Add parallel server launching with --parallel-launch flag

[Copilot]

Gateway now launches MCP servers concurrently during startup. Previously, servers were launched sequentially during tool registration, causing O(n) startup latency. Parallel launching reduces this to O(max) with proper timeout handling preserved.

Changes

Command-line interface:

• Added --parallel-launch flag (default: true)

Server launching:

• registerAllToolsParallel(): Launches each server in a goroutine, collects results via buffered channel
• registerAllToolsSequential(): Preserves original sequential behavior when flag disabled
• launchResult struct: Captures serverID, error, and duration from each launch
• Uses sync.WaitGroup for synchronization (no sleep-based waiting)

Configuration:

• Added ParallelLaunch field to Config struct

Implementation

// Launch each server in its own goroutine
for _, serverID := range serverIDs {
    wg.Add(1)
    go func(sid string) {
        defer wg.Done()
        
        startTime := time.Now()
        err := us.registerToolsFromBackend(sid)
        duration := time.Since(startTime)
        
        results <- launchResult{
            serverID: sid,
            err:      err,
            duration: duration,
        }
    }(serverID)
}

// Wait for all goroutines to complete
wg.Wait()
close(results)

Log output includes per-server timing and success/failure counts:

Parallel tool registration complete: 3 succeeded, 1 failed, total tools=42

Timeout handling inherited from existing GetOrLaunch() implementation ensures individual server failures don't block gateway startup.

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-build233922285/b269/launcher.test /tmp/go-build233922285/b269/launcher.test -test.testlogfile=/tmp/go-build233922285/b269/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true p/go-build (dns block)
• this-host-does-not-exist-12345.com
  • Triggering command: /tmp/go-build233922285/b278/mcp.test /tmp/go-build233922285/b278/mcp.test -test.testlogfile=/tmp/go-build233922285/b278/testlog.txt -test.paniconexit0 -test.timeout=10m0s -test.v=true 64/src/runtime/cgo 2xn6GOEZ9 x_amd64/compile (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)

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