Merge pull request #122 from mrtheb/multihosts

Support for multiple hosts on KafkaClient boostrap (improves on #70)

Author: rdiomar

README.md

@@ -29,7 +29,7 @@ from kafka.client import KafkaClient
 from kafka.consumer import SimpleConsumer
 from kafka.producer import SimpleProducer, KeyedProducer
 
-kafka = KafkaClient("localhost", 9092)
+kafka = KafkaClient("localhost:9092")
 
 # To send messages synchronously
 producer = SimpleProducer(kafka)
@@ -80,7 +80,7 @@ from kafka.client import KafkaClient
 from kafka.producer import KeyedProducer
 from kafka.partitioner import HashedPartitioner, RoundRobinPartitioner
 
-kafka = KafkaClient("localhost", 9092)
+kafka = KafkaClient("localhost:9092")
 
 # HashedPartitioner is default
 producer = KeyedProducer(kafka)
@@ -95,7 +95,7 @@ producer = KeyedProducer(kafka, partitioner=RoundRobinPartitioner)
 from kafka.client import KafkaClient
 from kafka.consumer import MultiProcessConsumer
 
-kafka = KafkaClient("localhost", 9092)
+kafka = KafkaClient("localhost:9092")
 
 # This will split the number of partitions among two processes
 consumer = MultiProcessConsumer(kafka, "my-group", "my-topic", num_procs=2)
@@ -115,7 +115,7 @@ for message in consumer.get_messages(count=5, block=True, timeout=4):
 
 ```python
 from kafka.client import KafkaClient
-kafka = KafkaClient("localhost", 9092)
+kafka = KafkaClient("localhost:9092")
 req = ProduceRequest(topic="my-topic", partition=1,
     messages=[KafkaProdocol.encode_message("some message")])
 resps = kafka.send_produce_request(payloads=[req], fail_on_error=True)

example.py

@@ -14,7 +14,7 @@ def consume_example(client):
         print(message)
 
 def main():
-    client = KafkaClient("localhost", 9092)
+    client = KafkaClient("localhost:9092")
     produce_example(client)
     consume_example(client)
 

kafka/NOTES.md

@@ -18,7 +18,7 @@ There are a few levels of abstraction:
 
 # Possible API
 
-    client = KafkaClient("localhost", 9092)
+    client = KafkaClient("localhost:9092")
 
     producer = KafkaProducer(client, "topic")
     producer.send_string("hello")

kafka/client.py

@@ -10,7 +10,7 @@
                           BrokerResponseError, PartitionUnavailableError,
                           KafkaUnavailableError, KafkaRequestError)
 
-from kafka.conn import KafkaConnection, DEFAULT_SOCKET_TIMEOUT_SECONDS
+from kafka.conn import collect_hosts, KafkaConnection, DEFAULT_SOCKET_TIMEOUT_SECONDS
 from kafka.protocol import KafkaProtocol
 
 log = logging.getLogger("kafka")
@@ -24,14 +24,15 @@ class KafkaClient(object):
     # NOTE: The timeout given to the client should always be greater than the
     # one passed to SimpleConsumer.get_message(), otherwise you can get a
     # socket timeout.
-    def __init__(self, host, port, client_id=CLIENT_ID,
+    def __init__(self, hosts, client_id=CLIENT_ID,
                  timeout=DEFAULT_SOCKET_TIMEOUT_SECONDS):
         # We need one connection to bootstrap
         self.client_id = client_id
         self.timeout = timeout
-        self.conns = {               # (host, port) -> KafkaConnection
-            (host, port): KafkaConnection(host, port, timeout=timeout)
-        }
+        self.hosts = collect_hosts(hosts)
+
+        # create connections only when we need them
+        self.conns = {}
         self.brokers = {}            # broker_id -> BrokerMetadata
         self.topics_to_brokers = {}  # topic_id -> broker_id
         self.topic_partitions = {}   # topic_id -> [0, 1, 2, ...]
@@ -41,6 +42,15 @@ def __init__(self, host, port, client_id=CLIENT_ID,
     #   Private API  #
     ##################
 
+    def _get_conn(self, host, port):
+        "Get or create a connection to a broker using host and port"
+
+        host_key = (host, port)
+        if host_key not in self.conns:
+            self.conns[host_key] = KafkaConnection(host, port)
+
+        return self.conns[host_key]
+
     def _get_conn_for_broker(self, broker):
         """
         Get or create a connection to a broker
@@ -49,7 +59,7 @@ def _get_conn_for_broker(self, broker):
             self.conns[(broker.host, broker.port)] = \
                 KafkaConnection(broker.host, broker.port, timeout=self.timeout)
 
-        return self.conns[(broker.host, broker.port)]
+        return self._get_conn(broker.host, broker.port)
 
     def _get_leader_for_partition(self, topic, partition):
         key = TopicAndPartition(topic, partition)
