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| # Meta-Proxy | ||
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| # Meta-Proxy: Pegasus表配置中心 | ||
| [](https://codecov.io/gh/pegasus-kv/meta-proxy) | ||
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| # 概述 | ||
| Meta-Proxy是Pegasus集群的表配置管理中心，客户端（兼容1.X和2.X的版本）在访问不同集群的表时不再配置不同Meta-Server地址，而是统一配置成Meta-Proxy的地址，这使得Pegasus的MetaServer变更对客户端侧完全透明。典型的应用场景包括： | ||
| * 下线/替换Meta Server机器 | ||
| * 主备集群容灾切换 | ||
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| # 设计 | ||
| Meta-Proxy本质是Pegasus MetaServer的无状态RPC代理服务，依靠ZK存储和监听表配置的变更，并反应到客户端侧。在ZK节点上存储的典型信息如下： | ||
| /ZKPathRoot/table/=> | ||
| ```json | ||
| { | ||
| "cluster_name" : "clusterName", | ||
| "meta_addrs" : "metaAddr1,metaAddr2,metaAddr3" | ||
| } | ||
| ``` | ||
| 当客户端向Meta-Proxy请求某个表的信息： | ||
| * 如果本地已经缓存的有表信息或者与Meta-Server的链接，将会优先使用缓存信息； | ||
| * 如果本地缓存无对应表的信息，Meta-Proxy会从ZK上获取该表所在集群的Meta-Server地址，并把表信息和连接缓存到本地缓存中； | ||
| * 如果ZK上的表信息发生变更，Meta-Proxy会通过zk watcher监听并实时变更表信息； | ||
| * 成功获取表信息并建立与Meta-Server的连接后，Meta-Proxy将向Pegasus发起请求并把结果返回给客户端。 | ||
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| # 使用 | ||
| ## 编译 | ||
| ```shell | ||
| make | ||
| ``` | ||
| 随后会在bin/目录下生成`meta-proxy`的二进制文件 | ||
| ## 运行 | ||
| ```shell | ||
| ./meta-proxy meta-proxy.yaml meta-proxy.log | ||
| ``` | ||
| 以上命令表明使用`meta-proxy.yaml`文件配置启动服务，并输出日志到`meta-proxy.log`， | ||
| 典型的`meta-proxy.yaml`配置如下所示： | ||
| ```yaml | ||
| zookeeper: | ||
| address: [127.0.0.1:22181,127.0.0.2:22181] # zk服务器地址 | ||
| root: /pegasus-cluster # zk节点存储表配置信息的根路径 | ||
| timeout: 1000 # ms, 连接zk节点时的超时阈值 | ||
| table_watcher_cache_capacity: 1024 # zk节点监控的最多表个数，也是meta-proxy缓存的表信息个数 | ||
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| metric: | ||
| type: prometheus # 监控系统类型，同时支持“falcon” | ||
| tags: [region=local_tst,service=meta_proxy] # 监控指标的默认tag | ||
| ``` | ||
| 启动成功将会看到如下连接ZK的输出： | ||
| ```log | ||
| 2021/02/07 14:26:46 connected to [127.0.0.1:22181,127.0.0.2:22181] | ||
| 2021/02/07 14:26:46 authenticated: id=321476486907785415, timeout=1000 | ||
| 2021/02/07 14:26:46 re-submitting `0` credentials after reconnect | ||
| ``` | ||
| 以及日志文件的输出： | ||
| ```shell | ||
| time="2021-02-07T14:26:46+08:00" level=info msg="init config: {{[127.0.0.1:22181,127.0.0.2:22181] /pegasus-cluster 1000 1024} {prometheus [region=local_tst,service=meta_proxy]}}" | ||
| time="2021-02-07T14:26:46+08:00" level=info msg="start server listen: [::]:34601" | ||
| ``` | ||
| ## 客户端配置 | ||
| 客户端只需把原来的meta-server地址改配置成meta-proxy的地址即可。 | ||
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| **注**：更换客户端配置前，请确保Meta-Proxy连接的ZK节点已经配置好对应表的信息 | ||
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| # 监控 | ||
| Meta-Proxy默认支持prometheus和falcon监控，并添加了三个监控指标以展示当前Meta-Proxy的服务状态： | ||
| * client_connection_count: 记录客户端的连接数 | ||
| * zk_request_count: 记录客户端的请求中从ZK上请求表信息的个数/QPS，即本地表信息缓存失效的请求数/QPS | ||
| * client_query_config_count: 客户端请求数/QPS | ||
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| 用户也可以根据实际服务需求配置自定义的监控指标。目前的支持的指标类型包括：count/meter、gauge | ||
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