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fix(bigtable): Use a different t4t7 latencies for directpath #2902

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fix(bigtable): Use a different t4t7 latencies for directpath #2902

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bc4e1cf
feat(bigtable): backfill gfe latency with headersout-headersout latency
sushanb Apr 23, 2026
0399eb1
fix
sushanb Apr 23, 2026
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10 changes: 10 additions & 0 deletions ...java/com/google/cloud/bigtable/data/v2/internal/csm/tracers/BigtableGrpcStreamTracer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,16 @@ public void outboundMessageSent(int seqNo, long optionalWireSize, long optionalU
tracer.grpcMessageSent();
}

@Override
public void outboundHeaders() {
tracer.grpcHeadersSent();
}

@Override
public void inboundHeaders() {
tracer.grpcHeadersReceived();
}

static class Factory extends ClientStreamTracer.Factory {

private final BigtableTracer tracer;
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29 changes: 28 additions & 1 deletion ...ain/java/com/google/cloud/bigtable/data/v2/internal/csm/tracers/BuiltinMetricsTracer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,8 @@ class BuiltinMetricsTracer extends BigtableTracer {
private final AtomicLong totalClientBlockingTime = new AtomicLong(0);

private final AtomicLong grpcMessageSentDelay = new AtomicLong(0);
private final AtomicLong grpcHeadersSentNanos = new AtomicLong(0);
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@igorbernstein2 igorbernstein2 Apr 23, 2026

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Why not a volatile Stopwatch? it would communicate the intent better:

  volatile Optional<Stopwatch> faket4t7 = Optional.empty();

public void grpcHeadersSent() {
  faket4t7 = Optional.of(Stopwatch.createStarted());
}

public void grpcHeadersReceived() {
  faket4t7.map(Stopwatch::stop);
}

recordAttemptCompletion() {
  if (sidebandData.getGfeTiming() != null) {
  } else if (faket4t7.isPresent()) {
     ....
  }
}
....

private final AtomicLong grpcHeadersOutHeaderInLatency = new AtomicLong(0);

private Deadline operationDeadline = null;
private volatile Duration remainingDeadlineAtAttemptStart = Duration.ZERO;
Expand Down Expand Up @@ -263,6 +265,18 @@ public void grpcMessageSent() {
grpcMessageSentDelay.set(attemptTimer.elapsed(TimeUnit.NANOSECONDS));
}

@Override
public void grpcHeadersSent() {
grpcHeadersSentNanos.set(attemptTimer.elapsed(TimeUnit.NANOSECONDS));
}

@Override
public void grpcHeadersReceived() {
long receivedNanos = attemptTimer.elapsed(TimeUnit.NANOSECONDS);
long sentNanos = grpcHeadersSentNanos.get();
grpcHeadersOutHeaderInLatency.set(receivedNanos - sentNanos);
}

@Override
public void setTotalTimeoutDuration(java.time.Duration totalTimeoutDuration) {
// This method is called by BigtableTracerStreamingCallable and
Expand Down Expand Up @@ -386,7 +400,8 @@ private void recordAttemptCompletion(@Nullable Throwable throwable) {
code,
Comparators.max(remainingDeadlineAtAttemptStart, Duration.ZERO));
}

// if we don't have t4t7 latency from gfe, we use dur between initial metadata sent and initial
// metadata recv
if (sidebandData.getGfeTiming() != null) {
recorder.serverLatency.record(
clientInfo,
Expand All @@ -395,6 +410,18 @@ private void recordAttemptCompletion(@Nullable Throwable throwable) {
sidebandData.getClusterInfo(),
code,
sidebandData.getGfeTiming());
} else {
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@igorbernstein2 igorbernstein2 Apr 23, 2026

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This is expanding scope to what we talked about. This was supposed to be only for DirectAccess. This implementation expands the scope to any time the header is missing. Which means that we wont be able to tell what we are actually measuring. In our original conversation scoping it only to DA, we could reason that when transport_type is DA, we measuring client headers until response headers. In all other cases we are measuring gfe latency. And if the DistributionCount() drops we know that we couldnt reach a gfe. With this approach, we muddy our ability to reason about the metric

// Fallback to header latency if GFE timing is not available
long fallbackLatencyNanos = grpcHeadersOutHeaderInLatency.get();
if (fallbackLatencyNanos > 0) {
recorder.serverLatency.record(
clientInfo,
tableId,
methodInfo,
sidebandData.getClusterInfo(),
code,
Duration.ofNanos(fallbackLatencyNanos));
}
}

boolean seenServer =
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14 changes: 14 additions & 0 deletions ...src/main/java/com/google/cloud/bigtable/data/v2/internal/csm/tracers/CompositeTracer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -241,6 +241,20 @@ public void grpcMessageSent() {
}
}

@Override
public void grpcHeadersSent() {
for (BigtableTracer tracer : bigtableTracers) {
tracer.grpcHeadersSent();
}
}

@Override
public void grpcHeadersReceived() {
for (BigtableTracer tracer : bigtableTracers) {
tracer.grpcHeadersReceived();
}
}

@Override
public void setTotalTimeoutDuration(java.time.Duration totalTimeoutDuration) {
for (BigtableTracer tracer : bigtableTracers) {
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10 changes: 10 additions & 0 deletions ...bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/metrics/BigtableTracer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,16 @@ public void grpcMessageSent() {
// noop
}

/** Called when the header is sent on a grpc channel. */
public void grpcHeadersSent() {
// noop
}

/** Called when the header is received on a grpc channel. */
public void grpcHeadersReceived() {
// noop
}

/**
* Record the operation timeout from user settings for calculating remaining deadline. Currently,
* it's called in BuiltinMetricsTracer on attempt start from {@link BigtableTracerUnaryCallable}
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14 changes: 14 additions & 0 deletions ...test/java/com/google/cloud/bigtable/data/v2/internal/csm/tracers/CompositeTracerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -271,4 +271,18 @@ public void testGrpcMessageSent() {
verify(child3, times(1)).grpcMessageSent();
verify(child4, times(1)).grpcMessageSent();
}

@Test
public void testGrpcHeadersSent() {
compositeTracer.grpcHeadersSent();
verify(child3, times(1)).grpcHeadersSent();
verify(child4, times(1)).grpcHeadersSent();
}

@Test
public void testGrpcHeadersReceived() {
compositeTracer.grpcHeadersReceived();
verify(child3, times(1)).grpcHeadersReceived();
verify(child4, times(1)).grpcHeadersReceived();
}
}
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