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Fix a P2P protocol hang

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When readContent got Nothing from prepSendAnnex, it did not run its
callback, and the callback is what sends the DATA reply.

sendContent checks with contentSize that the object file is present, but
that doesn't really guarantee that prepSendAnnex won't return Nothing.

So, it was possible for a P2P protocol GET to not receive a response,
and appear to hang. When what it's really doing is waiting for the next
protocol command.

This seems most likely to happen when the annex is in direct mode, and the
file being requested has been modified. It could also happen in an indirect
mode repository if genInodeCache somehow failed. Perhaps due to a race
with a drop of the content file.

Fixed by making readContent behave the way its spec said it should,
and run the callback with L.empty in this case.

Note that, it's finee for readContent to send any amount of data
to the callback, including L.empty. sendBytes deals with that
by making sure it sends exactly the specified number of bytes,
aborting the protocol if it's too short. So, when L.empty is sent,
the protocol will end up aborting.

This work is supported by the NIH-funded NICEMAN (ReproNim TR&D3) project.
This commit is contained in:
Joey Hess 2018-11-02 13:41:50 -04:00
parent 5ad5d45d4c
commit 0b053b9611
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3 changed files with 15 additions and 12 deletions
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21
P2P/Annex.hs
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@ -50,18 +50,19 @@ runLocal runst runner a = case a of
size <- inAnnex' isJust Nothing getsize k
runner (next (Len <$> size))
ReadContent k af o sender next -> do
let proceed c = do
r <- tryNonAsync c
case r of
Left e -> return $ Left $ ProtoFailureException e
Right (Left e) -> return $ Left e
Right (Right ok) -> runner (next ok)
v <- tryNonAsync $ prepSendAnnex k
case v of
Right (Just (f, checkchanged)) -> do
v' <- tryNonAsync $
transfer upload k af $
sinkfile f o checkchanged sender
case v' of
Left e -> return $ Left $ ProtoFailureException e
Right (Left e) -> return $ Left e
Right (Right ok) -> runner (next ok)
-- content not available
Right Nothing -> runner (next False)
Right (Just (f, checkchanged)) -> proceed $
transfer upload k af $
sinkfile f o checkchanged sender
Right Nothing -> proceed $
runner (sender mempty (return Invalid))
Left e -> return $ Left $ ProtoFailureException e
StoreContent k af o l getb validitycheck next -> do
-- This is the same as the retrievalSecurityPolicy of