@@ -72,7 +82,8 @@ def _send_broker_unaware_request(self, requestId, request):
         Attempt to send a broker-agnostic request to one of the available
         brokers. Keep trying until you succeed.
         """
-        for conn in self.conns.values():
+        for (host, port) in self.hosts:
+            conn = self._get_conn(host, port)
             try:
                 conn.send(requestId, request)
                 response = conn.recv(requestId)

kafka/conn.py

@@ -2,13 +2,39 @@
 import logging
 import socket
 import struct
+from random import shuffle
 from threading import local
 
 from kafka.common import ConnectionError
 
 log = logging.getLogger("kafka")
 
 DEFAULT_SOCKET_TIMEOUT_SECONDS = 120
+DEFAULT_KAFKA_PORT = 9092
+
+
+def collect_hosts(hosts, randomize=True):
+    """
+    Collects a comma-separated set of hosts (host:port) and optionnaly
+    randomize the returned list.
+    """
+
+    if isinstance(hosts, str):
+        hosts = hosts.strip().split(',')
+
+    result = []
+    for host_port in hosts:
+
+        res = host_port.split(':')
+        host = res[0]
+        port = int(res[1]) if len(res) > 1 else DEFAULT_KAFKA_PORT
+        result.append((host.strip(), port))
+
+    if randomize:
+        shuffle(result)
+
+    return result
+
 
 class KafkaConnection(local):
     """
@@ -81,7 +107,7 @@ def send(self, request_id, payload):
             sent = self._sock.sendall(payload)
             if sent is not None:
                 self._raise_connection_error()
-        except socket.error, e:
+        except socket.error:
             log.exception('Unable to send payload to Kafka')
             self._raise_connection_error()
 

setup.py

@@ -1,10 +1,10 @@
-import os.path
 import sys
 
 from setuptools import setup, Command
 
 
 class Tox(Command):
+
     user_options = []
 
     def initialize_options(self):

test/test_integration.py

@@ -33,7 +33,7 @@ def ensure_topic_creation(client, topic_name):
 
 class KafkaTestCase(unittest.TestCase):
     def setUp(self):
-        self.topic = "%s-%s" % (self.id()[self.id().rindex(".")+1:], random_string(10))
+        self.topic = "%s-%s" % (self.id()[self.id().rindex(".") + 1:], random_string(10))
         ensure_topic_creation(self.client, self.topic)
 
 
@@ -42,7 +42,7 @@ class TestKafkaClient(KafkaTestCase):
     def setUpClass(cls):  # noqa
         cls.zk = ZookeeperFixture.instance()
         cls.server = KafkaFixture.instance(0, cls.zk.host, cls.zk.port)
-        cls.client = KafkaClient(cls.server.host, cls.server.port)
+        cls.client = KafkaClient('%s:%d' % (cls.server.host, cls.server.port))
 
     @classmethod
     def tearDownClass(cls):  # noqa
@@ -578,7 +578,7 @@ def setUpClass(cls):
         cls.zk = ZookeeperFixture.instance()
         cls.server1 = KafkaFixture.instance(0, cls.zk.host, cls.zk.port)
         cls.server2 = KafkaFixture.instance(1, cls.zk.host, cls.zk.port)
-        cls.client = KafkaClient(cls.server2.host, cls.server2.port)
+        cls.client = KafkaClient('%s:%d' % (cls.server2.host, cls.server2.port))
 
     @classmethod
     def tearDownClass(cls):  # noqa
@@ -826,23 +826,26 @@ def test_large_messages(self):
 
 class TestFailover(KafkaTestCase):
 
-    def setUp(self):
+    @classmethod
+    def setUpClass(cls):  # noqa
         zk_chroot = random_string(10)
         replicas = 2
         partitions = 2
 
         # mini zookeeper, 2 kafka brokers
-        self.zk = ZookeeperFixture.instance()
-        kk_args = [self.zk.host, self.zk.port, zk_chroot, replicas, partitions]
-        self.brokers = [KafkaFixture.instance(i, *kk_args) for i in range(replicas)]
-        self.client = KafkaClient(self.brokers[0].host, self.brokers[0].port)
-        super(TestFailover, self).setUp()
-
-    def tearDown(self):
-        self.client.close()
-        for broker in self.brokers:
+        cls.zk = ZookeeperFixture.instance()
+        kk_args = [cls.zk.host, cls.zk.port, zk_chroot, replicas, partitions]
+        cls.brokers = [KafkaFixture.instance(i, *kk_args) for i in range(replicas)]
+
+        hosts = ['%s:%d' % (b.host, b.port) for b in cls.brokers]
+        cls.client = KafkaClient(hosts)
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.client.close()
+        for broker in cls.brokers:
             broker.close()
-        self.zk.close()
+        cls.zk.close()
 
     def test_switch_leader(self):
         key, topic, partition = random_string(5), self.topic, 0
