ops: Signal disk-full and eviction capacity pressure

When the disk (or memory) tier is at cap or the volume returns ENOSPC, ops currently look like random misses with no clear "we are dropping data." Count those events as capacity_pressure_events on /metrics and log tier plus reason so operators can tell capacity pressure from a cold cache, without changing the existing evictions counter. Link: #36
2026-09-07 19:23:55 +00:00
parent a0e929c525
commit de43a71929
12 changed files with 382 additions and 78 deletions
@@ -0,0 +1,56 @@
+//go:build windows
+
+package disk
+
+import (
+	"io"
+	"os"
+	"testing"
+
+	"golang.org/x/sys/windows"
+
+	"s1d3sw1ped/steamcache2/steamcache/metrics"
+)
+
+func TestIsNoSpaceError(t *testing.T) {
+	t.Parallel()
+	if isNoSpaceError(nil) {
+		t.Error("nil must not be disk-full")
+	}
+	if isNoSpaceError(io.EOF) {
+		t.Error("EOF must not be disk-full")
+	}
+	if !isNoSpaceError(windows.ERROR_DISK_FULL) {
+		t.Error("ERROR_DISK_FULL should match")
+	}
+	if !isNoSpaceError(windows.ERROR_HANDLE_DISK_FULL) {
+		t.Error("ERROR_HANDLE_DISK_FULL should match")
+	}
+	wrapped := &os.PathError{Op: "write", Path: "x", Err: windows.ERROR_DISK_FULL}
+	if !isNoSpaceError(wrapped) {
+		t.Error("PathError wrapping ERROR_DISK_FULL should match")
+	}
+}
+
+func TestDiskFS_ENOSPCCapacityPressure(t *testing.T) {
+	t.Parallel()
+	d, err := New(t.TempDir(), 1024, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	met := metrics.NewMetrics()
+	d.SetMetrics(met)
+
+	d.recordIfNoSpace(io.EOF)
+	if got := met.GetStats().CapacityPressureEvents; got != 0 {
+		t.Fatalf("non-ENOSPC counted: %d", got)
+	}
+
+	d.recordIfNoSpace(windows.ERROR_DISK_FULL)
+	if got := met.GetStats().CapacityPressureEvents; got != 1 {
+		t.Fatalf("ERROR_DISK_FULL: CapacityPressureEvents=%d, want 1", got)
+	}
+	if got := met.GetStats().Evictions; got != 0 {
+		t.Fatalf("disk-full must not increment evictions, got %d", got)
+	}
+}