add(observation): db pool flushes observation

CHANGELOG.md

@@ -14,6 +14,7 @@ All notable changes to this project will be documented in this file. From versio
 - Add config `client-error-verbosity` to customize error verbosity by @taimoorzaeem in #4088, #3980, #3824
 - Add `Vary` header to responses by @develop7 in #4609
 - Add config `db-timezone-enabled` for optional querying of timezones by @taimoorzaeem in #4751
+- Log when the pool is released during schema cache reload on `log-level=debug` by @mkleczek in #4668
 
 ### Changed
 

postgrest.cabal

@@ -308,6 +308,7 @@ test-suite observability
   other-modules:      ObsHelper
                       Observation.JwtCache
                       Observation.MetricsSpec
+                      Observation.SchemaCacheSpec
   build-depends:      base              >= 4.9 && < 4.20
                     , base64-bytestring >= 1 && < 1.3
                     , bytestring        >= 0.10.8 && < 0.13

src/PostgREST/AppState.hs

@@ -225,10 +225,14 @@ usePool AppState{stateObserver=observer, stateMainThreadId=mainThreadId, ..} ses
 
 -- | Flush the connection pool so that any future use of the pool will
 -- use connections freshly established after this call.
+-- | Emits PoolFlushed observation
 flushPool :: AppState -> IO ()
-flushPool AppState{..} = SQL.release statePool
+flushPool AppState{..} = do
+  SQL.release statePool
+  stateObserver PoolFlushed
 
 -- | Destroy the pool on shutdown.
+-- | Differs from flushPool in not emiting PoolFlushed observation.
 destroyPool :: AppState -> IO ()
 destroyPool AppState{..} = SQL.release statePool
 

src/PostgREST/Logger.hs

@@ -111,6 +111,9 @@ observationLogger loggerState logLevel obs = case obs of
   o@PoolRequestFullfilled ->
     when (logLevel >= LogDebug) $ do
       logWithZTime loggerState $ observationMessages o
+  o@PoolFlushed ->
+    when (logLevel >= LogDebug) $ do
+      logWithZTime loggerState $ observationMessages o
   o@JwtCacheEviction ->
     when (logLevel >= LogDebug) $ do
       logWithZTime loggerState $ observationMessages o
@@ -224,6 +227,8 @@ observationMessages = \case
     pure "Trying to borrow a connection from pool"
   PoolRequestFullfilled ->
     pure "Borrowed a connection from the pool"
+  PoolFlushed ->
+    pure "Database connection pool flushed"
   JwtCacheLookup _ ->
     pure "Looked up a JWT in JWT cache"
   JwtCacheEviction ->

src/PostgREST/Observation.hs

@@ -53,6 +53,7 @@ data Observation
   | HasqlPoolObs SQL.Observation
   | PoolRequest
   | PoolRequestFullfilled
+  | PoolFlushed
   | JwtCacheLookup Bool
   | JwtCacheEviction
   | TerminationUnixSignalObs Text

test/io/test_io.py

@@ -21,6 +21,19 @@
 )
 
 
+def match_log(output, matchers):
+    ito = iter(output)
+    itm = iter(matchers)
+    nextMatcher = next(itm, None)
+    while nextMatcher is not None and (line := next(ito, None)) is not None:
+        if re.match(nextMatcher, line) is not None:
+            nextMatcher = next(itm, None)
+    if nextMatcher is not None:
+        raise AssertionError(
+            f"Expected log line matching {nextMatcher} not found in output"
+        )
+
+
 def test_connect_with_dburi(dburi, defaultenv):
     "Connecting with db-uri instead of LIPQ* environment variables should work."
     defaultenv_without_libpq = {
@@ -768,54 +781,44 @@ def test_log_level(level, defaultenv):
         response = postgrest.session.get("/")
         assert response.status_code == 200
 
