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281 lines
8.8 KiB
281 lines
8.8 KiB
package protocol
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import (
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"bufio"
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"encoding/binary"
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"fmt"
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"io"
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"net"
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)
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// Handler processes Kafka protocol requests from clients
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type Handler struct {
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}
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func NewHandler() *Handler {
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return &Handler{}
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}
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// HandleConn processes a single client connection
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func (h *Handler) HandleConn(conn net.Conn) error {
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defer conn.Close()
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r := bufio.NewReader(conn)
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w := bufio.NewWriter(conn)
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defer w.Flush()
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for {
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// Read message size (4 bytes)
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var sizeBytes [4]byte
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if _, err := io.ReadFull(r, sizeBytes[:]); err != nil {
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if err == io.EOF {
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return nil // clean disconnect
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}
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return fmt.Errorf("read size: %w", err)
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}
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size := binary.BigEndian.Uint32(sizeBytes[:])
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if size == 0 || size > 1024*1024 { // 1MB limit
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return fmt.Errorf("invalid message size: %d", size)
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}
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// Read the message
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messageBuf := make([]byte, size)
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if _, err := io.ReadFull(r, messageBuf); err != nil {
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return fmt.Errorf("read message: %w", err)
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}
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// Parse at least the basic header to get API key and correlation ID
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if len(messageBuf) < 8 {
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return fmt.Errorf("message too short")
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}
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apiKey := binary.BigEndian.Uint16(messageBuf[0:2])
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apiVersion := binary.BigEndian.Uint16(messageBuf[2:4])
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correlationID := binary.BigEndian.Uint32(messageBuf[4:8])
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// Handle the request based on API key
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var response []byte
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var err error
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switch apiKey {
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case 18: // ApiVersions
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response, err = h.handleApiVersions(correlationID)
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case 3: // Metadata
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response, err = h.handleMetadata(correlationID, messageBuf[8:]) // skip header
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case 2: // ListOffsets
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response, err = h.handleListOffsets(correlationID, messageBuf[8:]) // skip header
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default:
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err = fmt.Errorf("unsupported API key: %d (version %d)", apiKey, apiVersion)
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}
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if err != nil {
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return fmt.Errorf("handle request: %w", err)
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}
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// Write response size and data
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responseSizeBytes := make([]byte, 4)
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binary.BigEndian.PutUint32(responseSizeBytes, uint32(len(response)))
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if _, err := w.Write(responseSizeBytes); err != nil {
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return fmt.Errorf("write response size: %w", err)
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}
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if _, err := w.Write(response); err != nil {
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return fmt.Errorf("write response: %w", err)
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}
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if err := w.Flush(); err != nil {
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return fmt.Errorf("flush response: %w", err)
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}
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}
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}
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func (h *Handler) handleApiVersions(correlationID uint32) ([]byte, error) {
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// Build ApiVersions response manually
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// Response format: correlation_id(4) + error_code(2) + num_api_keys(4) + api_keys + throttle_time(4)
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response := make([]byte, 0, 64)
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// Correlation ID
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correlationIDBytes := make([]byte, 4)
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binary.BigEndian.PutUint32(correlationIDBytes, correlationID)
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response = append(response, correlationIDBytes...)
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// Error code (0 = no error)
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response = append(response, 0, 0)
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// Number of API keys (compact array format in newer versions, but using basic format for simplicity)
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response = append(response, 0, 0, 0, 3) // 3 API keys
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// API Key 18 (ApiVersions): api_key(2) + min_version(2) + max_version(2)
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response = append(response, 0, 18) // API key 18
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response = append(response, 0, 0) // min version 0
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response = append(response, 0, 3) // max version 3
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// API Key 3 (Metadata): api_key(2) + min_version(2) + max_version(2)
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response = append(response, 0, 3) // API key 3
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response = append(response, 0, 0) // min version 0
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response = append(response, 0, 7) // max version 7
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// API Key 2 (ListOffsets): api_key(2) + min_version(2) + max_version(2)
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response = append(response, 0, 2) // API key 2
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response = append(response, 0, 0) // min version 0
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response = append(response, 0, 5) // max version 5
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// Throttle time (4 bytes, 0 = no throttling)
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response = append(response, 0, 0, 0, 0)
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return response, nil
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}
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func (h *Handler) handleMetadata(correlationID uint32, requestBody []byte) ([]byte, error) {
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// For now, ignore the request body content (topics filter, etc.)
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// Build minimal Metadata response
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// Response format: correlation_id(4) + throttle_time(4) + brokers + cluster_id + controller_id + topics
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response := make([]byte, 0, 256)
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// Correlation ID
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correlationIDBytes := make([]byte, 4)
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binary.BigEndian.PutUint32(correlationIDBytes, correlationID)
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response = append(response, correlationIDBytes...)
