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What synchronous and asynchronous notifications are

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FPolicy sends notifications to external FPolicy servers via the FPolicy interface. The notifications are sent either in synchronous or asynchronous mode. The notification mode determines what ONTAP does after sending notifications to FPolicy servers.

  • Asynchronous notifications

    With asynchronous notifications, the node does not wait for a response from the FPolicy server, which enhances overall throughput of the system. This type of notification is suitable for applications where the FPolicy server does not require that any action be taken as a result of notification evaluation. For example, asynchronous notifications are used when the storage virtual machine (SVM) administrator wants to monitor and audit file access activity.

    If an FPolicy server operating in asynchronous mode experiences a network outage, FPolicy notifications generated during the outage are stored on the storage node. When the FPolicy server comes back online, it is alerted of the stored notifications and can fetch them from the storage node. The length of time the notifications can be stored during an outage is configurable up to 10 minutes.

    Beginning with ONTAP 9.14.1, FPolicy allows you to set up a persistent store to capture file access events for asynchronous non-mandatory policies in the SVM. Persistent stores can help decouple client I/O processing from FPolicy notification processing to reduce client latency. Synchronous (mandatory or non-mandatory) and asynchronous mandatory configurations are not supported.

  • Synchronous notifications

    When configured to run in synchronous mode, the FPolicy server must acknowledge every notification before the client operation is allowed to continue. This type of notification is used when an action is required based on the results of notification evaluation. For example, synchronous notifications are used when the SVM administrator wants to either allow or deny requests based on criteria specified on the external FPolicy server.

Synchronous and asynchronous applications

There are many possible uses for FPolicy applications, both asynchronous and synchronous.

Asynchronous applications are ones where the external FPolicy server does not alter access to files or directories or modify data on the storage virtual machine (SVM). For example:

  • File access and audit logging

  • Storage resource management

Synchronous applications are ones where data access is altered or data is modified by the external FPolicy server. For example:

  • Quota management

  • File access blocking

  • File archiving and hierarchical storage management

  • Encryption and decryption services

  • Compression and decompression services