Lookout.ini SymLinkCacheSeconds Settings

[Big Dog]

I'm trying to have Lookout retain it's values indefinitely for symbolic links even though the link's focus has been adjusted. The Lookout.ini files has a parameter called 'SymLinkCacheSeconds' which defaults to 600 seconds. I've tried zero (0) and negative one (-1), but not sure if either one is correct as the process behaves the same regardless if I use the default, 0, or -1. Any suggestions on which one or neither is correct?

[Roli]

Big Dog,

I've created a knowladgebase (which is still NI internal, but might go online) that explains your question.

Hope this helps.

Regards
Roland
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Lookout and Symbolic Links - How Does the Caching Works?

Product Group: Lookout Software

Product Name: Lookout

Version/Revision: 4.5.1.18

Problem: Lookout as application does communicate its values through the underneath networking protocol (aka Logos). If you have symbolic links as subscriber and/or publisher Lookout's Logos interfaces (the client and the server) handle the symbolic link'ed object in as cached objects before they get destroyed. How do you customize this caching mechanisme?


Solution: Subscription Cache Overview:
For each Logos subscription or remoted UI CBX there exists an internal LookoutLogosSubscription (LLS) object. It is this LLS object that implements symbolic links when they are being used for real time data. For efficiency (and to cover up a limitation with some drivers that causes writes to be lost if the write connection is deleted too soon after the write) the LLS maintains a cache of old subscriptions. When the symbolic link source changes, it caches the current subscription and looks in the cache for the new source. If it found the new source, it removes it from the cache and makes it active, otherwise it subscribes to the source
as usual. When a subscription is in the cache, it is deactivated so that no network bandwidth will be used. The LogosServer part of Lookout does not delete the connections for subscriptions that are deactivated.

The LookoutLogosClient object also maintains a global list of subscriptions so that it can flush subscriptions that haven't been used in a while. The timeout for cached subscriptions is configured in the Lookout INI file ([Network] SymlinkCacheSeconds) and defaults to 10 minutes (600 seconds). The cache flushing is driven by an internal Lookout timer.

Lookout.ini Setting:
[network]
SymlinkCacheSeconds=600
Default value is 600, meaning 600 seconds or 10 minutes. This sets the time that Lookout will keep track of values from a given symbolic link focus after that symbolic link has changed focus.
Special values: 0, should disable any caching of inactive symbolic links. -1, should be converted to the biggest possible amount of seconds to cache the symbolic links.

There is no way to specify an infinite time.

[Big Dog]

Thanks Roland, I've been looking for the relationship between Logos and Symbolic Links. Nice app note!!