Store and Forward in Thingworx Industrial Connectivity

[Swetha]

With reference to enabling of "Store and Forward" option in TWX Industrial Connectivity, I would like to get clarity on the following:

1. When there is a connectivity loss, does TWX Industrial Connectivity continuously check Thingworx for the instance of connection loss and retrieval (or) does Thingworx requests for lost data once when the connection is regained? In simple words, which side initiates the process?
2. When "Store and Forward" is enabled, does TWX Industrial Connectivity store each and every data regardless of connectivity or does it store only when there is a connectivity loss? 

[aservetas · Accepted solution]

1. TWX Industrial Connectivity manages the web socket connection and will continue to retry to connect to the Thingworx instance.

2. The Store and Forward buffer will only populate when the connection is lost, not continuously during normal communications.

Please note, buffered updates will not be sent to the ThingWorx application unless the forwarding mode is changed.  Per our help documentation:

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Forward Mode: Select a method to determine which updates are sent to ThingWorx when the connection is
restored. In situations that require active monitoring of production data without any data loss when
disconnected from the platform, it is possible to store and forward upon reconnect or to schedule
forwarding the stored updates for a time when production is not being actively monitored (for example,
during production downtime). Options include Active and On Hold:

- Active Mode - When the Forward Mode is set to Active, stored property updates are sent in the order
they were received until the ThingWorx Platform has received all updates. Updates are then sent to
the platform in real time. Property updates can be delayed due to the first In, first out nature of
property update forwarding when many updates are collected during a ThingWorx platform
disconnect.

- On Hold Mode - When the Forward Mode is set to On Hold, only the latest updates are sent to the
platform after recovering from a disconnect. This ensures that ThingWorx applications that are
actively monitoring production and get the freshest data available. When production is not being
actively monitored, the mode can be set to Active to start forwarding the older updates that were
stored while the server was disconnected from the platform. The industrial server buffers up to
25,000 property updates in memory before storing them to disk. Once the 25,000 update limit is
reached, the property updates are pushed to disk and held until the Forward Mode is set to Active.
This allows the industrial server to prioritize the most recent 25,000 updates when the connection to
the ThingWorx platform is restored, hold on to updates so they they’re not lost, and forward them
later. New updates are dropped when the datastore size limit is reached, or the disk is filled past the
500MB limit, whichever occurs first. The in-memory buffer is only typically filled when the connection
to the ThingWorx platform is lost; however, this can also occur when property updates are collected
at a rate faster than can be forwarded to the platform.

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Best regards,

Andy Servetas
Senior Technical Support Engineer | Kepware Technologies