http://www.codership.com/wiki/ 2012-05-18T04:11:38+03:00 http://www.codership.com/wiki/ http://www.codership.com/wiki/lib/tpl/vector/images/favicon.ico text/html 2011-04-24T22:17:59+03:00 http://www.codership.com/wiki/doku.php?id=certification&rev=1303672679&do=diff How multi-master Galera replication works. text/html 2011-12-11T04:48:56+03:00 http://www.codership.com/wiki/doku.php?id=cluster_control_galera_ec2&rev=1323571736&do=diff Severalnines team has added Galera cluster support to its ClusterControl(tm) configurator. Now it has become even easier and faster to deploy a 10-node Galera cluster anywhere from your private LAN to Amazon EC2. Plus it allows to conveniently monitor the cluster and individual nodes using nothing but a web browser. This page explains how to use ClusterControl to install and monitor Galera cluster in EC2. text/html 2012-03-29T17:24:44+03:00 http://www.codership.com/wiki/doku.php?id=compile_galera&rev=1333031084&do=diff Linux Coming later. Nothing special there. Check Solaris section for tips. RHEL/CentOS/Oracle Linux Debian Solaris Currently the latest revision of Galera is known to compile on Solaris 11 x86 in addition to Linux. It may not compile on Solaris 10, and will not work on big-endian machines (as we don't have any, we simply can't fix all the endian-related stuff). text/html 2011-12-29T03:09:17+03:00 http://www.codership.com/wiki/doku.php?id=configuration_tips&rev=1325120957&do=diff Parallel Applying (wsrep_slave_threads) There is no rigorous rule about how many slave threads one should configure as well as having parallel threads won't guarantee better performance -- a lot depends on the application and use case. However parallel applying won't hurt regular operation performance and most likely will drastically speed up syncing new nodes with the cluster. text/html 2012-02-16T21:47:38+03:00 http://www.codership.com/wiki/doku.php?id=faq&rev=1329421658&do=diff Q: What is Galera? Galera is a wsrep service provider in a form of dlopenable library. It provides synchronous replication guarantees and supports multi-master replication. Among other things Galera is capable of unconstrained parallel applying AKA “parallel replication”, multicast replication and automatic node provisioning. Galera primary focus is data consistency: transaction is either applied on every node or not at all. See CaP theorem for consequences. text/html 2011-06-07T20:56:36+03:00 http://www.codership.com/wiki/doku.php?id=flow_control&rev=1307469396&do=diff To ensure temporal synchrony and consistency (as opposed to logical which is provided by virtual synchrony), Galera implements several forms of low control depending on the node state: writeset cacheslave queue OPEN & PRIMARY The node is not considered to be a part of the cluster, it is not allowed to replicate, apply or cache any writesets. No flow control. text/html 2011-09-03T18:25:49+03:00 http://www.codership.com/wiki/doku.php?id=galera_arbitrator&rev=1315063549&do=diff Starting with version 0.8.2 Galera comes with an “arbitrator” garbd, a stateless daemon which acts as a lightweight group member and can serve two purposes: * Help to avoid split-brain situation by acting as an odd node * Request a consistent application state snapshot text/html 2011-08-27T14:45:15+03:00 http://www.codership.com/wiki/doku.php?id=galera_deployment&rev=1314445515&do=diff Due to its synchronous multi-master qualities Galera cluster can be thought of simply as a single server listening at many interfaces. This however does not suggest any of the many possible Galera deployment variants. Just to give an idea of what is possible we'll consider a typical N-tier application and discuss different ways, benefits and drawbacks of deploying Galera cluster there. text/html 2011-06-03T17:04:25+03:00 http://www.codership.com/wiki/doku.php?id=galera_node_fsm&rev=1307109865&do=diff Different Galera layers have different state machines, depending on their semantics. The top layer that represents “node” state has the following FSM: Regular Transitions: [Galera Node FSM] * Node establishes connection to a primary component. * Node succeeds in state transfer request. It starts to cache the writesets. * Node receives state snapshot. Now it has all cluster data and can start applying the cached writesets. Flow control is turned on to ensure eventual slave queue decrease… text/html 2011-12-29T03:15:29+03:00 http://www.codership.com/wiki/doku.php?id=galera_parameters&rev=1325121329&do=diff Galera Parameters As of 0.8 Galera accepts parameters in the form of semicolon-separated key=value pair list: “key1 = value1; key2 = value2” (in addition to Galera URL). It can be used to configure arbitrary number of Galera parameters in one call. A key consists of parameter group and parameter name: <group>.