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// Throttle time (4 bytes, 0 = no throttling)
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response = append(response, 0, 0, 0, 0)
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// Brokers array length (4 bytes) - 1 broker (this gateway)
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response = append(response, 0, 0, 0, 1)
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// Broker 0: node_id(4) + host + port(4) + rack
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response = append(response, 0, 0, 0, 0) // node_id = 0
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// Host string: length(2) + "localhost"
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host := "localhost"
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response = append(response, 0, byte(len(host)))
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response = append(response, []byte(host)...)
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// Port (4 bytes) - 9092 (standard Kafka port)
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response = append(response, 0, 0, 0x23, 0x84) // 9092 in big-endian
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// Rack - nullable string, using null (-1 length)
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response = append(response, 0xFF, 0xFF) // null rack
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// Cluster ID - nullable string, using null
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response = append(response, 0xFF, 0xFF) // null cluster_id
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// Controller ID (4 bytes) - -1 (no controller)
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response = append(response, 0xFF, 0xFF, 0xFF, 0xFF)
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// Topics array length (4 bytes) - 0 topics for now
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response = append(response, 0, 0, 0, 0)
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return response, nil
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}
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func (h *Handler) handleListOffsets(correlationID uint32, requestBody []byte) ([]byte, error) {
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// Parse minimal request to understand what's being asked
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// For this stub, we'll just return stub responses for any requested topic/partition
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// Request format after client_id: topics_array
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if len(requestBody) < 6 { // at minimum need client_id_size(2) + topics_count(4)
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return nil, fmt.Errorf("ListOffsets request too short")
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}
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// Skip client_id: client_id_size(2) + client_id_data
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clientIDSize := binary.BigEndian.Uint16(requestBody[0:2])
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offset := 2 + int(clientIDSize)
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if len(requestBody) < offset+4 {
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return nil, fmt.Errorf("ListOffsets request missing topics count")
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}
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topicsCount := binary.BigEndian.Uint32(requestBody[offset : offset+4])
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offset += 4
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response := make([]byte, 0, 256)
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// Correlation ID
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correlationIDBytes := make([]byte, 4)
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binary.BigEndian.PutUint32(correlationIDBytes, correlationID)
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response = append(response, correlationIDBytes...)
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// Throttle time (4 bytes, 0 = no throttling)
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response = append(response, 0, 0, 0, 0)
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// Topics count (same as request)
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topicsCountBytes := make([]byte, 4)
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binary.BigEndian.PutUint32(topicsCountBytes, topicsCount)
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response = append(response, topicsCountBytes...)
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// Process each requested topic
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for i := uint32(0); i < topicsCount && offset < len(requestBody); i++ {
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if len(requestBody) < offset+2 {
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break
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}
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// Parse topic name
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topicNameSize := binary.BigEndian.Uint16(requestBody[offset : offset+2])
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offset += 2
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if len(requestBody) < offset+int(topicNameSize)+4 {
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break
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}
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topicName := requestBody[offset : offset+int(topicNameSize)]
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offset += int(topicNameSize)
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// Parse partitions count for this topic
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partitionsCount := binary.BigEndian.Uint32(requestBody[offset : offset+4])
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offset += 4
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// Response: topic_name_size(2) + topic_name + partitions_array
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response = append(response, byte(topicNameSize>>8), byte(topicNameSize))
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response = append(response, topicName...)
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partitionsCountBytes := make([]byte, 4)
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binary.BigEndian.PutUint32(partitionsCountBytes, partitionsCount)
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response = append(response, partitionsCountBytes...)
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// Process each partition
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for j := uint32(0); j < partitionsCount && offset+12 <= len(requestBody); j++ {
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// Parse partition request: partition_id(4) + timestamp(8)
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partitionID := binary.BigEndian.Uint32(requestBody[offset : offset+4])
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timestamp := int64(binary.BigEndian.Uint64(requestBody[offset+4 : offset+12]))
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offset += 12
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// Response: partition_id(4) + error_code(2) + timestamp(8) + offset(8)
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partitionIDBytes := make([]byte, 4)
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binary.BigEndian.PutUint32(partitionIDBytes, partitionID)
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response = append(response, partitionIDBytes...)
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// Error code (0 = no error)
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response = append(response, 0, 0)
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// For stub: return the original timestamp for timestamp queries, or current time for earliest/latest
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var responseTimestamp int64
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var responseOffset int64
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switch timestamp {
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case -2: // earliest offset
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responseTimestamp = 0
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responseOffset = 0
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case -1: // latest offset
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responseTimestamp = 1000000000 // some timestamp
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responseOffset = 0 // stub: no messages yet
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default: // specific timestamp
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responseTimestamp = timestamp
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responseOffset = 0 // stub: no messages at any timestamp
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}
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timestampBytes := make([]byte, 8)
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binary.BigEndian.PutUint64(timestampBytes, uint64(responseTimestamp))
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response = append(response, timestampBytes...)
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offsetBytes := make([]byte, 8)
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binary.BigEndian.PutUint64(offsetBytes, uint64(responseOffset))
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response = append(response, offsetBytes...)
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}
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}
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return response, nil
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}
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