Text Cache

Overview

Projects often make use of data which requires considerable time to obtain due to costly computations, network and database lag, and API calls pricing. Text Cache provides the functionality to temporarily store Text values in Appian for very low latency access. Expiration policies can be specified for each individual cache entry, allowing for flexible cache configurations. Experienced designers may utilize this plug-in in conjunction with Appian's internalize/externalize functions to directly cache queryEntity, queryProcessAnalytics or integration results.

Key Features & Functionality

Lightweight in-memory cache for Text values
Can store up to 10.000 entries. Once the limit is reached old entries will be overwritten following the configured expiration policy:
- Access: expires entries based on when they were last accessed
- Create: expires entries based on when they were they were created
Data is compressed to minimize memory usage without impacting retrieval performance.

Functions:

textcacheget(key) Retrieve an entry from cache (returns null if not in cache)
textcacheset(key, value, expireAfter, expirationPolicy) Set an entry in cache, if the key already exists the data will be updated. Expire after given minutes (default 5)
textcacheremove(key) Removes an entry from cache
textcachelifetime(key) Expected expiration, in milliseconds from the current time, for a given key.
textcachesize() Number of entries in cache.

*This plug-in is not designed to store extremely large text values, caution is advised*

Parents

derekl over 3 years ago
Something else we observed that may need some clarification in your description. The description states that the expiration policy is used "once the limit is reached". However, we've found that the expiration policy actually prevents items from getting expired even if the cache is not full. For example, consider:
1. An item is cached for 8 hours
2. After 1 hour without accessing the cache, the textcachelifetime is 7 hours
3. If the item is then accessed in the cache after 1 hour, the result of textcachelifetime is back to 8 hours
This may have some unintended consequences, such as if your system gets heavy usage, an item may never get removed from cache. In our case, we used it to cache access tokens that expire, and found that they were cached for too long because they were regularly accessed, resulting in authentication errors.

After we figured this out, it makes sense and we resolved our issue by switching to the "CREATE" expirationPolicy. However, this behavior wasn't clear to us from the description, so may be useful to clarify!

It might also be useful if there was some feature like a "maximumExpireAfter" that would allow you to utilize the "ACCESS" expiration policy, but cap it out so that it eventually expires.

ricardop thank you for the extremely useful plug-in!
- Cancel
- Up 0 Down
- Reply
- More
- Cancel

Comment

derekl over 3 years ago
Something else we observed that may need some clarification in your description. The description states that the expiration policy is used "once the limit is reached". However, we've found that the expiration policy actually prevents items from getting expired even if the cache is not full. For example, consider:
1. An item is cached for 8 hours
2. After 1 hour without accessing the cache, the textcachelifetime is 7 hours
3. If the item is then accessed in the cache after 1 hour, the result of textcachelifetime is back to 8 hours
This may have some unintended consequences, such as if your system gets heavy usage, an item may never get removed from cache. In our case, we used it to cache access tokens that expire, and found that they were cached for too long because they were regularly accessed, resulting in authentication errors.

After we figured this out, it makes sense and we resolved our issue by switching to the "CREATE" expirationPolicy. However, this behavior wasn't clear to us from the description, so may be useful to clarify!

It might also be useful if there was some feature like a "maximumExpireAfter" that would allow you to utilize the "ACCESS" expiration policy, but cap it out so that it eventually expires.

ricardop thank you for the extremely useful plug-in!
- Cancel
- Up 0 Down
- Reply
- More
- Cancel

Children

No Data