<name>, where group roughly corresponds to some Galera module. text/html 2011-03-31T23:05:12+03:00 http://www.codership.com/wiki/doku.php?id=galera_parameters_0.7&rev=1301601912&do=diff Galera 0.7.x parameters Galera group communication backend properties can be customized through the option list in the cluster address URL. Time periods must be expressed in ISO8601 format. Also see examples below. Parameter Default Description evs.consensus_timeout PT30S Timeout on reaching the consensus about cluster membership. evs.debug_log_mask 0x1 Control EVS debug logging, only effective when wsrep_debug is turned on. evs.inactive_check_period PT… text/html 2011-09-29T03:24:32+03:00 http://www.codership.com/wiki/doku.php?id=galera_parameters_0.8&rev=1317255872&do=diff Galera 0.8.x parameters As of 0.8 Galera accepts parameters in the form of semicolon-separated key=value pair list: “key1 = value1; key2 = value2” (in addition to Galera URL). It can be used to configure arbitrary number of Galera parameters in one call. text/html 2011-03-31T23:41:02+03:00 http://www.codership.com/wiki/doku.php?id=galera_status_0.7&rev=1301604062&do=diff Status Variable Example Value Description wsrep_local_state_uuid G e2c9a15e-5485-11e0-0800-6bbb637e7211 UUID of the state stored on this node. wsrep_last_committed G 409745 Sequence number of the last committed transaction. wsrep_replicated G 16109 Total number of writesets replicated (sent to other nodes). wsrep_replicated_bytes G 6526788 … text/html 2011-06-08T04:40:02+03:00 http://www.codership.com/wiki/doku.php?id=galera_status_0.8&rev=1307497202&do=diff There two types of wsrep-related status variables: those exported by Galera (and therefore Galera-specific) and those exported by MySQL, which are of general wsrep provider purpose. This distinction is of importance only from the developer point of view, and therefor for convenience all those status variables are presented as a single list: text/html 2011-03-31T03:01:53+03:00 http://www.codership.com/wiki/doku.php?id=galera_url&rev=1301529713&do=diff For the cluster address (where to connect to cluster at) Galera takes URL in the form <backend schema>://<cluster address>[?option1=value1[&option2=value2]] which can be optionally followed by a list of key=value queries according to URL standard. In 0.7 it is the only way to customized Galera parameters. In 0.8 values supplied in the URL take precedence over the values supplied in wsrep_provider_options variable. text/html 2011-08-04T23:30:05+03:00 http://www.codership.com/wiki/doku.php?id=galera_wiki&rev=1312489805&do=diff General Information Reference FAQ HOWTO text/html 2011-10-04T15:23:43+03:00 http://www.codership.com/wiki/doku.php?id=gcache&rev=1317731023&do=diff Starting with version 1.0 Galera stores writesets in a special cache. It's purpose is to improve control of Galera memory usage and offload writeset storage to disk (see also this faq). Galera cache has 3 types of stores: * A permanent in-memory store, where writesets are allocated by a default OS memory allocator. It can be useful for systems with spare RAM. It has a hard size limit. By default it is disabled (size set to 0). * A permanent ring-buffer file which is preallocated on disk dur… text/html 2012-03-18T14:29:33+03:00 http://www.codership.com/wiki/doku.php?id=herethefirst_title&rev=1332073773&do=diff Hi to all on this page its content text/html 2012-03-29T17:06:52+03:00 http://www.codership.com/wiki/doku.php?id=howto&rev=1333030012&do=diff * Galera cluster deployment variants * MySQL/Galera cluster upgrade * Use ClusterControl(tm) to deploy Galera cluster in Amazon EC2 in less than 10 minutes * Compile Galera from source