= Jetpants
== OVERVIEW:
\Jetpants is an automation toolkit for handling monstrously large MySQL database topologies. It is geared towards common operational tasks like cloning slaves, rebalancing shards, and performing master promotions. It features a command suite for easy use by operations staff, though it's also a full Ruby library for use in developing custom migration scripts and database automation.
\Jetpants supports a range-based sharding scheme for MySQL by providing a fast way to split shards that are approaching capacity or I/O limitations. \Jetpants is able to accomplish this without any locking, downtime, data inconsistency, or query failures. Dynamically resizable range-based sharding allows you to scale MySQL horizontally in a sane manner, without any need for a central lookup service or massive pre-allocation of tiny shards.
== MOTIVATION:
\Jetpants was created by {Tumblr}[http://www.tumblr.com/] to help manage our database infrastructure. It handles automation tasks for our entire database topology, which as of May 2013 consists of over 215 dedicated database servers and nearly 200 billion total distinct relational rows.
One of the primary requirements for \Jetpants was speed. On our hardware, \Jetpants can divide a 750GB, billion-row shard in half in about six hours -- or even faster if you're diving into thirds or fourths.
For more background on the motivations behind \Jetpants, please see {Evan Elias's presentation at Percona Live 2013}[https://github.com/tumblr/jetpants/blob/master/doc/PerconaLive2013Presentation.pdf?raw=true].
== COMMAND SUITE FEATURES:
The \Jetpants command suite offers easy command-line interaction with complex MySQL automation tasks.
- Clone slaves efficiently, including to multiple targets simultaneously
- Split a range-based shard into N new shards with zero downtime and no failed queries
- Perform master promotions and other pool topology changes
- Defragment tables quickly in parallelized chunks
- Interact with your database topology in a REPL environment via jetpants console mode
For more information on the command suite, please see doc/commands.rdoc ({view on GitHub}[https://github.com/tumblr/jetpants/blob/master/doc/commands.rdoc]).
== LIBRARY FEATURES:
\Jetpants is also a Ruby module which you can use to build complex database migration scripts and other customized automation. It provides object modeling for databases, hosts, global/functional pools, sharded pools, and your database topology as a whole.
- Utilize scriptable versions of all command suite functionality
- Crawl replication topology programmatically
- Import or export arbitrary portions of a data set
- Copy large files quickly and efficiently, including to multiple simultaneous destinations. Flexibility in terms of single threaded copy or multi-threaded copy is provided based on the resources available (large network bandwidth, PCIe flash devices). Supporting scripts (jetpants_clone_sender and jetpants_clone_receiver) are present in bin/ directory.
- Manipulate server settings or concurrently execute arbitrary UNIX commands / administrative MySQL queries on multiple servers
== ASSUMPTIONS AND REQUIREMENTS:
Percona Toolkit of at least 2.2.15.
The base classes of \Jetpants currently make a number of assumptions about your environment and database topology. Please see doc/requirements.rdoc ({view on GitHub}[https://github.com/tumblr/jetpants/blob/master/doc/requirements.rdoc]).
== CONFIGURATION:
\Jetpants supports a global configuration file at /etc/jetpants.yaml, as well as per-user configuration files at ~/.jetpants.yaml.
At least one of these files must exist for \Jetpants to function properly, since certain options (database schema name, database credentials, etc) are mandatory and cannot be inferred.
Please see doc/configuration.rdoc ({view on GitHub}[https://github.com/tumblr/jetpants/blob/master/doc/configuration.rdoc]) for information on configuring \Jetpants.
== PLUGINS:
\Jetpants offers an extensible plugin system. Plugins are Ruby code (such as stand-alone gems) that add to \Jetpants by supplying callback methods, and/or overriding core methods.
It is highly recommended that you tie \Jetpants into your site's asset tracker / hardware management system by writing a custom plugin. This will allow \Jetpants to automatically know what database pools and shards are present, and to make topological changes immediately be reflected in your site's configuration. Several complex \Jetpants features (including shard splits) actually require an asset tracker plugin in order to function, since these processes involve obtaining spare nodes and manipulating multiple pools in your database topology.
Other recommended uses of plugins include integration with your site's monitoring system, trending system, query killers, and environment-specific overrides to various core methods.
If you are using \Collins for asset management, \Jetpants now ships with a plugin that offers integration. Please see doc/jetpants_collins.rdoc ({view on GitHub}[https://github.com/tumblr/jetpants/blob/master/doc/jetpants_collins.rdoc]) for usage.
For more information on how to write plugins and use the Jetpants::CallbackHandler system, please see doc/plugins.rdoc ({view on GitHub}[https://github.com/tumblr/jetpants/blob/master/doc/plugins.rdoc])
== FREQUENTLY ASKED QUESTIONS:
Please see doc/faq.rdoc ({view on GitHub}[https://github.com/tumblr/jetpants/blob/master/doc/faq.rdoc]) for answers to common questions.
If you have a question that isn't covered here, please feel free to email the authors at the addresses listed in jetpants.gemspec.
== CREDITS:
- Evan Elias: Creator and developer
- Dallas Marlow: Developer
- Bob Patterson Jr: Developer
- Tom Christ: Developer
- Tyler Neely: Developer
- Kiril Angov: Developer
- Amar Mudrankit: Developer
- Duan Wang: Developer
- Akshay Suryawanshi: Developer
- Graham Christensen: Developer
Special thanks to Tim Ellis for testing and bug reports.
== LICENSE:
Copyright 2013 Tumblr, Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
[http://www.apache.org/licenses/LICENSE-2.0]
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.