yesodweb / yesodweb/persistent
Segmentation fault: 11 on macOS
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- Dominant language
- Haskell
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Description
We are using Nix and Haskell in production with Persistent and MySQL
We get a Segmentation fault: 11 on macOS, but not on Linux (works on Ubuntu and NixOS).
You may find our setup on gist.github
In the script below, the functions base, simple and persistent use increasingly higher-level mysql packages. base and simple cause no problem, but persistent does.
For example, in ghci, persistent 1 100 may perform the first 20 insertions successfully, only to segfault on the 21th. Other times, it will segfault on the first insertion. It does seem to be "random".
In addition, printMigration and runMigration reliably cause a segfault.
The local test database and the foo table have been created manually from mysql command line. The same problem occurs when connecting to our remote database.
import qualified Database.MySQL.Base as MySQL.Base
import qualified Control.Monad.Logger as Logger
import qualified Database.Persist.MySQL as Persist.MySQL
import qualified Database.MySQL.Simple as MySQL.Simple
import qualified Database.Persist.TH as TH
import Data.Monoid ((<>))
import Data.String (fromString)
import Control.Monad (forM_, void)
import Control.Monad.IO.Class (liftIO)
import Control.Exception.Safe (tryAny)
TH.share [TH.mkPersist TH.sqlSettings, TH.mkMigrate "migrateTables"] [TH.persistLowerCase|
Foo
i Int
deriving Show
|]
persist :: Int -> Int -> IO ()
persist from n = do
let info = Persist.MySQL.defaultConnectInfo
{ Persist.MySQL.connectHost = "localhost"
, Persist.MySQL.connectDatabase = "test"
, Persist.MySQL.connectUser = "root"
, Persist.MySQL.connectPassword = "root"
}
Logger.runNoLoggingT $ Persist.MySQL.withMySQLConn info $ \(be :: Persist.MySQL.SqlBackend) -> do
forM_ [from..from + n] $ \i -> do
r <- tryAny $ flip Persist.MySQL.runSqlConn be $ do
void $ Persist.MySQL.insert $ Foo i
liftIO $ print (i, r)
simple :: Int -> Int -> IO ()
simple from n = do
conn <- MySQL.Simple.connect MySQL.Simple.defaultConnectInfo
{ MySQL.Simple.connectHost = "localhost"
, MySQL.Simple.connectDatabase = "test"
, MySQL.Simple.connectUser = "root"
, MySQL.Simple.connectPassword = "root"
}
forM_ [from..from + n] $ \i -> do
r <- tryAny (MySQL.Simple.execute conn "INSERT INTO `foo`(`i`) VALUES(?)" $ MySQL.Simple.Only i)
print (i, r)
MySQL.Simple.close conn
base :: Int -> Int -> IO ()
base from n = do
conn <- MySQL.Base.connect MySQL.Base.defaultConnectInfo
{ MySQL.Base.connectHost = "localhost"
, MySQL.Base.connectDatabase = "test"
, MySQL.Base.connectUser = "root"
, MySQL.Base.connectPassword = "root"
}
forM_ [from..from + n] $ \i -> do
r <- tryAny (MySQL.Base.query conn $ "INSERT INTO `foo`(`i`) VALUES(" <> fromString (show i) <> ");")
print (i, r)
MySQL.Base.close conn
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the supplied reproducer and linked gist, comparing the base, simple, and persistent functions on macOS. Focus first on the persistent path and the calls to printMigration and runMigration; done means the reproducer no longer segfaults on macOS and the affected insert and migration operations complete reliably.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- haskell, macos, mysql
- Domain
- backend, databases
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 30/100