn-router/templates/

debian-package/debian/postinst

@@ -70,6 +70,12 @@ case "$1" in
         # The firewall is not touched here. Enabling it, allowing SSH and
         # setting the forward policy all belong to vpn-router-setup, which does
         # them only once the configuration says this host is a router.
+
+        # The web service waits for libpq in the linker cache, which dpkg
+        # refreshes after this script, so it is started without waiting for it.
+        if [ -d /run/systemd/system ]; then
+            systemctl --no-block restart vpn-router-web.service >/dev/null 2>&1 || true
+        fi
         ;;
 esac
 

debian-package/debian/rules

@@ -5,5 +5,5 @@
 override_dh_installsystemd:
 	dh_installsystemd --name=vpn-router-setup
 	dh_installsystemd --name=vpn-router-docker
-	dh_installsystemd --name=vpn-router-web
+	dh_installsystemd --name=vpn-router-web --no-start
 	dh_installsystemd --name=vpn-router-bootstrap --no-enable --no-start

debian-package/debian/vpn-router.vpn-router-web.service

@@ -6,7 +6,9 @@ Wants=network-online.target
 
 [Service]
 Type=simple
+ExecStartPre=/usr/lib/vpn-router/wait-for-libpq
 ExecStart=/usr/bin/python3 /usr/lib/vpn-router/web
+TimeoutStartSec=5min
 Restart=on-failure
 RestartSec=15
 NoNewPrivileges=yes

debian-package/src/usr/lib/vpn-router/vpnrouter_auth.py

@@ -5,12 +5,15 @@ router and that never leaves it. /auth issues an access token naming the user in
 a refresh token valid REFRESH_SECONDS; vpn-router-token issues tokens with the admin claim and
 any lifetime. A token without the admin claim must expire within MAX_LIFETIME seconds.
 
+Every failure of the database raises DatabaseError, the only database exception callers see.
+
 Refresh tokens are random strings kept in PostgreSQL as their SHA-256, in the database of
 web.database, by default the vpn-router database on this host that provision() creates on the
 web service's first run, with the password in DATABASE_SECRET. A refresh token is used once: refreshing replaces it.
 """
 
 import base64
+import contextlib
 import hashlib
 import hmac
 import json
@@ -20,7 +23,6 @@ import subprocess
 import time
 
 import psycopg
-from psycopg.conninfo import make_conninfo
 
 WEB_KEY = pathlib.Path('/etc/vpn-router/web.key')
 DATABASE_SECRET = pathlib.Path('/etc/vpn-router/database.secret')
@@ -41,6 +43,10 @@ LEEWAY = 60
 SCHEMA = 'CREATE TABLE IF NOT EXISTS refresh_tokens (hash text PRIMARY KEY, name text NOT NULL, expires timestamptz NOT NULL)'
 
 
+class DatabaseError(Exception):
+    """The database of the refresh tokens failed."""
+
+
 def key():
     """The signing key, or '' while the web service has not made it."""
     try:
@@ -112,19 +118,23 @@ def admin_token(seconds):
 
 
 def connection_string(cfg):
-    """web.database, or the database provision() creates."""
+    """web.database, or the database provision() creates; its password, of URL-safe characters, is written unquoted."""
     configured = cfg['web']['database'].strip()
     if configured:
         return configured
     password = DATABASE_SECRET.read_text(encoding='utf-8').strip()
-    return make_conninfo(host='localhost', dbname=DATABASE, user=DATABASE, password=password)
+    return f'host=localhost dbname={DATABASE} user={DATABASE} password={password}'
 
 
-def connect(cfg):
-    """A connection to the database of the refresh tokens, with their table."""
-    connection = psycopg.connect(connection_string(cfg), autocommit=True)
-    connection.execute(SCHEMA)
-    return connection
+@contextlib.contextmanager
+def database(cfg):
+    """A connection to the database of the refresh tokens, with their table, closed at the end; DatabaseError on any failure."""
+    try:
+        with psycopg.connect(connection_string(cfg), autocommit=True) as connection:
+            connection.execute(SCHEMA)
+            yield connection
+    except psycopg.Error as exc:
+        raise DatabaseError(f'the token database failed: {exc}') from exc
 
 
 def digest(token):
@@ -136,7 +146,7 @@ def issue(cfg, name):
     secret = key()
     now = int(time.time())
     refresh = secrets.token_urlsafe(32)
-    with connect(cfg) as connection:
+    with database(cfg) as connection:
         connection.execute('DELETE FROM refresh_tokens WHERE expires < now()')
         connection.execute("INSERT INTO refresh_tokens VALUES (%s, %s, now() + make_interval(secs => %s))",
                            (digest(refresh), name, REFRESH_SECONDS))
@@ -153,7 +163,7 @@ def take(cfg, token):
     """Remove an unexpired refresh token and return the user it was issued to, or None."""
     if not isinstance(token, str) or not token:
         return None
-    with connect(cfg) as connection:
+    with database(cfg) as connection:
         row = connection.execute('DELETE FROM refresh_tokens WHERE hash = %s RETURNING name, expires > now()',
                                  (digest(token),)).fetchone()
     return row[0] if row and row[1] else None
@@ -161,7 +171,7 @@ def take(cfg, token):
 
 def revoke(cfg, name):
     """Remove all refresh tokens of the user."""
-    with connect(cfg) as connection:
+    with database(cfg) as connection:
         connection.execute('DELETE FROM refresh_tokens WHERE name = %s', (name,))
 
