Wolfgang WaltherandGitHub
6e04fe7454
* Include hidden views from the search path. Hidden views are views in unexposed schemas that are part of a view dependency chain. * Change allSourceColumns to only return pk and fk columns
312 lines
14 KiB
Haskell
312 lines
14 KiB
Haskell
{-# LANGUAGE CPP #-}
|
||
|
||
module Main where
|
||
|
||
import qualified Data.ByteString as BS
|
||
import qualified Hasql.Connection as C
|
||
import qualified Hasql.Notifications as N
|
||
import qualified Hasql.Pool as P
|
||
import qualified Hasql.Transaction.Sessions as HT
|
||
|
||
import Control.AutoUpdate (defaultUpdateSettings, mkAutoUpdate,
|
||
updateAction)
|
||
import Control.Debounce (debounceAction, debounceEdge,
|
||
debounceFreq,
|
||
defaultDebounceSettings, mkDebounce,
|
||
trailingEdge)
|
||
import Control.Retry (RetryStatus, capDelay,
|
||
exponentialBackoff, retrying,
|
||
rsPreviousDelay)
|
||
import Data.IORef (IORef, atomicWriteIORef, newIORef,
|
||
readIORef)
|
||
import Data.String (IsString (..))
|
||
import Data.Text.IO (hPutStrLn)
|
||
import Data.Time.Clock (getCurrentTime)
|
||
import Network.Wai.Handler.Warp (defaultSettings, runSettings,
|
||
setHost, setPort, setServerName)
|
||
import System.IO (BufferMode (..), hSetBuffering)
|
||
|
||
import PostgREST.App (postgrest)
|
||
import PostgREST.Config (AppConfig (..), configPoolTimeout',
|
||
prettyVersion, readPathShowHelp,
|
||
readValidateConfig)
|
||
import PostgREST.DbStructure (getDbStructure, getPgVersion)
|
||
import PostgREST.Error (PgError (PgError), checkIsFatal,
|
||
errorPayload)
|
||
import PostgREST.Types (ConnectionStatus (..), DbStructure,
|
||
PgVersion (..), minimumPgVersion)
|
||
import Protolude hiding (hPutStrLn, head, toS)
|
||
import Protolude.Conv (toS)
|
||
|
||
|
||
#ifndef mingw32_HOST_OS
|
||
import System.Posix.Signals
|
||
import UnixSocket
|
||
#endif
|
||
|
||
-- | This is where everything starts.
|
||
main :: IO ()
|
||
main = do
|
||
--
|
||
-- LineBuffering: the entire output buffer is flushed whenever a newline is
|
||
-- output, the buffer overflows, a hFlush is issued or the handle is closed
|
||
--
|
||
-- NoBuffering: output is written immediately and never stored in the buffer
|
||
hSetBuffering stdout LineBuffering
|
||
hSetBuffering stdin LineBuffering
|
||
hSetBuffering stderr NoBuffering
|
||
|
||
-- read path from commad line
|
||
path <- readPathShowHelp
|
||
|
||
-- build the 'AppConfig' from the config file path
|
||
conf <- readValidateConfig path
|
||
|
||
-- These are config values that can't be reloaded at runtime. Reloading some of them would imply restarting the web server.
|
||
let
|
||
host = configHost conf
|
||
port = configPort conf
|
||
maybeSocketAddr = configSocket conf
|
||
#ifndef mingw32_HOST_OS
|
||
socketFileMode = configSocketMode conf
|
||
#endif
|
||
dbUri = toS (configDbUri conf)
|
||
(dbChannelEnabled, dbChannel) = (configDbChannelEnabled conf, toS $ configDbChannel conf)
|
||
serverSettings =
|
||
setHost ((fromString . toS) host) -- Warp settings
|
||
. setPort port
|
||
. setServerName (toS $ "postgrest/" <> prettyVersion) $
|
||
defaultSettings
|
||
poolSize = configPoolSize conf
|
||
poolTimeout = configPoolTimeout' conf
|
||
logLevel = configLogLevel conf
|
||
|
||
-- create connection pool with the provided settings, returns either a 'Connection' or a 'ConnectionError'. Does not throw.
