Merge pull request #2 from RefaceAI/add-docs

Add docs

Author: antonmyronyuk

README.md

@@ -6,3 +6,81 @@ Prometheus summary with quantiles over configurable sliding time window
 ```
 pip install prometheus-summary==0.0.1
 ```
+This package can be found on [PyPI](https://pypi.org/project/prometheus-summary/).
+
+## Collecting
+
+### Basic usage
+
+```python
+from prometheus_summary import Summary
+
+s = Summary("request_latency_seconds", "Description of summary")
+s.observe(4.7)
+```
+
+### With labels
+
+```python
+from prometheus_summary import Summary
+
+s = Summary("request_latency_seconds", "Description of summary", ["method", "endpoint"])
+s.labels(method="GET", endpoint="/profile").observe(1.2)
+s.labels(method="POST", endpoint="/login").observe(3.4)
+```
+
+### With custom quantiles and precisions
+
+By default, metrics are observed for next quantile-precision pairs
+`((0.50, 0.05), (0.90, 0.01), (0.99, 0.001))`
+but you can provide your own value when creating the metric.
+
+```python
+from prometheus_summary import Summary
+
+s = Summary(
+    "request_latency_seconds", "Description of summary",
+    invariants=((0.50, 0.05), (0.75, 0.02), (0.90, 0.01), (0.95, 0.005), (0.99, 0.001)),
+)
+s.observe(4.7)
+```
+
+### With custom time window settings
+
+Typically, you don't want to have a Summary representing the entire runtime of the application,
+but you want to look at a reasonable time interval. Summary metrics implement a configurable sliding time window.
+
+The default is a time window of 10 minutes and 5 age buckets, i.e. the time window is 10 minutes wide, and
+we slide it forward every 2 minutes, but you can configure this values for your own purposes.
+
+```python
+from prometheus_summary import Summary
+
+s = Summary(
+    "request_latency_seconds", "Description of summary",
+    # time window 5 minutes wide with 10 age buckets (sliding every 30 seconds)
+    max_age_seconds=5 * 60,
+    age_buckets=10,
+)
+s.observe(4.7)
+```
+
+## Querying
+
+Suppose we have a metric:
+
+```python
+from prometheus_summary import Summary
+
+s = Summary("request_latency_seconds", "Description of summary", ["method", "endpoint"])
+```
+
+To show request latency by `method`, `endpoint` and `quntile` use next query:
+```
+max by (method, endpoint, quantile) (request_latency_seconds)
+```
+
+To only 99-th quantile:
+```
+max by (method, endpoint) (request_latency_seconds{quantile="0.99")
+```