Allow adding 'service' label to Prometheus metrics (#269)

* Add support for service label Signed-off-by: Alex Perez-Pujol <alexperez@paradigmadigital.com> * Initialize to none for a more idiomatic approach Signed-off-by: Alex Perez-Pujol <alexperez@paradigmadigital.com> * Make the name_label parameter optional Signed-off-by: Alex Perez-Pujol <alexperez@paradigmadigital.com> * Change label name Signed-off-by: Alex Perez-Pujol <alexperez@paradigmadigital.com> * Add tests Signed-off-by: Alex Perez-Pujol <alexperez@paradigmadigital.com> * DRY Signed-off-by: Yuri Shkuro <ys@uber.com> * Fix readme Signed-off-by: Yuri Shkuro <ys@uber.com> * Delint Signed-off-by: Yuri Shkuro <ys@uber.com> * Bump code coverage Signed-off-by: Yuri Shkuro <ys@uber.com>
jaegertracing · Dec 6, 2019 · 51d9027 · 51d9027
1 parent 900c509
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diff --git a/README.md b/README.md
@@ -36,7 +36,7 @@ if __name__ == "__main__":
                 'param': 1,
             },
             'logging': True,
-        },  
+        },
         service_name='your-app-name',
         validate=True,
     )
@@ -67,7 +67,7 @@ if __name__ == "__main__":
                 'reporting_port': 'your-reporting-port',
             },
             'logging': True,
-        },  
+        },
         service_name='your-app-name',
         validate=True,
     )
@@ -89,7 +89,7 @@ after all the imports are done.
 
 
 Also note that using `gevent.monkey` in asyncio-based applications (python 3+) may need to pass current event loop explicitly (see issue #256):
- 
+
  ```python
 from tornado import ioloop
 from jaeger_client import Config
@@ -115,7 +115,7 @@ If you need to create additional tracers (e.g., to create spans on the client si
 
 #### Prometheus metrics
 
-This module brings a [Prometheus](https://github.com/prometheus/client_python) integration to the internal Jaeger metrics.  
+This module brings a [Prometheus](https://github.com/prometheus/client_python) integration to the internal Jaeger metrics.
 The way to initialize the tracer with Prometheus metrics:
 
 ```python
@@ -125,19 +125,23 @@ config = Config(
         config={},
         service_name='your-app-name',
         validate=True,
-        metrics_factory=PrometheusMetricsFactory(namespace='your-app-name')
+        metrics_factory=PrometheusMetricsFactory(service_name_label='your-app-name')
 )
 tracer = config.initialize_tracer()
 ```
 
+Note that the optional argument `service_name_label` to the factory constructor
+will force it to tag all Jaeger client metrics with a label `service: your-app-name`.
+This way you can distinguish Jaeger client metrics produced by different services.
+
 ### Development
 
 For development, some parameters can be passed via `config` dictionary, as in the Getting Started example above. For more details please see the [Config class](jaeger_client/config.py).
 
 ### WSGI, multi-processing, fork(2)
 
-When using this library in applications that fork child processes to handle individual requests, 
-such as with [WSGI / PEP 3333](https://wsgi.readthedocs.io/), care must be taken when initializing the tracer. 
+When using this library in applications that fork child processes to handle individual requests,
+such as with [WSGI / PEP 3333](https://wsgi.readthedocs.io/), care must be taken when initializing the tracer.
 When Jaeger tracer is initialized, it may start a new background thread. If the process later forks,
 it might cause issues or hang the application (due to exclusive lock on the interpreter).
 Therefore, it is recommended that the tracer is not initialized until after the child processes

diff --git a/jaeger_client/metrics/prometheus.py b/jaeger_client/metrics/prometheus.py
@@ -21,9 +21,10 @@ class PrometheusMetricsFactory(MetricsFactory):
     """
     Provides metrics backed by Prometheus
     """
-    def __init__(self, namespace=''):
+    def __init__(self, namespace='', service_name_label=None):
         self._cache = defaultdict(object)
         self._namespace = namespace
+        self._service_name_label = service_name_label
 
     def _get_tag_name_list(self, tags):
         if tags is None:
@@ -33,28 +34,36 @@ def _get_tag_name_list(self, tags):
             tag_name_list.append(key)
         return tag_name_list
 
-    def _get_metric(self, metric, name, label_name_list):
-        cache_key = name + ''.join(label_name_list)
-        if self._cache.get(cache_key) is None:
-            self._cache[cache_key] = metric(name=name, documentation=name,
-                                            labelnames=label_name_list, namespace=self._namespace)
-        return self._cache[cache_key]
+    def _get_metric(self, metricType, name, tags):
+        if self._service_name_label:
+            if tags is None:
+                tags = {'service': self._service_name_label}
+            else:
+                tags['service'] = self._service_name_label
 
-    def create_counter(self, name, tags=None):
         label_name_list = self._get_tag_name_list(tags)
-        counter = self._get_metric(Counter, name, label_name_list)
+        cache_key = name + '@@'.join(label_name_list)
+
+        metric = self._cache.get(cache_key)
+        if metric is None:
+            metric = metricType(name=name, documentation=name,
+                                labelnames=label_name_list, namespace=self._namespace)
+            self._cache[cache_key] = metric
+
         if tags is not None and len(tags) > 0:
-            counter = counter.labels(**tags)
+            metric = metric.labels(**tags)
+
+        return metric
+
+    def create_counter(self, name, tags=None):
+        counter = self._get_metric(Counter, name, tags)
 
         def increment(value):
             counter.inc(value)
         return increment
 
     def create_gauge(self, name, tags=None):
-        label_name_list = self._get_tag_name_list(tags)
-        gauge = self._get_metric(Gauge, name, label_name_list)
-        if tags is not None and len(tags) > 0:
-            gauge = gauge.labels(**tags)
+        gauge = self._get_metric(Gauge, name, tags)
 
         def update(value):
             gauge.set(value)

diff --git a/tests/test_prometheus.py b/tests/test_prometheus.py
@@ -54,3 +54,30 @@ def test_prometheus_metrics_gauge_without_tags():
     gauge(1)
     after = REGISTRY.get_sample_value('jaeger:test_gauge_no_tags')
     assert 1 == after
+
+
+def test_prometheus_metrics_metric_with_service_name_label():
+    metrics = PrometheusMetricsFactory(service_name_label='test')
+    gauge = metrics.create_gauge(name='jaeger:test_gauge_with_service_name_label')
+    gauge(1)
+    gauge_after = REGISTRY.get_sample_value('jaeger:test_gauge_with_service_name_label',
+                                            {'service': 'test'})
+    counter = metrics.create_counter(name='jaeger:test_counter_with_service_name_label',
+                                     tags={'x': 'y'})
+    counter(1)
+    counter_after = REGISTRY.get_sample_value('jaeger:test_counter_with_service_name_label',
+                                              {'service': 'test', 'x': 'y'})
+    assert 1 == counter_after
+    assert 1 == gauge_after
+
+
+def test_prometheus_metrics_metric_without_service_name_label():
+    metrics = PrometheusMetricsFactory()
+    gauge = metrics.create_gauge(name='jaeger:test_gauge_without_service_name_label')
+    gauge(1)
+    gauge_after = REGISTRY.get_sample_value('jaeger:test_gauge_without_service_name_label')
+    counter = metrics.create_counter(name='jaeger:test_counter_without_service_name_label')
+    counter(1)
+    counter_after = REGISTRY.get_sample_value('jaeger:test_counter_without_service_name_label')
+    assert 1 == counter_after
+    assert 1 == gauge_after