Producer support for per-topic configs

CHANGELOG.md

@@ -3,6 +3,8 @@
 ## 0.16.0 (Unreleased)
 - **[Feature]** Support incremental config describe + alter API.
 - **[Feature]** Oauthbearer token refresh callback (bruce-szalwinski-he)
+- **[Feature]** Provide ability to use topic config on a producer for custom behaviors per dispatch.
+- [Enhancement] Use topic config reference cache for messages production to prevent topic objects allocation with each message.
 - [Enhancement] Provide `Rrdkafka::Admin#describe_errors` to get errors descriptions (mensfeld)
 - [Enhancement] Replace time poll based wait engine with an event based to improve response times on blocking operations and wait (nijikon + mensfeld)
 - [Enhancement] Allow for usage of the second regex engine of librdkafka by setting `RDKAFKA_DISABLE_REGEX_EXT` during build (mensfeld)

lib/rdkafka/bindings.rb

@@ -167,6 +167,9 @@ class NativeErrorDesc < FFI::Struct
     # Log queue
     attach_function :rd_kafka_set_log_queue, [:pointer, :pointer], :void
     attach_function :rd_kafka_queue_get_main, [:pointer], :pointer
+    # Per topic configs
+    attach_function :rd_kafka_topic_conf_new, [], :pointer
+    attach_function :rd_kafka_topic_conf_set, [:pointer, :string, :string, :pointer, :int], :kafka_config_response
 
     LogCallback = FFI::Function.new(
       :void, [:pointer, :int, :string, :string]

lib/rdkafka/producer.rb

@@ -9,7 +9,10 @@ class Producer
     # Cache partitions count for 30 seconds
     PARTITIONS_COUNT_TTL = 30
 
-    private_constant :PARTITIONS_COUNT_TTL
+    # Empty hash used as a default
+    EMPTY_HASH = {}.freeze
+
+    private_constant :PARTITIONS_COUNT_TTL, :EMPTY_HASH
 
     # @private
     # Returns the current delivery callback, by default this is nil.
@@ -28,6 +31,8 @@ class Producer
     # @param partitioner_name [String, nil] name of the partitioner we want to use or nil to use
     #   the "consistent_random" default
     def initialize(native_kafka, partitioner_name)
+      @topics_refs_map = {}
+      @topics_configs = {}
       @native_kafka = native_kafka
       @partitioner_name = partitioner_name || "consistent_random"
 
@@ -54,6 +59,48 @@ def initialize(native_kafka, partitioner_name)
       end
     end
 
+    # Sets alternative set of configuration details that can be set per topic
+    # @note It is not allowed to re-set the same topic config twice because of the underlying
+    #   librdkafka caching
+    # @param topic [String] The topic name
+    # @param config [Hash] config we want to use per topic basis
+    # @param config_hash [Integer] hash of the config. We expect it here instead of computing it,
+    #   because it is already computed during the retrieval attempt in the `#produce` flow.
+    def set_topic_config(topic, config, config_hash)
+      # Ensure lock on topic reference just in case
+      @native_kafka.with_inner do |inner|
+        @topics_refs_map[topic] ||= {}
+        @topics_configs[topic] ||= {}
+
+        return if @topics_configs[topic].key?(config_hash)
+
+        # If config is empty, we create an empty reference that will be used with defaults
+        rd_topic_config = if config.empty?
+                            nil
+                          else
+                            Rdkafka::Bindings.rd_kafka_topic_conf_new.tap do |topic_config|
+                              config.each do |key, value|
+                                error_buffer = FFI::MemoryPointer.from_string(" " * 256)
+                                result = Rdkafka::Bindings.rd_kafka_topic_conf_set(
+                                  topic_config,
+                                  key.to_s,
+                                  value.to_s,
+                                  error_buffer,
+                                  256
+                                )
+
+                                unless result == :config_ok
+                                  raise Config::ConfigError.new(error_buffer.read_string)
+                                end
+                              end
+                            end
+                          end
+
+        @topics_configs[topic][config_hash] = config
+        @topics_refs_map[topic][config_hash] = Bindings.rd_kafka_topic_new(inner, topic, rd_topic_config)
+      end
+    end
+
     # Starts the native Kafka polling thread and kicks off the init polling
     # @note Not needed to run unless explicit start was disabled
     def start
@@ -83,7 +130,18 @@ def delivery_callback=(callback)
     def close
       return if closed?
       ObjectSpace.undefine_finalizer(self)
-      @native_kafka.close
+
+      @native_kafka.close do
+        # We need to remove the topics references objects before we destroy the producer,
+        # otherwise they would leak out
+        @topics_refs_map.each_value do |refs|
+          refs.each_value do |ref|
+            Rdkafka::Bindings.rd_kafka_topic_destroy(ref)
+          end
+        end
+      end
+
+      @topics_refs_map.clear
     end
 
