fix(comms): simplify and remove possibility of deadlock from pipelines and substream close #4676
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hansieodendaal
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Sep 14, 2022
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LGTM, I like the simplified approach.
(I am going to run a biggish stress test with this code, maybe it will solve #4637)
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* development: (72 commits) fix: reinsert transactions from failed block (tari-project#4675) fix: stray clippy error (tari-project#4685) fix(wallet): mark mined_height as null when pending outputs are cancelled (tari-project#4686) chore: updated dependancies (tari-project#4684) fix(p2p): remove DETACH flag usage (tari-project#4682) fix(comms): simplify and remove possibility of deadlock from pipelines and substream close (tari-project#4676) feat(ci): add default CI and FFI testing with custom dispatch (tari-project#4672) chore: remove broken test (tari-project#4678) fix: fix potential race condition between add_block and sync (tari-project#4677) fix deadlock (tari-project#4674) fix: add burn funds command to console wallet (see issue tari-project#4547) (tari-project#4655) v0.38.3 fix: fee estimate (tari-project#4656) fix(comms/messaging): fix possible deadlock in outbound pipeline (tari-project#4657) fix: replace Luhn checksum with DammSum (tari-project#4639) fix(core/sync): handle deadline timeouts by changing peer (tari-project#4649) fix(ci): libtor build on Ubuntu (tari-project#4644) chore: fix log (tari-project#4634) v0.38.2 fix(comms/rpc): detect early close in all cases (tari-project#4647) ...
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Description
Motivation and Context
The outbound pipeline needed to poll two channels in order to make progress, some code branches in the outbound pipeline may need to use the other channel, and if that channel is full and the number of concurrent outbound tasks are full, a deadlock will occur. This case has not been directly observed, but is technically possible so should be eliminated.
This PR removes the [pipeline] -> [messaging] channel, making the outbound pipeline only have to poll one channel. It also directly pipes
OutboundMessages to the messaging protocol.EDIT: I believe I've found the root cause. The connectivity manager would rarely "lock up" causing the pipelines to lock up (both pipelines require calls to connectivity manager). I traced this in the logs and found that the last thing the connectivity manager does is resolve a tie break before locking up. This involves disconnecting one of the peer connections, and it appeared this future, extremely rarely, did not resolve. Digging deeper from there, I was able to track down a flaw in the substream close procedure, write a test that reproduces it and make a fix.
How Has This Been Tested?
Number of ~1000-2000tx stress tests, leaving base nodes overnight (none of these are conclusive but no issues were encountered)