295 lines
13 KiB
Haskell
295 lines
13 KiB
Haskell
{-# LANGUAGE LambdaCase #-}
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{-# LANGUAGE MultiWayIf #-}
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{-# LANGUAGE NamedFieldPuns #-}
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{-# LANGUAGE RecordWildCards #-}
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module PostgREST.AppState.Reload
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( isSchemaCacheLoaded
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, readInDbConfig
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, retryingSchemaCacheLoad
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, runListener
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, waitForSchemaCacheInit
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, waitForSchemaCacheLoaded
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) where
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import qualified Data.ByteString.Char8 as BS
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import qualified Data.Text as T
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import qualified Database.PostgreSQL.LibPQ as LibPQ
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import qualified Hasql.Connection as SQL
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import qualified Hasql.Notifications as SQL
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import qualified Hasql.Session as SQL
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import qualified Hasql.Transaction.Sessions as SQL
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import qualified PostgREST.Config as Config
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import Control.Arrow ((&&&))
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import Control.Concurrent.STM (putTMVar, readTMVar, tryReadTMVar, tryTakeTMVar)
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import Control.Retry (RetryPolicy, RetryStatus (..), capDelay,
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exponentialBackoff, retrying, rsPreviousDelay)
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import Data.Bitraversable (bisequence)
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import Data.Either.Combinators (whenRight)
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import Data.IORef (IORef, newIORef, readIORef, writeIORef)
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import PostgREST.AppState.Pool (flushPool, usePool)
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import PostgREST.Auth.JwtCache (update)
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import PostgREST.Config (AppConfig (..), readAppConfig)
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import PostgREST.Config.Database (queryDbSettings, queryPgVersion,
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queryRoleSettings)
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import PostgREST.Config.PgVersion (PgVersion (..), minimumPgVersion)
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import PostgREST.Observation (Observation (..))
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import PostgREST.SchemaCache (SchemaCache (..), querySchemaCache,
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showSummary)
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import PostgREST.SchemaCache.Identifiers (quoteQi)
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import PostgREST.TimeIt (timeItT)
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import PostgREST.AppState.Types
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import Protolude
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-- | Try to load the schema cache and retry if it fails.
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--
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-- This is done by repeatedly: 1) flushing the pool, 2) querying the version and validating that the postgres version is supported by us, and 3) loading the schema cache.
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-- It's necessary to flush the pool:
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--
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-- + Because connections cache the pg catalog(see #2620)
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-- + For rapid recovery. Otherwise, the pool idle or lifetime timeout would have to be reached for new healthy connections to be acquired.
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retryingSchemaCacheLoad :: AppState -> IO ()
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retryingSchemaCacheLoad appState@AppState{stateObserver=observer} =
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void $ retrying retryPolicy shouldRetry (\RetryStatus{rsIterNumber, rsPreviousDelay} -> do
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when (rsIterNumber > 0) $ do
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let delay = fromMaybe 0 rsPreviousDelay `div` oneSecondInUs
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observer $ ConnectionRetryObs delay
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(,) <$> qPgVersion <*> (qInDbConfig *> qSchemaCache)
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)
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where
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qPgVersion :: IO (Maybe PgVersion)
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qPgVersion = do
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AppConfig{..} <- getConfig appState
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pgVersion <- usePool appState queryPgVersion
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case pgVersion of
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Left e -> do
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observer $ QueryPgVersionError e
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unless configDbPoolAutomaticRecovery $ do
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observer ExitDBNoRecoveryObs
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killApp appState
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return Nothing
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Right actualPgVersion ->
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if actualPgVersion < minimumPgVersion then do
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observer $ ExitUnsupportedPgVersion actualPgVersion minimumPgVersion
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killApp appState
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return Nothing
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else do
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observer $ DBConnectedObs $ pgvFullName actualPgVersion
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observer $ PoolInit configDbPoolSize
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putPgVersion appState actualPgVersion
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return $ Just actualPgVersion
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qInDbConfig :: IO ()
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qInDbConfig = do
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AppConfig{..} <- getConfig appState
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when configDbConfig $ readInDbConfig False appState
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qSchemaCache :: IO (Maybe SchemaCache)
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qSchemaCache = do
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conf@AppConfig{..} <- getConfig appState
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pgVer <- getPgVersion appState
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(resultTime, result) <-
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timeItT $ usePool appState (SQL.transactionNoRetry SQL.ReadCommitted SQL.Read $ querySchemaCache pgVer conf)
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case result of
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Left e -> do
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markSchemaCachePending appState
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observer $ SchemaCacheErrorObs configDbSchemas configDbExtraSearchPath e
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return Nothing
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Right (sCache, queryTimings) -> do
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-- IMPORTANT: While the pending schema cache state starts from running the above querySchemaCache, only at this stage we block API requests due to the usage of an
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-- IORef on putSchemaCache. This is why schema cache status is marked as pending here to signal the Admin server (using isPending) that we're on a recovery state.
