mysql group replication @osi days 2014

2 Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Open Source India | Bangalore, India, 8th November, 2014. |

Open Source India, 2014

MySQL Group Replication

Manish Kumar ([email protected])Senior Member technical Staff, MySQL Replication Team

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Copyright © 2014, Oracle and/or its affiliates. All rights reserved. | Open Source India | Bangalore, India, 8th November, 2014. |


MySQL Labs features are not fit for production.

They are provided solely for testing purposes, to try the latest bug fixes and generally to keep up with the development.

Please, do not use these binaries in production.

Instead, install them on a spare server.

If you are looking for production ready binaries, please visit MySQL Downloads.

http://dev.mysql.com/downloads/


MySQL Group Replication :

Multi-master update everywhere with conflict resolution.

Automatic distributed member recovery— When a server joins the group, it gets all the missing transactions before actually

start serving requests.


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ReplicationPlugin

API

MySQLServer

Group Comm.System (Corosync)Group Comm.

System (Corosync)

Group-Based Replication Plugin

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ReplicationPlugin

API

MySQLServer

Group Comm.System (Corosync)



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Update ...

Application issues an update.



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ReplicationEvents


Master executes and multi/broadcasts the update to the other servers.



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Servers receive same transaction in the same order and check for conflicts.



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All servers, independently, decide to commit the transaction – no conflicts.






All servers, independently, decide to commit the transaction – no conflicts.

Originating master replies to the application.

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MySQL Group Replication: Use Cases

● Automatic group membership management and failure detection - No need for server fail-over

● No single point of failure - Automatic reconfiguration


Under the hood

● Each server can belong to a group.

● The Group is identified by a name which is the Group UUID string, so group behaves like a single server.

● The Group UUID is used to log transactions.

● Whenever a server joins or leaves, it will start a new stable period in time on which servers can agree on distributed decisions. A special message called View Message is sent to each group member notifying that.

● Server join/leave can be issue manually or by scripts by DBA.

● Server leave can be caused also by node failures.


Current used group communication toolkit is Corosync. It provides:— Virtual synchrony guarantees for creating replicated state machines.

Replicated state machine simple definition:— If a set of processes with the same initial state receives the same set of deterministic

messages at the same order, them will reach the same state.

All write operations are sent to all group members for certification.

Read operations are only local.

Under the hood


s1

s2

UPDATEdbv: 1

dbv: 2

s3dbv: 2

dbv: 2COMMIT

COMMIT

COMMIT

cv: 11 >= 1

OK

1 >= 1

OK

1 >= 1

OK

cv: 1

cv: 1

dbv: 1

dbv: 1

cv: 2

cv: 2

cv: 2

s ← serverv ← snapshot versionsn ← certifier sequence number (write set version)

Certification - Positive


s1

s2

T1: UPDATEdbv: 1

dbv: 2

s3dbv: 2

dbv: 2T1: COMMIT

T1: COMMIT

T1: COMMIT

cv: 1

cv: 1

cv: 1

1 >= 1

OK

1 >= 1

OK

1 >= 1

OK

T2: UPDATE cv: 2

cv: 2

cv: 2

1 >= 2

KO

1 >= 2

KO

1 >= 2

KO

dbv: 1

dbv: 1

s ← serverv ← snapshot versionsn ← certifier sequence number (write set version)

Certification - Negative


Automated distributed member recovery

R1

R2

R3

R4

GCS

R1

R2

R3

R4

R4 joins the group.

GCS



R1

R2

R3

R4

R1 is R4 Donor

GCS

R1

R2

R3

R4

GCS



R1

R2

R3

R4

GCS

R1

R2

R3

R4

GCS



R1

R2

R3

R4

GCS

R1

R2

R3

R4

R4 has caught upwith the view!

GCS


R1

R2

R3

R4

GCS

R1

R2

R3

R4

GCS

Execute bufferedtransactions from the view.



– REPLICATION_NODE_STATUS● Statistics regarding Applier and Certifier module.

– REPLICATION_CONNECTION_NODES● Information regarding different nodes in the group and its

connection details

– REPLICATION_CONNECTION_STATUS● Extended table to give details about the group connection status.

PERFORMANCE SCHEMA TABLE


node1> SELECT * FROM performance_schema.replication_node_status\G *************************** 1. row *************************** GROUP_NAME: 8a84f397-aaa4-18df-89ab-c70aa9823561 NODE_ID: 2af09cb1-3e46-11e4-9e45-ecf4bb227f3b TRANSACTIONS_IN_QUEUE: 0 CERTIFIED_TRANSACTIONS: 12 POSITIVELY_CERTIFIED: 7 NEGATIVELY_CERTIFIED: 5 CERTIFICATION_DB_SIZE: 6 STABLE_SET: 8a84f397-aaa4-18df-89ab-c70aa9823561:1-7 LAST_CERTIFIED_TRANSACTION: 8a84f397-aaa4-18df-89ab-c70aa9823561:7 APPLIER_MODULE_STATUS: ON

Replication Monitoring: replication_node_status


node1> SELECT * FROM performance_schema.replication_connection_nodes\G *************************** 1. row *************************** GROUP_NAME 8a94f357-aab4-11df-86ab-c80aa9429573 NODE_ID 597dbb72-3e2c-11e4-9d9d-ecf4bb227f3b NODE_HOST nightfury NODE_PORT 13000 NODE_STATE ONLINE *************************** 2. row *************************** GROUP_NAME 8a94f357-aab4-11df-86ab-c80aa9429573 NODE_ID 59efb8a1-3e2c-11e4-9d9d-ecf4bb227f3b NODE_HOST nightfury NODE_PORT 13001 NODE_STATE ONLINE *************************** 3. row *************************** GROUP_NAME 8a94f357-aab4-11df-86ab-c80aa9429573 NODE_ID 5a706f6b-3e2c-11e4-9d9d-ecf4bb227f3b NODE_HOST nightfury NODE_PORT 13002 NODE_STATE RECOVERING




node1> SELECT * FROM performance_schema.replication_connection_status\G *************************** 1. row *************************** GROUP_NAME: 8a94f357-aab4-11df-86ab-c80aa9429563 SOURCE_UUID: 8a94f357-aab4-11df-86ab-c80aa9429563 THREAD_ID: NULL SERVICE_STATE: ON COUNT_RECEIVED_HEARTBEATS: 0 LAST_HEARTBEAT_TIMESTAMP: 0000-00-00 00:00:00 RECEIVED_TRANSACTION_SET: LAST_ERROR_NUMBER: 0 LAST_ERROR_MESSAGE: LAST_ERROR_TIMESTAMP: 0000-00-00 00:00:00 TOTAL_MESSAGES_RECEIVED: 9 TOTAL_MESSAGES_SENT: 5 TOTAL_BYTES_RECEIVED: 1891 TOTAL_BYTES_SENT: 1065 LAST_MESSAGE_TIMESTAMP: 2014-09-23 09:20:26 MAX_MESSAGE_LENGTH: 358 MIN_MESSAGE_LENGTH: 51 VIEW_ID: 2 NUMBER_OF_NODES: 2


Only transactional engines are supported (currently only InnoDB).

All tables must have primary key

GTID must be enabled.

Only deterministic DDL is allowed.

Optimistic execution: transactions may abort on COMMIT.

Limitations


Read More About MySQL Group Replication● Read a feature preview of MySQL Group replication on Luis' blog:

http://mysqlhighavailability.com/mysql-group-replication-hello-world/

Read about how to get started with MySQL Group replication on Pedro's blog:http://mysqlhighavailability.com/getting-started-with-mysql-group-replication/

● Read about Transaction life cycle in MySQL Group replication on Nuno's blog:http://mysqlhighavailability.com/mysql-group-replication-transaction-life-cycle-explained/

● Read about Distributed recovery in MySQL Group Replication on Pedro's blog:http://mysqlhighavailability.com/distributed-recovery-behind-the-scenes/

● Read about Monitoring for MySQL Group Replication on Manish's blog:http://mysqlhighavailability.com/mysql-group-replication-monitoring/

● Read about Corosync and Group Communication details on Tiago's blog:http://mysqlhighavailability.com/group-communication-behind-the-scenes/http://mysqlhighavailability.com/mysql-group-replication-a-small-corosync-guide/

● Read about Testing of MySQL Group Replication on Manish's blog:http://mysqlhighavailability.com/mysql-group-replication-testing/

http://mysqlhighavailability.com/group-communication-behind-the-scenes/

mysql group replication @osi days 2014

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