forked from wrenn/wrenn
pptx704
2b4c5e0176
Introduce ConnTracker (atomic.Bool + WaitGroup) to track in-flight proxy connections per sandbox. Before pausing a VM, the manager drains active connections with a 2s grace period, preventing Go runtime corruption inside the guest caused by stale TCP state surviving Firecracker snapshot/restore. Also add: - AcquireProxyConn on Manager for atomic lookup + connection tracking - Proxy cache (120s TTL) on CP SandboxProxyWrapper with single-query DB lookup (GetSandboxProxyTarget) to avoid two round-trips - Reset() on ConnTracker to re-enable connections if pause fails
67 lines
1.7 KiB
Go
67 lines
1.7 KiB
Go
package sandbox
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import (
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"sync"
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"sync/atomic"
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"time"
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)
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// ConnTracker tracks active proxy connections for a single sandbox and
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// provides a drain mechanism for pre-pause graceful shutdown.
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// It is safe for concurrent use.
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type ConnTracker struct {
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draining atomic.Bool
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wg sync.WaitGroup
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}
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// Acquire registers one in-flight connection. Returns false if the tracker
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// is already draining; the caller must not call Release in that case.
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func (t *ConnTracker) Acquire() bool {
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if t.draining.Load() {
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return false
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}
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t.wg.Add(1)
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// Re-check after Add: Drain may have set draining between our Load
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// and Add. If so, undo the Add and reject the connection.
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if t.draining.Load() {
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t.wg.Done()
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return false
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}
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return true
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}
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// Release marks one connection as complete. Must be called exactly once
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// per successful Acquire.
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func (t *ConnTracker) Release() {
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t.wg.Done()
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}
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// Drain marks the tracker as draining (all future Acquire calls return
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// false) and waits up to timeout for in-flight connections to finish.
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//
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// Note: if the timeout expires with connections still in-flight, the
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// internal goroutine waiting on wg.Wait() will remain until those
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// connections complete. This is bounded by the number of hung connections
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// at drain time and self-heals once they close.
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func (t *ConnTracker) Drain(timeout time.Duration) {
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t.draining.Store(true)
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done := make(chan struct{})
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go func() {
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t.wg.Wait()
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close(done)
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}()
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select {
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case <-done:
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case <-time.After(timeout):
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}
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}
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// Reset re-enables the tracker after a failed drain. This allows the
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// sandbox to accept proxy connections again if the pause operation fails
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// and the VM is resumed.
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func (t *ConnTracker) Reset() {
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t.draining.Store(false)
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}
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