MyRocks引擎:入坑须知

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For bulk loads, you may face problems trying to load large amounts of data into MyRocks (and unfortunately this might be the very first operation when you start playing with MyRocks as you try to LOAD DATA, INSERT INTO myrocks_table SELECT * FROM innodb_table or ALTER TABLE innodb_table ENGINE=ROCKSDB). If your table is big enough and you do not have enough memory, RocksDB crashes. As a workaround, you should set rocksdb_bulk_load=1 for the session where you load data. See more on this page: https://github.com/facebook/mysql-5.6/wiki/data-loading.

原文发布时间为:2018-03-27

as you can see, there are about 20mln records in this table. MyRocks (with default LZ4 compression) uses 828MB. InnoDB (uncompressed) uses 37400MB.

注意,现在MyRocks只支持 READ-COMMITTED 隔离级别。并好难 REPEATABLE-READ 隔离级别,也好难 像InnoDB里一样的gap锁。理论上, RocksDB 只支持 SNAPSHOT 隔离级别。然而,MySQL 当中并好难 SNAPSHOT 隔离级别的概念,什么都大伙好难 实现特殊的语法去支持。将会你对你什么都感兴趣,请联系大伙。

We are looking for feedback on your MyRocks experience!

There are some major and minor differences when comparing it to typical InnoDB deployments, and I want to highlight them here. The first important difference is that MyRocks (based on RocksDB) uses Log Structured Merge Tree data structure, not a B+ tree like InnoDB.

Online Binary Backup Tool There is an open source online binary backup tool for MyRocks — myrocks_hotabackuphttps://github.com/facebook/mysql-5.6/blob/fb-mysql-5.6.35/scripts/myrocks_hotbackup

隔离级别 MyRocks 支持READ COMMITTED 和 REPEATABLE READ隔离级别,不支持 SERIALIZABLE。想了解更全版的信息都还都可否阅读https://github.com/facebook/mysql-5.6/wiki/Transaction-Isolation。MyRocks 实现REPETABLE READ的法子 和InnoDB不一样 — MyRocks 使用累似 PostgreSQL 的snapshot isolation。 在Percona server 中,不允许在MyRocks 表上使用 REPEATABLE READ 隔离级别,将会REPEATABLE READ 隔离级别在innodb和myrocks db上的正确处理法子 不一样。

What other differences should you be aware of?

By default in Percona Server for MySQL, MyRocks will use LZ4 compression for all tables. You can change compression settings by changing the rocksdb_default_cf_options server variable. By default it set to compression=kLZ4Compression;bottommost_compression=kLZ4Compression. We chose LZ4 compression as it provides acceptable compression level with very little CPU overhead. Other possible compression methods are Zlib and ZSTD, or no compression at all. You can learn more about compression ratio vs. speed in Peter’s and my post.To compare the data size of a MyRocks table loaded with traffic statistic data from my homebrew router, I’ve used the following table created for pmacct collector:

让大伙看一下目录价值形式。当前,所有的表和数据库后会存储在mysqldir的.rocksdb隐藏目录当中。名字和地址都还都可否改变,怎么让 所有的数据库当中的所有表还是存储在一系列的.sst文件当中,好难 per-table / per-database的区分。

本文作者:魏新平

还有你什么都什么都须要注意的区别的吗?

大伙期待大伙的反馈 。

Let’s look at the directory layout. Right now, all tables and all databases are stored in a hidden .rocksdb directory inside mysqldir. The name and location can be changed, but still all tables from all databases are stored in just a series of .sst files. There is no per-table / per-database separation.

You can find more MyRocks specifics and limitations in our docs at https://www.percona.com/doc/percona-server/LATEST/myrocks/limitations.html.

Percona recently released Percona Server with MyRocks as GA. You can see how Facebook explains wins they see in production with MyRocks. Now if you use Percona repositories, you can simply install MyRocks plugin and enable it with ps-admin --enable-rocksdb.

UPDATES (12-Feb-2018) Updates to the original post with the feedback provided by Facebook MyRocks team

现在还好难 累似 于Percona XtraBackup一样的热备软件来执行MyRocks表的热备份(大伙正在研究你什么都)。不想使用mysqldump 来进行逻辑备份,将会使用文件系统层面的snapshots ,比如LVM 或 ZFS 。

本文来自云栖社区战略企业合作伙伴“

在线二进制备份工具 网上有一1个多多开源的在线二进制备份工具—myrocks_hotabackup:

你都还都可否在我发布在DZone的文章 当中了解到更多关于LSM引擎的信息 。总的来说,LSM引擎更适合写密集型的应用场景,读取速率单位将会会好难,全表扫描对于引擎来说负担会太重。当使用MyRocks作为应用底层时,须要有点儿注意你什么都点。MyRocks 后会加强版的InnoDB,可是 能在所有应用场景下替换InnoDB。他有另一方的优势/局限,就像InnoDB一样,你须要根据你数据的存取模式来选用使用哪一1个多多引擎。

”,了解相关信息都还都可否关注“

You can find very verbose information about your RocksDB instance in the LOG file located in .rocksdb directory. Check this file for more diagnostics. You can also try the SHOW ENGINE ROCKSDB STATUS command, but it is even more cryptic than SHOW ENGINE INNODB STATUS. It takes time to parse and to understand it.

