for kafka, support correlation id cache.

@@ -221,8 +221,8 @@ int SrsKafkaBytes::decode(SrsBuffer* buf)
 SrsKafkaRequestHeader::SrsKafkaRequestHeader()
 {
     _size = 0;
-    api_key = api_version = 0;
-    correlation_id = 0;
+    _api_key = api_version = 0;
+    _correlation_id = 0;
     client_id = new SrsKafkaString();
 }
 
@@ -246,49 +246,69 @@ int SrsKafkaRequestHeader::total_size()
     return 4 + _size;
 }
 
+void SrsKafkaRequestHeader::set_total_size(int s)
+{
+    _size = s - 4;
+}
+
+int32_t SrsKafkaRequestHeader::correlation_id()
+{
+    return _correlation_id;
+}
+
+void SrsKafkaRequestHeader::set_correlation_id(int32_t cid)
+{
+    _correlation_id = cid;
+}
+
+SrsKafkaApiKey SrsKafkaRequestHeader::api_key()
+{
+    return (SrsKafkaApiKey)_api_key;
+}
+
+void SrsKafkaRequestHeader::set_api_key(SrsKafkaApiKey key)
+{
+    _api_key = (int16_t)key;
+}
+
 bool SrsKafkaRequestHeader::is_producer_request()
 {
-    return api_key == SrsKafkaApiKeyProduceRequest;
+    return _api_key == SrsKafkaApiKeyProduceRequest;
 }
 
 bool SrsKafkaRequestHeader::is_fetch_request()
 {
-    return api_key == SrsKafkaApiKeyFetchRequest;
+    return _api_key == SrsKafkaApiKeyFetchRequest;
 }
 
 bool SrsKafkaRequestHeader::is_offset_request()
 {
-    return api_key == SrsKafkaApiKeyOffsetRequest;
+    return _api_key == SrsKafkaApiKeyOffsetRequest;
 }
 
 bool SrsKafkaRequestHeader::is_metadata_request()
 {
-    return api_key == SrsKafkaApiKeyMetadataRequest;
+    return _api_key == SrsKafkaApiKeyMetadataRequest;
 }
 
 bool SrsKafkaRequestHeader::is_offset_commit_request()
 {
-    return api_key == SrsKafkaApiKeyOffsetCommitRequest;
+    return _api_key == SrsKafkaApiKeyOffsetCommitRequest;
 }
 
 bool SrsKafkaRequestHeader::is_offset_fetch_request()
 {
-    return api_key == SrsKafkaApiKeyOffsetFetchRequest;
+    return _api_key == SrsKafkaApiKeyOffsetFetchRequest;
 }
 
 bool SrsKafkaRequestHeader::is_consumer_metadata_request()
 {
-    return api_key == SrsKafkaApiKeyConsumerMetadataRequest;
-}
-
-void SrsKafkaRequestHeader::set_api_key(SrsKafkaApiKey key)
-{
-    api_key = (int16_t)key;
+    return _api_key == SrsKafkaApiKeyConsumerMetadataRequest;
 }
 
 int SrsKafkaRequestHeader::size()
 {
-    return 4 + _size;
+    return 4 + header_size();
 }
 
 int SrsKafkaRequestHeader::encode(SrsBuffer* buf)
@@ -302,9 +322,9 @@ int SrsKafkaRequestHeader::encode(SrsBuffer* buf)
     }
     
     buf->write_4bytes(_size);
-    buf->write_2bytes(api_key);
+    buf->write_2bytes(_api_key);
     buf->write_2bytes(api_version);
-    buf->write_4bytes(correlation_id);
+    buf->write_4bytes(_correlation_id);
     
     if ((ret = client_id->encode(buf)) != ERROR_SUCCESS) {
         srs_error("kafka encode request client_id failed. ret=%d", ret);
@@ -335,9 +355,9 @@ int SrsKafkaRequestHeader::decode(SrsBuffer* buf)
         srs_error("kafka decode request message failed. ret=%d", ret);
         return ret;
     }
-    api_key = buf->read_2bytes();
+    _api_key = buf->read_2bytes();
     api_version = buf->read_2bytes();
-    correlation_id = buf->read_4bytes();
+    _correlation_id = buf->read_4bytes();
     
     if ((ret = client_id->decode(buf)) != ERROR_SUCCESS) {
         srs_error("kafka decode request client_id failed. ret=%d", ret);
@@ -372,9 +392,14 @@ int SrsKafkaResponseHeader::total_size()
     return 4 + _size;
 }
 
