fix: let props_to_labels take properties from log line

logging_loki/emitter.py

@@ -20,8 +20,6 @@ class LokiEmitter:
     """Base Loki emitter class."""
 
     success_response_code = const.success_response_code
-    level_tag = const.level_tag
-    logger_tag = const.logger_tag
     label_allowed_chars = const.label_allowed_chars
     label_replace_with = const.label_replace_with
     session_class = requests.Session
@@ -32,7 +30,9 @@ def __init__(self,
         headers: Optional[dict] = None, 
         auth: BasicAuth = None, 
         as_json: bool = False,
-        props_to_labels: Optional[list[str]] = None
+        props_to_labels: Optional[list[str]] = None,
+        level_tag: Optional[str] = const.level_tag,
+        logger_tag: Optional[str] = const.logger_tag
     ):
         """
         Create new Loki emitter.
@@ -53,8 +53,12 @@ def __init__(self,
         self.auth = auth
         #: Optional bool, send record as json?
         self.as_json = as_json
-        #: Optional list, send record as json?
+        #: Optional list, convert properties to loki labels
         self.props_to_labels = props_to_labels or []
+        #: Label name indicating logging level.
+        self.level_tag: str = level_tag
+        #: Label name indicating logger name.
+        self.logger_tag: str = logger_tag
 
         self._session: Optional[requests.Session] = None
         self._lock = threading.Lock()
@@ -102,14 +106,21 @@ def format_label(self, label: str) -> str:
             label = label.replace(char_from, char_to)
         return "".join(char for char in label if char in self.label_allowed_chars)
 
-    def build_tags(self, record: logging.LogRecord) -> Dict[str, Any]:
+    def build_tags(self, record: logging.LogRecord, line: str) -> Dict[str, Any]:
         """Return tags that must be send to Loki with a log record."""
         tags = dict(self.tags) if isinstance(self.tags, ConvertingDict) else self.tags
         tags = copy.deepcopy(tags)
-        tags[self.level_tag] = record.levelname.lower()
-        tags[self.logger_tag] = record.name
-
-        extra_tags = {k: getattr(record, k) for k in self.props_to_labels if getattr(record, k, None)}
+        if self.level_tag:
+            tags[self.level_tag] = record.levelname.lower()
+        if self.logger_tag:
+            tags[self.logger_tag] = record.name
+
+        extra_tags = {}
+        if self.props_to_labels:
+            jsonline = json.loads(line)
+            for k in self.props_to_labels:
+                if prop_value := getattr(record, k, None) or jsonline.get(k, None):
+                    extra_tags.update({k: prop_value})
         if isinstance(passed_tags := getattr(record, "tags", {}), dict):
             extra_tags = extra_tags | passed_tags
 
@@ -121,9 +132,9 @@ def build_tags(self, record: logging.LogRecord) -> Dict[str, Any]:
 
         return tags
 
-    def build_payload(self, record: logging.LogRecord, line) -> dict:
+    def build_payload(self, record: logging.LogRecord, line: str) -> dict:
         """Build JSON payload with a log entry."""
-        labels = self.build_tags(record)
+        labels = self.build_tags(record, line)
         ns = 1e9
         ts = str(int(time.time() * ns))
 

logging_loki/handlers.py

@@ -7,6 +7,7 @@
 from queue import Queue
 import time
 from typing import Optional, Union
+from logging_loki import const
 
 from logging_loki.emitter import BasicAuth, LokiEmitter
 
@@ -51,6 +52,8 @@ def __init__(
         auth: Optional[BasicAuth] = None,
         as_json: Optional[bool] = False,
         props_to_labels: Optional[list[str]] = None,
+        level_tag: Optional[str] = const.level_tag,
+        logger_tag: Optional[str] = const.logger_tag
     ):
         """
         Create new Loki logging handler.
@@ -62,10 +65,12 @@ def __init__(
             headers: Optional record with headers that are send with each POST to loki.
             as_json: Flag to support sending entire JSON record instead of only the message.
             props_to_labels: List of properties that should be converted to loki labels.
+            level_tag: Label name indicating logging level.
+            logger_tag: Label name indicating logger name.
 
         """
         super().__init__()
-        self.emitter = LokiEmitter(url, tags, headers, auth, as_json, props_to_labels)
+        self.emitter = LokiEmitter(url, tags, headers, auth, as_json, props_to_labels, level_tag, logger_tag)
 
     def handleError(self, record):  # noqa: N802
         """Close emitter and let default handler take actions on error."""

tests/test_emitter_v1.py

@@ -174,7 +174,7 @@ def test_can_build_tags_from_converting_dict(emitter_v1):
 
     logger = logging.getLogger(logger_name)
     emitter: LokiEmitter = logger.handlers[0].handler.emitter
-    emitter.build_tags(create_record())
+    emitter.build_tags(create_record(), '{}')
 
 def test_batch_records_sent_to_emitter_url(emitter_v1):
     emitter, session = emitter_v1