Grid Properties

Property Contexts

If you have chosen to edit a property in different contexts by clicking on the property link, you will be shown a matrix. The matrix displays the values of this property in the different contexts and lets you override the values.

By default, contexts that are not used will be hidden. This is done in an attempt to make the configuration of properties less complicated. If no overrides have been done in other contexts, only the global context and the host contexts are shown. If possible, it is recommended to use only those contexts. However, there are situations when you need to use the other contexts.

If you need to use a context that is hidden, you need to change the display complexity at the top of the page in order to see and edit them.

Example:

Consider an application that uses lots of memory and you want to override the Max Heap property. Typically you would give this property a value in the global context. That means that all application instances on any host will get this value when reading this property.

However, assume that if the application is started using a particular node type, additional tasks will be assigned to it and you need even more memory. What you do in that case is to also override the Max Heap property in the context of that node type. So the property will have the global value in all application instances except instances belonging to this specific node type.

The contexts have different priorities, so a property may be defined in several contexts, and the one with the highest priority will be the actual runtime value depending on how and where the application is running.

The matrix displays the different values and how they are resolved. So, by overriding in one context it is easy to see what other contexts are overridden (because of lower priority) and what contexts inherit this value.

To help the user to understand how different contexts override other contexts, the matrix is displayed using overlapping boxes. Each context box encompasses all other contexts that it may influence. At the same time, it is easy to see if other context boxes overlap this box and thus have the potential of overriding the first context box.

The contexts are (lowest priority first):

Global (Grid-Wide & Any Host): This is the base context (lowest priority). Use this context to give a property a value regardless of other contexts (for example, host, binding). It is good practice to define a value even if you intend to override it in one of the other contexts. In the matrix the global value is shown in the first row (Grid-Wide) and first column (Any Host).

Node Type (Node Type & Any Host): Use this context to override a property for all application instances that are running in a node of this node type regardless of host or binding. In the matrix this value is shown in the row corresponding to the node type and the first column (Any Host).

Specific Host (Application Global & Specific Host): Use this context to override a property on a specific host. Any node and application instance started on that host will use this value unless overridden by one of the other contexts with higher priority. In the matrix this value is shown the first row (Grid-Wide) and the column corresponding to the specific host.

Binding (Binding & Any Host): Use this context to override a property in the context of a binding. Any node and application instance started with this binding will use this value unless overridden by a context with higher priority. In the matrix this value is shown in the row corresponding to the binding and the first column (Any Host).

Node Type & Specific Host: Use this context to override a property in the context of a node type on a specific host. In the matrix this value is shown in the row corresponding to the node type and the column corresponding to the host.

Binding & Specific Host: This is the context with the highest priority. It overrides a property value for application instances started with a particular binding on a particular host.

In runtime, resolving a property value will be done in the following fashion:

Each node and application instance is started using exactly one binding on exactly one host, so when resolving a property, the system will first look for a property override for exactly that binding on exactly that host (Binding & Specific Host context). If it finds one, the system has found the applicable runtime value and is finished. If not, the system will continue to look for a property override in contexts with lower priority until it finds a context that has defined an override. The last context to look in is the global context.

If a property has been overridden in a given context, a small black bullet will be displayed in front of the value. To remove an override, edit the value in the context that you want to remove, and click Remove.