|
||
pool <- P.acquire (poolSize, poolTimeout, dbUri)
|
||
|
||
-- Used to sync the listener(NOTIFY reload) with the connectionWorker. No connection for the listener at first. Only used if dbChannelEnabled=true.
|
||
mvarConnectionStatus <- newEmptyMVar
|
||
|
||
-- No schema cache at the start. Will be filled in by the connectionWorker
|
||
refDbStructure <- newIORef Nothing
|
||
|
||
-- Helper ref to make sure just one connectionWorker can run at a time
|
||
refIsWorkerOn <- newIORef False
|
||
|
||
-- Config that can change at runtime
|
||
refConf <- newIORef conf
|
||
|
||
-- This is passed to the connectionWorker method so it can kill the main thread if the PostgreSQL's version is not supported.
|
||
mainTid <- myThreadId
|
||
|
||
let connWorker = connectionWorker mainTid pool refConf refDbStructure refIsWorkerOn (dbChannelEnabled, mvarConnectionStatus)
|
||
|
||
-- Sets the initial refDbStructure
|
||
connWorker
|
||
|
||
#ifndef mingw32_HOST_OS
|
||
-- Only for systems with signals:
|
||
--
|
||
-- releases the connection pool whenever the program is terminated,
|
||
-- see https://github.com/PostgREST/postgrest/issues/268
|
||
forM_ [sigINT, sigTERM] $ \sig ->
|
||
void $ installHandler sig (Catch $ do
|
||
P.release pool
|
||
throwTo mainTid UserInterrupt
|
||
) Nothing
|
||
|
||
-- The SIGUSR1 signal updates the internal 'DbStructure' by running 'connectionWorker' exactly as before.
|
||
void $ installHandler sigUSR1 (
|
||
Catch connWorker
|
||
) Nothing
|
||
|
||
-- Re-read the config on SIGUSR2
|
||
void $ installHandler sigUSR2 (
|
||
Catch $ reReadConfig path refConf
|
||
) Nothing
|
||
#endif
|
||
|
||
-- reload schema cache on NOTIFY
|
||
when dbChannelEnabled $
|
||
listener dbUri dbChannel pool refConf refDbStructure mvarConnectionStatus connWorker
|
||
|
||
-- ask for the OS time at most once per second
|
||
getTime <- mkAutoUpdate defaultUpdateSettings {updateAction = getCurrentTime}
|
||
|
||
let postgrestApplication =
|
||
postgrest
|
||
logLevel
|
||
refConf
|
||
refDbStructure
|
||
pool
|
||
getTime
|
||
connWorker
|
||
|
||
#ifndef mingw32_HOST_OS
|
||
-- run the postgrest application with user defined socket. Only for UNIX systems.
|
||
whenJust maybeSocketAddr $
|
||
runAppInSocket serverSettings postgrestApplication socketFileMode
|
||
#endif
|
||
|
||
-- run the postgrest application
|
||
whenNothing maybeSocketAddr $ do
|
||
putStrLn $ ("Listening on port " :: Text) <> show port
|
||
runSettings serverSettings postgrestApplication
|
||
|
||
-- Time constants
|
||
_32s :: Int
|
||
_32s = 32000000 :: Int -- 32 seconds
|
||
|
||
_1s :: Int
|
||
_1s = 1000000 :: Int -- 1 second
|
||
|
||
{-|
|
||
The purpose of this worker is to obtain a healthy connection to pg and an up-to-date schema cache(DbStructure).
|
||
This method is meant to be called by multiple times by the same thread, but does nothing if
|
||
the previous invocation has not terminated. In all cases this method does not
|
||
halt the calling thread, the work is preformed in a separate thread.
|
||
|
||
Note: 'atomicWriteIORef' is essentially a lazy semaphore that prevents two
|
||
threads from running 'connectionWorker' at the same time.
|
||
|
||
Background thread that does the following :
|
||
1. Tries to connect to pg server and will keep trying until success.
|
||
2. Checks if the pg version is supported and if it's not it kills the main
|
||
program.
