Add CalDAV intermittent-connection probe + log correlation#232
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Add CalDAV intermittent-connection probe + log correlation#232aatchison wants to merge 1 commit into
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Diagnostic tooling for the intermittent 'failed to connect to server mail.thundermail.com' calendar errors seen in Thunderbird desktop. A once-a-day integration test cannot catch a failure that occurs ~once every 2-3 hours, so this polls the CalDAV endpoint frequently and records which connection phase fails, then correlates failures against Stalwart CloudWatch logs to determine whether the root cause is Stalwart, the network/edge, or the client. - probe.py: stdlib-only poller timing DNS/TCP/TLS/PROPFIND phases with granular failure classification; appends JSONL results. - correlate.py: matches probe failures against /tb/prod/stalwart logs by public IP and timestamp window. - .env/.jsonl gitignored; README documents usage and result interpretation. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Why
Thunderbird desktop users have been intermittently seeing "failed to connect to server mail.thundermail.com" for the calendar (Stalwart CalDAV), roughly once every 2–3 hours. Monitoring is green and the nightly integration test passes — but a once-a-day connect test cannot catch a failure that happens intermittently. Multiple people have observed it.
This adds diagnostic tooling to answer one question: is the root cause Stalwart, the network/edge, or the Thunderbird client? The cause may well be unrelated to Stalwart — this is how we find out for sure.
What
Under
research/caldav-probe/:probe.py— stdlib-only poller (runs locally, no install step). Pollshttps://<host>/dav/cal/on an interval and times each connection phase separately — DNS → TCP → TLS → CalDAVPROPFIND— classifying failures granularly (DNS_FAIL,TCP_FAIL,TLS_FAIL,AUTH_FAIL,HTTP_5XX,TIMEOUT,DAV_ERROR,OK). Appends one JSON line per attempt. Thecaldavlib was intentionally avoided because it collapses every failure into one opaque exception; raw sockets give true per-phase attribution.correlate.py— reads the JSONL, finds failures, and queries/tb/prod/stalwartCloudWatch logs in a window around each failure, filtered to this machine's public IP, so we see the server's view of our connections (or that it logged nothing).README.md,.env.example,.gitignore(.env+*.jsonlnever committed).Interpreting results
TLS_FAIL(cert)TCP_FAIL/TIMEOUTOKValidation
Verified end-to-end against prod with dummy creds: DNS/TCP/TLS phases all time correctly and the request classifies as
AUTH_FAIL(401). Resolved host3.78.21.144.🤖 Generated with Claude Code