-        output = sorted(postgrest.read_stdout(nlines=7))
+        output = postgrest.read_stdout(nlines=7)
 
         if level == "crit":
             assert len(output) == 0
         elif level == "error":
-            assert re.match(
-                r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
-                output[0],
+            match_log(
+                output,
+                [r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"'],
             )
             assert len(output) == 1
         elif level == "warn":
-            assert re.match(
-                r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
-                output[0],
-            )
-            assert re.match(
-                r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 \d+ "" "python-requests/.+"',
-                output[1],
+            match_log(
+                output,
+                [
+                    r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
+                    r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 \d+ "" "python-requests/.+"',
+                ],
             )
             assert len(output) == 2
         elif level == "info":
-            assert re.match(
-                r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
-                output[0],
-            )
-            assert re.match(
-                r'- - postgrest_test_anonymous \[.+\] "GET / HTTP/1.1" 200 \d+ "" "python-requests/.+"',
-                output[1],
-            )
-            assert re.match(
-                r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 \d+ "" "python-requests/.+"',
-                output[2],
+            match_log(
+                output,
+                [
+                    r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
+                    r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 \d+ "" "python-requests/.+"',
+                    r'- - postgrest_test_anonymous \[.+\] "GET / HTTP/1.1" 200 \d+ "" "python-requests/.+"',
+                ],
             )
             assert len(output) == 3
         elif level == "debug":
-            assert re.match(
-                r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
-                output[0],
+            match_log(
+                output,
+                [
+                    r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
+                    r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 \d+ "" "python-requests/.+"',
+                    r'- - postgrest_test_anonymous \[.+\] "GET / HTTP/1.1" 200 \d+ "" "python-requests/.+"',
+                ],
             )
-            assert re.match(
-                r'- - postgrest_test_anonymous \[.+\] "GET / HTTP/1.1" 200 \d+ "" "python-requests/.+"',
-                output[1],
-            )
-            assert re.match(
-                r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 \d+ "" "python-requests/.+"',
-                output[2],
-            )
-
             assert len(output) == 7
             assert any("Connection" and "is available" in line for line in output)
             assert any("Connection" and "is used" in line for line in output)
@@ -1453,16 +1456,21 @@ def test_db_error_logging_to_stderr(level, defaultenv, metapostgrest):
         assert response.status_code == 500
 
         # ensure the message appears on the logs
-        output = sorted(postgrest.read_stdout(nlines=6))
+        output = postgrest.read_stdout(nlines=6)
 
         if level == "crit":
             assert len(output) == 0
         elif level == "debug":
-            assert " 500 " in output[0]
-            assert "canceling statement due to statement timeout" in output[5]
+            match_log(
+                output,
+                [
+                    r".*canceling statement due to statement timeout.*",
+                    r".*500.*",
+                ],
+            )
         else:
-            assert " 500 " in output[0]
-            assert "canceling statement due to statement timeout" in output[1]
+            assert " 500 " in output[1]
+            assert "canceling statement due to statement timeout" in output[0]
 
     reset_statement_timeout(metapostgrest, role)
 
@@ -1656,18 +1664,17 @@ def test_log_pool_req_observation(level, defaultenv):
 
     headers = jwtauthheader({"role": "postgrest_test_author"}, SECRET)
 
-    pool_req = "Trying to borrow a connection from pool"
-    pool_req_fullfill = "Borrowed a connection from the pool"
+    pool_req = r".*Trying to borrow a connection from pool.*"
+    pool_req_fullfill = r".*Borrowed a connection from the pool.*"
 
     with run(env=env) as postgrest:
 
         postgrest.session.get("/authors_only", headers=headers)
 
         if level == "debug":
-            output = postgrest.read_stdout(nlines=5)
-            assert pool_req in output[1]
-            assert pool_req_fullfill in output[4]
-            assert len(output) == 5
+            output = postgrest.read_stdout(nlines=7)
+            assert len(output) == 6
+            match_log(output, [pool_req, pool_req_fullfill])
         elif level == "info":
             output = postgrest.read_stdout(nlines=4)
             assert len(output) == 1

test/observability/Main.hs

@@ -17,10 +17,11 @@ import           PostgREST.SchemaCache     (querySchemaCache)
 import qualified Observation.JwtCache
 import qualified Observation.MetricsSpec
 
