Parallel apply is enabled using the
svc-parallelization-type and
channels options of
tpm. The parallelization type defaults to
none which is to say
that parallel apply is disabled. You should set it to
disk. The
channels option sets the the number of
channels (i.e., threads) you propose to use for applying data. Here is a
code example of a MySQL Applier installation with parallel apply enabled. The
Replica will apply transactions using 30 channels.
shell>./tools/tpm configure defaults \ --reset \ --install-directory=/opt/continuent \ --user=tungsten \ --mysql-allow-intensive-checks=true \ --profile-script=~/.bash_profile \ --start-and-report=trueshell>./tools/tpm configure alpha \ --master=sourcehost \ --members=localhost,sourcehost \ --datasource-type=mysql \ --replication-user=tungsten \ --replication-password=secret \ --svc-parallelization-type=disk \ --channels=10
shell> vi /etc/tungsten/tungsten.ini[defaults] install-directory=/opt/continuent user=tungsten mysql-allow-intensive-checks=true profile-script=~/.bash_profile start-and-report=true[alpha] master=sourcehost members=localhost,sourcehost datasource-type=mysql replication-user=tungsten replication-password=secret svc-parallelization-type=disk channels=10
Configuration group defaults
The description of each of the options is shown below; click the icon to hide this detail:
For staging configurations, deletes all pre-existing configuration information between updating with the new configuration values.
--install-directory=/opt/continuent
install-directory=/opt/continuent
Path to the directory where the active deployment will be installed. The configured directory will contain the software, THL and relay log information unless configured otherwise.
System User
--mysql-allow-intensive-checks=true
mysql-allow-intensive-checks=true
For MySQL installation, enables detailed checks on the supported data types within the MySQL database to confirm compatibility. This includes checking each table definition individually for any unsupported data types.
--profile-script=~/.bash_profile
profile-script=~/.bash_profile
Append commands to include env.sh in this profile script
Start the services and report out the status after configuration
Configuration group alpha
The description of each of the options is shown below; click the icon to hide this detail:
The hostname of the primary (extractor) within the current service.
--members=localhost,sourcehost
Hostnames for the dataservice members
Database type
For databases that required authentication, the username to use when connecting to the database using the corresponding connection method (native, JDBC, etc.).
The password to be used when connecting to the database using
the corresponding
--replication-user.
--svc-parallelization-type=disk
Method for implementing parallel apply
Number of replication channels to use for parallel apply.
If the installation process fails, check the output of the
/tmp/tungsten-configure.log file for
more information about the root cause.
There are several additional options that default to reasonable values. You may wish to change them in special cases.
buffer-size — Sets the
replicator block commit size, which is the number of transactions to
commit at once on Replicas. Values up to 100 are normally fine.
native-slave-takeover — Used
to allow Tungsten to take over from native MySQL replication and
parallelize it. See here for more.
You can check the number of active channels on a Replica by looking at the "channels" property once the replicator restarts.
Replica shell> trepctl -service alpha status| grep channels
channels : 10The channel count for a Primary will ALWAYS be 1 because extraction is single-threaded:
Primary shell> trepctl -service alpha status| grep channels
channels : 1Enabling parallel apply will dramatically increase the number of connections to the database server.
Typically the calculation on a Replica would be: Connections = Channel_Count x Sevice_Count x 2, so for a 4-way Composite Composite Active/Active topology with 30 channels there would be 30 x 4 x 2 = 240 connections required for the replicator alone, not counting application traffic.
You may display the currently used number of connections in MySQL:
mysql> SHOW STATUS LIKE 'max_used_connections';
+----------------------+-------+
| Variable_name | Value |
+----------------------+-------+
| Max_used_connections | 190 |
+----------------------+-------+
1 row in set (0.00 sec)Below are suggestions for how to change the maximum connections setting in MySQL both for the running instance as well as at startup:
mysql>SET GLOBAL max_connections = 512;mysql>SHOW VARIABLES LIKE 'max_connections';+-----------------+-------+ | Variable_name | Value | +-----------------+-------+ | max_connections | 512 | +-----------------+-------+ 1 row in set (0.00 sec) shell>vi /etc/my.cnf#max_connections = 151 max_connections = 512