Add logging for misbehaving distribution metrics (#4429)

### Motivation

Some cumulative distribution metrics (build age, retrieval, testcase
age, testcase triage duration) are misbehaving and capping at 1. This PR
intends to aid in debugging that.

src/clusterfuzz/_internal/bot/tasks/utasks/fuzz_task.py

@@ -1887,12 +1887,15 @@ def run(self):
     self.fuzz_task_output.crash_groups.extend(crash_groups)
 
     fuzzing_session_duration = time.time() - start_time
-    monitoring_metrics.FUZZING_SESSION_DURATION.add(
-        fuzzing_session_duration, {
-            'fuzzer': self.fuzzer_name,
-            'job': self.job_type,
-            'platform': environment.platform()
-        })
+    labels = {
+        'fuzzer': self.fuzzer_name,
+        'job': self.job_type,
+        'platform': environment.platform()
+    }
+    logs.info(f'FUZZING_SESSION_DURATION: add {fuzzing_session_duration} '
+              'for {labels}.')
+    monitoring_metrics.FUZZING_SESSION_DURATION.add(fuzzing_session_duration,
+                                                    labels)
 
     return uworker_msg_pb2.Output(fuzz_task_output=self.fuzz_task_output)  # pylint: disable=no-member
 

src/clusterfuzz/_internal/build_management/build_manager.py

@@ -300,14 +300,17 @@ def set_env_var(name, value):
 
 
 def _emit_job_build_retrieval_metric(start_time, step, build_type):
+  """Emits a metrick to track the distribution of build retrieval times."""
   elapsed_minutes = (time.time() - start_time) / 60
-  monitoring_metrics.JOB_BUILD_RETRIEVAL_TIME.add(
-      elapsed_minutes, {
-          'job': os.getenv('JOB_NAME'),
-          'platform': environment.platform(),
-          'step': step,
-          'build_type': build_type,
-      })
+  labels = {
+      'job': os.getenv('JOB_NAME'),
+      'platform': environment.platform(),
+      'step': step,
+      'build_type': build_type,
+  }
+  logs.info(f'JOB_BUILD_RETRIEVAL_TIME: adding {elapsed_minutes} '
+            f'for labels {labels}.')
+  monitoring_metrics.JOB_BUILD_RETRIEVAL_TIME.add(elapsed_minutes, labels)
 
 
 class BaseBuild:
@@ -1220,6 +1223,7 @@ def _emit_build_age_metric(gcs_path):
         'platform': environment.platform(),
         'task': os.getenv('TASK_NAME'),
     }
+    logs.info(f'JOB_BUILD_AGE: adding {elapsed_time_in_hours} for {labels}')
     monitoring_metrics.JOB_BUILD_AGE.add(elapsed_time_in_hours, labels)
     # This field is expected as a datetime object
     # https://cloud.google.com/storage/docs/json_api/v1/objects#resource

src/clusterfuzz/_internal/common/testcase_utils.py

@@ -61,12 +61,17 @@ def emit_testcase_triage_duration_metric(testcase_id: int, step: str):
                  ' failed to emit TESTCASE_UPLOAD_TRIAGE_DURATION metric.')
     return
 
+  labels = {
+      'job': testcase.job_type,
+      'step': step,
+  }
+
+  logs.info(
+      f'TESTCASE_UPLOAD_TRIAGE_DURATION: adding {elapsed_time_since_upload} for {labels}.'
+  )
+
   monitoring_metrics.TESTCASE_UPLOAD_TRIAGE_DURATION.add(
-      elapsed_time_since_upload,
-      labels={
-          'job': testcase.job_type,
-          'step': step,
-      })
+      elapsed_time_since_upload, labels=labels)
 
 
 def get_testcase_upload_metadata(

src/clusterfuzz/_internal/cron/triage.py

@@ -306,12 +306,16 @@ def _emit_untriaged_testcase_age_metric(critical_tasks_completed: bool,
   if not testcase.timestamp:
     return
 
+  labels = {
+      'job': testcase.job_type,
+      'platform': testcase.platform,
+  }
+
+  logs.info(f'UNTRIAGED_TESTCASE_AGE: adding {testcase.get_age_in_seconds()}'
+            ' for {labels}')
+
   monitoring_metrics.UNTRIAGED_TESTCASE_AGE.add(
-      testcase.get_age_in_seconds(),
-      labels={
-          'job': testcase.job_type,
-          'platform': testcase.platform,
-      })
+      testcase.get_age_in_seconds(), labels=labels)
 
 
 def main():