Deprecate queuing.strategy=lifo and msg_order_cmp

Author: edenhill

CONFIGURATION.md

@@ -128,11 +128,11 @@ acks                                     |  P  |                 |
 request.timeout.ms                       |  P  | 1 .. 900000     |          5000 | The ack timeout of the producer request in milliseconds. This value is only enforced by the broker and relies on `request.required.acks` being != 0. <br>*Type: integer*
 message.timeout.ms                       |  P  | 0 .. 900000     |        300000 | Local message timeout. This value is only enforced locally and limits the time a produced message waits for successful delivery. A time of 0 is infinite. This is the maximum time librdkafka may use to deliver a message (including retries). Delivery error occurs when either the retry count or the message timeout are exceeded. <br>*Type: integer*
 delivery.timeout.ms                      |  P  |                 |               | Alias for `message.timeout.ms`
-queuing.strategy                         |  P  | fifo, lifo      |          fifo | Producer queuing strategy. FIFO preserves produce ordering, while LIFO prioritizes new messages. WARNING: `lifo` is experimental and subject to change or removal. <br>*Type: enum value*
+queuing.strategy                         |  P  | fifo, lifo      |          fifo | **DEPRECATED** Producer queuing strategy. FIFO preserves produce ordering, while LIFO prioritizes new messages. WARNING: `lifo` is experimental and subject to change or removal. <br>*Type: enum value*
 produce.offset.report                    |  P  | true, false     |         false | **DEPRECATED** No longer used. <br>*Type: boolean*
 partitioner                              |  P  |                 | consistent_random | Partitioner: `random` - random distribution, `consistent` - CRC32 hash of key (Empty and NULL keys are mapped to single partition), `consistent_random` - CRC32 hash of key (Empty and NULL keys are randomly partitioned), `murmur2` - Java Producer compatible Murmur2 hash of key (NULL keys are mapped to single partition), `murmur2_random` - Java Producer compatible Murmur2 hash of key (NULL keys are randomly partitioned. This is functionally equivalent to the default partitioner in the Java Producer.). <br>*Type: string*
 partitioner_cb                           |  P  |                 |               | Custom partitioner callback (set with rd_kafka_topic_conf_set_partitioner_cb()) <br>*Type: pointer*
-msg_order_cmp                            |  P  |                 |               | Message queue ordering comparator (set with rd_kafka_topic_conf_set_msg_order_cmp()). Also see `queuing.strategy`. <br>*Type: pointer*
+msg_order_cmp                            |  P  |                 |               | **DEPRECATED** Message queue ordering comparator (set with rd_kafka_topic_conf_set_msg_order_cmp()). Also see `queuing.strategy`. WARNING: this is an experimental interface, subject to change or removal. <br>*Type: pointer*
 opaque                                   |  *  |                 |               | Application opaque (set with rd_kafka_topic_conf_set_opaque()) <br>*Type: pointer*
 compression.codec                        |  P  | none, gzip, snappy, lz4, zstd, inherit |       inherit | Compression codec to use for compressing message sets. inherit = inherit global compression.codec configuration. <br>*Type: enum value*
 compression.type                         |  P  |                 |               | Alias for `compression.codec`

src/rdkafka_conf.c

@@ -1020,7 +1020,7 @@ static const struct rd_kafka_property rd_kafka_properties[] = {
 	  0, 900*1000, 300*1000 },
         { _RK_TOPIC|_RK_PRODUCER, "delivery.timeout.ms", _RK_C_ALIAS,
           .sdef = "message.timeout.ms" },
-        { _RK_TOPIC|_RK_PRODUCER, "queuing.strategy", _RK_C_S2I,
+        { _RK_TOPIC|_RK_PRODUCER|_RK_DEPRECATED, "queuing.strategy", _RK_C_S2I,
           _RKT(queuing_strategy),
           "Producer queuing strategy. FIFO preserves produce ordering, "
           "while LIFO prioritizes new messages. "
@@ -1050,11 +1050,13 @@ static const struct rd_kafka_property rd_kafka_properties[] = {
 	  _RKT(partitioner),
 	  "Custom partitioner callback "
 	  "(set with rd_kafka_topic_conf_set_partitioner_cb())" },
-	{ _RK_TOPIC|_RK_PRODUCER, "msg_order_cmp", _RK_C_PTR,
+	{ _RK_TOPIC|_RK_PRODUCER|_RK_DEPRECATED, "msg_order_cmp", _RK_C_PTR,
 	  _RKT(msg_order_cmp),
 	  "Message queue ordering comparator "
 	  "(set with rd_kafka_topic_conf_set_msg_order_cmp()). "
-          "Also see `queuing.strategy`." },
+          "Also see `queuing.strategy`. "
+          "WARNING: this is an experimental interface, subject "
+          "to change or removal." },
 	{ _RK_TOPIC, "opaque", _RK_C_PTR,
 	  _RKT(opaque),
 	  "Application opaque (set with rd_kafka_topic_conf_set_opaque())" },

src/rdkafka_msg.c

@@ -1502,7 +1502,6 @@ int unittest_msg (void) {
         int fails = 0;
 
         fails += unittest_msgq_order("FIFO", 1, rd_kafka_msg_cmp_msgid);
-        fails += unittest_msgq_order("LIFO", 0, rd_kafka_msg_cmp_msgid_lifo);
         fails += unittest_msg_seq_wrap();
 
         return fails;