Stackdriver poll-based metrics (#593)

Move stackdriver stats exporter to metrics model, consume stats as metric
producer and stop exporting on record.

Author: c24t

README.rst

@@ -54,7 +54,7 @@ Installation & basic usage
 
         from opencensus.stats import stats as stats_module
 
-        stats = stats_module.Stats()
+        stats = stats_module.stats
         view_manager = stats.view_manager
         stats_recorder = stats.stats_recorder
 

contrib/opencensus-ext-prometheus/README.rst

@@ -45,7 +45,7 @@ Register the Prometheus exporter
 
     .. code:: python
 
-        stats = stats_module.Stats()
+        stats = stats_module.stats
         view_manager = stats.view_manager
 
         exporter = prometheus.new_stats_exporter(prometheus.Options(namespace="<namespace>"))

contrib/opencensus-ext-prometheus/examples/prometheus.py

@@ -40,7 +40,7 @@
 
 
 def main():
-    stats = stats_module.Stats()
+    stats = stats_module.stats
     view_manager = stats.view_manager
     stats_recorder = stats.stats_recorder
 

contrib/opencensus-ext-prometheus/tests/test_prometheus_stats.py

@@ -280,7 +280,7 @@ def test_exporter_constructor_no_namespace(self):
 
     def test_emit(self):
         options = prometheus.Options(namespace="opencensus", port=9005)
-        stats = stats_module.Stats()
+        stats = stats_module.stats
         view_manager = stats.view_manager
         stats_recorder = stats.stats_recorder
         exporter = prometheus.new_stats_exporter(options)

contrib/opencensus-ext-stackdriver/README.rst

@@ -89,7 +89,7 @@ Register the Stackdriver exporter
 
     .. code:: python
 
-        stats = stats_module.Stats()
+        stats = stats_module.stats
         view_manager = stats.view_manager
 
         exporter = stackdriver.new_stats_exporter(stackdriver.Options(project_id="<id_value>"))

contrib/opencensus-ext-stackdriver/examples/stackdriver.py

@@ -30,7 +30,7 @@
     "task_latency", "The task latency in milliseconds", "ms")
 
 # The stats recorder
-stats = stats_module.Stats()
+stats = stats_module.stats
 view_manager = stats.view_manager
 stats_recorder = stats.stats_recorder