Improve metadata protocol handling

  - add MetadataRequest and MetadataResponse namedtuples
  - add TopicMetadata namedtuple
  - add error codes to Topic and Partition Metadata
  - add KafkaClient.send_metadata_request() method
  - KafkaProtocol.decode_metadata_response changed
    to return a MetadataResponse object
    so that it is consistent with server api: [broker_list, topic_list]

1 files changed, 21 insertions, 9 deletions

diff --git a/kafka/client.py b/kafka/client.py
index 8630f66..e14694f 100644
--- a/kafka/client.py
+++ b/kafka/client.py
@@ -6,7 +6,7 @@ import logging
 import time
 import kafka.common
 
-from kafka.common import (TopicAndPartition,
+from kafka.common import (TopicAndPartition, BrokerMetadata,
                           ConnectionError, FailedPayloadsError,
                           PartitionUnavailableError, LeaderUnavailableError, KafkaUnavailableError,
                           KafkaTimeoutError,
@@ -83,20 +83,26 @@ class KafkaClient(object):
         """
         return KafkaClient.ID_GEN.next()
 
-    def _send_broker_unaware_request(self, requestId, request):
+    def _send_broker_unaware_request(self, payloads, encoder_fn, decoder_fn):
         """
         Attempt to send a broker-agnostic request to one of the available
         brokers. Keep trying until you succeed.
         """
         for (host, port) in self.hosts:
+            requestId = self._next_id()
             try:
                 conn = self._get_conn(host, port)
+                request = encoder_fn(client_id=self.client_id,
+                                     correlation_id=requestId,
+                                     payloads=payloads)
+
                 conn.send(requestId, request)
                 response = conn.recv(requestId)
-                return response
+                return decoder_fn(response)
+
             except Exception as e:
                 log.warning("Could not send request [%r] to server %s:%i, "
-                            "trying next server: %s" % (request, host, port, e))
+                            "trying next server: %s" % (requestId, host, port, e))
 
         raise KafkaUnavailableError("All servers failed to process request")
 
@@ -246,13 +252,11 @@ class KafkaClient(object):
         Discover brokers and metadata for a set of topics. This function is called
         lazily whenever metadata is unavailable.
         """
-        request_id = self._next_id()
-        request = KafkaProtocol.encode_metadata_request(self.client_id,
-                                                        request_id, topics)
 
-        response = self._send_broker_unaware_request(request_id, request)
+        resp = self.send_metadata_request(topics)
 
-        (brokers, topics) = KafkaProtocol.decode_metadata_response(response)
+        brokers = dict([(broker.nodeId, broker) for broker in resp.brokers])
+        topics = dict([(t.topic, dict([(p.partition, p) for p in t.partitions]) ) for t in resp.topics])
 
         log.debug("Broker metadata: %s", brokers)
         log.debug("Topic metadata: %s", topics)
@@ -276,6 +280,14 @@ class KafkaClient(object):
                 else:
                     self.topics_to_brokers[topic_part] = brokers[meta.leader]
 
+    def send_metadata_request(self, payloads=[], fail_on_error=True,
+                              callback=None):
+
+        encoder = KafkaProtocol.encode_metadata_request
+        decoder = KafkaProtocol.decode_metadata_response
+
+        return self._send_broker_unaware_request(payloads, encoder, decoder)
+
     def send_produce_request(self, payloads=[], acks=1, timeout=1000,
                              fail_on_error=True, callback=None):
         """