Logstash is a versatile, plugin-based data collection and processing engine that enables users to efficiently parse, process, and forward data into Elasticsearch using customizable pipelines and configuration files. This blog post provides a detailed introduction to Logstash, focusing on its ability to handle various log formats with minimal configuration through plugins like Filebeat, and showcases the development of a configuration for parsing Squid cache access logs. Using both the dissect and grok filters, Logstash can parse logs into distinct fields, with grok offering the flexibility of regular expression matching for more complex log formats. The post also highlights the importance of type conversion and the use of the date filter to ensure data is appropriately formatted before being sent to Elasticsearch, where specific mappings can be applied to fields to optimize data retrieval and aggregation. The article underscores Logstash's role as a powerful tool in data processing pipelines, encouraging readers to explore further resources and examples to fully leverage its capabilities.