@@ -918,7 +921,8 @@ def _kill_leader(self, topic, partition):
         return broker
 
     def _count_messages(self, group, topic):
-        client = KafkaClient(self.brokers[0].host, self.brokers[0].port)
+        hosts = '%s:%d' % (self.brokers[0].host, self.brokers[0].port)
+        client = KafkaClient(hosts)
         consumer = SimpleConsumer(client, group, topic, auto_commit=False, iter_timeout=0)
         all_messages = []
         for message in consumer:

test/test_unit.py

@@ -3,11 +3,16 @@
 import struct
 import unittest
 
+from mock import MagicMock, patch
+
+
+from kafka import KafkaClient
 from kafka.common import (
     ProduceRequest, FetchRequest, Message, ChecksumError,
     ConsumerFetchSizeTooSmall, ProduceResponse, FetchResponse,
     OffsetAndMessage, BrokerMetadata, PartitionMetadata
 )
+from kafka.common import KafkaUnavailableError
 from kafka.codec import (
     has_gzip, has_snappy, gzip_encode, gzip_decode,
     snappy_encode, snappy_decode
@@ -405,7 +410,6 @@ def test_encode_offset_request(self):
     def test_decode_offset_response(self):
         pass
 
-
     @unittest.skip("Not Implemented")
     def test_encode_offset_commit_request(self):
         pass
@@ -423,5 +427,83 @@ def test_decode_offset_fetch_response(self):
         pass
 
 
+class TestKafkaClient(unittest.TestCase):
+
+    def test_init_with_list(self):
+
+        with patch.object(KafkaClient, 'load_metadata_for_topics'):
+            client = KafkaClient(
+                hosts=['kafka01:9092', 'kafka02:9092', 'kafka03:9092'])
+
+        self.assertItemsEqual(
+            [('kafka01', 9092), ('kafka02', 9092), ('kafka03', 9092)],
+            client.hosts)
+
+    def test_init_with_csv(self):
+
+        with patch.object(KafkaClient, 'load_metadata_for_topics'):
+            client = KafkaClient(
+                hosts='kafka01:9092,kafka02:9092,kafka03:9092')
+
+        self.assertItemsEqual(
+            [('kafka01', 9092), ('kafka02', 9092), ('kafka03', 9092)],
+            client.hosts)
+
+    def test_send_broker_unaware_request_fail(self):
+        'Tests that call fails when all hosts are unavailable'
+
+        mocked_conns = {
+            ('kafka01', 9092): MagicMock(),
+            ('kafka02', 9092): MagicMock()
+        }
+        # inject KafkaConnection side effects
+        mocked_conns[('kafka01', 9092)].send.side_effect = RuntimeError("kafka01 went away (unittest)")
+        mocked_conns[('kafka02', 9092)].send.side_effect = RuntimeError("Kafka02 went away (unittest)")
+
+        def mock_get_conn(host, port):
+            return mocked_conns[(host, port)]
+
+        # patch to avoid making requests before we want it
+        with patch.object(KafkaClient, 'load_metadata_for_topics'), \
+                patch.object(KafkaClient, '_get_conn', side_effect=mock_get_conn):
+
+            client = KafkaClient(hosts=['kafka01:9092', 'kafka02:9092'])
+
+            self.assertRaises(
+                KafkaUnavailableError,
+                client._send_broker_unaware_request,
+                1, 'fake request')
+
+            for key, conn in mocked_conns.iteritems():
+                conn.send.assert_called_with(1, 'fake request')
+
+    def test_send_broker_unaware_request(self):
+        'Tests that call works when at least one of the host is available'
+
+        mocked_conns = {
+            ('kafka01', 9092): MagicMock(),
+            ('kafka02', 9092): MagicMock(),
+            ('kafka03', 9092): MagicMock()
+        }
+        # inject KafkaConnection side effects
+        mocked_conns[('kafka01', 9092)].send.side_effect = RuntimeError("kafka01 went away (unittest)")
+        mocked_conns[('kafka02', 9092)].recv.return_value = 'valid response'
+        mocked_conns[('kafka03', 9092)].send.side_effect = RuntimeError("kafka03 went away (unittest)")
+
+        def mock_get_conn(host, port):
+            return mocked_conns[(host, port)]
+
+        # patch to avoid making requests before we want it
+        with patch.object(KafkaClient, 'load_metadata_for_topics'), \
+                patch.object(KafkaClient, '_get_conn', side_effect=mock_get_conn):
+
+            client = KafkaClient(hosts='kafka01:9092,kafka02:9092')
+
+            resp = client._send_broker_unaware_request(1, 'fake request')
+
+            self.assertEqual('valid response', resp)
+            mocked_conns[('kafka02', 9092)].recv.assert_called_with(1)
+
+
 if __name__ == '__main__':
     unittest.main()