 

debian-package/src/usr/lib/vpn-router/wait-for-libpq

@@ -0,0 +1,12 @@
+#!/bin/sh
+# Wait until libpq is in the dynamic linker cache, where psycopg looks it up.
+# ExecStartPre= of vpn-router-web.service; TimeoutStartSec= of the unit bounds the wait.
+
+reported=
+until ldconfig -p | grep -q '^[[:space:]]*libpq\.so\.5 '; do
+    if [ -z "$reported" ]; then
+        echo 'waiting for libpq.so.5 in the linker cache'
+        reported=yes
+    fi
+    sleep 2
+done

debian-package/src/usr/lib/vpn-router/web

@@ -32,7 +32,8 @@ WireGuard. No configuration data, key or address is shown.
 
 The service first initializes, without listening: it makes the signing key and the refresh
 tokens' database (vpnrouter_auth), retrying every INIT_RETRY_SECONDS until both are ready and
-logging each failure. Then it listens.
+logging each failure. Then it listens. Its unit starts it only once wait-for-libpq has found libpq
+in the linker cache, where psycopg looks it up.
 
 The service needs nothing else to start and does not end on its own. Every DISCOVERY_SECONDS it
 works out the internal address from /etc/vpn-router/vpn-router.json as general.mode directs,
@@ -58,7 +59,6 @@ from http.server import BaseHTTPRequestHandler
 sys.path.insert(0, os.path.dirname(os.path.realpath(__file__)))
 
 import ldap
-import psycopg
 
 import vpnrouter
 import vpnrouter_auth
@@ -440,8 +440,8 @@ def users(state, method, path, body):
         return USER_STATUS.get(failure.status, 500), {'error': str(failure)}
     except (ldap.LDAPError, OSError) as exc:
         return 500, {'error': f'the user directory failed: {exc}'}
-    except psycopg.Error as exc:
-        return 500, {'error': f'the token database failed: {exc}'}
+    except vpnrouter_auth.DatabaseError as exc:
+        return 500, {'error': str(exc)}
     except SystemExit as exc:
         # vpnrouter ends with SystemExit, carrying the reason, on a configuration it cannot read.
         return 500, {'error': str(exc.code)}
@@ -544,8 +544,8 @@ def auth(path, body):
         return (401 if failure.status == 3 else USER_STATUS.get(failure.status, 500)), {'error': str(failure)}
     except (ldap.LDAPError, OSError) as exc:
         return 500, {'error': f'the user directory failed: {exc}'}
-    except psycopg.Error as exc:
-        return 500, {'error': f'the token database failed: {exc}'}
+    except vpnrouter_auth.DatabaseError as exc:
+        return 500, {'error': str(exc)}
     except SystemExit as exc:
         return 500, {'error': str(exc.code)}
 
@@ -707,8 +707,9 @@ def initialize():
             phase = 'creating the token database'
             vpnrouter_auth.provision(cfg)
             phase = 'connecting to the token database'
-            vpnrouter_auth.connect(cfg).close()
-        except (OSError, psycopg.Error, SystemExit) as exc:
+            with vpnrouter_auth.database(cfg):
+                pass
+        except (OSError, SystemExit, vpnrouter_auth.DatabaseError) as exc:
             error = f'{phase} failed: {exc.code if isinstance(exc, SystemExit) else exc}'
             if error != reported:
                 log(f'{error}; retrying every {INIT_RETRY_SECONDS} seconds')

debian-package/src/usr/sbin/vpn-router-user

@@ -29,8 +29,8 @@ import sys
 sys.path.insert(0, '/usr/lib/vpn-router')
 
 import ldap
-import psycopg
 
+import vpnrouter_auth
 import vpnrouter_users
 from vpnrouter_users import Failure
 
@@ -135,8 +135,8 @@ def main(argv):
         message, status = str(failure), failure.status
     except (ldap.LDAPError, OSError) as exc:
         message, status = f'the user directory failed: {exc}', 1
-    except psycopg.Error as exc:
-        message, status = f'the token database failed: {exc}', 1
+    except vpnrouter_auth.DatabaseError as exc:
+        message, status = str(exc), 1
     else:
         print(json.dumps(answer) if as_json else text_of(answer))
         return 0