feat: optimize disk buffer writes

README.md

@@ -161,6 +161,8 @@ wolff:send(Producers, [Msg], AckFun).
 * `max_linger_ms`: Age in milliseconds a batch can stay in queue when the connection
    is idle (as in no pending acks from kafka). Default=0 (as in send immediately).
 
+* `max_linger_bytes`: Number of bytes to collect before sending it to Kafka. If set to 0, `max_batch_bytes` is taken for mem-only mode, otherwise it's 10 times `max_batch_bytes` (but never exceeds 10MB) to optimize disk write.
+
 * `max_send_ahead`: Number of batches to be sent ahead without receiving ack for
    the last request. Must be 0 if messages must be delivered in strict order.
 

changelog.md

@@ -1,5 +1,8 @@
 * 4.0.0
   - Delete global stats (deprecated since 1.9).
+  - Move linger delay to front of the buffer queue.
+    The default value for `max_linger_ms` is `0` as before.
+    Setting `max_linger_ms=10` will make the disk write batch larger when buffer is configured to disk mode or disk-offload mode.
 
 * 3.0.4
   - Upgrade to kafka_protocol-4.1.8

src/wolff.app.src

@@ -1,6 +1,6 @@
 {application, wolff,
  [{description, "Kafka's publisher"},
-  {vsn, "4.0.0"},
+  {vsn, "git"},
   {registered, []},
   {applications,
    [kernel,

src/wolff.erl

@@ -34,11 +34,13 @@
 
 %% Messaging APIs
 -export([send/3,
-         send_sync/3
+         send_sync/3,
+         cast/3
         ]).
 
 %% Messaging APIs of dynamic producer.
 -export([send2/4,
+         cast2/4,
          send_sync2/4,
          add_topic/2,
          remove_topic/2
@@ -120,8 +122,8 @@ stop_and_delete_supervised_producers(Producers) ->
 %% In case `required_acks' is configured to `none', the callback is evaluated immediately after send.
 %% The partition number and the per-partition worker pid are returned in a tuple to caller,
 %% so it may use them to correlate the future `AckFun' evaluation.
-%% NOTE: This API has no backpressure,
-%%       high produce rate may cause execussive ram and disk usage.
+%% NOTE: This API is blocked until the batch is enqueued to the producer buffer, otherwise no backpressure.
+%%       High produce rate may cause excessive ram and disk usage.
 %% NOTE: In case producers are configured with `required_acks = none',
 %%       the second arg for callback function will always be `?UNKNOWN_OFFSET' (`-1').
 -spec send(producers(), [msg()], ack_fun()) -> {partition(), pid()}.
@@ -137,6 +139,22 @@ send2(Producers, Topic, Batch, AckFun) ->
   ok = wolff_producer:send(ProducerPid, Batch, AckFun),
   {Partition, ProducerPid}.
 
+%% @doc Cast a batch to a partition producer.
+%% Even less backpressure than `send/3'.
+%% It does not wait for the batch to be enqueued to the producer buffer.
+-spec cast(producers(), [msg()], ack_fun()) -> {partition(), pid()}.
+cast(Producers, Batch, AckFun) ->
+  {Partition, ProducerPid} = wolff_producers:pick_producer(Producers, Batch),
+  ok = wolff_producer:send(ProducerPid, Batch, AckFun, no_wait_for_queued),
+  {Partition, ProducerPid}.
+
+%% @doc Topic as argument for dynamic producers, otherwise equivalent to `cast/3'.
+-spec cast2(producers(), topic(), [msg()], ack_fun()) -> {partition(), pid()}.
+cast2(Producers, Topic, Batch, AckFun) ->
+  {Partition, ProducerPid} = wolff_producers:pick_producer2(Producers, Topic, Batch),
+  ok = wolff_producer:send(ProducerPid, Batch, AckFun, no_wait_for_queued),
+  {Partition, ProducerPid}.
+
 %% @doc Pick a partition producer and send a batch synchronously.
 %% Raise error exception in case produce pid is down or when timed out.
 %% NOTE: In case producers are configured with `required_acks => none',