Expand readme

Author: brian-brazil

README.md

@@ -10,21 +10,110 @@ pip install prometheus_client
 
 This package can be found on [PyPI](https://pypi.python.org/pypi/prometheus_client).
 
-## Example Usage
+## Instrumenting
+
+Three types of metric are offered: Counter, Gauge, and Summary.
+See the documentation on [metric types](http://prometheus.io/docs/concepts/metric_types/)
+and [instrumentation best practices](http://prometheus.io/docs/practices/instrumentation/#counter-vs.-gauge-vs.-summary)
+on how to use them.
+
+### Counter
+
+Counters go up, and reset when the process restarts.
+
 
 ```python
-from prometheus_client import *
-from prometheus_client import MetricsHandler
+from prometheus_client import Counter
+c = Counter('my_failures_total', 'Description of counter')
+c.inc()    # Increment by 1
+c.inc(10)  # Increment by given value
+```
+
+There are utilities to count exceptions raised:
+
+```python
+@c.countExceptions()
+def f():
+  pass
+
+with c.countExceptions():
+  pass
+
+with c.countExceptions(ValueError):
+  pass
+```
+
+### Gauge
+
+Gauges can go up and down.
+
+
+```python
+from prometheus_client import Gauge
+g = Gauge('my_inprogress_requests', 'Description of gauge')
+g.inc()    # Increment by 1
+g.dev(10)  # Decrement by given value
+g.set(7)   # Set to a given value
+```
+
+There are utilities for common use cases:
+
+```python
+g.setToCurrentTime()   # Set to current unixtime
 
-c = Counter('cc', 'A counter')
-c.inc()
+# Increment when entered, decrement when exited.
+@g.trackInprogress()
+def f():
+  pass
 
-g = Gauge('gg', 'A gauge')
-g.set(17)
+with g.trackInprogress():
+  pass
+```
+
+### Summaries
+
+Summaries track the size and number of events.
+
+```python
+from prometheus_client import Summary
+s = Summary('request_latency_seconds', 'Description of summary')
+s.observe(5)    # Observe 5 (seconds)
+```
+
+There are utilities for common use cases:
+
+```python
+# Increment when entered, decrement when exited.
+@g.time()
+def f():
+  pass
+
+with g.time():
+  pass
+```
 
-s = Summary('ss', 'A summary', ['a', 'b'])
-s.labels('c', 'd').observe(17)
+### Labels
 
+All metrics can have labels, allowing grouping of related time series.
+
+See the best practices on [naming](http://prometheus.io/docs/practices/naming/)
+and [labels](http://prometheus.io/docs/practices/instrumentation/#use-labels).
+
+Taking a counter as an example:
+
+```python
+from prometheus_client import Counter
+c = Counter('my_requests_total', 'HTTP Failures', ['method', 'endpoint'])
+c.labels('get', '/').inc()
+c.labels('post', '/submit').inc()
+```
+
+## Exporting
+
+Metrics are exposed over HTTP, to be read by the Prometheus server. For example:
+
+```python
+from prometheus_client import MetricsHandler
 from BaseHTTPServer import HTTPServer
 server_address = ('', 8000)
 httpd = HTTPServer(server_address, MetricsHandler)

prometheus_client/__init__.py

@@ -8,7 +8,7 @@
 from functools import wraps
 from threading import Lock
 
-__all__ = ['Counter', 'Gauge', 'Summary']
+__all__ = ['Counter', 'Gauge', 'Summary', 'CollectorRegistry']
 
 _METRIC_NAME_RE = re.compile(r'^[a-zA-Z_:][a-zA-Z0-9_:]*$')
 _METRIC_LABEL_NAME_RE = re.compile(r'^[a-zA-Z_:][a-zA-Z0-9_:]*$')