|
||
3. Obtains the dbStructure.
|
||
-}
|
||
connectionWorker
|
||
:: ThreadId -- ^ Main thread id. Killed if pg version is unsupported
|
||
-> P.Pool -- ^ The pg connection pool
|
||
-> IORef AppConfig -- ^ mutable reference to AppConfig
|
||
-> IORef (Maybe DbStructure) -- ^ mutable reference to 'DbStructure'
|
||
-> IORef Bool -- ^ Used as a binary Semaphore
|
||
-> (Bool, MVar ConnectionStatus) -- ^ For interacting with the LISTEN channel
|
||
-> IO ()
|
||
connectionWorker mainTid pool refConf refDbStructure refIsWorkerOn (dbChannelEnabled, mvarConnectionStatus) = do
|
||
isWorkerOn <- readIORef refIsWorkerOn
|
||
unless isWorkerOn $ do -- Prevents multiple workers to be running at the same time. Could happen on too many SIGUSR1s.
|
||
atomicWriteIORef refIsWorkerOn True
|
||
void $ forkIO work
|
||
where
|
||
work = do
|
||
putStrLn ("Attempting to connect to the database..." :: Text)
|
||
connected <- connectionStatus pool
|
||
when dbChannelEnabled $
|
||
void $ tryPutMVar mvarConnectionStatus connected -- tryPutMVar doesn't lock the thread. It should always succeed since the worker is the only mvar producer.
|
||
case connected of
|
||
FatalConnectionError reason -> hPutStrLn stderr reason >> killThread mainTid -- Fatal error when connecting
|
||
NotConnected -> return () -- Unreachable because connectionStatus will keep trying to connect
|
||
Connected actualPgVersion -> do -- Procede with initialization
|
||
putStrLn ("Connection successful" :: Text)
|
||
fillSchemaCache pool actualPgVersion refConf refDbStructure
|
||
liftIO $ atomicWriteIORef refIsWorkerOn False
|
||
|
||
{-|
|
||
Check if a connection from the pool allows access to the PostgreSQL database.
|
||
If not, the pool connections are released and a new connection is tried.
|
||
Releasing the pool is key for rapid recovery. Otherwise, the pool timeout would have to be reached for new healthy connections to be acquired.
|
||
Which might not happen if the server is busy with requests. No idle connection, no pool timeout.
|
||
|
||
The connection tries are capped, but if the connection times out no error is thrown, just 'False' is returned.
|
||
-}
|
||
connectionStatus :: P.Pool -> IO ConnectionStatus
|
||
connectionStatus pool =
|
||
retrying (capDelay _32s $ exponentialBackoff _1s)
|
||
shouldRetry
|
||
(const $ P.release pool >> getConnectionStatus)
|
||
where
|
||
getConnectionStatus :: IO ConnectionStatus
|
||
getConnectionStatus = do
|
||
pgVersion <- P.use pool getPgVersion
|
||
case pgVersion of
|
||
Left e -> do
|
||
let err = PgError False e
|
||
hPutStrLn stderr . toS $ errorPayload err
|
||
case checkIsFatal err of
|
||
Just reason -> return $ FatalConnectionError reason
|
||
Nothing -> return NotConnected
|
||
|
||
Right version ->
|
||
if version < minimumPgVersion
|
||
then return . FatalConnectionError $ "Cannot run in this PostgreSQL version, PostgREST needs at least " <> pgvName minimumPgVersion
|
||
else return . Connected $ version
|
||
|
||
shouldRetry :: RetryStatus -> ConnectionStatus -> IO Bool
|
||
shouldRetry rs isConnSucc = do
|
||
let delay = fromMaybe 0 (rsPreviousDelay rs) `div` _1s
|
||
itShould = NotConnected == isConnSucc
|
||
when itShould $
|
||
putStrLn $ "Attempting to reconnect to the database in " <> (show delay::Text) <> " seconds..."
|
||
return itShould
|
||
|
||
-- | Fill the DbStructure by using a connection from the pool
|
||
fillSchemaCache :: P.Pool -> PgVersion -> IORef AppConfig -> IORef (Maybe DbStructure) -> IO ()
|
||
fillSchemaCache pool actualPgVersion refConf refDbStructure = do
|
||
conf <- readIORef refConf
|
||
result <- P.use pool $ HT.transaction HT.ReadCommitted HT.Read $ getDbStructure (toList $ configSchemas conf) (configExtraSearchPath conf) actualPgVersion
|
||
case result of
|
||
Left e -> do
|
||
-- If this error happens it would mean the connection is down again. Improbable because connectionStatus ensured the connection.
