Public Access
jaap-jan
e41eca01a8
The suite fails intermittently with SshConnectionException "The connection was closed by the remote host", within tens of milliseconds, on whichever test happens to connect first. It has been seen in CI and reproduces locally. This raises sshd's MaxStartups in the fixture, which is the most likely cause and is worth doing regardless. sshd's compiled-in default is 10:30:100: past ten unauthenticated connections in flight it refuses new ones at random, thirty percent of the time, rising to always at a hundred. The image ships the line commented out, so that default was what ran. xUnit runs test classes in parallel and most of the classes here open a connection, so ten in flight is reachable during the opening seconds — and a refusal presents to the client exactly as observed, because a dropped connection and a server that never answered are indistinguishable from that end. ◆ IT IS A MITIGATION AND NOT A DEMONSTRATED CURE, AND THE COMMENT SAYS SO. The flake rate could not be measured. On the Windows development machine the identical unmodified suite ran 85/85 clean and, an hour later, failed 13 runs out of 15; a Linux container gave 30/30 clean and then failed on the first run of the next batch. Docker throughput on that host swings far enough to swamp the effect, so every before/after comparison taken there was noise — including two that were briefly believed. It is committed on the narrower argument that it is right either way. A connection throttle is hardening this suite has no interest in reproducing: it exists to test an SSH client, not to survive a rate limit, and a test server that drops connections at random is a bad test server whether or not it is the cause of this particular flake. The other candidate was the reload window — pkill returns when SIGHUP is delivered, not when sshd has finished closing its listeners and re-execing, so a connection immediately afterwards can be refused the same way. A wait that required three consecutive banner reads before returning was written and then removed: it could not be shown to change anything either, and a fixture carrying two unproven fixes for one symptom is worse than one, because the next person has to disprove both. Both candidates, and how to tell them apart with sshd's own log, are recorded in the fixture and in docs/platform-flags.md.