Prototype the per-account connection reuse the #125 investigation recommended
and deferred, behind an OFF-by-default flag so it cannot destabilize `main`.
- ImapConnectionCache: keeps one authenticated Store alive per account, guarded
by a per-account mutex, keyed by connection identity (not the rotating
secret), with lazy catch-and-retry-once stale handling. No eviction policy
yet beyond an explicit closeReusedConnections() hook.
- ImapClient gains a `reuseConnections` flag (default false via the @Inject
no-arg constructor). With it off, withStore is byte-for-byte the previous
connect + LOGOUT-per-call; with it on, calls borrow the kept-alive Store.
- ImapFolderOpenLatencyTest flips the flag on: the same real-IMAP operations
that cost N connections / N LOGINs collapse to 1 connection / 1 LOGIN, with
the necessary per-open EXAMINE unchanged (proven via CountingImapProxy +
GreenMail; localhost is ~0 RTT so this proves structure, not wall-clock).
- docs/perf/issue-125-connection-reuse-spike.md: prototype design, the
flag-off-vs-on proof, per-decision trade-offs, and the refined real-device
validation plan. References #125; does not close it (needs device validation).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
JMR-devandClaude Fable 5
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