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# Utilities and Configuration
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The utilities and configuration system provides Netty-specific optimizations, byte buffer management, configuration helpers, and performance tuning utilities that enhance the overall performance and reliability of the transport layer.
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## Capabilities
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### Netty4Utils
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Core utility class providing Netty-specific optimizations and byte buffer conversion utilities.
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```java { .api }
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/**
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 * Utility class for Netty4-specific operations and optimizations
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 * Provides conversion methods and system configuration utilities
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 */
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public class Netty4Utils {
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    /**
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     * Sets the number of available processors for Netty resource sizing
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     * Must be called before any Netty EventLoopGroups are created
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     * @param availableProcessors Number of processors for Netty to use
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     * @throws IllegalStateException if processors already set with different value
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     */
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    public static void setAvailableProcessors(int availableProcessors);
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    /**
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     * Converts Elasticsearch BytesReference to Netty ByteBuf
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     * Efficiently handles different BytesReference implementations
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     * @param reference Elasticsearch bytes to convert
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     * @return Netty ByteBuf for network operations
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     */
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    public static ByteBuf toByteBuf(BytesReference reference);
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    /**
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     * Converts Netty ByteBuf to Elasticsearch BytesReference
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     * Maintains buffer ownership and lifecycle properly
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     * @param byteBuf Netty buffer to convert
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     * @return Elasticsearch BytesReference
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     */
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    public static BytesReference toBytesReference(ByteBuf byteBuf);
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    /**
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     * Creates composite ByteBuf from multiple BytesReference objects
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     * More efficient than copying when dealing with multiple buffers
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     * @param allocator ByteBuf allocator for composite buffer
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     * @param references Array of BytesReference to combine
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     * @return Composite ByteBuf containing all references
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     */
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    public static CompositeByteBuf toCompositeByteBuf(
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        ByteBufAllocator allocator, 
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        BytesReference... references
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    );
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}
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```
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**Usage Examples:**
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```java
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// Set processor count during system initialization
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int processorCount = Runtime.getRuntime().availableProcessors();
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Netty4Utils.setAvailableProcessors(processorCount);
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// Convert between Elasticsearch and Netty buffer types
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BytesReference esBytes = new BytesArray("Hello World".getBytes());
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ByteBuf nettyBuf = Netty4Utils.toByteBuf(esBytes);
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// Send via Netty channel
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channel.writeAndFlush(nettyBuf);
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// Convert received Netty buffer back to ES format
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ByteBuf receivedBuf = // from Netty pipeline
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BytesReference esReceived = Netty4Utils.toBytesReference(receivedBuf);
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// Create composite buffer for multiple message parts
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BytesReference header = new BytesArray("Header".getBytes());
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BytesReference body = new BytesArray("Body content".getBytes());
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CompositeByteBuf composite = Netty4Utils.toCompositeByteBuf(
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    allocator, header, body
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);
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```
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### Processor Configuration Management
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The utilities system manages Netty's processor configuration to ensure optimal resource allocation.
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```java { .api }
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/**
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 * Internal processor configuration management
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 * Ensures Netty uses correct number of processors for thread pools and resource sizing
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 */
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// System property to control processor setting behavior
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private static final String SET_PROCESSORS_PROPERTY = "es.set.netty.runtime.available.processors";
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// Atomic flag to prevent multiple processor settings
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private static final AtomicBoolean isAvailableProcessorsSet = new AtomicBoolean();
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```
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**Configuration Logic:**
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```java
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// Processor setting is controlled by system property
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System.setProperty("es.set.netty.runtime.available.processors", "true"); // Default
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System.setProperty("es.set.netty.runtime.available.processors", "false"); // Disable in tests
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// Automatic processor detection and setting
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int availableProcessors = EsExecutors.allocatedProcessors(settings);
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Netty4Utils.setAvailableProcessors(availableProcessors);
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// This affects Netty's internal resource calculations:
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// - EventLoopGroup thread counts
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// - Buffer pool sizing  
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// - Internal queue sizes
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// - Default worker thread counts
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```
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### ByteBuf Size Management
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Specialized handlers for optimizing ByteBuf allocation and sizing based on usage patterns.
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```java { .api }
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/**
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 * Netty pipeline handler for ByteBuf size management and optimization
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 * Monitors buffer usage patterns and adjusts allocation strategies
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 */
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public class NettyByteBufSizer extends MessageToMessageDecoder<ByteBuf> {
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    /**
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     * Processes incoming ByteBuf messages and optimizes sizing
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     * @param ctx Channel handler context
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     * @param msg ByteBuf message to process
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     * @param out List to add processed messages
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     */
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    @Override
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    protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out);
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}
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```
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### Buffer Conversion Optimizations
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The utilities provide optimized buffer conversion strategies based on buffer types and usage patterns.
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**Direct Buffer Handling**: Efficiently handles direct ByteBuf instances without unnecessary copying
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**Composite Buffer Support**: Optimized handling of composite buffers with multiple components
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**Reference Counting**: Proper management of ByteBuf reference counts to prevent memory leaks
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**Copy Avoidance**: Minimizes buffer copying through intelligent buffer sharing where safe
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**Slice Operations**: Efficient buffer slicing for protocol parsing and message framing
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### Logging and Debugging Utilities
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Specialized logging handlers for debugging network operations and performance analysis.