+void SrsKafkaResponseHeader::set_total_size(int s)
+{
+    _size = s - 4;
+}
+
 int SrsKafkaResponseHeader::size()
 {
-    return 4 + _size;
+    return 4 + header_size();
 }
 
 int SrsKafkaResponseHeader::encode(SrsBuffer* buf)
@@ -452,12 +477,28 @@ SrsKafkaMessageSet::~SrsKafkaMessageSet()
 
 SrsKafkaRequest::SrsKafkaRequest()
 {
+    header.set_correlation_id(SrsKafkaCorrelationPool::instance()->generate_correlation_id());
 }
 
 SrsKafkaRequest::~SrsKafkaRequest()
 {
 }
 
+void SrsKafkaRequest::update_header(int s)
+{
+    header.set_total_size(s);
+}
+
+int32_t SrsKafkaRequest::correlation_id()
+{
+    return header.correlation_id();
+}
+
+SrsKafkaApiKey SrsKafkaRequest::api_key()
+{
+    return header.api_key();
+}
+
 int SrsKafkaRequest::size()
 {
     return header.size();
@@ -481,6 +522,11 @@ SrsKafkaResponse::~SrsKafkaResponse()
 {
 }
 
+void SrsKafkaResponse::update_header(int s)
+{
+    header.set_total_size(s);
+}
+
 int SrsKafkaResponse::size()
 {
     return header.size();
@@ -589,6 +635,50 @@ int SrsKafkaTopicMetadataResponse::decode(SrsBuffer* buf)
     return ret;
 }
 
+SrsKafkaCorrelationPool* SrsKafkaCorrelationPool::_instance = new SrsKafkaCorrelationPool();
+
+SrsKafkaCorrelationPool* SrsKafkaCorrelationPool::instance()
+{
+    return _instance;
+}
+
+SrsKafkaCorrelationPool::SrsKafkaCorrelationPool()
+{
+}
+
+SrsKafkaCorrelationPool::~SrsKafkaCorrelationPool()
+{
+    correlation_ids.clear();
+}
+
+int32_t SrsKafkaCorrelationPool::generate_correlation_id()
+{
+    static int32_t cid = 1;
+    return cid++;
+}
+
+void SrsKafkaCorrelationPool::set(int32_t correlation_id, SrsKafkaApiKey request)
+{
+    correlation_ids[correlation_id] = request;
+}
+
+void SrsKafkaCorrelationPool::unset(int32_t correlation_id)
+{
+    std::map<int32_t, SrsKafkaApiKey>::iterator it = correlation_ids.find(correlation_id);
+    if (it != correlation_ids.end()) {
+        correlation_ids.erase(it);
+    }
+}
+
+SrsKafkaApiKey SrsKafkaCorrelationPool::get(int32_t correlation_id)
+{
+    if (correlation_ids.find(correlation_id) == correlation_ids.end()) {
+        return SrsKafkaApiKeyUnknown;
+    }
+    
+    return correlation_ids[correlation_id];
+}
+
 SrsKafkaProtocol::SrsKafkaProtocol(ISrsProtocolReaderWriter* io)
 {
     skt = io;
@@ -610,6 +700,13 @@ int SrsKafkaProtocol::send_and_free_message(SrsKafkaRequest* msg)
         return ret;
     }
     
+    // update the header of message.
+    msg->update_header(size);
+    
+    // cache the request correlation id to discovery response message.
+    SrsKafkaCorrelationPool* pool = SrsKafkaCorrelationPool::instance();
+    pool->set(msg->correlation_id(), msg->api_key());
+    
     // TODO: FIXME: refine for performance issue.
     char* bytes = new char[size];
     SrsAutoFree(char, bytes);