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markSchemaCachePending appState
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putSchemaCache appState $ Just sCache
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(loadTime, summary) <- timeItT (evaluate $ showSummary sCache)
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-- Flush the pool after loading the schema cache to reset any stale session cache entries
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-- We do it after successfully querying the schema cache (because this can fail and during retries we would flush the pool repeatedly unnecessarily)
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-- and after marking sCacheStatus as pending,
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flushPool appState
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observer $ SchemaCacheQueriedObs resultTime queryTimings
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observer $ SchemaCacheLoadedObs loadTime summary
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markSchemaCacheLoaded appState
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return $ Just sCache
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shouldRetry :: RetryStatus -> (Maybe PgVersion, Maybe SchemaCache) -> IO Bool
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shouldRetry _ (pgVer, sCache) = do
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AppConfig{..} <- getConfig appState
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let itShould = configDbPoolAutomaticRecovery && (isNothing pgVer || isNothing sCache)
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return itShould
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retryPolicy :: RetryPolicy
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retryPolicy =
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let delayMicroseconds = 32*oneSecondInUs {-32 seconds-} in
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capDelay delayMicroseconds $ exponentialBackoff oneSecondInUs
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oneSecondInUs = 1_000_000 -- one second in microseconds
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markSchemaCachePending :: AppState -> IO ()
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markSchemaCachePending = atomically . liftA2 (*>) tryTakeTMVar (`putTMVar` False) . getSCStatusTMVar . stateSCacheStatus
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markSchemaCacheLoaded :: AppState -> IO ()
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markSchemaCacheLoaded = atomically . liftA2 (*>) tryTakeTMVar (`putTMVar` True) . getSCStatusTMVar . stateSCacheStatus
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isSchemaCacheLoaded :: AppState -> IO Bool
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isSchemaCacheLoaded = atomically . (pure . fromMaybe False <=< tryReadTMVar) . getSCStatusTMVar . stateSCacheStatus
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-- | Wait for initial schema cache load to either finish or retry
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-- | We wait until scStatusTMVar is not empty.
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waitForSchemaCacheInit :: AppState -> IO ()
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waitForSchemaCacheInit = atomically . void . readTMVar . getSCStatusTMVar . stateSCacheStatus
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waitForSchemaCacheLoaded :: AppState -> IO ()
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waitForSchemaCacheLoaded = atomically . (check <=< readTMVar) . getSCStatusTMVar . stateSCacheStatus
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-- | Reads the in-db config and reads the config file again
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-- | We don't retry reading the in-db config after it fails immediately, because it could have user errors. We just report the error and continue.
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readInDbConfig :: Bool -> AppState -> IO ()
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readInDbConfig startingUp appState@AppState{stateObserver=observer} = do
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oldConf <- getConfig appState
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pgVer <- getPgVersion appState
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dbSettings <-
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if configDbConfig oldConf then do
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qDbSettings <- usePool appState (queryDbSettings (quoteQi <$> configDbPreConfig oldConf))
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case qDbSettings of
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Left e -> do
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observer $ ConfigReadErrorObs e
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pure mempty
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Right x -> pure x
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else
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pure mempty
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(roleSettings, roleIsolationLvl) <-
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if configDbConfig oldConf then do
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rSettings <- usePool appState (queryRoleSettings pgVer)
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case rSettings of
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Left e -> do
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observer $ QueryRoleSettingsErrorObs e
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pure (mempty, mempty)
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Right x -> pure x
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else
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pure mempty
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readAppConfig dbSettings (configFilePath oldConf) (Just $ configDbUri oldConf) roleSettings roleIsolationLvl >>= \case
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Left err ->
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if startingUp then
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panic err -- die on invalid config if the program is starting up
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else
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observer $ ConfigInvalidObs err
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Right newConf -> do
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putConfig appState newConf
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-- After the config has reloaded, jwt-secret might have changed, so
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-- if it has changed, it is important to invalidate the jwt cache
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-- entries, because they were cached using the old secret
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update (getJwtCacheState appState) newConf
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-- If db-channel-enabled is changed, then reload listener
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when (((/=) `on` configDbChannelEnabled) newConf oldConf) $ do
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-- 1. Kill the listener thread
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getListenerThreadId appState >>= mapM_ (`throwTo` ListenerRestart)
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putIsListenerOn appState False
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-- 2. Restart listener
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runListener appState
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if startingUp then
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pass
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else
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observer ConfigSucceededObs
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-- | Starts the Listener in a thread
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runListener :: AppState -> IO ()
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runListener appState = do
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AppConfig{..} <- getConfig appState
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when configDbChannelEnabled $ do
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nextDelay <- newIORef 1
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listenerThreadId <- forkIO . void $ retryingListen appState nextDelay False
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putListenerThreadId appState (Just listenerThreadId)
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-- | Starts a LISTEN connection and handles notifications. It recovers with exponential backoff with a cap of 32 seconds, if the LISTEN connection is lost.
