Format Caching

There are a lot of data tables being transferred between Iotellect servers, clients and agents in every installation. Every table has a format descriptor that may contain significant amount of data, such as detailed descriptions (help texts) of fields, string-type or table-type default values, validators with their error messages, etc. In most cases, if a data table with 1-10 rows is encoded into a string for network transfer its format occupies more space then the data itself.

At the same time there are many tables that share same table formats. For example, there might be a thousand users that have different properties, but all those property tables have the same format.

Once tables that share the same format are transferred to a remote server (e.g. a client opens properties of multiple users for editing) it's important to avoid sending the shared table format multiple times. This is ensured by format caching technology of Iotellect Protocol.

Format caching works according to the following rules:

  • Once a data table with certain format is first encoded for network transfer, its format gets stored in Iotellect Server central format cache implemented by instance of FormatCache object and available via Server.getFormatCache() static method. The format gets a unique ID once it is cached.
  • If a table with the above ID is first sent through an Iotellect Protocol connection, both the format itself and its ID are sent. Connection client stores format and its ID in a connection's local cache available via AbstractAggreGateDeviceController.getFormatCache().
  • If a table with the same format is sent through the same connection again, only format ID is encoded and sent (the format itself is not sent). Connection client gets table format from its local cache once it's received such table.

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