Use specified partitioner for partition key (#173)

Rdkafka allows us to specify the partition key but always calculates the partition using consistent_random partitioner even if a partitioner is specified in the configuration. This commit makes it use the specified partitioner.

Author: abicky

lib/rdkafka/bindings.rb

@@ -246,14 +246,21 @@ class TopicPartitionList < FFI::Struct
     attach_function :rd_kafka_conf_set_dr_msg_cb, [:pointer, :delivery_cb], :void
 
     # Partitioner
-    attach_function :rd_kafka_msg_partitioner_consistent_random, [:pointer, :pointer, :size_t, :int32, :pointer, :pointer], :int32
+    PARTITIONERS = %w(random consistent consistent_random murmur2 murmur2_random fnv1a fnv1a_random).each_with_object({}) do |name, hsh|
+      method_name = "rd_kafka_msg_partitioner_#{name}".to_sym
+      attach_function method_name, [:pointer, :pointer, :size_t, :int32, :pointer, :pointer], :int32
+      hsh[name] = method_name
+    end
 
-    def self.partitioner(str, partition_count)
+    def self.partitioner(str, partition_count, partitioner_name = "consistent_random")
       # Return RD_KAFKA_PARTITION_UA(unassigned partition) when partition count is nil/zero.
       return -1 unless partition_count&.nonzero?
 
       str_ptr = FFI::MemoryPointer.from_string(str)
-      rd_kafka_msg_partitioner_consistent_random(nil, str_ptr, str.size, partition_count, nil, nil)
+      method_name = PARTITIONERS.fetch(partitioner_name) do
+        raise Rdkafka::Config::ConfigError.new("Unknown partitioner: #{partitioner_name}")
+      end
+      public_send(method_name, nil, str_ptr, str.size, partition_count, nil, nil)
     end
 
     # Create Topics

lib/rdkafka/config.rb

@@ -179,7 +179,7 @@ def producer
       # Set callback to receive delivery reports on config
       Rdkafka::Bindings.rd_kafka_conf_set_dr_msg_cb(config, Rdkafka::Callbacks::DeliveryCallbackFunction)
       # Return producer with Kafka client
-      Rdkafka::Producer.new(Rdkafka::Producer::Client.new(native_kafka(config, :rd_kafka_producer))).tap do |producer|
+      Rdkafka::Producer.new(Rdkafka::Producer::Client.new(native_kafka(config, :rd_kafka_producer)), self[:partitioner]).tap do |producer|
         opaque.producer = producer
       end
     end

lib/rdkafka/producer.rb

@@ -10,8 +10,9 @@ class Producer
     attr_reader :delivery_callback
 
     # @private
-    def initialize(client)
+    def initialize(client, partitioner_name)
       @client = client
+      @partitioner_name = partitioner_name || "consistent_random"
 
       # Makes sure, that the producer gets closed before it gets GCed by Ruby
       ObjectSpace.define_finalizer(self, client.finalizer)
@@ -85,7 +86,7 @@ def produce(topic:, payload: nil, key: nil, partition: nil, partition_key: nil,
       if partition_key
         partition_count = partition_count(topic)
         # If the topic is not present, set to -1
-        partition = Rdkafka::Bindings.partitioner(partition_key, partition_count) if partition_count
+        partition = Rdkafka::Bindings.partitioner(partition_key, partition_count, @partitioner_name) if partition_count
       end
 
       # If partition is nil, use -1 to let librdafka set the partition randomly or

spec/rdkafka/bindings_spec.rb

@@ -76,6 +76,13 @@
       result_2 = (Zlib.crc32(partition_key) % partition_count)
       expect(result_1).to eq(result_2)
     end
+
+    it "should return the partition calculated by the specified partitioner" do
+      result_1 = Rdkafka::Bindings.partitioner(partition_key, partition_count, "murmur2")
+      ptr = FFI::MemoryPointer.from_string(partition_key)
+      result_2 = Rdkafka::Bindings.rd_kafka_msg_partitioner_murmur2(nil, ptr, partition_key.size, partition_count, nil, nil)
+      expect(result_1).to eq(result_2)
+    end
   end
 
   describe "stats callback" do