Hi Fusanmu,
On top of my colleague's advice, I would like to share a bit of experience around the usage of Auto-Refresh.
Auto-refresh, as the name says, will trigger the bound services at a fixed refresh rate. This means that regardless of the user interaction, your ThingWorx server will experience a constant load when users access mashups that contain such a widget+its triggered services. Depending on the services triggered, this is potentially something that you might not want, especially when building applications that will be used by a larger number of users, not just 1 or 5.
If the services/s triggered by autorefresh are reading/writing from disk or doing any complicated logic, the result will probably be that when you will hit a limit of 10-20 concurrent users your system will be quite stressed and possibly will not handle that load.
Therefore my advices regarding the auto-refresh are the following:
-ONLY use autorefresh if your usecase really requires the use of Auto-Refresh. Example: if there is a process in the production line that requires data to be displayed automatically without user interaction. If not, remove it and implement a manual "Refresh data" button. You need to think along the following line here: what value do I have for my user if the data refreshes automatically? Some people are tempted to say: if I see something wrong, then I act on it, but in this case you should send an alert to the user via other mechanism (email, sms etc) and not rely on him to have his eyes glued to the screen.
-If you can, instead of AutoRefresh, use the GetProperties with the "Automatically send properties when able" checkbox and implement the required information as a Thing Property. Why this? Because properties are stored in memory, and do not require any read/writes from the disk, hence being extremely fast.
-do not trigger services which execute read/write operations from the disk. This includes reading from files, reading from a database...and query a thing's historical properties (since that executes an SQL query). I can not provide all the list of services that read/write from the disk, but with a bit of experience, you should figure them out.
Keep in mind that all the things said above might not be true to all the situations, and try to think when it makes sense and when not.
And yes, if you carefully size your ThingWorx server, know the number of users that will use the application, Auto-Refresh will work
Good luck!