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-- | This function never returns (but can throw) and return type enforces that.
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retryingListen :: AppState -> IORef Int -> Bool -> IO ()
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retryingListen appState nextDelay hasDbListenerBug = do
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cfg@AppConfig{..} <- getConfig appState
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let
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dbChannel = toS configDbChannel
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onError err = case fromException err of
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Just ListenerRestart -> traverse_ killThread =<< getListenerThreadId appState
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Nothing -> do -- for any other exception
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putIsListenerOn appState False
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observer $ DBListenFail dbChannel (Right err)
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when (isDbListenerBug err) $
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observer DBListenBugCallQueryFix
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unless configDbPoolAutomaticRecovery $
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killApp appState
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-- retry the listener
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delay <- readIORef nextDelay
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observer $ DBListenRetry delay
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threadDelay (delay * oneSecondInMicro)
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unless (delay == maxDelay) $
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writeIORef nextDelay (delay * 2)
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-- loop running the listener
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retryingListen appState nextDelay (isDbListenerBug err)
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-- Execute the listener with error handling
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handle onError $ do
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-- Make sure we don't leak connections on errors
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bracket
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-- acquire connection
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(SQL.acquire $
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Config.toConnectionSettings Config.addTargetSessionAttrs cfg)
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-- release connection
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(`whenRight` releaseConnection) $
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-- use connection
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\case
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Right db -> do
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(pqHost, pqPort) <- SQL.withLibPQConnection db $ bisequence . (LibPQ.host &&& LibPQ.port)
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pgFullName <- SQL.run queryPgVersion db >>= either throwIO (pure . pgvFullName)
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when hasDbListenerBug $ SQL.run callNotifQueryUsage db >>= either throwIO pure
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SQL.listen db $ SQL.toPgIdentifier dbChannel
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putIsListenerOn appState True
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delay <- readIORef nextDelay
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when (delay > 1) $ do -- if we did a retry
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-- assume we lost notifications, refresh the schema cache
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schemaCacheLoader appState
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-- reset the delay
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writeIORef nextDelay 1
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observer $ DBListenStart pqHost pqPort pgFullName dbChannel
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-- wait for notifications
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-- this will never return, in case of an error it will throw and be caught by onError
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forever $ SQL.waitForNotifications handleNotification db
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Left err -> do
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observer $ DBListenFail dbChannel (Left err)
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exitFailure
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where
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observer = getObserver appState
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oneSecondInMicro = 1_000_000
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maxDelay = 32
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handleNotification channel msg =
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if | BS.null msg -> observer (DBListenerGotSCacheMsg channel) >> cacheReloader
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| msg == "reload schema" -> observer (DBListenerGotSCacheMsg channel) >> cacheReloader
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| msg == "reload config" -> observer (DBListenerGotConfigMsg channel) >> readInDbConfig False appState
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| otherwise -> pure () -- Do nothing if anything else than an empty message is sent
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cacheReloader =
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schemaCacheLoader appState
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releaseConnection = void . forkIO . handle (observer . DBListenerConnectionCleanupFail) . SQL.release
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isDbListenerBug e = "could not access status of transaction" `T.isInfixOf` show e
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-- Used to fix a Postgres bug in the listener, see: https://github.com/PostgREST/postgrest/issues/3147#issuecomment-3494591361
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-- This query advances the async notification query tail, which solves this issue.
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callNotifQueryUsage :: SQL.Session ()
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callNotifQueryUsage = SQL.sql "SELECT pg_notification_queue_usage();"
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