| # 事件通道 |
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| Alpha 收到 Omeag 发送的事件后放入事件通道等待 Akka 处理，事件通道有三种实现方式，一种是内存通道另外是 Kafka,Rabbit 通道 |
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| | 通道类型 | 模式 | 说明 | |
| | -------- | ---- | ------------------------------------------------------------ | |
| | memory | 单例 | 使用内存作为数据通道，不建议在生产环境使用 | |
| | kafka | 集群 | 使用 Kafka 作为数据通道，使用全局事务ID作为分区策略，集群中的所有节点同时工作，可水平扩展，当配置了 spring.profiles.active=prd,cluster 参数后默认就使用 kafka 通道 | |
| | rabbit | 集群 | 使用 rabbit 作为数据通道，使用全局事务ID作为分区策略, 由于rabbit 原生不支持分区，所以引用了 [spring-cloud-stream](https://github.com/spring-cloud/spring-cloud-stream-binder-rabbit) | |
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| 可以使用参数 `alpha.spec.saga.akka.channel.name` 配置通道类型 |
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| - Memory 通道参数 |
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| | 参数名 | 参数值 | 说明 | |
| | -------------------------------------- | ------ | ------------------------------------------- | |
| | alpha.spec.saga.akka.channel.name | memory | | |
| | alpha.spec.saga.akka.channel.max-length | -1 | momory类型时内存队列大小，-1表示Integer.MAX | |
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| - Kafka 通道参数 |
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| | 参数名 | 参数值 | 说明 | |
| |---------------------------------------------------------------| -------- | ------------------------------------------- | |
| | alpha.spec.saga.akka.channel.name | kafka | | |
| | alpha.spec.saga.akka.channel.kafka.bootstrap-servers | -1 | momory类型时内存队列大小，-1表示Integer.MAX | |
| | alpha.spec.saga.akka.channel.kafka.producer.batch-size | 16384 | | |
| | alpha.spec.saga.akka.channel.kafka.producer.retries | 0 | | |
| | alpha.spec.saga.akka.channel.kafka.producer.buffer.memory | 33554432 | | |
| | alpha.spec.saga.akka.channel.kafka.consumer.auto.offset.reset | earliest | | |
| | alpha.spec.saga.akka.channel.kafka.listener.pollTimeout | 1500 | | |
| | alpha.spec.saga.akka.channel.kafka.numPartitions | 6 | | |
| | alpha.spec.saga.akka.channel.kafka.replicationFactor | 1 | | |
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| - Rabbit 通道参数 |
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| | 参数名 | 参数值 | 说明 | |
| |-------------------------------------------------------------------------------------------|----------------------------|------------------------------| |
| | alpha.spec.saga.akka.channel.name | rabbit | | |
| | spring.cloud.stream.instance-index | 0 | 分区索引 | |
| | spring.cloud.stream.instance-count | 1 | | |
| | spring.cloud.stream.bindings.service-comb-pack-producer.producer.partition-count | 1 | 分区数量，分区数量需要与alpha-server保持一致 | |
| | spring.cloud.stream.binders.defaultRabbit.environment.spring.rabbitmq.virtual-host | servicecomb-pack | | |
| | spring.cloud.stream.binders.defaultRabbit.environment.spring.rabbitmq.host | rabbitmq.servicecomb.io | | |
| | spring.cloud.stream.binders.defaultRabbit.environment.spring.rabbitmq.username | servicecomb-pack | | |
| | spring.cloud.stream.binders.defaultRabbit.environment.spring.rabbitmq.password | H123213PWD | | |
| | spring.cloud.stream.binders.defaultRabbit.type | rabbit | | |
| | spring.cloud.stream.bindings.service-comb-pack-producer.destination | exchange-service-comb-pack | | |
| | spring.cloud.stream.bindings.service-comb-pack-producer.content-type | application/json | | |
| | spring.cloud.stream.bindings.service-comb-pack-producer.producer.partition-key-expression | headers['partitionKey'] | 分区表达式 | |
| | spring.cloud.stream.bindings.service-comb-pack-consumer.group | group-pack | | |
| | spring.cloud.stream.bindings.service-comb-pack-consumer.content-type | application/json | | |
| | spring.cloud.stream.bindings.service-comb-pack-consumer.destination | exchange-service-comb-pack | | |
| | spring.cloud.stream.bindings.service-comb-pack-consumer.consumer.partitioned | true | | |
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