Retry mechanism ensures the guaranteed delivery of messages from CentraSite to API Portal, and protects requests from transient failures that might occur while sending messages from CentraSite to API Portal.

When an API developer requests an API access token (access token of the type, API key or OAuth2 token) in API Portal, CentraSite receives the request for the access token, and processes the request. CentraSite then generates the access token and sends the access token details to API Portal. If a transient failure occurs while sending the access token to API Portal, CentraSite uses the retry mechanism to resend the token. Requests for renewal and revocation of access tokens are also handled in a similar manner.

Beginning with version 9.12, API Portal is configurable to work as a standalone component. This means that an instance of API Portal can be integrated with any third-party API Management tool (other than CentraSite or Mediator) for the access token retrieval functions of APIs deployed in the third-party environments.

For CentraSite instances configured to API Portal 9.12, CentraSite uses default scheduler to resend the undelivered access tokens to API Portal. The PollingInterval of the default scheduler is set to 120 minutes. CentraSite resends the undelivered access tokens at a regular time interval of 2 hours (120 minutes).

You can view and change the default scheduler settings using the centrasite.xml configuration. For more information, see Changing the Default Scheduler for Resending Undelivered Access Tokens later in this chapter.

CentraSite uses the global values set for numberOfRetries and retryIntervals to resend the undelivered tokens to API Portal. For n retries, specify n number of values (comma separated) for retry intervals. By default, numberOfRetries = 5 and retryIntervals = 10,300,900,1800,3600 seconds. In case of a transient failure, CentraSite tries to resend the token 5 times at time intervals of 10,300,900,1800 and 3600 seconds respectively.

You can view and change the default values of numberOfRetries and retryIntervals using the command line interface CentraSiteCommand.cmd (Windows) or CentraSiteCommand.sh (UNIX) of CentraSite Command. For usage description of the command line, see Managing Access Tokens through Command Line Interface later in this chapter.