Ilia Denisov
e2771826fd
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The loadtest harness never modelled game.evaluate — the debounced per-tile play preview a real client fires several times per turn, the hottest gameplay call. Model it (one evaluate per placed tile + reconsideration re-previews + draft.save, human-paced; --eval / --eval-recon toggle it). That realistic load surfaced the real bottleneck: the gateway's backend HTTP client used the default transport (MaxIdleConnsPerHost=2), so every sync call to the single backend host churned a fresh TCP connection — ~26500 TIME_WAIT sockets at 500 players (near the ephemeral-port ceiling), burning ~1.75 gateway cores while the backend sat near-idle. It was the unfixed root of the residual transport_error the earlier passes chased on the client side. Widen the keep-alive pool (backendMaxIdleConns=512, ~2x the observed 225-conn peak). At 500 players the churn collapses to ~0 and peak gateway CPU drops ~7x (~1.75 -> ~0.26 cores); postgres (~1.65 cores) becomes the busiest service. This overturns the earlier "gateway is the binding constraint, scale it horizontally" sizing — that was sizing around this bug, not a real floor. Consolidate the loadtest trip reports into one loadtest/REPORT.md (drop the R2/R7 split) and bake the finding into README / PRERELEASE / ARCHITECTURE / TESTING.
32 lines
1.2 KiB
Go
32 lines
1.2 KiB
Go
package backendclient
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import (
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"net/http"
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"testing"
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"time"
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)
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// TestBackendTransportPoolsConnections guards the fix for the gateway->backend
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// connection churn. Every synchronous client call proxies to the single backend host,
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// so the REST client must widen the idle-connection pool past the default per-host cap
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// of 2 (http.DefaultMaxIdleConnsPerHost) — otherwise almost every request under load
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// opens a fresh TCP connection that then lingers in TIME_WAIT, burning gateway CPU and
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// exhausting ephemeral ports. Reverting to the default transport (`&http.Client{...}`
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// with no Transport) would silently reintroduce that, so assert the pool is widened.
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func TestBackendTransportPoolsConnections(t *testing.T) {
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c, err := New("http://backend.invalid", "localhost:9090", time.Second)
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if err != nil {
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t.Fatalf("New: %v", err)
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}
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defer func() { _ = c.Close() }()
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tr, ok := c.http.Transport.(*http.Transport)
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if !ok {
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t.Fatalf("REST transport = %T, want a *http.Transport with a widened idle pool", c.http.Transport)
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}
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if tr.MaxIdleConnsPerHost <= http.DefaultMaxIdleConnsPerHost {
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t.Errorf("MaxIdleConnsPerHost = %d, want > default %d (else per-call connection churn)",
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tr.MaxIdleConnsPerHost, http.DefaultMaxIdleConnsPerHost)
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}
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}
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