Redundant Connections

What are redundant Connections

Since v3.1.0, Alpana implements a redundancy mechanism on Connections that allows to store multiple connection configurations inside a single Connection.
Each connection configuration is defined by a set of parameters (database name, user name, etc…), called a Parameter Set.

This can be used in basically 3 types of scenarios :

1. Using different databases for design time and run time
2. Implementing a fail-over mechanism to keep Dashboards working even when the primary database is down
3. a combination of scenario 1 and 2
   

Scenario 1 : Design Time / Run Time

You can select a different Parameter Set for Alpana Designer and Alpana Server.

This is useful for example if the developer doesn’t have access to the production database from the development machine, maybe because they are on a different network.
In this case, you can configure 2 different Parameter Sets :

1. one to work in the Designer by pointing on the local development database
2. one for the published Dashboards by pointing to the production database
   

Scenario 2 : Database1 / Database2

The Primary Parameter Set is where Alpana will try to connect first.
If the connection fails, Alpana will use the Secondary Parameter Set.

This is useful for example to ensure that Dashboards can always get data, even when the main database is unavailable.
In this case, you can configure 2 different Parameter Sets :

1. one pointing to the main database
2. one pointing to the backup database
   

Scenario 3 : combine

You can create 3 parameter sets for handling both scenarios above :

1. Parameter Set 1 : primary development
2. Parameter Set 2 : primary production
3. Parameter Set 3 : backup production
   

Fallback Logic

When a primary connection fails, Alpana will check the next one in order until it succeeds, or until all fail.

!Sometimes the connection failure is slow to detect, for example on some network timeouts.
If the primary connection fails with a 30s timeout, it means the fallback mechanism won’t kick in until then.
This delay will be repeated each time the dashboard is loaded, and until the primary connection is back online.

As a mitigation, all widgets that use the same connection will inherit the fallback.
This means that during a single page load, the timeout will happen only once per Connection.

*Note : there is a caching mechanism, so you may not notice the redundancy immediately.
When redundancy happens, you may need to refresh the page.
When the connection becomes good again, you may need to wait a few minutes for the dashboards to apply the primary connection again.

Alpana Designer

In Alpana Designer, the order is :

1. try to connect to the Primary parameters at design time
2. if it fails, try to connect to the Primary parameters after publication
3. if it fails, try to connect to other parameters
   

Alpana Server

In Alpana Server, the order is :

1. try to connect to the Primary parameters after publication
2. if it fails, try to connect to the Primary parameters at design time
3. if it fails, try to connect to other parameters
   

Connection Types

Redundant connections are supported by the following Connection types :

• SQL
• Historian
• Web
  

Managing Parameter Sets

A Parameter Set is the set of all the parameters required to connect to the data.

Default behavior

By default, only one Parameter Set is created for the current connection, and is used for both Designer and Server.

Renaming Parameter Sets

You can rename each Parameter Set :

Creating Parameter Sets

Click the + icon to create a new Parameter Set :

Editing other Parameter Sets

To edit a Parameter Set, click on the corresponding tab :

Deleting Parameter Sets

Click on the red cross to delete the corresponding Parameter Set :

Designer ⇔ Server switching

To choose which Parameter Set to use for Designer or Server, select the desired Parameter Set in each list :

1. Primary parameters at design time : primary connection to use while in Alpana Designer
2. Primary parameters after publication : primary connection to use while published in Alpana Server
   

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