HTTP Server Transport

/**
 * Netty4 implementation of HTTP server transport for REST API access
 * Handles HTTP requests, response processing, and client connections
 */
public class Netty4HttpServerTransport extends AbstractHttpServerTransport {
    // HTTP-specific configuration settings
    public static Setting<Integer> SETTING_HTTP_NETTY_MAX_COMPOSITE_BUFFER_COMPONENTS;
    public static final Setting<Integer> SETTING_HTTP_WORKER_COUNT;
    public static final Setting<ByteSizeValue> SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_SIZE;
}

/**
 * Maximum number of components in composite buffers for HTTP responses
 * Higher values allow more efficient memory usage for large responses
 */
public static Setting<Integer> SETTING_HTTP_NETTY_MAX_COMPOSITE_BUFFER_COMPONENTS = new Setting<>(
    "http.netty.max_composite_buffer_components",
    (s) -> {
        // Calculate based on max content length
        ByteSizeValue maxContentLength = SETTING_HTTP_MAX_CONTENT_LENGTH.get(s);
        return Integer.toString(Math.max((int) (maxContentLength.getBytes() / 1024), 64));
    },
    (s) -> Setting.parseInt(s, 2, "http.netty.max_composite_buffer_components"),
    Property.NodeScope
);

/**
 * Number of worker threads for HTTP request processing
 * 0 means shared with transport layer, >0 creates dedicated HTTP workers
 */
public static final Setting<Integer> SETTING_HTTP_WORKER_COUNT = Setting.intSetting(
    "http.netty.worker_count", 
    0, 
    Property.NodeScope
);

/**
 * Initial buffer size for HTTP receive buffer prediction
 * Netty adaptively adjusts based on actual request sizes
 */
public static final Setting<ByteSizeValue> SETTING_HTTP_NETTY_RECEIVE_PREDICTOR_SIZE = Setting.byteSizeSetting(
    "http.netty.receive_predictor_size",
    new ByteSizeValue(64, ByteSizeUnit.KB),
    Property.NodeScope
);

Settings httpSettings = Settings.builder()
    .put("http.netty.worker_count", 0) // Share with transport
    .put("http.netty.max_composite_buffer_components", 128)
    .put("http.netty.receive_predictor_size", "64kb")
    .build();

/**
 * Netty4 implementation of HTTP request interface
 * Wraps Netty HttpRequest with Elasticsearch-specific methods
 */
public class Netty4HttpRequest implements HttpRequest {
    /**
     * Gets HTTP method for this request
     * @return REST request method (GET, POST, PUT, DELETE, etc.)
     */
    RestRequest.Method method();
    
    /**
     * Gets request URI including path and query parameters
     * @return Full request URI string
     */
    String uri();
    
    /**
     * Gets request body content as bytes
     * @return BytesReference containing request body
     */
    BytesReference content();
    
    /**
     * Releases request resources immediately
     * Must be called when request processing is complete
     */
    void release();
    
    /**
     * Creates a copy of request and releases original
     * Useful for async processing where original request lifecycle differs
     * @return New HttpRequest copy with independent lifecycle
     */
    HttpRequest releaseAndCopy();
    
    /**
     * Gets all HTTP headers as map
     * @return Map of header names to list of values
     */
    Map<String, List<String>> getHeaders();
    
    /**
     * Gets cookies from request headers
     * @return List of cookie strings
     */
    List<String> strictCookies();
    
    /**
     * Gets HTTP protocol version
     * @return HttpVersion (HTTP/1.0, HTTP/1.1, etc.)
     */
    HttpVersion protocolVersion();
    
    /**
     * Removes specific header from request
     * @param header Header name to remove
     * @return Modified HttpRequest instance
     */
    HttpRequest removeHeader(String header);
    
    /**
     * Creates HTTP response for this request
     * @param status HTTP status code
     * @param contentRef Response body content
     * @return Netty4HttpResponse ready to send
     */
    Netty4HttpResponse createResponse(RestStatus status, BytesReference contentRef);
    