|
||
-- It's not a problem though, because App.postgrest would retry the connectionWorker or the user can do a SIGSUR1 again.
|
||
hPutStrLn stderr . toS . errorPayload $ PgError False e
|
||
putStrLn ("Failed to load the schema cache" :: Text)
|
||
|
||
Right dbStructure -> do
|
||
atomicWriteIORef refDbStructure $ Just dbStructure
|
||
putStrLn ("Schema cache loaded" :: Text)
|
||
|
||
{-|
|
||
Starts a dedicated pg connection to LISTEN for notifications.
|
||
When a NOTIFY <db-channel> - with an empty payload - is done, it refills the schema cache.
|
||
It uses the connectionWorker in case the LISTEN connection dies.
|
||
-}
|
||
listener :: ByteString -> Text -> P.Pool -> IORef AppConfig -> IORef (Maybe DbStructure) -> MVar ConnectionStatus -> IO () -> IO ()
|
||
listener dbUri dbChannel pool refConf refDbStructure mvarConnectionStatus connWorker = start
|
||
where
|
||
start = do
|
||
connStatus <- takeMVar mvarConnectionStatus -- takeMVar makes the thread wait if the MVar is empty(until there's a connection).
|
||
case connStatus of
|
||
Connected actualPgVersion -> void $ forkFinally (do -- forkFinally allows to detect if the thread dies
|
||
dbOrError <- C.acquire dbUri
|
||
-- Debounce in case too many NOTIFYs arrive. Could happen on a migration(assuming a pg EVENT TRIGGER is set up).
|
||
scFiller <- mkDebounce (defaultDebounceSettings {
|
||
debounceAction = fillSchemaCache pool actualPgVersion refConf refDbStructure,
|
||
debounceEdge = trailingEdge, -- wait until the function hasn’t been called in _1s
|
||
debounceFreq = _1s })
|
||
case dbOrError of
|
||
Right db -> do
|
||
putStrLn $ "Listening for notifications on the " <> dbChannel <> " channel"
|
||
let channelToListen = N.toPgIdentifier dbChannel
|
||
N.listen db channelToListen
|
||
N.waitForNotifications (\_ msg ->
|
||
if BS.null msg
|
||
then scFiller -- reload the schema cache
|
||
else pure ()) db -- Do nothing if anything else than an empty message is sent
|
||
_ -> die errorMessage)
|
||
(\_ -> do -- if the thread dies, we try to recover
|
||
putStrLn retryMessage
|
||
connWorker -- assume the pool connection was also lost, call the connection worker
|
||
start) -- retry the listener
|
||
_ ->
|
||
putStrLn errorMessage -- Should be unreachable. connectionStatus will retry until there's a connection.
|
||
errorMessage = "Could not listen for notifications on the " <> dbChannel <> " channel" :: Text
|
||
retryMessage = "Retrying listening for notifications on the " <> dbChannel <> " channel.." :: Text
|
||
|
||
-- | Re-reads the config at runtime. Invoked on SIGUSR2.
|
||
-- | If it panics(config path was changed, invalid setting), it'll show an error but won't kill the main thread.
|
||
reReadConfig :: FilePath -> IORef AppConfig -> IO ()
|
||
reReadConfig path refConf = do
|
||
conf <- readValidateConfig path
|
||
atomicWriteIORef refConf conf
|
||
putStrLn ("Config file reloaded" :: Text)
|
||
|
||
-- Utilitarian functions.
|
||
whenJust :: Applicative f => Maybe a -> (a -> f ()) -> f ()
|
||
whenJust (Just x) f = f x
|
||
whenJust Nothing _ = pass
|
||
|
||
whenNothing :: Applicative f => Maybe a -> f () -> f ()
|
||
whenNothing Nothing f = f
|
||
whenNothing _ _ = pass
|