External resources * Fromdual: Migrating from MySQL replication to Galera cluster * Fromdual: Rolling upgrade from Galera-1.0/MySQL-5.1 to Galera-1.1/MySQL-5.5 text/html 2012-01-20T21:07:31+03:00 http://www.codership.com/wiki/doku.php?id=info&rev=1327086451&do=diff What we'll be talking here is a generic pluggable replication architecture of the form: clients | | | V V V ,----------------. | | | application | <-- e.g. MySQL server | | ================== <-- wsrep API | wsrep provider | <-- e.g. Galera `----------------' | V replication to other nodes text/html 2012-03-18T14:29:33+03:00 http://www.codership.com/wiki/doku.php?id=ist&rev=1332073773&do=diff Galera 2.x introduces a long awaited functionality: incremental state transfer. It means that if * the joining node state UUID is the same as that of the group and * all of the writesets that it missed can be found in the donor's Gcache then instead of whole state snapshot it will receive the missing writesets and catch up with the group by replaying them. text/html 2011-07-28T02:57:41+03:00 http://www.codership.com/wiki/doku.php?id=limitations&rev=1311811061&do=diff This page lists limitations of MySQL/Galera replication. * Currently replication works only with InnoDB storage engine. Any writes to tables of other types, including system (mysql.*) tables are not replicated. However, DDL statements are replicated in statement level, and changes to mysql.* tables will get replicated that way. So, you can safely issue:CREATE USER... or GRANT... but issuing: INSERT INTO mysql.user... will not be replicated. In general, non-transactional engines cannot be supp… text/html 2012-03-01T00:26:19+03:00 http://www.codership.com/wiki/doku.php?id=manual&rev=1330554379&do=diff A Little Bit Of Theory We strongly advise you to take time to familiarize yourself with the theory behind Galera operation. It is not that big or complex, however it will help you to understand Galera versatility and take you much farther than a thousand of examples or recipes. Galera takes data replication to a whole new level and to achieve that it does away with many “traditional” concepts and misconceptions. Whether you're a fledging DBA or a seasoned systems integrator with tens of “tradit… text/html 2012-03-18T14:29:33+03:00 http://www.codership.com/wiki/doku.php?id=monitoring&rev=1332073773&do=diff All wsrep-related (in this case - Galera) status variables are prefixed with 'wsrep_' so it is easy to check them with mysql> SHOW VARIABLES LIKE 'wsrep_%'; Status variables described in chapter 3 and below are differential and reset on every SHOW STATUS command. Thus it is recommended that two SHOW STATUS commands be executed on the node with an interval of ~1 minute and then the output of the last invocation will correspond to the current moment. text/html 2011-08-05T23:40:51+03:00 http://www.codership.com/wiki/doku.php?id=mysql_galera_cluster_upgrade&rev=1312576851&do=diff This article discusses a situation where you might need to update the cluster software. Rolling upgrade is thought to be the alpha and omega of cluster software upgrade, but we'll looks at other possibilities too. 1. Rolling Upgrade This is a type of upgrade everybody is talking about when they talk about “High Availability”. It is supposed to provide uninterruptible service during upgrade. The idea is that you text/html 2012-03-18T14:29:33+03:00 http://www.codership.com/wiki/doku.php?id=mysql_galera_howto&rev=1332073773&do=diff * Galera cluster deployment variants * MySQL/Galera cluster upgrade text/html 2011-03-31T03:18:49+03:00 http://www.codership.com/wiki/doku.php?id=mysql_options_0.7&rev=1301530729&do=diff These are MySQL system variables introduced by wsrep patch v0.8. All variables are global except where marked by (L). Option Default Description wsrep_auto_increment_control ON Automatically adjust auto_increment_increment and auto_increment_offset system variables when cluster membership changes. wsrep_cluster_address Address to connect to cluster. Provider specific. Galera takes addresses in URL format: <backend schema>://<cluster … text/html 2011-12-11T05:28:37+03:00 http://www.codership.com/wiki/doku.php?id=mysql_options_0.8&rev=1323574117&do=diff These are MySQL system variables