Make clock sync latency metric go between each pair of clock domains.

tracing/tracing/metrics/system_health/clock_sync_latency_metric.html

Index: tracing/tracing/metrics/system_health/clock_sync_latency_metric.html
diff --git a/tracing/tracing/metrics/system_health/clock_sync_latency_metric.html b/tracing/tracing/metrics/system_health/clock_sync_latency_metric.html
index 641479ab9ead550f785ca2ea4996ca530698934e..3273f763eac548900d6c5ee180262f992aa6b37d 100644
--- a/tracing/tracing/metrics/system_health/clock_sync_latency_metric.html
+++ b/tracing/tracing/metrics/system_health/clock_sync_latency_metric.html
@@ -15,40 +15,23 @@ found in the LICENSE file.
 'use strict';
 
 tr.exportTo('tr.metrics.sh', function() {
-  function syncIsComplete(markers) {
-    return markers.length === 2;
-  }
-
-  function syncInvolvesTelemetry(markers) {
-    for (var marker of markers)
-      if (marker.domainId === tr.model.ClockDomainId.TELEMETRY)
-        return true;
-
-    return false;
-  }
 
   function clockSyncLatencyMetric(values, model) {
-    for (var markers of model.clockSyncManager.markersBySyncId.values()) {
-      var latency = undefined;
-      var targetDomain = undefined;
-      if (!syncIsComplete(markers) || !syncInvolvesTelemetry(markers))
-        continue;
-
-      for (var marker of markers) {
-        var domain = marker.domainId;
-        if (domain === tr.model.ClockDomainId.TELEMETRY)
-          latency = (marker.endTs - marker.startTs);
-        else
-          targetDomain = domain.toLowerCase();
+    var domains = Array.from(model.clockSyncManager.domainsSeen).sort();
+    for (var i = 1; i < domains.length; i++) {

[charliea (OOO until 10-5), 2016/09/21 18:05:33]

I think the more idiomatic way to write these loops is to do:

for (var i = 0; i < domains.length; i++) {
  for (var j = i + 1; j < domains.length; i++) {
    // Do whatever specific to combination (i, j)
  }
}

[alexandermont, 2016/09/21 19:26:40]

Done

+      for (var j = 0; j < i; j++) {
+        var latency = model.clockSyncManager.getModelTimeTransformerError(
+            domains[i], domains[j]);
+        var hist = new tr.v.Histogram(
+            tr.b.Unit.byName.timeDurationInMs_smallerIsBetter,
+            tr.v.HistogramBinBoundaries.createExponential(1e-3, 1e3, 30));
+        hist.addSample(latency);
+        values.addValue(new tr.v.NumericValue(
+            'clock_sync_latency_' + domains[i].toLowerCase() + '_to_' +
+            domains[j].toLowerCase(), hist,
+            {description: 'Clock sync latency from domain ' + domains[i] +
+             ' to domain ' + domains[j]}));
       }
-
-      var hist = new tr.v.Histogram(
-          tr.b.Unit.byName.timeDurationInMs_smallerIsBetter,
-          tr.v.HistogramBinBoundaries.createExponential(1e-3, 1e3, 30));
-      hist.addSample(latency);
-      values.addValue(new tr.v.NumericValue(
-          'clock_sync_latency_' + targetDomain, hist,
-          {description: 'Clock sync latency for domain ' + targetDomain}));
     }
   }