Persistence configuration
Transformer’s built-in Persistence Service provides a persistent key-value store, shareable between nodes in a Transformer cluster. The configuration items here are used to define how persistence databases and files are accessed and controlled.
Overview
The Persistence Service is disabled by default. To activate the Persistence Service, see Activating the Persistence Service 7.
The Persistence Service 7 persists data to a JDBC-compliant relational database server or to the local file system. From version 7 of the Persistence Service, a JDBC database server is the only persistence store that can be used in a Transformer cluster. File-backed persistence (persisting data to the local file system) is provided as an option of convenience for development environments, but it is unsupported in production environments.
| File-backed persistence is unsupported in production environments, and, from version 7 of the Persistence Service, file-backed persistence cannot be used in Transformer clusters. |
To configure persistence to a database, besides defining the relevant configuration items that are documented here, you’ll also need to set up the persistence database, giving it a name, defining the table and columns needed to store the persisted data, and defining the usernames(s) and access permissions that will allow Transformer to write and read the data.
Add your persistence configuration to the file <Framework-root>/global_config/overrides/PersistenceService/Transformer/etc/persistence.conf, where <Framework-root> is your Deployment Framework’s top-level directory.
| In the following documentation, the term "this Transformer" means the Transformer for which you are defining the configuration, and "this node" means the cluster node that "this Transformer" represents. |
Example configuration
Example persistence configuration for Transformer 6.2 and Transformer 7:
persistence-classid com/caplin/transformer/persistence/JdbcPersistorImpl add-database-params init-string jdbc:mysql://192.168.1.50:3306/rtas driver-name org.mariadb.jdbc.Driver username admin password admin end-add-database-params
persistence-classid com/caplin/transformer/persistence/JdbcPersistorImpl add-database-params init-string jdbc:mysql://192.168.1.50:3306/rtas driver-name org.mariadb.jdbc.Driver table-name persistence columns pers_key pers_val username admin password admin end-add-database-params
enable-file-database
add-database-params
init-string ${ccd}/persistence.db
end-add-database-params
add-database-params
add-database-params specifies parameters for the database or file used to persist data.
Syntax:
add-database-params init-string [string] driver-name [string] username [string] password [string] table-name [string] columns [array of strings] extra-params [array of strings] end-add-database-params
add-database-params init-string [string] end-add-database-params
| Option | Type | Default | Description | ||
|---|---|---|---|---|---|
array of strings |
[none] |
A space-separated list of the names of the database columns where the persisted data is stored. Each piece of data is stored as a key-value pair. The names of the database columns should be listed in this order: <key column> <value column>. For example, to persist keys to a column called 'pers_key' and values to a column called 'pers_val', use the configuration below: columns pers_key pers_val
|
|||
string |
[none] |
The name of the JDBC driver. For example: |
|||
array of strings |
[implementation dependent] |
An optional list of additional parameters recognised by the The default JDBC implementation of extra-params <connection-validation-timeout> <query-execution-timeout>
|
|||
string |
[none] |
Initialisation string for the persistence database or file.
|
|||
string |
[none] |
The database access password associated with |
|||
string |
[none] |
The name of the database table where the persisted data is stored.
|
|||
string |
[none] |
The username that allows access to the database. |
disable-cluster-replication
| Persistence Service 6.2 only. The Persistence Service 7 does not replicate persisted values between nodes in a cluster. |
disable-cluster-replication when TRUE, prevents this Transformer from sending to the other Transformers in the cluster data that it has already persisted.
When persistence is file-based, don’t specify disable-cluster-replication. The default value of FALSE then applies, and, although each Transformer in the cluster maintains its own persistence file, this Transformer sends a copy of its persisted data to every other Transformer so that they can also write it to their own persistence files.
Conversely, when a (shared) persistence database is used, you should set disable-cluster-replication to TRUE on every node in the cluster to prevent multiple copies of the same data being persisted to the (shared) database. You should set dont-persist-cluster-messages to TRUE as well.
Version: 6.2
Syntax: disable-cluster-replication <boolean>
Type: boolean
Default value: FALSE
dont-persist-cluster-messages
| Persistence Service 6.2 only. The Persistence Service 7 does not replicate persisted values between nodes in a cluster. |
dont-persist-cluster-messages when TRUE, ensures that messages received from another Transformer in the cluster are not persisted on this Transformer.
When persistence is file-based, don’t specify dont-persist-cluster-messages. The default value of FALSE then applies, so that this Transformer saves to its own persistence file all the persisted data that other Transformers in the cluster send to it.
Conversely, when a (shared) persistence database is used, you should set dont-persist-cluster-messages to TRUE on every node in the cluster, to prevent the same data being persisted to the database multiple times (the data’s then persisted solely by the Transformer where it originated). You should set disable-cluster-replication to TRUE as well.
Version: 6.2
Syntax: dont-persist-cluster-messages <boolean>
Type: boolean
Default value: FALSE (messages from another cluster node are always persisted on this node)
enable-file-database
enable-file-database when TRUE, enables file-based persistence.
| File-backed persistence is unsupported in production environments, and, from version 7 of the Persistence Service, file-backed persistence cannot be used in Transformer clusters. |
Version: 6.2, 7.0+
Syntax: enable-file-database <boolean>
Type: boolean
Default value: FALSE (data is persisted to a database)
logfile
logfile specifies the name of the file in which events about persisting data are recorded.
The filename can contain the parameters %a and %h At run time, %a is replaced by the Transformer’s application name (see the DataSource configuration item application-name), and %h is replaced by the host name of the machine on which the Transformer is running.
Version: 6.2, 7.0+
Syntax: logfile <log-file-name>
Type: string
Default value: persistence.log
log-level
log-level specifies the severity of the errors and events that Transformer’s persistence module writes to its log file (see logfile).
Version: 6.2, 7.0+
Syntax: log-level <log-level-name>
Type: string
Default value: INFO
Values accepted:
| Level | Description |
|---|---|
|
Reports all errors and events. |
|
Reports events and information regarding normal operation of the persistence module, and all errors included in the |
|
Reports minor errors and all errors included in the |
|
Reports errors regarding data corruptions and all errors included in the |
|
Reports serious errors and all errors included in the |
|
Reports critical errors that prevent the persistence module from running. |
persistence-classid
persistence-classid specifies the Java class ID of the implementation of the Java Persistor interface that provides this Transformer’s database persistence capability. There’s a basic JDBC implementation of Persistor that’s provided with, and used by, Transformer’s Persistence Config blade; it’s called JdbcPersistorImpl. (For more about Persistor and JdbcPersistorImpl, see the Transformer Persistence API for Java documentation.)
The class ID is conventionally the fully-qualified name of the implementation of Persistor, with periods (.) replaced by foward slashes (/).
Version: 6.2, 7.0+
Syntax: persistence-classid <java-class-id>
Type: string
Default value: (none; but persistence-classid is only required if enable-file-database is FALSE)
Example:
persistence-classid com/caplin/transformer/persistence/JdbcPersistorImpl
If you’ve created your own implementation of Persistor, you must also specify your implementation class in an add-javaclass configuration item. Set the add-javaclass::class-id option to the same value that you used for persistence-classid.
See also: