The coverage on source/server recently has been flaky between 94.4 and 95.1 on unrelated PRs, for example #15210 and #15117.

What I have observed:

• This is somehow deterministic, i.e. on some commits, retesting would not work to go green.
• The root cause sits in source/server/connection_handler_impl.cc
  • by digging into the report, you can see that these lines would not be covered sometimes.

Temporarily the coverage threshold is loosen in #15238 to stop this being a blocker on unrelated PRs. We should not tighten again the corresponding threshold until we resolve this flakiness.