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How To: Author a ForgeTree
How-To: Author a ForgeTree
This page provides a detailed guide how to author a ForgeTree and utilize the various features of Forge.
Overview of ForgeTree Properties
How Forge TreeWalker Walks the ForgeTree
{
"RootTreeNodeKey": "Root",
"Tree": {
"Root": {
"Type": "Selection",
"ChildSelector": [
{
"Label": "Container",
"ShouldSelect": "C#|UserContext.ResourceType == \"Container\"",
"Child": "Container"
},
{
"Label": "Node",
"ShouldSelect": "C#|UserContext.ResourceType == \"Node\"",
"Child": "Node"
}
]
},
"Container": {
"Type": "Action",
"Actions": {
"CollectDiagnosticsAction_Container": {
"Action": "CollectDiagnosticsAction"
}
},
"ChildSelector": [
{
"Label": "Tardigrade",
"ShouldSelect": "C#|Session.GetLastActionResponse().Status == \"Success\"",
"Child": "Tardigrade"
}
]
},
"Tardigrade": {
"Type": "Action",
"Actions": {
"TardigradeAction_Tardigrade": {
"Action": "TardigradeAction",
"Input": {
"Context": "ContainerFault",
"EnableV2": true,
"DiagnosticData": "C#|Session.GetLastActionResponse().Output"
}
}
},
"ChildSelector": [
{
"Label": "Tardigrade_Success",
"ShouldSelect": "C#|(await Session.GetOutputAsync(\"Tardigrade_TardigradeAction\")).Status == \"Success\"",
"Child": "Tardigrade_Success"
},
{
"Label": "Tardigrade_Failure",
"Child": "Tardigrade_Failure"
}
]
},
"Tardigrade_Failure": {
"Type": "Leaf"
},
"Tardigrade_Success": {
"Type": "Leaf",
"Actions": {
"LeafNodeSummaryAction_Tardigrade_Success": {
"Action": "LeafNodeSummaryAction",
"Input": {
"Status": "C#|string.Format(\"{0}_{1}\", \"ContainerFaultScenario\", (await Session.GetLastActionResponseAsync()).Status)",
"StatusCode": 0,
"Output": {
"ActionOutput": "C#|(await Session.GetLastActionResponseAsync()).Output",
"DiagnosticsOutput": "C#|(await Session.GetOutputAsync(\"Container_CollectDiagnosticsAction\")).Output"
}
}
}
}
},
"Node": {
"Type": "Selection",
"Properties": {
"Notes": "Decision to Reboot or Evacuate is decided in UserContext.ShouldReboot()."
},
"ChildSelector": [
{
"Label": "Reboot",
"ShouldSelect": "C#|UserContext.ShouldReboot()",
"Child": "Reboot"
},
{
"Label": "Evacuate",
"Child": "Evacuate"
}
]
},
"Reboot": {
"Type": "Action",
"Actions": {
"RebootAction_Reboot": {
"Action": "RebootAction",
"RetryPolicy": {
"Type": "FixedCount",
"MaxRetryCount": 3,
"MinBackoffMs": 1000
},
"ContinuationOnRetryExhaustion": true
}
}
},
"Evacuate": {
"Type": "Action",
"Actions": {
"EvacuateAction_Evacuate": {
"Action": "EvacuateAction",
"Timeout": 60000,
"RetryPolicy": {
"Type": "ExponentialBackoff",
"MinBackoffMs": 1000,
"MaxBackoffMs": 30000
},
"ContinuationOnTimeout": true
},
"NotifyCustomerAction_Evacuate": {
"Action": "NotifyCustomerAction",
"Properties": "Notify customer in parallel with the impact."
}
},
"Timeout": "C#|UserContext.GetTimeoutForEvacuatingAndNotifyingCustomer()"
}
}
}{
"RootTreeNodeKey": "Root",
"Tree": {
"Root": {Tree is a dictionary that maps unique TreeNodeKey strings to TreeNodes. In the example we see several TreeNodeKeys, such as: Root, Container, Node, etc..
RootTreeNodeKey defines the suggested "Root" TreeNodeKey that should be visited first when walking the tree. Without this property, the callers of WalkTree would not know which TreeNodeKey to visit first since the TreeNodes are organized in a dictionary.
The default value of RootTreeNodeKey is "Root."
"Root": {
"Type": "Selection",
"ChildSelector": [
{
"Label": "Container",
"ShouldSelect": "C#|UserContext.ResourceType == \"Container\"",
"Child": "Container"
},
{
"Label": "Node",
"ShouldSelect": "C#|UserContext.ResourceType == \"Node\"",
"Child": "Node"
}
]
},Let's look at our first TreeNode, which is a Selection node. There are 4 TreeNodeTypes: Selection, Action, Leaf, and Subroutine. Selection type nodes have the following behavior:
- ChildSelector is defined. Attempts to select a child node to visit next.
- Does not execute any Actions.
- Does not consume the TreeNode Timeout.
ChildSelectors define the connections to child TreeNodes, as well as the conditions required to visit each child. Several TreeNodeTypes can use ChildSelectors, including: Selection, Action, Subroutine. Let's break down each property:
- Label - This is used only in ForgeEditor for visualization purposes. It is the text that hovers above each child TreeNode. Recommend using this to describe the ShouldSelect statement. This gives context to why the child is being visited.
- ShouldSelect - A string code-snippet that can be parsed and evaluated to a boolean value. If the expression is true, visit the attached Child TreeNode. If the expression is empty, evaluate to true by default. We'll dive more into "C#|" and Roslyn further down. For now, you can read the first ShouldSelect statement as follows: If the ResourceType equals Container, then visit the Container TreeNode.
- Child - The string TreeNodeKey that will be visited if the attached ShouldSelect expression evaluates to true.