feat: Refactor log-alert application into modular structure

- Introduced alerters package with base Alerter class and implementations for LogAlerter and GotifyAlerter.
- Created fetchers package with abstract LogFetcher class and implementations for FileLogFetcher, LokiLogFetcher, and ParseableLogFetcher.
- Added filters package with base Filter class and implementations for RegexpFilter and GeolocationFilter.
- Implemented rules package with base AlertRule class and SimpleAlertRule for alerting logic.
- Enhanced configuration handling with utilities for loading and validating JSON configuration.
- Updated logging setup for better logging management.
- Modified main application logic to utilize the new modular structure, improving maintainability and readability.
- Updated config.json and config.schema.json to reflect changes in alerting and fetching configurations.
- Added python-dateutil to requirements for date parsing functionality.

log-alert/fetchers/loki.py

@@ -0,0 +1,60 @@
+"""Loki log fetcher implementation."""
+
+import logging
+from time import time
+import requests
+from typing import Dict, Any, List
+
+from .base import LogFetcher
+
+logger = logging.getLogger("log-alert")
+
+
+class LokiLogFetcher(LogFetcher):
+    """Concrete implementation for fetching logs from Loki."""
+
+    def __init__(self, config: Dict[str, Any]):
+        self.url = config["url"]
+        self.last_fetched_time = int(time.time())
+
+    def fetch_logs(self, filters: Dict[str, Any]) -> List[Dict[str, Any]]:
+        """Fetch logs from Loki without time range."""
+        old_time = self.last_fetched_time
+        self.last_fetched_time = int(time.time())
+        return self.fetch_logs_time_range(filters, old_time, self.last_fetched_time)
+
+    def fetch_logs_time_range(self, filters: Dict[str, Any], start_time: int, end_time: int) -> List[Dict[str, Any]]:
+        """Fetch logs from Loki within the specified time range."""
+        query = '{'
+        for label in filters.get("labels", {}):
+            if len(query) > 1:
+                query += ','
+            query += f'{label}="{filters["labels"][label]}"'
+        query += '}'
+        if "text" in filters:
+            query += f' |= "{filters["text"]}"'
+        logger.debug(f"Executing Loki query: {query}")
+        payload = {
+            "query": query,
+            "limit": 1000,
+            "start": str(int(start_time) * 1000000000),  # Convert to nanoseconds
+            "end": str(int(end_time) * 1000000000),
+            "direction": "forward"
+        }
+        try:
+            response = requests.get(f"{self.url}/loki/api/v1/query_range", params=payload)
+            response.raise_for_status()
+            data = response.json()
+            logs = []
+            for stream in data.get("data", {}).get("result", []):
+                for value in stream.get("values", []):
+                    timestamp, log = value
+                    logs.append({
+                        "timestamp": timestamp,
+                        "log": log,
+                        "labels": stream.get("stream", {})
+                    })
+            return logs
+        except requests.exceptions.RequestException as e:
+            logger.error(f"Error fetching logs from Loki: {e}")
+            return []