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perf(server): touch a known session without allocating #1026

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Merged
ezynda3 merged 1 commit into from
Oct 8, 2026
Merged

perf(server): touch a known session without allocating #1026

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7 changes: 6 additions & 1 deletion server/streamable_http.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1400,12 +1400,17 @@ func (s *StreamableHTTPServer) nextRequestID(sessionID string) int64 {

// touchSession records the current time as the last activity for the given session.
// It is a no-op when the sweeper is disabled (sessionIdleTTL <= 0) or sessionID is empty.
// It runs on every request, so a known session is found with Load and touched
// without allocating; only a session's first touch pays for LoadOrStore.
func (s *StreamableHTTPServer) touchSession(sessionID string) {
if sessionID == "" || s.sessionIdleTTL <= 0 {
return
}
now := time.Now().UnixNano()
actual, _ := s.sessionLastActive.LoadOrStore(sessionID, new(atomic.Int64))
actual, ok := s.sessionLastActive.Load(sessionID)
if !ok {
actual, _ = s.sessionLastActive.LoadOrStore(sessionID, new(atomic.Int64))
}
actual.(*atomic.Int64).Store(now)
}

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41 changes: 41 additions & 0 deletions server/streamable_http_touch_test.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,41 @@
package server

import (
"testing"
"time"

"github.com/stretchr/testify/require"
)

// newTouchTestServer builds a streamable server with the idle sweeper on, so
// touchSession is live; the caller shuts it down.
func newTouchTestServer() *StreamableHTTPServer {
return NewStreamableHTTPServer(NewMCPServer("test", "1.0.0"), WithSessionIdleTTL(time.Hour))
}

// TestTouchSessionKnownSessionAllocatesNothing pins that a session that is
// already tracked is touched without allocating: touchSession runs on every
// request once WithSessionIdleTTL is set.
func TestTouchSessionKnownSessionAllocatesNothing(t *testing.T) {
s := newTouchTestServer()
defer func() { _ = s.Shutdown(t.Context()) }()
const sessionID = "mcp-session-known"
s.touchSession(sessionID)

allocs := testing.AllocsPerRun(1000, func() { s.touchSession(sessionID) })
require.Zero(t, allocs, "touchSession on a known session must not allocate")
}

// BenchmarkTouchSessionKnown measures touchSession on a session that is
// already tracked, the per-request path once WithSessionIdleTTL is set.
func BenchmarkTouchSessionKnown(b *testing.B) {
s := newTouchTestServer()
defer func() { _ = s.Shutdown(b.Context()) }()
const sessionID = "mcp-session-known"
s.touchSession(sessionID)

b.ReportAllocs()
for b.Loop() {
s.touchSession(sessionID)
}
}
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