In a post last week, I described the difference in concurrency behavior between MongoDB’s oplog and TokuMX’s oplog. In short, here are the key differences: MongoDB protects access to the oplog with a database level reader/writer lock, whereas TokuMX does not. TokuMX can write data to the oplog concurrently, whereas MongoDB cannot. As a result, […]
Read MoreIn my last post, I describe the differences between a TokuMX oplog entry and a MongoDB oplog entry. One reason why the entries are so different is that TokuMX supports multi-statement and multi-document transactions. In this post, I want to elaborate on why multi-statement transactions cause changes to the oplog, and explain how we changed […]
Read MoreAs I mentioned in my last post, TokuMX replication is completely incompatible with MongoDB replication. Replica sets (and sharded clusters, but that is for another blog) must be either entirely TokuMX or entirely MongoDB. This is by design. While elections and failover are basically the same, we have completely changed the oplog protocol. In the […]
Read MoreMongoDB replication has some great features. As I discussed in my last post, MongoDB’s crash safety design is very elegant. In addition to that, MongoDB has automatic failover, parallel slave replication, and prefetch threads on secondaries. The latter, as Mark Callaghan points out, is similar to “InnoDB fake changes”, a feature that has helped Facebook […]
Read MoreAt an extremely high level, replication in MongoDB and MySQL are similar. Both databases have exactly one machine, the primary (or master), that accepts writes from clients. With a single transaction (or atomic operation, in MongoDB’s case), the tables and oplog (or binary log in MySQL) are modified to reflect the change. The log captures […]
Read MoreWe just released version 1.4.0 of TokuMX, our high-performance distribution of MongoDB. There are a lot of improvements in this version (release notes), the most of any release yet. In this series of blog posts, we describe the most interesting changes and how they’ll affect users. In TokuMX 1.4.0, we improved performance by making two […]
Read MoreWe just released version 1.4.0 of TokuMX, our high-performance distribution of MongoDB. There are a lot of improvements in this version (release notes), the most of any release yet. In this series of blog posts, we describe the most interesting changes and how they’ll affect users. In MongoDB, the replication oplog is a capped collection, […]
Read MoreToday we are thrilled to announce the availability of the latest release (1.4.0) of TokuMX, our high-performance distribution of MongoDB. For those of you just joining us, TokuMX is an open-source distribution of MongoDB that shares much of the code, and all of the driver protocols, data model, and programming interface with MongoDB, but which […]
Read MoreJanuary 22 I gave a presentation on “How to Avoid Common (but Deadly) MySQL Operations Mistakes” for Percona MySQL Webinars. If you missed it, you can still register to view the recording and my slides. Thanks to everyone who attended, and especially to folks who asked the great questions. I answered as many as we […]
Read MoreThe other day I was working on an issue where one of the slaves was showing unexpected lag. Interestingly with only the IO thread running the slave was doing significantly more IO as compared to the rate at which the IO thread was fetching the binary log events from the master. I found this out […]
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