fix: add default HTTP request timeout to prevent indefinite hangs

[Alfredo Garcia (agarctfi)]

fix: add default HTTP request timeout to prevent indefinite hangs

Summary

Adds a default timeout of (30s connect, 300s read) to HttpClient.send_request(). Without this, requests.Session.send() blocks indefinitely when a server accepts a TCP connection but never responds or stalls mid-transfer.

Context: An Intercom → Snowflake sync (Job 73656607) hung for 80+ minutes at 2.21M records after a 500 error. The CDK retried the request, but the subsequent HTTP call blocked forever with no timeout, no error, and no log output. This fix prevents that class of failure for all declarative connectors.

How it works:

• Two class-level constants added to HttpClient: _DEFAULT_CONNECT_TIMEOUT = 30, _DEFAULT_READ_TIMEOUT = 300
• In send_request(), if request_kwargs does not already contain a "timeout" key (after merging env settings), the default tuple is injected
• Explicit timeouts passed by callers are never overridden
• ConnectTimeout and ReadTimeout are already in the CDK's TRANSIENT_EXCEPTIONS, so timeouts trigger automatic retries with exponential backoff — no new error paths introduced

Note: This PR targets the tolik0/concurrent-source/add-block_simultaneous_read branch (PR #870) because the affected connector is pinned to a dev image from that branch.

Review & Testing Checklist for Human

• Verify timeout values are appropriate across connectors: 30s connect / 300s read is generous, but confirm no known connectors have legitimately slower endpoints that would regress (e.g., large export APIs, batch endpoints). If a connector needs longer, it can pass an explicit timeout in request_kwargs.
• Verify retry-on-timeout behavior end-to-end: The CDK already retries on ConnectTimeout/ReadTimeout (they're in TRANSIENT_EXCEPTIONS), but worth confirming with a real connector that a timeout → retry → success path works as expected and doesn't surface confusing user-facing errors.
• Test with source-intercom specifically: Run a sync that exercises the contacts stream to verify the fix prevents the indefinite hang scenario that motivated this change.

Notes

• Replaces the closed PR fix: add default HTTP request timeout to prevent indefinite hangs #938 (which targeted main). This PR applies the same fix on top of the feat: Add block_simultaneous_read with top-level stream_groups interface #870 feature branch.
• Sanity-checked PR feat: Add block_simultaneous_read with top-level stream_groups interface #870's ConcurrentReadProcessor changes for stuck-sync potential: the blocking/deferral logic is not the cause of the hang. The root cause is purely the missing HTTP timeout. However, the group-based blocking in feat: Add block_simultaneous_read with top-level stream_groups interface #870 does mean a hung stream blocks the entire group, making this timeout fix even more important.
• Link to Devin Session
• Requested by: Alfredo Garcia (@agarctfi)

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[devin-ai-integration]

Closing this PR. The changes have been rebased into a new PR against main that includes both the PR #870 changes and this timeout fix together.

[devin-ai-integration]

Closing this PR — the timeout fix has been consolidated into #940 which rebases both the block_simultaneous_read feature (from #870) and the HTTP timeout fix onto a single branch targeting main.