Add startup timeout to prevent gateway hanging on unresponsive MCP servers

[Copilot]

Gateway would hang indefinitely during initialization if any backend MCP server failed to respond, blocking all other backends from starting.

Changes

Configuration: Added startupTimeout field (default: 60s) to gateway config with package-level constants (DefaultStartupTimeout, DefaultToolTimeout, DefaultPort).

Timeout enforcement: Implemented goroutine + buffered channel pattern in GetOrLaunch() and GetOrLaunchForSession():

// Launch connection in goroutine with buffered channel to prevent leaks
resultChan := make(chan connectionResult, 1)
go func() {
    conn, err := mcp.NewConnection(l.ctx, cmd, args, env)
    resultChan <- connectionResult{conn, err}
}()

// Timeout via select instead of context.WithTimeout to preserve connection after startup
select {
case result := <-resultChan:
    return result.conn, result.err
case <-time.After(l.startupTimeout):
    return nil, fmt.Errorf("server startup timeout after %v", l.startupTimeout)
}

Graceful degradation: Failed backends log warnings and gateway continues initialization with remaining backends.

Technical decisions

• Goroutine + time.After() instead of context.WithTimeout to avoid canceling connection after successful startup
• Buffered channel (size 1) allows goroutine to complete without blocking if timeout occurs first
• Enhanced error messages with actionable suggestions to increase timeout if needed

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• nonexistent.local
  • Triggering command: /tmp/go-build3377049250/b269/launcher.test /tmp/go-build3377049250/b269/launcher.test -test.testlogfile=/tmp/go-build3377049250/b269/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true go user.email t[bot] (dns block)
  • Triggering command: /tmp/go-build481144272/b273/launcher.test /tmp/go-build481144272/b273/launcher.test -test.testlogfile=/tmp/go-build481144272/b273/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true dleware.test /tmp/go-build3677275879/b097/ ortcfg.link . --gdwarf2 --64 GL0vaMStIAuGbawbr5/sWo5QoaFO32xMT3YHtp6/k1XMsJiotFONAaFTgZJc (dns block)
  • Triggering command: /tmp/go-build3502506537/b273/launcher.test /tmp/go-build3502506537/b273/launcher.test -test.testlogfile=/tmp/go-build3502506537/b273/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true -lang=go1.25 docker-buildx x_amd64/vet se 7049250/b028/vetls-files x_amd64/cgo x_amd64/vet 791 6791 791 aw-mcpg/awmg se 7049250/b141/vet-c x_amd64/vet aw-mcpg/awmg (dns block)
• this-host-does-not-exist-12345.com
  • Triggering command: /tmp/go-build3377049250/b278/mcp.test /tmp/go-build3377049250/b278/mcp.test -test.testlogfile=/tmp/go-build3377049250/b278/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true g_.a --global rgo/bin/bash credential.helpe/opt/hostedtoolcache/go/1.25.6/x64/pkg/tool/linux_amd64/vet (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>gateway need to handle dangling mcp servers</issue_title>
<issue_description>See errors: githubnext/gh-aw#11814</issue_description>

Comments on the Issue (you are @copilot in this section)

@pelikhan https://github.com/githubnext/gh-aw/pull/11817

• Fixes gateway need to handle dangling mcp servers #469

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