What’s new in Galera 4

Galera 4 in MariaDB 10.4
Seppo Jaakola
Codership

2
www.galeracluster.com
➢
Seppo Jaakola
➢
One of the Founders of Codership
➢
Codership – Galera Replication developers
➢
Partner of MariaDB for developing and supporting MariaDB
Galera Cluster
➢
Galera releases since 2009

3
Agenda
●
Galera Cluster Overview
●
Galera 4 in 10.4 Features
●
Upgrading 10.3 Cluster to 10.4
●
Galera 4 Streaming Replication
●
Additional Galera 4 Feature Road Map

4
MariaDB MariaDB MariaDB
Synchronous Multi-Master Replication
Galera Replication
Replication is synchronous
read & write read & write read & write
Client can connect to any node
There can be several nodes
Read & write access to any node

5
MariaDB
a
Multi-master cluster looks
like one big database with
multiple entry points
read & write read & write read & write

6
MariaDB
a
Adding more nodes
Opens new connection
ports
read & write read & writeread & write read & write

7
Galera Cluster
➢
Good Performance
➢
Optimistic concurrency control
➢
Parallel Replication
➢
Optimized Group Communication
➢
99.99% transparent
➢
InnoDB look & feel
➢
Automatic node joining
➢
Works in LAN / WAN / Cloud

8
Galera Cluster
➢
Synchronous multi-master cluster
➢
no data loss
➢
no slave lag
➢
no slave failover
➢
For MySQL/InnoDB
➢
3 or more nodes needed for HA
➢
No single point of failure

9
Galera Replication Plugin
DBMS
wsrep provider
GCS framework
replication
wsrep hookswsrep API
certification
vsbes gcommspread
Galera
Plugin
v25
v25

Galera Version 4 in MariaDB 10.4

11
●
MariaDB 10.4 RC has Galera 4 Replication
●
10.4 other features shown in other
presentations
●
wsrep API #26
●
Impacts upgrading
●
wsrep patch integration in 10.4 codebase
●
Impacts code stability
●
bug fi & new features turnover

12
●
Streaming Replication
●
Support for large transactions
●
Platform for other new features
●
Group commit support
●
10.4 Backup locks
●
mariabackup SST with “light weight lock”

14
Huge Transaction Support
●
In Galera 3, transaction processes in
master node until commit time
●
For large transactions, the write size will
be big, and is hard to handle
●
There are means to prevent too large
transactions
●
wsrep_mai_ws_size

15
●
Streaming replication is new technology
developed for Galera Replication 4 to
enable running transaction of unlimited
size in cluster
●
Transaction size limits will remain, and
cluster can still reject too large
transactions

16
●
Transaction is replicated, gradually in small
fragments, during transaction processing
●
i.e. before actual commit, we replicate a number of
small size fragments
●
Size threshold for fragment replication is
confgurable
●
Replicated fragments are applied in slave
threads preserving transactions in all
cluster nodes
➔
Fragments hold locks in all nodes and cannot be
conficted later

17
Huge transaction
Galera Replication
Node A Node B
Huge trx
Update, update, update....
Begin

18
Huge transaction
Galera Replication
Node A Node B
Huge trx
WS

19
Huge transaction
Galera Replication
Node A Node B
Huge trx
WS

20
Huge transaction
Galera Replication
Node A Node B
Huge trx
WS
commit

21
Huge transaction
Galera Replication
Node A Node B
OK

22
Fragment Applying
SR transaction pool
SR#1 THD
SR#2 THD
SR#n THD
WS
SR trx :2
CF: 0
applier
applier
applier
certification

23
applier
Fragment Applying
SR transaction pool
SR#1 THD
SR#2 THD
SR#n THD
WS
SR trx :2
CF: 0
applier
applier
ev→apply_event()
…
ev->apply_event()
wsrep_SR_store->append_frag_apply())

24
Fragment Applying
SR transaction pool
SR#1 THD
SR#2 THD
SR#n THD
applier
applier
applier

25
Fragment Applying
SR transaction pool
SR#1 THD
SR#2 THD
SR#n THD
WS
SR trx :2
CF: 1
applier
applier
applier
certification

