Home
Reference
Find details on the SPL language, toolkits, APIs, commands, and more.
Toolkits
A toolkit is a set of SPL artifacts, which are organized into a package. Toolkits make SPL or native functions and primitive or composite operators reusable across different applications.
Toolkits
Toolkit com.teracloud.streams.crossdcfailover 2.0.0
Failover in a passive mode data center

Welcome
Learn about the core capabilities of Teracloud® Streams, its architecture, and key concepts.
Installing
Use this information to install, upgrade, and uninstall the Teracloud® Streams product.
Configuring
Create a basic or an enterprise domain which is a single point for configuring and managing common resources, security, and instances.
Administering
Administer the product by using the Teracloud® Streams graphical user interface, APIs, or the streamtool command-line interface.
Developing
Develop stream applications with the Streams Processing Language (SPL), Java, and Python.
Troubleshooting
Resolve problems with Teracloud® Streams using the troubleshooting tools provided with the product as well as the resources offered by Teracloud Support.
Reference
Find details on the SPL language, toolkits, APIs, commands, and more.
- APIs
  Application programming interfaces (APIs) provide functions that simplify applications development.
- Job configuration overlays
  You can specify or change configuration parameters when you use the submitjob or updateoperators operations. The settings control submission constraints, host constraints and locations, and operator status. Parameters are captured and updated in the configuration JSON file. When you change the values in the job configuration overlay file, the changes override any previously set values.
- Commands
  Teracloud® Streams provides a number of commands you use to perform tasks.
- Operator model
  An operator model is an XML document that describes the basic properties of a primitive operator.
- Streams Processing Language (SPL)
  Streams Processing Language (SPL) is a distributed data flow composition language that is used in Teracloud® Streams. SPL has primitive types, program structures, and definitions that are tailored for streaming data.
- Toolkits
  A toolkit is a set of SPL artifacts, which are organized into a package. Toolkits make SPL or native functions and primitive or composite operators reusable across different applications.
  - Specialized toolkit requirements and restrictions
    Several of the specialized toolkits require RPMs that are not required by the Teracloud® Streams product. There are also toolkit restrictions on some platforms.
  - Toolkits
- SPLDOC markup
  You can use SPLDOC markup in the descriptions associated with the SPL artifacts in a toolkit. The spl-make-doc command generates HTML documentation from the marked up artifacts.
Glossary
Use this glossary to find terms and definitions for Teracloud® Streams.

Failover in a passive mode data center

When one DC goes down in active/active mode, failover will happen automatically in the other DC's active copy of that same application. However, in an active/passive mode, the application in the passive data center only monitors the health of the active DC. When that active DC fails, the passive side should detect the failure and start the application. This task can be automated via a shell script.

The CrossDataCenterFailoverPassiveSample application from Learning through samples demonstrates this flow by calling the launch_app(rstring) native function to launch a shell script which starts the required application in the DC that is failing over. Please refer to that sample to learn more.

Additionally, see the etc/crossdc-failover.sh script in the toolkit for an example of a shell script that starts an application.