Investigate IMAP folder-open latency (follow-up to #86). Localhost GreenMail
has ~0 RTT, so real wall-clock latency can't be measured here; instead this
pins the folder-open round-trip STRUCTURE deterministically.
Finding: ImapClient.withStore wraps every operation in its own short-lived
Store, so each folder-open pays a full CONNECT + TLS + LOGIN + EXAMINE +
FETCH + LOGOUT. Only EXAMINE + FETCH is intrinsic to opening a folder; the
whole connection-setup group is avoidable on the 2nd+ operation if a
connection were reused. Optimistic render-from-cache already exists
(selectFolder renders cached rows; the network sync is a background refresh).
Adds:
- CountingImapProxy: a localhost TCP proxy that forwards a cleartext IMAP
session to GreenMail while counting TCP connections and parsing IMAP
command words.
- ImapFolderOpenLatencyTest: asserts the current no-reuse behaviour (N opens
=> N connections and N LOGINs; list+read => 2 connections) against a real
in-process IMAP server. Doubles as the harness to validate a future
connection-reuse fix (flip the counts to assert reuse).
- docs/perf/issue-125-imap-folder-open.md: the per-open round-trip sequence,
avoidable vs. necessary round-trips, and the recommended per-account
connection-reuse/keep-alive mitigation with its IDLE / thread-safety /
battery / stale-connection constraints.
Analysis + harness only; the connection-reuse fix is deferred pending
real-network + real-device measurement (see the doc's measurement plan), so
this references #125 without closing it.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
JMR-devandClaude Fable 5
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