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go.sync_dns_lookup

Performance Medium

Detects synchronous DNS lookups that can block for seconds during resolution failures.

Why It Matters

Synchronous DNS:

Blocks goroutines — DNS can take seconds to timeout
Exhausts workers — Blocked goroutines can’t serve requests
Cascades failures — DNS issues affect all requests

Example

// ❌ Before (synchronous)
func connect(host string) error {
    addrs, err := net.LookupHost(host) // Can block for seconds
    if err != nil {
        return err
    }
    // ...
}

// ✅ After (with timeout)
func connect(ctx context.Context, host string) error {
    resolver := &net.Resolver{}
    addrs, err := resolver.LookupHost(ctx, host) // Respects context timeout
    if err != nil {
        return err
    }
    // ...
}

What Unfault Detects

net.LookupHost() without context
net.LookupAddr() without timeout
DNS lookups in critical paths

Auto-Fix

Unfault adds context-aware DNS resolution:

ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
defer cancel()

resolver := &net.Resolver{}
addrs, err := resolver.LookupHost(ctx, host)