bug#67629: [Cuirass] ‘remote-server’ wrecks havoc when misbehaving clients connect

[Ludovic Courtès]

The ‘cuirass remote-server’ process goes awry when misbehaved clients
connect; specifically, some of its fibers crash, leaving it running but
inactive:

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2023-12-04 10:13:14 periodic update: 0 resumable, 0 failed builds
2023-12-04 10:13:28 error: Connection reset by peer when replying to 
xx.xx.xx.254.
2023-12-04 10:13:42 error: invalid log received from xx.xx.xx.254
2023-12-04 10:13:42 error: EOF while receiving log from xx.xx.xx.254
2023-12-04 10:13:48 Uncaught exception in task:
2023-12-04 10:13:48 In fibers.scm:
2023-12-04 10:13:48    186:20  8 (_)
2023-12-04 10:13:48    145:21  7 (_)
2023-12-04 10:13:48 In ice-9/boot-9.scm:
2023-12-04 10:13:48   1752:10  6 (with-exception-handler _ _ #:unwind? _ 
#:unwind-for-type _)
2023-12-04 10:13:48 In cuirass/scripts/remote-server.scm:
2023-12-04 10:13:48    695:11  5 (_)
2023-12-04 10:13:48 In ice-9/boot-9.scm:
2023-12-04 10:13:48   1747:15  4 (with-exception-handler #<procedure 
7f982c2abd50 at ice-9/boot-9.scm:1831:7 (exn)> _ #:unwind? _ #:unwind-for-type 
_)
2023-12-04 10:13:48 In cuirass/scripts/remote-server.scm:
2023-12-04 10:13:48    437:23  3 (serve-build-requests _ #<<channel> getq: 
#<atomic-box 7f982e764390 value: (() #(#<atomic-box 7f98283753a0 value: W> 
#<procedure resume (thunk)>))> getq-gc-co
unter: #<atomic-box 7f982e764320 value: 16> putq: #<atomic-box 7f982e764240 
value: (())> putq-gc-counter: #<atomic-box 7f982e764230 value: 31>>)
2023-12-04 10:13:48 In cuirass/remote.scm:
2023-12-04 10:13:48     466:6  2 (receive-message _ #:router? _)
2023-12-04 10:13:48 In ice-9/boot-9.scm:
2023-12-04 10:13:48   1685:16  1 (raise-exception _ #:continuable? _)
2023-12-04 10:13:48   1685:16  0 (raise-exception _ #:continuable? _)
2023-12-04 10:13:48 ice-9/boot-9.scm:1685:16: In procedure raise-exception:
2023-12-04 10:13:48 Throw to key `match-error' with args `("match" "no matching 
pattern" (#<zmq-message 7f981881d9a0> #<zmq-message 7f981881d900> #<zmq-message 
7f981881d860>))'.
2023-12-04 10:13:48 Uncaught exception in task:
2023-12-04 10:13:48 In fibers.scm:
2023-12-04 10:13:48     172:8  2 (_)
2023-12-04 10:13:48 In cuirass/notification.scm:
2023-12-04 10:13:48    162:15  1 (_)
2023-12-04 10:13:48 In ice-9/boot-9.scm:
2023-12-04 10:13:48   1685:16  0 (raise-exception _ #:continuable? _)
2023-12-04 10:13:48 ice-9/boot-9.scm:1685:16: In procedure raise-exception:
2023-12-04 10:13:48 Throw to key `psql-query-error' with args `(#f #f "no 
connection to the server\n")'.
2023-12-04 10:14:06 0 items queued for eventual download
2023-12-04 10:14:07 Uncaught exception in task:
2023-12-04 10:14:07 In fibers.scm:
2023-12-04 10:14:07     172:8  2 (_)
2023-12-04 10:14:07 In cuirass/scripts/remote-server.scm:
2023-12-04 10:14:07    430:10  1 (_)
2023-12-04 10:14:07 In ice-9/boot-9.scm:
2023-12-04 10:14:07   1685:16  0 (raise-exception _ #:continuable? _)
2023-12-04 10:14:07 ice-9/boot-9.scm:1685:16: In procedure raise-exception:
2023-12-04 10:14:07 Throw to key `psql-query-error' with args `(#f #f "no 
connection to the server\n")'.
2023-12-04 10:14:30 error: invalid log received from xx.xx.xx.254
2023-12-04 10:14:30 error: invalid log received from xx.xx.xx.254
2023-12-04 10:14:35 error: invalid log received from xx.xx.xx.254
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Ludo’.