26
applier
Fragment Applying
SR transaction pool
SR#1 THD
SR#2 THD
SR#n THD
WS
SR trx :2
CF: 1
applier
applier
trans_commit()
wsrep_SR_store->append_frag_commit())

27
Configuring Streaming Replication
wsrep_trx_fragment_unit Unit metrics for fragmenting, options are:
●
bytes WS size in bytes
●
rows # of rows modified
●
statements # of SQL statements issued
wsrep_trx_fragment_size ●
Threshold size (in units), when fragment will be
replicated
●
0 = no streaming
●
Session variables and can be dynamically set

28
Using Streaming Replication
●
Due to excessive logging and elevated
replication overhead, streaming replication will
cause degraded transaction throughput rate
●
Best use case is to use streaming replication
for cutting large transactions
●
Set fragment size to ~10K rows
●
Fragment variables are session variables and
can be dynamically set
●
Intelligent application can set streaming
replication on/off on need basis

31
MariaDB [(none)]> select * from mysql.wsrep_clusterG
*************************** 1. row ***************************
cluster_uuid: 0be6f4d6-35da-11e9-b8a0-d6501fb08579
view_id: 2
view_seqno: 2
protocol_version: 4
capabilities: 184703
1 row in set (0.005 sec)

32
MariaDB [(none)]> select * from mysql.wsrep_cluster_membersG
*************************** 1. row ***************************
node_uuid: ea306990-35b0-11e9-9841-366f30fba24f
cluster_uuid: ea317655-35b0-11e9-9ac4-9f27c3510851
node_name: labrador
node_incoming_address: 127.0.0.1:16000
*************************** 2. row ***************************
node_uuid: eb29a68c-35b0-11e9-ac23-e2418aae257d
node_name: poodle
*************************** 3. row ***************************
node_uuid: eb29e56c-35b0-11e9-a328-fe229f8ae4cb
node_name: rotweiler
3 rows in set (0.006 sec)

33
MariaDB [(none)]> show create table mysql.wsrep_streaming_logG
*************************** 1. row ***************************
Table: wsrep_streaming_log
Create Table: CREATE TABLE `wsrep_streaming_log` (
`node_uuid` char(36) NOT NULL,
`trx_id` bigint(20) NOT NULL,
`seqno` bigint(20) NOT NULL,
`flags` int(11) NOT NULL,
`frag` longblob NOT NULL,
PRIMARY KEY (`node_uuid`,`trx_id`,`seqno`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.004 sec)

35
Galera 3
Galera Rolling Upgrades
Galera Replication
read & write
MariaDB
10.3
Galera 3
read & write
MariaDB
10.3
Galera 3
MariaDB
10.3
Wsrep-API 25
read & write

36
Galera 3
Galera Replication
read & write
MariaDB
10.3
Galera 3
read & write
MariaDB
10.3
Galera 3
MariaDB
10.3
Wsrep-API 25
Upgrade for 10.4
Shutdown server
Install 10.4
Start with wsrep_provider
mysql_upgrade
Shutdown server
Start without wsrep_provider
Isolate node
Galera 4
Galera 4
MariaDB
10.4
Allow read only access
read only

37
Galera 3
Galera Replication
read & write
MariaDB
10.3
Galera 3
MariaDB
10.3
Wsrep-API 25
Galera 4
MariaDB
10.4
read only
Galera 4
MariaDB
10.4
read only
Upgrade for 10.4
Upgrade node 2

38
Galera 3
Galera Replication
read & write
MariaDB
10.3
Wsrep-API 25
Galera 4
MariaDB
10.4
read only
Galera 4
MariaDB
10.4
read only
Wsrep-API 26
read & write read & write
Upgrade for 10.4
Shutdown node 1
Allow read-write
Complete node1 upgrade
wsrep API #26 features now
Enabled in replication

