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avoid double-connect to unreachable ssh remote

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When git-annex-shell p2pstdio fails with 255, it's because the ssh
server is not reachable. Avoid running the fallback action in this case,
since it would just try a second time to connect, and presumably fail.

Note that the closed P2PSshConnection will not be stored in the pool,
so the next request tries again to connect. This is just the right
behavior; when the remote becomes reachable again, the same git-annex
process will start using it.

This commit was sponsored by Ole-Morten Duesund on Patreon.
This commit is contained in:
Joey Hess 2018-03-12 16:50:21 -04:00
parent e36ceb7448
commit c3df5d1f10
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GPG key ID: DB12DB0FF05F8F38
6 changed files with 43 additions and 37 deletions
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34
Remote/Helper/Ssh.hs
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@ -189,12 +189,12 @@ contentLockedMarker = "OK"
type P2PSshConnection = P2P.ClosableConnection
(P2P.RunState, P2P.P2PConnection, ProcessHandle)
closeP2PSshConnection :: P2PSshConnection -> IO P2PSshConnection
closeP2PSshConnection P2P.ClosedConnection = return P2P.ClosedConnection
closeP2PSshConnection :: P2PSshConnection -> IO (P2PSshConnection, Maybe ExitCode)
closeP2PSshConnection P2P.ClosedConnection = return (P2P.ClosedConnection, Nothing)
closeP2PSshConnection (P2P.OpenConnection (_st, conn, pid)) = do
P2P.closeConnection conn
void $ waitForProcess pid
return P2P.ClosedConnection
exitcode <- waitForProcess pid
return (P2P.ClosedConnection, Just exitcode)
-- Pool of connections over ssh to git-annex-shell p2pstdio.
type P2PSshConnectionPool = TVar (Maybe P2PSshConnectionPoolState)
@ -270,17 +270,26 @@ openP2PSshConnection r connpool = do
Right (Right (Just theiruuid)) | theiruuid == uuid r ->
return $ Just c
_ -> do
void $ closeP2PSshConnection c
rememberunsupported
return Nothing
(cclosed, exitcode) <- closeP2PSshConnection c
-- ssh exits 255 when unable to connect to
-- server. Return a closed connection in
-- this case, to avoid the fallback action
-- being run instead, which would mean a
-- second connection attempt to this server
-- that is down.
if exitcode == Just (ExitFailure 255)
then return (Just cclosed)
else do
rememberunsupported
return Nothing
rememberunsupported = atomically $
modifyTVar' connpool $
maybe (Just P2PSshUnsupported) Just
-- Runs a P2P Proto action on a remote when it supports that,
-- otherwise the fallback action.
runProto :: Remote -> P2PSshConnectionPool -> Annex a -> P2P.Proto a -> Annex (Maybe a)
runProto r connpool fallback proto = Just <$>
runProto :: Remote -> P2PSshConnectionPool -> a -> Annex a -> P2P.Proto a -> Annex (Maybe a)
runProto r connpool bad fallback proto = Just <$>
(getP2PSshConnection r connpool >>= maybe fallback go)
where
go c = do
@ -290,9 +299,8 @@ runProto r connpool fallback proto = Just <$>
liftIO $ storeP2PSshConnection connpool c'
return res
-- Running the proto failed, either due to a protocol
-- error or a network error, so discard the
-- connection, and run the fallback.
Nothing -> fallback
-- error or a network error.
Nothing -> return bad
runProtoConn :: P2P.Proto a -> P2PSshConnection -> Annex (P2PSshConnection, Maybe a)
runProtoConn _ P2P.ClosedConnection = return (P2P.ClosedConnection, Nothing)
@ -303,7 +311,7 @@ runProtoConn a conn@(P2P.OpenConnection (runst, c, _pid)) = do
-- usable, so close it.
Left e -> do
warning $ "Lost connection (" ++ e ++ ")"
conn' <- liftIO $ closeP2PSshConnection conn
conn' <- fst <$> liftIO (closeP2PSshConnection conn)
return (conn', Nothing)
-- Allocates a P2P ssh connection from the pool, and runs the action with it,