Add timer for git/upload-pack/phase_negotiating

JGit packer tracks time spent in the negotiation phase.
This statistic was only exposed in the sshd_log and is not available
when the client uses Git/HTTP, which is counter-intuitive.

Having the statistics in log files is not ideal, though, because
for the Gerrit administrator, it takes more time to surface them
and defining alerts or monitoring:
- Logs need to be collected
- Metrics extracted
- Calculate the KPIs
- Graph and alert based on KPIs

Gerrit already has an out-of-the-box capability for
tracking JGit protocol-level metrics, but did not cover until
now, the negotiation phase, which is critical for an optimal Git/HTTP
performance.

Add the git/upload-pack/phase_negotiating so that the Gerrit admin
can graph how these are performing and spot any potential issues.

Release-Notes: Add timer for git/upload-pack/phase_negotiating
Change-Id: If185e0a1b4a4418243a2273ec850de01337afdd8

2 files changed, 13 insertions, 0 deletions

diff --git a/Documentation/metrics.txt b/Documentation/metrics.txt
index 49ac84c461..2ed2c2e23b 100644
--- a/Documentation/metrics.txt
+++ b/Documentation/metrics.txt
@@ -374,6 +374,9 @@ Each queue provides the following metrics:
 * `git/upload-pack/phase_compressing`: Time spent in the 'Compressing...' phase.
 ** `operation`:
    The name of the operation (CLONE, FETCH).
+* `git/upload-pack/phase_negotiating`: Time spent in the negotiation phase.
+** `operation`:
+   The name of the operation (CLONE, FETCH).
 * `git/upload-pack/phase_writing`: Time spent transferring bytes to client.
 ** `operation`:
    The name of the operation (CLONE, FETCH).
diff --git a/java/com/google/gerrit/server/git/UploadPackMetricsHook.java b/java/com/google/gerrit/server/git/UploadPackMetricsHook.java
index 1619addd75..e1403828b9 100644
--- a/java/com/google/gerrit/server/git/UploadPackMetricsHook.java
+++ b/java/com/google/gerrit/server/git/UploadPackMetricsHook.java
@@ -39,6 +39,7 @@ public class UploadPackMetricsHook implements PostUploadHook {
   private final Counter1<Operation> requestCount;
   private final Timer1<Operation> counting;
   private final Timer1<Operation> compressing;
+  private final Timer1<Operation> negotiating;
   private final Timer1<Operation> writing;
   private final Histogram1<Operation> packBytes;
 
@@ -72,6 +73,14 @@ public class UploadPackMetricsHook implements PostUploadHook {
                 .setUnit(Units.MILLISECONDS),
             operationField);
 
+    negotiating =
+        metricMaker.newTimer(
+            "git/upload-pack/phase_negotiating",
+            new Description("Time spent in the negotiation phase")
+                .setCumulative()
+                .setUnit(Units.MILLISECONDS),
+            operationField);
+
     writing =
         metricMaker.newTimer(
             "git/upload-pack/phase_writing",
@@ -99,6 +108,7 @@ public class UploadPackMetricsHook implements PostUploadHook {
     requestCount.increment(op);
     counting.record(op, stats.getTimeCounting(), MILLISECONDS);
     compressing.record(op, stats.getTimeCompressing(), MILLISECONDS);
+    negotiating.record(op, stats.getTimeNegotiating(), MILLISECONDS);
     writing.record(op, stats.getTimeWriting(), MILLISECONDS);
     packBytes.record(op, stats.getTotalBytes());
   }