    /**
     * Gets exception from inbound request processing if any
     * @return Exception or null if no error
     */
    Exception getInboundException();
    
    /**
     * Gets underlying Netty HTTP request object
     * @return Native Netty HttpRequest for low-level access
     */
    io.netty.handler.codec.http.HttpRequest getNettyRequest();
}

// Request received by HTTP transport
Netty4HttpRequest request = // from transport pipeline

// Process request details
RestRequest.Method method = request.method(); // GET, POST, etc.
String uri = request.uri(); // "/index/_search?q=query"
BytesReference body = request.content(); // Request payload

// Access headers
Map<String, List<String>> headers = request.getHeaders();
String contentType = headers.get("Content-Type").get(0);

// Create response
Netty4HttpResponse response = request.createResponse(
    RestStatus.OK, 
    new BytesArray("{\"result\":\"success\"}")
);

// Always release request resources
request.release();

/**
 * Translates Netty HTTP method to Elasticsearch REST method
 * @param httpMethod Netty HttpMethod instance
 * @return Corresponding RestRequest.Method
 */
public static RestRequest.Method translateRequestMethod(HttpMethod httpMethod);

/**
 * Converts Netty HTTP headers to standard Java map format
 * @param httpHeaders Netty HttpHeaders instance
 * @return Map with header names and values
 */
public static Map<String, List<String>> getHttpHeadersAsMap(HttpHeaders httpHeaders);

/**
 * Netty4 implementation of HTTP response
 * Extends Netty's DefaultFullHttpResponse with Elasticsearch functionality
 */
public class Netty4HttpResponse extends DefaultFullHttpResponse implements HttpResponse {
    // Response creation and content management
    // Headers manipulation and status setting
    // Resource lifecycle management
}

/**
 * HTTP channel for client connections
 * Handles request/response exchange with individual HTTP clients
 */
public class Netty4HttpChannel implements HttpChannel {
    /**
     * Sends HTTP response to client asynchronously
     * @param response HTTP response to send
     * @param listener Callback for send completion
     */
    void sendResponse(HttpResponse response, ActionListener<Void> listener);
    
    /**
     * Gets local address for this HTTP connection
     * @return Local InetSocketAddress
     */
    InetSocketAddress getLocalAddress();
    
    /**
     * Gets remote client address for this connection
     * @return Remote InetSocketAddress of HTTP client
     */
    InetSocketAddress getRemoteAddress();
    
    /**
     * Closes HTTP connection to client
     */
    void close();
}

/**
 * HTTP server channel for accepting client connections
 * Binds to configured port and accepts HTTP connections
 */
public class Netty4HttpServerChannel implements HttpServerChannel {
    /**
     * Gets local socket address server is bound to
     * @return Local InetSocketAddress for HTTP server
     */
    InetSocketAddress getLocalAddress();
    
    /**
     * Adds listener for server channel close events
     * @param listener Callback for close notification
     */
    void addCloseListener(ActionListener<Void> listener);
    
    /**
     * Checks if HTTP server is currently accepting connections
     * @return true if server is open, false otherwise
     */
    boolean isOpen();
    
    /**
     * Closes HTTP server and stops accepting connections
     */
    void close();
}

/**
 * HTTP request pipelining handler supporting concurrent request processing
 * Ensures responses are sent in same order as requests even with async processing
 */
public class Netty4HttpPipeliningHandler extends ChannelDuplexHandler {
    // Manages request/response ordering for HTTP pipelining
    // Handles concurrent request processing with proper sequencing
}

/**
 * HTTP header validation handler
 * Validates headers according to HTTP specifications and security policies
 */
public class Netty4HttpHeaderValidator extends ChannelInboundHandlerAdapter {
    // Validates HTTP headers for security and compliance
    // Rejects malformed or dangerous header combinations
}