Creating Collaborative Widgets Using Storage Service

When using a collaborative widget, you actually enrich your document with data corresponding to the user’s inputs. This data can be stored using the storage service.

This page discusses:

See Also
Storage type scopes
Common operations
How clients communicate with the Storage Service

The storage service is an untyped key/value storage that is accessed through a HTTP REST interface using simple commands such as get or put.

The storage service main intent is to provide persistence for Mashup UI applications that stretches beyond HTTP cookies and flat file storage. It is not a general-purpose database, and does not support SQL or any other query language.

Two client wrapper implementations exist for Javascript client use (asynchronous) and Java client use (synchronous).

Using the storage, you can:

  • Get arbitrary chunks of data (JSON strings, images, Java objects, etc.) attached to your Mashup UI application.

  • Delete, replace and append metas and categories to Exalead CloudView documents.

  • Store private data per user.

    Note: Keep in mind that data consistency/operation atomicity is not supported (not suitable for sensitive data).

Limitations

The storage does not:

  • Support any kind of typing - All data that is put in the storage is treated as binary blobs, which means that they are not treated at all.

  • Support transactions or ACID.

  • Guarantee data consistency.

By default the storage works with an SQLite engine and is therefore limited in terms of:

  • concurrent accesses, as each write action blocks the whole database,

  • scalability, when the number of entries is really big.

However, you can configure its JDBC connection to work with compatible databases (SQL Server, MySQL or Oracle) if you need the storage to be more scalable.

For more information, see Configure a compatible database for better performance.

Key/value pairs

Each key can be associated with one or [1:M] values. If a key name ends with '[]' it points to [1:M] values.

Examples:

  • single value pair: shoppingListLength -> 3

  • multi-valued pair: shoppingList[] -> [eggs, milk, toast]

The same key can exist in several scopes. Each pair is scoped using:

  • The Mashup UI application ID. If you are running multiple Mashup UI applications in your Exalead CloudView instance they have different ids.

  • The storage type scope which can be DOCUMENT, SHARED or USER.

Configure a compatible database for better performance

Tweaking the settings of the StorageService.xml file allows you to:

  • Switch from SQLite to another RDBMS for storage backend.

  • Change connection pooling parameters.

  • Disable the internal locking mechanism for SQLite.

The Storage does not expose its settings in any GUI, instead you have to manipulate the <DATADIR>/config/360/StorageService.xml file directly.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<StorageService xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="">
<StorageEngine className="com.exalead.cv360.storage.engine.jdbc.JdbcStorageEngine">

<!-- The JDBC driver's class name -->
<Parameter value="org.sqlite.JDBC" name="driver"/>

<!-- JDBC connection string, vendor-specific -->
<Parameter value="jdbc:sqlite:{dataDir}/storageService/storage.db.sqlite"
name="connection"/>

<!-- Tables are prefixed, useful if you are using the same database for many
different applications -->
<Parameter value="cv360" name="tablePrefix"/>

<!-- Internal read/write synchronization, disable for performance gain. Tries to
avoid potential file-system-level locking problems that can can occur if any
of the following applies:
1. You are using SQLite over a networked file-system
2. You are using SQLite under Mac OS/X
3. You are using an old version of SQLite
If none of the above applies you can safely disable this option.See http://
www.sqlite.org/lockingv3.html for more information on this issue -->
<Parameter value="true" name="synchronizedWrites"/>

<!-- DB username / password -->
<Parameter value="" name="username"/>
<Parameter value="" name="password"/>

<!-- The database connections are pooled, to avoid reconnecting every time. When
using a non-SQLite RDBMS, You can tweak (increase) the settings below for a
performance gain.poolMaxActive: Max. num opened connections - Keep low for -->
<Parameter value="1" name="poolInitialSize"/>
<Parameter value="3" name="poolMaxActive"/>
<Parameter value="2" name="poolMaxIdle"/>

</StorageEngine>
<RepushDocuments>false</RepushDocuments>
</StorageService>
Important: After each configuration change, you need to run the <DATADIR>/bin/cvcmd.sh applyConfig script and restart your Exalead CloudView instance.