Combines prologue and headers into a single write in WebClient #9842
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…l TCP delays when using TLS. With TLS, each write becomes a record and a small record can be delayed due to Nagle's algorithm.
romain-grecourt
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Feb 27, 2025
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Description
Combines prologue and headers into a single write to prevent potential TCP delays when using TLS. With TLS, each write becomes a record and a small record can be delayed due to Nagle's algorithm. See #9839.
This problem appears to only impact the WebClient with TLS and output streams (e.g. when used via the Helidon connector). Every small write to the output stream is turned into a TLS record, encrypted and written to the socket. When small packets (such as just the HTTP prologue without headers) are written, it can result in delays due to Nagle's algorithm. Turning on TPC_NO_DELAY can help, but it may not be the ideal solution in all environments.
Writting a unit test for this PR is just awkward: would require lots of mocking and also exposing several private methods. Simply passing all the existing pipeline tests should be proof that the change is sound.
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