Redis 持久化方式-RDB

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"针对Redis的话题估计有些读者已经开始反感了，昨天还是有一些读者困惑，这就具体讲述下","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"Redis持久化方式-RDB","attrs":{}},{"type":"text","text":"的实现方式~","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":" 触发时机","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"手动触发:","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"save: 阻塞当前 Redis 服务器, 直到 RDB 过程完成为止, 对于内存比较大的实例会造成长时间阻塞, 线上环境不建议使用","attrs":{}}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"bgsave: Redis 进程执行 fork 操作创建子进程, RDB 持久化过程由子进程负责, 完成后自动结束。阻塞只发生在 fork 阶段, 一般时间很短","attrs":{}}]}],"attrs":{}}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"自动触发 RDB 的持久化机制, 例如以下场景:","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"使用 save 相关配置, 如 “save m n”。表示 m 秒内数据集存在 n 次修改时, 自动触发 bgsave。","attrs":{}}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"如果从节点执行全量复制操作, 主节点自动执行 bgsave 生成RDB文件并发送给从节点, 更多细节见6.3节介绍的复制原理。","attrs":{}}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"执行 debug reload 命令重新加载 Redis 时, 也会自动触发 save 操作。(不清楚是 save 还是 bgsave)","attrs":{}}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"默认情况下执行 shutdown 命令时, 如果没有开启 AOF 持久化功能则自动执行 bgsave。","attrs":{}}]}],"attrs":{}}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":" 流程说明","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/2e/2e2a7c30ce28b2c87f5d60e6f3cff945.webp","alt":"图片","title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":" RDB的文件处理","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"保存","attrs":{}},{"type":"text","text":": RDB 文件保存在 dir 配置指定的目录下, 文件名通过 dbfilename 配置指定。可以通过执行 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"config set dir {newDir}","attrs":{}}],"attrs":{}},{"type":"text","text":" 和 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"config set dbfilename {newFileName}","attrs":{}}],"attrs":{}},{"type":"text","text":" 运行期动态执行, 当下次运行时 RDB 文件会保存到新目录。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"压缩","attrs":{}},{"type":"text","text":": Redis 默认采用 LZF 算法对生成的 RDB 文件做压缩处理, 压缩后的文件远远小于内存大小, 默认开启, 可以通过参数 ","attrs":{}},{"type":"codeinline","content":[{"type":"text","text":"config set rdbcompression {yes|no}","attrs":{}}],"attrs":{}},{"type":"text","text":" 动态修改。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"校验","attrs":{}},{"type":"text","text":": 如果 Redis 加载损坏 的RDB 文件时拒绝启动, 并打印如下日志:","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}],"attrs":{}}],"attrs":{}},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"# Short read or OOM loading DB. Unrecoverable error, aborting now.","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"这时可以使用 Redis 提供的 redis-check-dump 工具检测 RDB 文件并获取对应的错误报告。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":" RDB的优缺点","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"优点","attrs":{}},{"type":"text","text":":","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"RDB 是一个紧凑压缩的二进制文件, 代表 Redis 在某个时间点上的数据快照。非常适用于备份, 全量复制等场景","attrs":{}}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Redis 加载 RDB 恢复数据远远快于 AOF 的方式","attrs":{}}]}],"attrs":{}}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"缺点","attrs":{}},{"type":"text","text":":","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"RDB 方式数据没办法做到实时持久化/秒级持久化。因为 bgsave 每次运行都要执行 fork 操作创建子进程, 属于重量级操作, 频繁执行成本过高","attrs":{}}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"RDB 文件使用特定二进制格式保存, Redis 版本演进过程中有多个格式的 RDB 版本, 存在老版本 Redis 服务无法兼容新版 RDB 格式的问题","attrs":{}}]}],"attrs":{}}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"Redis持久化推荐","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"http://mp.weixin.qq.com/s?__biz=MzU3OTc1MDM1Mg==&mid=2247493665&idx=1&sn=5ec9d3d4dbd568c57e4967ae6d66f569&chksm=fd63f89eca147188fa3bb62f661d2c118aebd21350a7d06a4b9bd4eaa6410ea9ec501c0c619c&scene=21#wechat_redirect","title":null},"content":[{"type":"text","text":"Redis 持久化方式-AOF","attrs":{}}]}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"http://mp.weixin.qq.com/s?__biz=MzU3OTc1MDM1Mg==&mid=2247493538&idx=1&sn=68ae9009394554294527af9ba0c7df11&chksm=fd63f71dca147e0b8256df08066d5ad977360e3ebe2d5409e40a15c66f18a398eb2a7eb740b4&scene=21#wechat_redirect","title":null},"content":[{"type":"text","text":"Redis 持久化方式-RDB","attrs":{}}]}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"http://mp.weixin.qq.com/s?__biz=MzU3OTc1MDM1Mg==&mid=2247494013&idx=1&sn=7b7feb4dc6eaafb239d0820d30f17414&chksm=fd63f9c2ca1470d44f1c8f745dff90ceeeafb55ed9a6133852c5b81ad8cedf30bb299757dc22&scene=21#wechat_redirect","title":null},"content":[{"type":"text","text":"Redis持久化问题定位与优化技巧","attrs":{}}]}]}],"attrs":{}},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"http://mp.weixin.qq.com/s?__biz=MzU3OTc1MDM1Mg==&mid=2247492366&idx=3&sn=f8ef038f85a97d990e019ac03adb1250&chksm=fd63f3b1ca147aa76e4cf07c5a91b1daff9ec368530abf5ff6007b510aadc5c2b05f6911547e&scene=21#wechat_redirect","title":null},"content":[{"type":"text","text":"Redis三种持久化方式","attrs":{}}]}]}],"attrs":{}}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}]}