Jump to: navigation, search

Difference between revisions of "Reddwarf-MySQL-Replication-and-Clustering"

(Replaced content with "Documentation how replication and clustering in Reddwarf works should go here.")
 
(8 intermediate revisions by the same user not shown)
Line 1: Line 1:
== MySQL Master/Slave Replication ==
+
Documentation how replication and clustering in Reddwarf works should go here.
 
 
'''How master-slave replication works:'''
 
* Replication in mysql works basically via log shipping. 
 
* The mysql master logs all data manipulation events in the mysql binary log. 
 
* While this is happening the slave instances are connected to the master via TCP and receive the same events and write them to their relay log. 
 
* Binary logging should be turned *on* on the master and *off* on the slaves. 
 
* If binary logging is turned on on the slave you will suffer massive IO hits as each log entry writes to the relay log, then the table, then the binary log.
 
* there are 2 internal mysql threads that exist on the slave, the SQL thread and the IO thread
 
* the IO thread is responsible for getting binary events from the master and the SQL thread is responsible for applying them locally.
 
* slaves should be read-only, allowing data manipulation statements on slaves will result in corrupt or out of sync slaves
 
 
 
 
 
'''How to know that replication broke:'''
 
* parse the output of "SHOW SLAVE STATUS" on the replicated slave.
 
* the IO thread is set to No
 
* the SQL thread is set to No
 
* the seconds_behind_master is > a set number and isn't reducing over time (this is a conditional case that we need to define). 
 
* This case is a failure because it means that for whatever reason the slave will never be in sync with the master.
 
* This can be due to the slave not having enough resources to keep up or that the master has too many slaves.
 
* If ever any of these 3 things are true it is assumed that replication is broken and the slave is to be destroyed and recreated.
 
 
 
 
 
'''Steps to setup replicaiton:'''<br />
 
* No point in rewriting known steps, follow instructions here: [http://dev.mysql.com/doc/refman/5.1/en/replication-howto.html MySQL Replication Documentation]
 
 
 
 
 
'''Pros/Cons'''
 
{| class="wikitable"
 
|-
 
! Pros !! Cons
 
|-
 
| Standard MySQL || Prior to MySQL 5.6 Replication is brittle (See notes on MyISAM)
 
|-
 
| Very well understood || Repairing can be time consuming
 
|-
 
| No special architecture needed || Creating new slaves can require downtime or read locking on the master
 
|-
 
| Easy to troubleshoot  || Only works well for scaling reads
 
|-
 
| Works with all storage engines (see notes on MyISAM) || Single threaded, high concurrency on the master can cause issues where slaves can't keep up
 
|-
 
| Offers simple and complex configurations for read scaling ||
 
|-
 
| Opensource tools available for monitoring/troubleshooting ||
 
|-
 
| Great for making backup or reporting slaves ||
 
|-
 
| Good general purpose replication ||
 
|}
 

Latest revision as of 16:16, 2 May 2013

Documentation how replication and clustering in Reddwarf works should go here.