rocketmq-client-rust 0.9.0

// Copyright 2023 The RocketMQ Rust Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use cheetah_string::CheetahString;
use rocketmq_common::common::message::message_queue::MessageQueue;

/// Trait for allocating message queues to consumers in a consumer group.
/// This trait is implemented by different strategies for message queue allocation.
pub trait AllocateMessageQueueStrategy: Send + Sync {
    /// Allocates message queues to a consumer in a consumer group.
    ///
    /// # Arguments
    ///
    /// * `consumer_group` - The name of the consumer group.
    /// * `current_cid` - The ID of the current consumer.
    /// * `mq_all` - A slice of all available message queues.
    /// * `cid_all` - A slice of all consumer IDs in the consumer group.
    ///
    /// # Returns
    ///
    /// A `Result` containing a vector of allocated message queues or an error.
    fn allocate(
        &self,
        consumer_group: &CheetahString,
        current_cid: &CheetahString,
        mq_all: &[MessageQueue],
        cid_all: &[CheetahString],
    ) -> rocketmq_error::RocketMQResult<Vec<MessageQueue>>;

    /// Returns the name of the allocation strategy.
    ///
    /// # Returns
    ///
    /// A static string slice representing the name of the strategy.
    fn get_name(&self) -> &'static str;
}

/// Java-compatible name for the abstract allocation strategy base type.
///
/// Java exposes `AbstractAllocateMessageQueueStrategy` as a base class that
/// implements shared validation before concrete allocation strategies run. In
/// Rust the behavior is represented by `AllocateMessageQueueStrategy` plus the
/// shared rebalance `check` helper, so the Java name maps to the trait object.
pub type AbstractAllocateMessageQueueStrategy = dyn AllocateMessageQueueStrategy;

#[cfg(test)]
mod tests {
    use super::*;

    struct NoopStrategy;

    impl AllocateMessageQueueStrategy for NoopStrategy {
        fn allocate(
            &self,
            _consumer_group: &CheetahString,
            _current_cid: &CheetahString,
            _mq_all: &[MessageQueue],
            _cid_all: &[CheetahString],
        ) -> rocketmq_error::RocketMQResult<Vec<MessageQueue>> {
            Ok(Vec::new())
        }

        fn get_name(&self) -> &'static str {
            "NOOP"
        }
    }

    #[test]
    fn abstract_allocate_message_queue_strategy_alias_accepts_real_strategy() {
        let strategy = NoopStrategy;
        let abstract_strategy: &AbstractAllocateMessageQueueStrategy = &strategy;

        assert_eq!(abstract_strategy.get_name(), "NOOP");
    }
}