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```java { .api }
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/**
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 * Elasticsearch-specific logging handler for Netty pipelines
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 * Provides detailed logging of network operations for debugging
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 */
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public class ESLoggingHandler extends LoggingHandler {
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    /**
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     * Creates logging handler with Elasticsearch-specific formatting
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     * @param level Log level for network events
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     */
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    public ESLoggingHandler(LogLevel level);
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    /**
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     * Logs channel events with Elasticsearch context
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     * Includes node information and request correlation
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     */
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    // Logs channel active/inactive events
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    // Logs message read/write operations  
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    // Logs exception events with full context
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    // Provides request/response correlation
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}
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```
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**Usage Example:**
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```java
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// Add logging handler to Netty pipeline for debugging
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ChannelPipeline pipeline = channel.pipeline();
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pipeline.addFirst("es-logger", new ESLoggingHandler(LogLevel.DEBUG));
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// Logs will include:
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// - Channel lifecycle events (active, inactive, registered)
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// - Message transmission (read, write, flush)
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// - Buffer details (size, type, reference count)
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// - Exception details with full stack traces
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// - Elasticsearch-specific context (node ID, request ID)
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```
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### System Property Configuration
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The utilities system respects various system properties for fine-tuning behavior.
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```java { .api }
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// Available system properties for configuration:
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// Control processor setting behavior
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"es.set.netty.runtime.available.processors" // Default: true
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// Force unpooled allocator usage
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"es.use_unpooled_allocator" // Default: false
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// Use Netty default allocator (not recommended)
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"es.unsafe.use_netty_default_allocator" // Default: false
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// Use Netty default chunk/page sizes (not recommended)  
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"es.unsafe.use_netty_default_chunk_and_page_size" // Default: false
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// Control network tracing for debugging
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"es.insecure_network_trace_enabled" // Default: false
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```
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**System Property Examples:**
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```java
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// Configure allocator behavior
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System.setProperty("es.use_unpooled_allocator", "true");
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ByteBufAllocator allocator = NettyAllocator.getAllocator(); // Will be unpooled
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// Enable network tracing for debugging (security warning applies)
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System.setProperty("es.insecure_network_trace_enabled", "true");
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// Enables detailed network packet tracing - should not be used in production
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// Disable processor setting in test environments
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System.setProperty("es.set.netty.runtime.available.processors", "false");
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```
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### Performance Monitoring Utilities
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Utilities for monitoring and analyzing Netty performance characteristics.
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```java { .api }
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/**
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 * Performance monitoring utilities for Netty operations
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 * Provides metrics collection and analysis capabilities
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 */
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public class NettyPerformanceUtils {
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    /**
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     * Gets current buffer pool statistics
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     * @return Map of buffer pool metrics
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     */
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    public static Map<String, Object> getBufferPoolStats();
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    /**
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     * Gets EventLoopGroup utilization metrics
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     * @param group EventLoopGroup to analyze
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     * @return Utilization statistics
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     */
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    public static Map<String, Object> getEventLoopStats(EventLoopGroup group);
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    /**
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     * Gets channel pipeline performance metrics
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     * @param channel Channel to analyze
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     * @return Pipeline performance data
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     */
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    public static Map<String, Object> getPipelineStats(Channel channel);
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}
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```
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### Configuration Validation Utilities
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Utilities for validating Netty configuration and identifying potential issues.
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```java { .api }
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/**
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 * Configuration validation utilities
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 * Helps identify configuration issues and optimization opportunities
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 */
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public class NettyConfigValidator {
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    /**
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     * Validates transport configuration settings
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     * @param settings Transport settings to validate
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     * @return List of validation issues or recommendations
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     */
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    public static List<String> validateTransportConfig(Settings settings);
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    /**
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     * Validates HTTP configuration settings
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     * @param settings HTTP settings to validate  
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     * @return List of validation issues or recommendations
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     */
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    public static List<String> validateHttpConfig(Settings settings);
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    /**
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     * Validates buffer allocation configuration
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     * @return List of allocation configuration issues
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     */
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    public static List<String> validateBufferConfig();
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}
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```
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**Configuration Validation Example:**
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```java
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Settings settings = Settings.builder()
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    .put("transport.netty.worker_count", 1000) // Too high
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    .put("http.netty.worker_count", -1) // Invalid
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    .build();
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List<String> transportIssues = NettyConfigValidator.validateTransportConfig(settings);
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// Returns: ["Worker count 1000 exceeds recommended maximum of 64"]
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List<String> httpIssues = NettyConfigValidator.validateHttpConfig(settings);  
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// Returns: ["HTTP worker count must be >= 0"]
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List<String> bufferIssues = NettyConfigValidator.validateBufferConfig();
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// Returns potential buffer allocation warnings based on JVM config
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```
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## Integration with Elasticsearch Infrastructure
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The utilities system integrates with Elasticsearch through several mechanisms:
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1. **Settings Integration**: Utilities respect Elasticsearch settings and configuration patterns
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2. **Logging Integration**: Uses Elasticsearch's logging framework for consistent log formatting
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3. **Metrics Integration**: Performance utilities integrate with Elasticsearch's metrics system
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4. **Error Handling**: Exceptions and errors follow Elasticsearch patterns and conventions
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5. **Resource Management**: Utilities coordinate with Elasticsearch's resource management systems
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6. **Plugin Integration**: Utilities can be extended by other plugins through standard Elasticsearch patterns
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The utilities provide the foundational optimizations and tools necessary for efficient, reliable, and maintainable Netty-based networking in Elasticsearch clusters.