     # Whether this producer has closed
@@ -182,11 +240,22 @@ def partition_count(topic)
     # @param timestamp [Time,Integer,nil] Optional timestamp of this message. Integer timestamp is in milliseconds since Jan 1 1970.
     # @param headers [Hash<String,String>] Optional message headers
     # @param label [Object, nil] a label that can be assigned when producing a message that will be part of the delivery handle and the delivery report
+    # @param topic_config [Hash] topic config for given message dispatch. Allows to send messages to topics with different configuration
     #
     # @return [DeliveryHandle] Delivery handle that can be used to wait for the result of producing this message
     #
     # @raise [RdkafkaError] When adding the message to rdkafka's queue failed
-    def produce(topic:, payload: nil, key: nil, partition: nil, partition_key: nil, timestamp: nil, headers: nil, label: nil)
+    def produce(
+      topic:,
+      payload: nil,
+      key: nil,
+      partition: nil,
+      partition_key: nil,
+      timestamp: nil,
+      headers: nil,
+      label: nil,
+      topic_config: EMPTY_HASH
+    )
       closed_producer_check(__method__)
 
       # Start by checking and converting the input
@@ -205,8 +274,20 @@ def produce(topic:, payload: nil, key: nil, partition: nil, partition_key: nil,
                    key.bytesize
                  end
 
+      topic_config_hash = topic_config.hash
+
+      # Checks if we have the rdkafka topic reference object ready. It saves us on object
+      # allocation and allows to use custom config on demand.
+      set_topic_config(topic, topic_config, topic_config_hash) unless @topics_refs_map.dig(topic, topic_config_hash)
+      topic_ref = @topics_refs_map.dig(topic, topic_config_hash)
+
       if partition_key
         partition_count = partition_count(topic)
+
+        # Check if there are no overrides for the partitioner and use the default one only when
+        # no per-topic is present.
+        partitioner_name = @topics_configs.dig(topic, topic_config_hash, :partitioner) || @partitioner_name
+
         # If the topic is not present, set to -1
         partition = Rdkafka::Bindings.partitioner(partition_key, partition_count, @partitioner_name) if partition_count.positive?
       end
@@ -236,7 +317,7 @@ def produce(topic:, payload: nil, key: nil, partition: nil, partition_key: nil,
       DeliveryHandle.register(delivery_handle)
 
       args = [
-        :int, Rdkafka::Bindings::RD_KAFKA_VTYPE_TOPIC, :string, topic,
+        :int, Rdkafka::Bindings::RD_KAFKA_VTYPE_RKT, :pointer, topic_ref,
         :int, Rdkafka::Bindings::RD_KAFKA_VTYPE_MSGFLAGS, :int, Rdkafka::Bindings::RD_KAFKA_MSG_F_COPY,
         :int, Rdkafka::Bindings::RD_KAFKA_VTYPE_VALUE, :buffer_in, payload, :size_t, payload_size,
         :int, Rdkafka::Bindings::RD_KAFKA_VTYPE_KEY, :buffer_in, key, :size_t, key_size,

spec/rdkafka/producer_spec.rb

@@ -31,6 +31,48 @@
     it { expect(producer.name).to include('rdkafka#producer-') }
   end
 
+  describe '#produce with topic config alterations' do
+    context 'when config is not valid' do
+      it 'expect to raise error' do
+        expect do
+          producer.produce(topic: 'test', payload: '', topic_config: { 'invalid': 'invalid' })
+        end.to raise_error(Rdkafka::Config::ConfigError)
+      end
+    end
+
+    context 'when config is valid' do
+      it 'expect to raise error' do
+        expect do
+          producer.produce(topic: 'test', payload: '', topic_config: { 'acks': 1 }).wait
+        end.not_to raise_error
+      end
+
+      context 'when alteration should change behavior' do
+        # This is set incorrectly for a reason
+        # If alteration would not work, this will hang the spec suite
+        let(:producer) do
+          rdkafka_producer_config(
+            'message.timeout.ms': 1_000_000,
+            :"bootstrap.servers" => "localhost:9094",
+          ).producer
+        end
+
+        it 'expect to give up on delivery fast based on alteration config' do
+          expect do
+            producer.produce(
+              topic: 'produce_config_test',
+              payload: 'test',
+              topic_config: {
+                'compression.type': 'gzip',
+                'message.timeout.ms': 1
+              }
+            ).wait
+          end.to raise_error(Rdkafka::RdkafkaError, /msg_timed_out/)
+        end
+      end
+    end
+  end
+
   context "delivery callback" do
     context "with a proc/lambda" do
       it "should set the callback" do