Extend write deadline for app install/uninstall RPCs

[mobile-kevin]

Summary

device.apps.install (and device.apps.uninstall) run under the HTTP server's default 10s WriteTimeout because they were never added to the per-method write-deadline extension in handleJSONRPC. On devices where an install legitimately takes longer than 10s, the server hits the write deadline and closes the connection mid-response. The caller — mobilefleet-client — sees an opaque:

mobilecli call failed: Post "http://localhost:12000/rpc": EOF

…and reports the install as failed, even when the app is valid (it installs fine from the web portal). Because the error is a bare transport EOF, it reads like a bad app rather than a timeout, which is exactly how it was mis-triaged.

Evidence

From production logs, install outcomes over 2 days:

Outcome	Attempts	avg	min	max
success	30	4.9s	0s	10s
fail (EOF)	11	19.9s	11s	68s

A clean split at the 10s boundary: every success finished ≤10s, every EOF failure took ≥11s — the signature of the WriteTimeout firing. The mobilecli process stays alive throughout (its heartbeat RPCs keep succeeding), so it isn't a crash; only the long install request is severed. mobilefleet-client's own RPC client timeout is 5 minutes, so it is not the limiter.

Fix

device.boot already extends the write deadline to 3 minutes for exactly this reason; install/uninstall are just as slow and were simply missing from the list. This adds them, and refactors the per-method deadlines into a small, testable extendedWriteDeadline() helper so a slow method can't be silently omitted again.

Testing

• go test ./server/ — full package green, including two new tests (TestExtendedWriteDeadlineForSlowMethods, TestNoExtendedWriteDeadlineForFastMethods).
• go vet ./server/, gofmt clean.

Notes / scope

• This stops installs from being killed at 10s. It does not make genuinely slow installs faster — if some devices take 60s+, that's a separate device-provisioning question worth its own look.
• The truly robust design is async install + poll rather than one long synchronous request, but that's a larger change across mobilecli and mobilefleet-client and isn't needed to stop the failures now.
• A complementary mobilefleet-client change (classify the transport EOF distinctly from a real install rejection so it isn't reported as a generic "Install failed") is worth doing separately.

https://claude.ai/code/session_01NTmaydwxEmvPEYdiK3Q4yS

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ca3ecf61-b850-43a1-8aa3-ccbd97cba9d8

📥 Commits

Reviewing files that changed from the base of the PR and between 9b99c19 and 3a1f211.

📒 Files selected for processing (2)

• server/deadline_test.go
• server/server.go

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Walkthrough

The server adds an extendedWriteDeadline helper that returns method-specific durations for long-running JSON-RPC methods. handleJSONRPC uses the helper to conditionally extend the HTTP response write deadline. Unit tests cover expected three-minute and 35-second extensions, plus fast and empty method names that receive no extension.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: extending write deadlines for app install/uninstall RPCs.
Description check	✅ Passed	The description is directly related to the change and explains the deadline extension, refactor, and tests.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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