introduced by wsrep patch v0.8. All variables are global except where marked by (L). Option Default Description wsrep_auto_increment_control ON Automatically adjust auto_increment_increment and auto_increment_offset system variables when cluster membership changes. wsrep_causal_reads (L) OFF Enforce strict cluster-wide “read committed” semantics on non-transactional reads. Results in larger read latencies. ws… text/html 2011-06-07T21:42:55+03:00 http://www.codership.com/wiki/doku.php?id=node_failure&rev=1307472175&do=diff Node failure is probably the most important concept to understand in Galera clustering. Galera cluster node can fail to operate for a variety of reasons: from hardware failure to software crash to loss of network connectivity and so on. All of these causes are generalized behind the concept of node failure and no distinction between them is made. text/html 2011-06-03T16:57:30+03:00 http://www.codership.com/wiki/doku.php?id=node_provisioning_recovery&rev=1307109450&do=diff Both new and failed nodes have the same property in common: their state is different from the state of the primary component and needs to be synchronized. As a result, new node provisioning and failed node recovery are essentially the same process and boils down to the node joining the cluster primary component. text/html 2012-04-05T13:24:12+03:00 http://www.codership.com/wiki/doku.php?id=notification_command&rev=1333621452&do=diff If wsrep_notify_cmd is set, the server will try to invoke this command every time cluster membership or local node status changes. This can be used to (re)configure load balancers, raise alarm and so on. Notification Command Arguments The command will be passed one or more of the following options: text/html 2012-03-24T02:31:42+03:00 http://www.codership.com/wiki/doku.php?id=reference&rev=1332549102&do=diff Operation Node Failure Node Provisioning/Recovery Galera Node State Machine Flow Control SSL Support Galera Arbitrator Scriptable State Snapshot Transfer Writeset cache Incremental State Transfer Rolling Schema Upgrade (MySQL >= 5.5.17 only) text/html 2011-12-11T05:37:48+03:00 http://www.codership.com/wiki/doku.php?id=rolling_schema_upgrade&rev=1323574668&do=diff Schema upgrade means any data definition statement (DDL statement) run for the database. They change the database structure and are non-transactional. Total Order Isolation (TOI) By default DDL processing in Galera happens by Total Order Isolation (TOI) method. With TOI, the DDL is processed in same order with regards to other transactions in each cluster node. With TOI method, the whole cluster has part of the database locked for the duration of the DDL processing (i.e. behaves like a single … text/html 2011-12-29T03:36:06+03:00 http://www.codership.com/wiki/doku.php?id=scriptable_state_snapshot_transfer&rev=1325122566&do=diff 0.8 series MySQL/Galera introduces interface to customize state snapshot transfer via external script (or program). The script is to work under assumption that storage engine initialization on the receiving node happens after state transfer is complete. In short, the idea of this transfer is to copy the contents of source data directory to destination data directory (with possible variations). text/html 2011-08-26T23:44:53+03:00 http://www.codership.com/wiki/doku.php?id=ssl_support&rev=1314391493&do=diff Starting with version 0.8.2 Galera library supports SSL for encryption of replication traffic. It is a cluster-wide option and should be enabled either on all of the nodes or none at all. To use it a private certificate/key pair should be generated for a cluster, for example, by the following command text/html 2011-02-10T05:33:05+03:00 http://www.codership.com/wiki/doku.php?id=start&rev=1297308785&do=diff Terms and Concepts wsrep API Galera 0.8 MySQL/Galera cluster 0.8 text/html 2012-03-18T14:29:33+03:00 http://www.codership.com/wiki/doku.php?id=state_transfer_protocol&rev=1332073773&do=diff text/html 2012-03-18T14:29:33+03:00 http://www.codership.com/wiki/doku.php?id=title_for_a_wiki_post&rev=1332073773&do=diff content for a wiki post text/html 2012-03-18T14:29:33+03:00 http://www.codership.com/wiki/doku.php?id=wiki_editing_title&rev=1332073773&do=diff wiki editing content