在MyRocks中的Block cache有点儿累似 于innodb_buffer_pool_size,怎么让 对于MyRocks它主要利于读取数据。您将会须要调整rocksdb_block_cache_size设置。另外,它默认使用buffered reads,在你什么都情况下,操作系统的cache缓存着压缩的数据,而RockDB block cache 会缓存未压缩的数据。不想保持你什么都两层的缓存机制,将会不想修改rocksdb_use_direct_reads=ON关闭缓存,强制block cache直接读取。LSM树的本质要求当一层变满时,有一1个多多合并过程将压缩数据推到下一层。你什么都过程将会相当密集并会影响用户查询速率单位。都还都可否将其调整为不好难 密集。

正如你所看见的,表含高要花费4000万条数据。MyRocks (用默认的 LZ4 压缩)使用了828MB。 InnoDB (默认,未压缩) 使用了37400MB。

Right now there is no hot backup software like Percona XtraBackup to perform a hot backup of MyRocks tables (we are looking into this). At this time you can use mysqldump for logical backups, or use filesystem-level snapshots like LVM or ZFS.

你都还都可否在 .rocksdb 目录的LOG文件当中找到RocksDB 实例的全版信息。查看你什么都日志,都还都可否进行更全版的诊断。你都上还都可否使用SHOW ENGINE ROCKSDB STATUS命令,怎么让 这会比SHOW ENGINE INNODB STATUS返回的内容更多样化,须要消耗几瓶的精力和时间去理解。

将它和典型的InnoDB进行比较时,位于什么都主要和累积区别,我都还都可否在此强调一下。第一1个多多主要的区别是MyRocks (based on RocksDB) 使用Log Structured Merge Tree数据价值形式,后会InnoDB的B+ tree数据价值形式。

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Block cache in MyRocks is somewhat similar to innodb_buffer_pool_size, however for MyRocks it’s mainly beneficial for reads. You may want to tune the rocksdb_block_cache_size setting. Also keep in mind it uses buffered reads by default, and in this case the OS cache contains cached compressed data and RockDB block cache will contain uncompressed data. You may keep this setup to have two levels of cache, or you can disable buffering by forcing block cache to use direct reads with rocksdb_use_direct_reads=ON. The nature of LSM trees requires that when a level becomes full, there is a merge process that pushes compacted data to the next level. This process can be quite intensive and affect user queries. It is possible to tune it to be less intensive.

You learn more about the LSM engine in my article for DZone.The summary is that an LSM data structure is good for write-intensive workloads, with the expense that reads might slow down (both point reads and especially range reads) and full table scans might be too heavy for the engine. This is important to keep in mind when designing applications for MyRocks. MyRocks is not an enhanced InnoDB, nor a one-size-fits-all replacement for InnoDB. It has its own pros/cons just like InnoDB. You need to decide which engine to use based on your applications data access patterns.

Keep in mind that at this time MyRocks supports only READ-COMMITTED isolation levels. There is no REPEATABLE-READ isolation level and no gap locking like in InnoDB. In theory, RocksDB should support SNAPSHOT isolation level. However, there is no notion of SNAPSHOT isolation in MySQL so we have not implemented the special syntax to support this level. Please let us know if you would be interested in this.

在大伙的官方文档当中,不想了解到更多关于MyRocks 的优势和局限性.

当你试图加载几瓶的数据到MyRocks 当中时,你将会会遇到什么的问题(不幸的是你什么都将会有你使用MyRocks 时的首次工作,当你使用LOAD DATA, INSERT INTO myrocks_table SELECT * FROM innodb_table 将会 ALTER TABLE innodb_table ENGINE=ROCKSDB)。怎么让我我你的表不要 ,怎么让 你好难 足够的内存,RocksDB 就会崩溃。在生产环境中,你应该为你加载数据的session设置rocksdb_bulk_load=1。了解更多请查看文章:https://github.com/facebook/mysql-5.6/wiki/data-loading

默认情况下,MyRocks 使用LZ4来压缩所有的表。都还都可否通过改变rocksdb_default_cf_options当中的变量来改变压缩的设置。默认值为compression=kLZ4Compression;bottommost_compression=kLZ4Compression。大伙选用 LZ4,是将会它在很小的cpu负载下提供了可接受的压缩比。什么都的压缩法子 包括Zlib 和 ZSTD,将会直接不压缩。你都还都可否在Peter和我的文章当中学习到更多关于压缩比VS速率单位 的信息。为了比较装载了来自我自制路由器软件的流量统计数据的MyRocks表的物理大小,我使用了为pmacct派发器软件创建的下表。

##更新(2018-02-12) 在获得Facebook MyRocks 团队的反馈后,我对好难 的文章进行了更新。

大伙a 最近发布了Percona Server with MyRocks的GA版本。本文会不想了解到为你什么都Facebook要在生产环境使用MyRocks了。将会你使用Percona repositories ,你都还都可否简单的安装MyRocks插件怎么让 用ps-admin --enable-rocksdb来启动它。

Isolation Levels MyRocks supports READ COMMITTED and REPEATABLE READ. MyRocks does not support SERIALIZABLE. Please read https://github.com/facebook/mysql-5.6/wiki/Transaction-Isolation for details. The way to implement REPETABLE READ was different from MyRocks and InnoDB — MyRocks used PostgreSQL style snapshot isolation. In Percona Server we do not allow REPEATABLE READ for MyRocks tables, as the behavior will be different from InnoDB.