Add fallback_application_name to db-uri

src/PostgREST/Config.hs

@@ -47,6 +47,7 @@ import Data.List               (lookup)
 import Data.List.NonEmpty      (fromList, toList)
 import Data.Maybe              (fromJust)
 import Data.Scientific         (floatingOrInteger)
+import Network.URI             (escapeURIString, isUnescapedInURI, parseURI, uriQuery)
 import Numeric                 (readOct, showOct)
 import System.Environment      (getEnvironment)
 import System.Posix.Types      (FileMode)
@@ -60,6 +61,7 @@ import PostgREST.Config.Proxy            (Proxy (..),
 import PostgREST.MediaType               (MediaType (..), toMime)
 import PostgREST.SchemaCache.Identifiers (QualifiedIdentifier, dumpQi,
                                           toQi)
+import PostgREST.Version                 (prettyVersion)
 
 import Protolude hiding (Proxy, toList)
 
@@ -219,7 +221,7 @@ readAppConfig dbSettings optPath prevDbUri roleSettings roleIsolationLvl = do
     decodeLoadFiles :: AppConfig -> IO AppConfig
     decodeLoadFiles parsedConfig =
       decodeJWKS <$>
-        (decodeSecret =<< readSecretFile =<< readDbUriFile prevDbUri parsedConfig)
+        (decodeSecret =<< readSecretFile =<< addPgrstVerToDbUri =<< readDbUriFile prevDbUri parsedConfig)
 
 parser :: Maybe FilePath -> Environment -> [(Text, Text)] -> RoleSettings -> RoleIsolationLvl -> C.Parser C.Config AppConfig
 parser optPath env dbSettings roleSettings roleIsolationLvl =
@@ -460,3 +462,19 @@ type Environment = M.Map [Char] Text
 readPGRSTEnvironment :: IO Environment
 readPGRSTEnvironment =
   M.map T.pack . M.fromList . filter (isPrefixOf "PGRST_" . fst) <$> getEnvironment
+
+-- | Allows querying the PostgREST version in SQL by adding `fallback_application_name` to the connection string
+addPgrstVerToDbUri :: AppConfig -> IO AppConfig
+addPgrstVerToDbUri conf = pure $ conf { configDbUri = dbUriWithFallAppName }
+  where
+    dbUriWithFallAppName = dbUri <>
+      case uriQuery <$> parseURI (toS dbUri) of
+        Nothing  -> " " <> keyValStr
+        Just ""  -> "?" <> uriStr
+        Just "?" -> uriStr
+        _        -> "&" <> uriStr
+    dbUri = configDbUri conf
+    uriStr = toS $ escapeURIString isUnescapedInURI $ toS $ pKeyWord <> pgrstVer
+    keyValStr = pKeyWord <> "'" <> pgrstVer <> "'"
+    pKeyWord = "fallback_application_name="
+    pgrstVer = "PostgREST " <> T.decodeUtf8 prettyVersion

test/io/fixtures.sql

@@ -158,3 +158,12 @@ create or replace function migrate_function() returns void as $_$
   $$ language sql;
   notify pgrst, 'reload schema';
 $_$ language sql security definer;
+
+create or replace function get_pgrst_version() returns text
+  language sql
+as $$
+select application_name
+from pg_stat_activity
+where application_name ilike 'postgrest%'
+limit 1;
+$$

test/io/test_io.py

@@ -998,3 +998,31 @@ def test_openapi_in_big_schema(defaultenv):
     with run(env=env) as postgrest:
         response = postgrest.session.get("/")
         assert response.status_code == 200
+
+def test_get_pgrst_version_with_uri_connection_string(dburi, defaultenv):
+    "The fallback_application_name should be added to the db-uri if it has a URI format"
+    defaultenv_without_libpq = {
+        key: value
+        for key, value in defaultenv.items()
+        if key not in ["PGDATABASE", "PGHOST", "PGUSER"]
+    }
+    env = {**defaultenv_without_libpq, "PGRST_DB_URI": dburi.decode()}
+
+    with run(env=env) as postgrest:
+        response = postgrest.session.post("/rpc/get_pgrst_version")
+        assert response.text.startswith('"PostgREST')
+
+
+def test_get_pgrst_version_with_keyval_connection_string(dburi, defaultenv):
+    "The fallback_application_name should be added to the db-uri if it has a keyword/value format"
+    uri = f'dbname={defaultenv["PGDATABASE"]} host={defaultenv["PGHOST"]} user={defaultenv["PGUSER"]}'
+    defaultenv_without_libpq = {
+        key: value
+        for key, value in defaultenv.items()
+        if key not in ["PGDATABASE", "PGHOST", "PGUSER"]
+    }
+    env = {**defaultenv_without_libpq, "PGRST_DB_URI": uri}
+
+    with run(env=env) as postgrest:
+        response = postgrest.session.post("/rpc/get_pgrst_version")
+        assert response.text.startswith('"PostgREST')