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Wait

  • Artikkeli

APPLIES TO: All API Management tiers

The wait policy executes its immediate child policies in parallel, and waits for either all or one of its immediate child policies to complete before it completes. The wait policy can have as its immediate child policies one or more of the following: send-request, cache-lookup-value, and choose policies.

Note

Set the policy's elements and child elements in the order provided in the policy statement. Learn more about how to set or edit API Management policies.

Policy statement

<wait for="all | any">
  <!--Wait policy can contain send-request, cache-lookup-value,
        and choose policies as child elements -->
</wait>

Attributes

Attribute Description Required Default
for Determines whether the wait policy waits for all immediate child policies to be completed or just one. Allowed values are:

- all - wait for all immediate child policies to complete
- any - wait for any immediate child policy to complete. Once the first immediate child policy has completed, the wait policy completes and execution of any other immediate child policies is terminated.

Policy expressions are allowed.		 No all

Elements

May contain as child elements only send-request, cache-lookup-value, and choose policies.

Usage

Example

In the following example, there are two choose policies as immediate child policies of the wait policy. Each of these choose policies executes in parallel. Each choose policy attempts to retrieve a cached value. If there is a cache miss, a backend service is called to provide the value. In this example the wait policy does not complete until all of its immediate child policies complete, because the for attribute is set to all. In this example the context variables (execute-branch-one, value-one, execute-branch-two, and value-two) are declared outside of the scope of this example policy.

<wait for="all">
  <choose>
    <when condition="@((bool)context.Variables["execute-branch-one="])">
      <cache-lookup-value key="key-one" variable-name="value-one" />
      <choose>
        <when condition="@(!context.Variables.ContainsKey("value-one="))">
          <send-request mode="new" response-variable-name="value-one">
            <set-url>https://backend-one</set-url>
            <set-method>GET</set-method>
          </send-request>
        </when>
      </choose>
    </when>
  </choose>
  <choose>
    <when condition="@((bool)context.Variables["execute-branch-two="])">
      <cache-lookup-value key="key-two" variable-name="value-two" />
      <choose>
        <when condition="@(!context.Variables.ContainsKey("value-two="))">
          <send-request mode="new" response-variable-name="value-two">
            <set-url>https://backend-two</set-url>
            <set-method>GET</set-method>
          </send-request>
        </when>
      </choose>
    </when>
  </choose>
</wait>

Related content

For more information about working with policies, see: