Apache Solr indexing performance guide

Goal

Apache Solr is a powerful and highly scalable search platform used to index and search large volumes of data efficiently. However, to ensure optimal performance, it is essential to fine-tune your Solr indexing process. This guide outlines key strategies and best practices for increasing Apache Solr indexing performance.

Environment

Fusion 4.x and below, Solr (standalone) of any version

Hardware considerations:

Memory

• Solr relies heavily on memory for caching frequently used data. Allocate at least 50% of your server's memory to Solr, but the exact amount will depend on the size of your dataset and your query patterns.
• Use the Solr GC logs to monitor memory usage, and ensure that the JVM heap size is appropriately configured in 'solrconfig.xml'.
• In solr environments, Set the starting and maximum JVM heap size to the same value.
  • -Xms<size> Sets the initial heap size e.g. -Xms=8g
  • -Xmx<size> Sets the maximum heap size e.g. -Xmx=8g

Storage

• Use SSDs (Solid-State Drives) rather than HDDs (Hard Disk Drives) for your Solr data. SSDs provide faster read and write speeds, which are crucial for efficient indexing.
• Monitor disk space regularly to prevent running out of storage, as it can lead to indexing errors and corrupted index segment files.

CPU

• Solr can take advantage of multi-core CPUs for parallel processing of indexing tasks. Ensure your server has enough CPU cores to handle concurrent indexing requests effectively.
• Monitor CPU usage, and if it's consistently high, consider adding more CPU cores or optimizing your indexing process to be more efficient.

Solr configuration:

Configuration files

• Carefully review and optimise your Solr configuration files. Overly complex configurations can lead to performance issues.
• Customise the '<updateHandler>' section in 'solrconfig.xml' to define settings for commit and auto-commit, which affect indexing performance.

 Merge policy

• Solr's merge policy dictates how segments are merged during indexing. Experiment with different settings to find the best balance between query and indexing performance.
• The 'TieredMergePolicy' is a commonly used merge policy that balances indexing and query performance.

AutoCommit and AutoSoftCommit

• 'AutoCommit' settings define when Solr automatically commits changes. Carefully adjust 'maxTime', 'maxDocs', and 'openSearcher' parameters to strike a balance between real-time updates and indexing efficiency.
• 'AutoSoftCommit' settings control when documents become visible for search. Customize these settings to suit your near-real-time search requirements.

Soft and Hard commit

• Soft commits are ideal for providing near-real-time search results, as they make documents visible without waiting for a hard commit. Hard commits are essential for durability and ensuring that documents are not lost.
• Adjust the 'commitWithin' parameter in your indexing requests to control when documents are automatically committed.

Caches

• Solr has various caches to improve query and indexing performance. Set appropriate cache sizes in 'solrconfig.xml' based on your workload.
• Monitor cache hit rates using the Solr Admin Dashboard and adjust cache sizes accordingly. Common caches to optimize include filter cache, query result cache, and document cache.

Indexing practices:

Batch indexing

• Utilize tools like DataImportHandler (DIH) for importing data in bulk from databases or SolrJ for programmatic indexing.
• Consider using Solr's delta-import functionality to update only the changed data, reducing the indexing load.

Avoid over-indexing

• Only index fields that are required for search and filtering. Eliminate unnecessary indexed fields to reduce the index size and improve performance.
• Minimise the use of dynamic fields to avoid unnecessary complexity.

Optimize data

• Clean and preprocess your data before indexing. This includes removing HTML tags, whitespace, and any non-essential content.
• Utilize data transformation techniques, such as tokenization and stemming, to enhance the quality of the indexed data.

Parallel indexing

• Consider parallel indexing using multiple threads or Solr instances when dealing with a large volume of data. This approach can significantly improve indexing speed and efficiency.
• Ensure proper synchronization mechanisms to prevent data corruption when using parallel indexing.

Delta updates

• Delta updates are crucial for efficiently updating existing data in the index without reindexing the entire dataset. Use the '_update' endpoint to apply changes incrementally.
• Maintain a system for tracking changes and efficiently applying delta updates.

Monitoring and Logging:

Monitoring

• Implement a monitoring solution that tracks key metrics like query response times, cache hit rates, and resource utilization (memory, CPU, and disk).
• Use tools like Prometheus, Grafana, and the Solr Admin Dashboard to visualize and analyze these metrics.

Logging

• Configure Solr's logging to capture important events, errors, and warnings. Centralize your logs for easy analysis and troubleshooting.
• Implement log rotation to manage log file sizes and avoid filling up your storage.

Scaling:

Distributed indexing

• If your dataset is extensive, consider setting up a distributed Solr cluster with multiple shards and replicas. This approach can distribute the indexing load across nodes, improving performance and fault tolerance.

Load balancing

• Use a load balancer to evenly distribute search and indexing requests across Solr instances. Common load balancers include Apache HTTP Server, Nginx, or cloud-based load balancers provided by hosting platforms.

Regular maintenance:

Optimize indexes

• Regularly optimize your Solr indexes to remove deleted documents and reduce index fragmentation. Use the 'optimize' command judiciously to consolidate smaller segments into larger, more efficient segments.

Compact segments

• The 'optimize' command can be used for segment merging and compaction. This process helps eliminate index fragmentation and enhances query performance.

By implementing these detailed strategies and best practices, you can fine-tune your Apache Solr indexing process to achieve optimal performance and search capabilities for your specific use case. Regular monitoring, tweaking, and maintenance are key to ensuring continued high performance as your data and query patterns evolve.