Creating and updating a subscription policy by using REST Administration APIs

http://<admin-endpoint-IP:Port>/ima/v1/configuration/

{    
   "SubscriptionPolicy": {
     "<NameOfSubscriptionPolicy>": {
       "Description": "string",
       "Subscription": "string",
       "ActionList": "string",
       "MaxMessages": integer,
       "MaxMessagesBehavior": "RejectNewMessages"|"DiscardOldMessages",
       "ClientID": "string",
       "UserID": "string",
       "GroupID": "string",
       "CommonNames": "string",
       "ClientAddress": "string",
       "Protocol": "string"             
    }
  }
}

NameOfSubscriptionPolicy

Required.

Specifies the name of the subscription policy.

The name must not have leading or trailing spaces and cannot contain control characters, commas, double quotation marks, backslashes, or equal signs. The first character must not be a number or any of the following special characters:

! # $ % & ' ( ) * + - . / : ; < > ? @

After the subscription policy is created, you cannot change this name.

Description

Optional.

Specifies a description for the subscription policy.

If you do not want a description, omit "Description":"description".

Subscription

Required if you are creating a subscription policy.

Specifies the global-shared durable subscription name that the subscription policy applies to.

If you are using MQTT global-shared subscriptions, you must configure a topic policy and a subscription policy. The Topic parameter in the topic policy and the Subscription parameter in the subscription policy must be correctly specified. For more information, see Topic filters for MQTT global-shared subscriptions.

You can use an asterisk (*) as a wildcard. You must take care when you use a wildcard to ensure that you do not grant greater authority to topics than intended. For more information about how wildcard characters can be used, see Wildcards.

If the subscription policy applies to a global-shared subscription that is to be used by MQTT applications, ensure that you do not include the forward slash character ( /) in Subscription.

The dollar sign ($) and asterisk (*) have special meanings in the Subscription field. To use these characters as literals, use ${$} for a dollar sign, and use ${*} for an asterisk.

You can use variable substitution to ensure that only clients with specific user IDs, group IDs, or client certificate common names can receive messages from a specified global-shared durable subscription. The variables are:

• ${UserID} for the user ID.
• ${GroupID} for the group ID.
• ${CommonName} for the client certificate common name.

ActionList

Required if you are creating a subscription policy.

Specifies which messaging actions can be used by clients that connect to endpoints associated with this subscription policy.

You can specify the following values for a subscription policy for global-shared durable subscriptions. To specify more than one, separate each value with a comma:

• Receive

  Allows clients to receive messages from the global-shared durable subscription that is specified in the Subscription field of the subscription policy.

• Control

  Allows global-shared durable subscriptions to be created and deleted. The name of the global-shared durable subscription is specified in the Subscription field of the subscription policy.

  To create or delete a global-shared durable subscription, a client must be allowed to receive messages. Therefore, if you select Control, you must also select Receive within the same subscription policy.

MaxMessages

Required for a global-shared durable subscription.

Specifies the maximum number of messages that are kept for a subscription. This value is a guideline, rather than an absolute limit. If the system is running under stress, then the number of buffered messages on a subscription might be slightly higher than the MaxMessages value.

The default value is 5000.

MaxMessagesBehavior

Optional.

Specifies the behavior that is applied when the number of messages in the buffer for a subscription reaches the max messages value. That is, when the buffer for a subscription is full. The behavior is applied only to global-shared durable subscriptions.

The behavior can be one of the following options:

• RejectNewMessages

  New messages are not accepted on the buffer for the subscription.

• DiscardOldMessages

  A percentage of the old messages on the buffer for the subscription are discarded. If a retained message is one of the old messages, it is discarded. The quality of service, persistence, and priority of the message does not prevent a message from being discarded. Therefore, if all messages must be received in order for your applications to function correctly, you cannot set MaxMessagesBehavior to DiscardOldMessages.

The default behavior is RejectNewMessages.

You can check that the configuration of your policy is as expected by using the Eclipse Amlen REST Administration API GET method. For more information about the GET method, see Viewing configuration details of objects that can be named by using REST Administration APIs.