39
Galera Replication
read & write
Wsrep-API 25
Galera 4
MariaDB
10.4
read only
Galera 4
MariaDB
10.4
read only
Wsrep-API 26
Galera 4
MariaDB
10.4

40
Galera Replication
read & write
Wsrep-API 25
Galera 4
MariaDB
10.4
read only
Galera 4
MariaDB
10.4
read only
Wsrep-API 26
Galera 4
MariaDB
10.4 join
Galera 3
MariaDB
10.3

42
4.0 Release Status
●
Part of Galera 4 feature set was merged
in MariaDB 10.4 beta 2 release and is
now in the new 10.4 RC release
●
Schedule of remaining Galera 4 features
is not yet confrmed

43
Features Missed in MariaDB 10.4
●
Gcache encryption
●
Data at rest encryption for full replication pipeline
●
XA transaction support
●
Will be needed in sharding cluster
●
Non blocking DDL
●
Co-incides with other MariaDB non-locking DDL work
●
Cluster error voting
●
Galera library feature, may be in later 10.4.* releases

44
R
A
M
Data at rest encryption
Client
thread
Client
threadClient
thread
Buffer pool
gcache
ibdataibdata redo logredo log redo logbinlog
D
I
S
K

45
R
A
M
Client
thread
Client
threadClient
thread
Buffer pool
gcache
D
I
S
K

46
R
A
M
Client
thread
Client
threadClient
thread
Buffer pool
gcache
D
I
S
K

47
●
Gcache encryption
●
●
●
●
Non blocking DDL
●
●
●

XA Transaction Support
In Galera 3

49
XA Transactions with Galera 3
TM
RM RM
XA start ‘foo’ XA start ‘bar’
foo bar
Work on ‘foo’ Work on ‘bar’XA prepare ‘foo’ XA prepare ‘bar’XA commit ‘foo’ XA commit ‘bar’
foo bar
MariaDB

50
● Galera replication is eager to replicate in
MariaDB 2PC prepare stage
● Prepared XA transaction cannot be rolled back
anymore

51
XA Start
Node A Node B
smith smith
XA trans

52
XA Insert into persons ‘’jones’
Node A Node B
smith smith
jones
XA trans

53
XA Prepare
Node A Node B
smith smith
jones
XA trans

54
XA Prepare
Node A Node B
smith smith
jones
XA trans
WS
jones

55
XA Prepare
Node A Node B
smith
smith
jones
jones
XA trans apply

56
OK
Node A Node B
smith
smith
jones
jones
XA trans

57
XA Rollback
Node A Node B
smith
Smith
jones
jones
XA trans

58
Node A Node B
smith
smith
jonesinconsistency

59
XA prepare Safety
●
XA prepare should guarantee that
transaction can commit
●
However, galera multi-master confict
resolving does honor XA transactions

60
XA Start
Node A Node B
smith smith
XA trans

61
UPDATE smith=kit
Node A Node B
smith smith
XA trans

62
Node A Node B
smith smith
XA trans
WS
jones
UPDATE smith=hannibal
WS
hannibal
XA Prepare

63
Node A Node B
hannibal hannibal
XA trans
OK

XA Transaction Support by Streaming
Replication

65
XA Start
Node A Node B
smith smith
XA trans

66
XA Insert into persons ‘’jones’
Node A Node B
smith smith
XA transXA transXA transXA trans
jones

67
XA Prepare
Node A Node B
smith smith
XA trans SR trans
WS
jonesjones

68
XA Rollback
Node A Node B
smith
Smith
jones
XA trans SR trans
WS
rollback
jonesjones

69
Node A Node B
smith
Smith

70
●
Gcache encryption
●
●
●
●
Non blocking DDL
●
●
●

71
Summary
●
MariaDB 10.4.3 has signifcant new
Galera 4 features
●
Streaming Replication implements new
replication protocol opening possibilities
for many unforeseen replication features
●
Other new Galera 4 related features to
come with later 10.4 or 10.i releases
●
Rolling cluster upgrade supported and
requires some care

72
4
Happy Clustering :-)
Thank you for listening!

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