-import ObsHelper
-import PostgREST.Observation (Observation (HasqlPoolObs))
-import Protolude             hiding (toList, toS)
-import Test.Hspec
+import qualified Observation.SchemaCacheSpec
+import           ObsHelper
+import           PostgREST.Observation       (Observation (HasqlPoolObs))
+import           Protolude                   hiding (toList, toS)
+import           Test.Hspec
 
 main :: IO ()
 main = do
@@ -64,6 +65,8 @@ main = do
       describe "Observation.JwtCacheObs" Observation.JwtCache.spec
     before (initApp baseSchemaCache testCfg) $
       describe "Feature.MetricsSpec" Observation.MetricsSpec.spec
+    before (initApp baseSchemaCache testCfg) $
+      describe "Feature.SchemaCacheSpec" Observation.SchemaCacheSpec.spec
 
   where
     loadSCache pool conf =

test/observability/Observation/SchemaCacheSpec.hs

@@ -0,0 +1,51 @@
+{-# LANGUAGE DataKinds           #-}
+{-# LANGUAGE MonadComprehensions #-}
+{-# LANGUAGE NamedFieldPuns      #-}
+module Observation.SchemaCacheSpec where
+
+import           Network.Wai           (Application)
+import           ObsHelper
+import qualified PostgREST.AppState    as AppState
+import           PostgREST.Config      (configDbSchemas)
+import           PostgREST.Observation
+import           Protolude
+import           Test.Hspec            (SpecWith, describe, it)
+import           Test.Hspec.Wai        (getState)
+
+spec :: SpecWith (SpecState, Application)
+spec = describe "Server started with metrics enabled" $ do
+
+  it "Should emit PoolFlushed, SchemaCacheQueriedObs and SchemaCacheLoadedObs when schema cache is reloaded" $ do
+    SpecState{specAppState = appState, specObsChan} <- getState
+    let waitFor = waitForObs specObsChan
+
+    liftIO $ do
+      AppState.schemaCacheLoader appState
+
+      waitFor (1 * sec) "PoolFlushed" $ \x -> [ o | o@PoolFlushed <- pure x ]
+      waitFor (1 * sec) "SchemaCacheQueriedObs" $ \x -> [ o | o@SchemaCacheQueriedObs{} <- pure x ]
+      waitFor (1 * sec) "SchemaCacheLoadedObs" $ \x -> [ o | o@SchemaCacheLoadedObs{} <- pure x ]
+
+
+  it "Should flush pool multiple times when schema reloading retries" $ do
+    SpecState{specAppState = appState, specObsChan} <- getState
+    let waitFor = waitForObs specObsChan
+
+    liftIO $ do
+        AppState.getConfig appState >>= \cfg -> do
+          AppState.putConfig appState $ cfg { configDbSchemas = pure "bad_schema" }
+          AppState.schemaCacheLoader appState
+
+          waitFor (1 * sec) "PoolFlushed 1" $ \x -> [ o | o@PoolFlushed <- pure x ]
+          waitFor (1 * sec) "SchemaCacheErrorObs" $ \x -> [ o | o@SchemaCacheErrorObs{} <- pure x ]
+
+          -- Restore configuration
+          AppState.putConfig appState cfg
+
+        -- Wait for 2 seconds so that retry can happen
+        waitFor (2 * sec) "PoolFlushed 2" $ \x -> [ o | o@PoolFlushed <- pure x ]
+        waitFor (1 * sec) "SchemaCacheQueriedObs" $ \x -> [ o | o@SchemaCacheQueriedObs{} <- pure x ]
+        waitFor (1 * sec) "SchemaCacheLoadedObs" $ \x -> [ o | o@SchemaCacheLoadedObs{} <- pure x ]
+
+  where
+    sec = 1000000