feat: add support for structured metadata

README.md

@@ -1,12 +1,13 @@
-python-logging-loki
+python-logging-loki (with structured metadata support)
 ===================
 
 [![PyPI version](https://img.shields.io/pypi/v/python-logging-loki.svg)](https://pypi.org/project/python-logging-loki/)
 [![Python version](https://img.shields.io/badge/python-3.6%20%7C%203.7%20%7C%203.8-blue.svg)](https://www.python.org/)
 [![License](https://img.shields.io/pypi/l/python-logging-loki.svg)](https://opensource.org/licenses/MIT)
 [![Build Status](https://travis-ci.org/GreyZmeem/python-logging-loki.svg?branch=master)](https://travis-ci.org/GreyZmeem/python-logging-loki)
 
-Python logging handler for Loki.  
+A fork of the python logging handler for Loki, supporting structured metadata.
+
 https://grafana.com/loki
 
 Installation
@@ -44,7 +45,16 @@ Example above will send `Something happened` message along with these labels:
 - Logger's name as `logger` 
 - Labels from `tags` item of `extra` dict
 
-The given example is blocking (i.e. each call will wait for the message to be sent).  
+To log structured metadata, simply add a `metadata` field to `extra`:
+
+```python
+logger.info(
+    f'Epoch [{epoch+1}/{epochs}], Loss: {loss:.4f}', 
+    extra={"tags": {"experiment": "example"}, "metadata": {"epoch": f"{epoch}", "loss": f"{loss:.4f}"}},
+    )
+```
+
+The given examples are blocking (i.e. each call will wait for the message to be sent).  
 But you can use the built-in `QueueHandler` and` QueueListener` to send messages in a separate thread.  
 
 ```python

logging_loki/emitter.py

@@ -136,8 +136,13 @@ def build_payload(self, record: logging.LogRecord, line) -> dict:
         labels = self.build_tags(record)
         ns = 1e9
         ts = str(int(time.time() * ns))
+
+        # Include structured metadata
+        metadata = getattr(record, "metadata", {})
+        value = [ts, line, metadata] if metadata else [ts, line]
+
         stream = {
             "stream": labels,
-            "values": [[ts, line]],
+            "values": [value],
         }
-        return {"streams": [stream]}
+        return {"streams": [stream]}