@@ -31,6 +31,7 @@
 
 #include <vector>
 #include <string>
+#include <map>
 
 #include <srs_kernel_buffer.hpp>
 #include <srs_kernel_error.hpp>
@@ -45,6 +46,8 @@ class ISrsProtocolReaderWriter;
  */
 enum SrsKafkaApiKey
 {
+    SrsKafkaApiKeyUnknown = -1,
+    
     SrsKafkaApiKeyProduceRequest = 0,
     SrsKafkaApiKeyFetchRequest = 1,
     SrsKafkaApiKeyOffsetRequest = 2,
@@ -203,7 +206,7 @@ private:
      * a metadata request, a produce request, a fetch request, etc).
      * @remark MetadataRequest | ProduceRequest | FetchRequest | OffsetRequest | OffsetCommitRequest | OffsetFetchRequest
      */
-    int16_t api_key;
+    int16_t _api_key;
     /**
      * This is a numeric version number for this api. We version each API and 
      * this version number allows the server to properly interpret the request 
@@ -216,7 +219,7 @@ private:
      * the response by the server, unmodified. It is useful for matching
      * request and response between the client and server.
      */
-    int32_t correlation_id;
+    int32_t _correlation_id;
     /**
      * This is a user supplied identifier for the client application. 
      * The user can use any identifier they like and it will be used
@@ -254,6 +257,28 @@ private:
     virtual int total_size();
 public:
     /**
+     * when got the whole message size, update the header.
+     * @param s the whole message, including the 4 bytes size size.
+     */
+    virtual void set_total_size(int s);
+    /**
+     * get the correlation id for message.
+     */
+    virtual int32_t correlation_id();
+    /**
+     * set the correlation id for message.
+     */
+    virtual void set_correlation_id(int32_t cid);
+    /**
+     * get the api key of header for message.
+     */
+    virtual SrsKafkaApiKey api_key();
+    /**
+     * set the api key of header for message.
+     */
+    virtual void set_api_key(SrsKafkaApiKey key);
+public:
+    /**
      * the api key enumeration.
      * @see https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol#AGuideToTheKafkaProtocol-ApiKeys
      */
@@ -264,8 +289,6 @@ public:
     virtual bool is_offset_commit_request();
     virtual bool is_offset_fetch_request();
     virtual bool is_consumer_metadata_request();
-    // set the api key.
-    virtual void set_api_key(SrsKafkaApiKey key);
 // interface ISrsCodec
 public:
     virtual int size();
@@ -321,6 +344,12 @@ private:
      * the total size of the request, includes the 4B size.
      */
     virtual int total_size();
+public:
+    /**
+     * when got the whole message size, update the header.
+     * @param s the whole message, including the 4 bytes size size.
+     */
+    virtual void set_total_size(int s);
 // interface ISrsCodec
 public:
     virtual int size();
@@ -403,6 +432,20 @@ protected:
 public:
     SrsKafkaRequest();
     virtual ~SrsKafkaRequest();
+public:
+    /**
+     * update the size in header.
+     * @param s an int value specifies the size of message in header.
+     */
+    virtual void update_header(int s);
+    /**
+     * get the correlation id of header for message. 
+     */
+    virtual int32_t correlation_id();
+    /**
+     * get the api key of request.
+     */
+    virtual SrsKafkaApiKey api_key();
 // interface ISrsCodec
 public:
     virtual int size();
@@ -420,6 +463,12 @@ protected:
 public:
     SrsKafkaResponse();
     virtual ~SrsKafkaResponse();
+public:
+    /**
+     * update the size in header.
+     * @param s an int value specifies the size of message in header.
+     */
+    virtual void update_header(int s);
 // interface ISrsCodec
 public:
     virtual int size();
@@ -478,6 +527,32 @@ public:
 };
 
 /**
+ * the poll to discovery reponse.
+ * @param CorrelationId This is a user-supplied integer. It will be passed back 
+ *          in the response by the server, unmodified. It is useful for matching 
+ *          request and response between the client and server.
+ * @see https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol#AGuideToTheKafkaProtocol-Requests
+ */
+class SrsKafkaCorrelationPool
+{
+private:
+    static SrsKafkaCorrelationPool* _instance;
+public:
+    static SrsKafkaCorrelationPool* instance();
+private:
+    std::map<int32_t, SrsKafkaApiKey> correlation_ids;
+private:
+    SrsKafkaCorrelationPool();
+public:
+    virtual ~SrsKafkaCorrelationPool();
+public:
+    virtual int32_t generate_correlation_id();
+    virtual void set(int32_t correlation_id, SrsKafkaApiKey request);
+    virtual void unset(int32_t correlation_id);
+    virtual SrsKafkaApiKey get(int32_t correlation_id);
+};
+
+/**
  * the kafka protocol stack, use to send and recv kakfa messages.
  */
 class SrsKafkaProtocol