Two caching bugs in CS

I use a lot of caching in my development and recently came across two bugs that I'd like to report to OpenText development.

The first bug is in $LLIAPI.CacheUtil.Update() in the part that invalidates the memached values:

// Invalidate the cache so that next access will request new data from the databaseif ( ok )    checkVal = $LLIAPI.MemcachedUtil.DeleteKey( prgCtx, .fMemcachedNamespace, objectID )    if ( checkVal.ok != TRUE )        EchoWarn( checkVal.errMsg )    endend

The code has no error handling if the $LLIAPI.MemcachedUtil.DeleteKey() call fails for any reason. This results in the subsequent $LLIAPI.CacheUtil.Load() call returning stale values rather than reloading the new values from the database. A possible fix is to roll back the transaction and return an error when the DeleteKey() call fails.

The second bug is with memcached. It seems Undefined can be stored as a value in memcached, but the $LLIAPI.MemcachedUtil.GetValue() call interprets this not being found (i.e., by returning found=false). For example:

Assoc resultsString namespace = "MyNamespace"String key = "MyKey"results = $LLIAPI.MemcachedUtil.GetValue(prgCtx, namespace, key)echo(results.found)// false, because a value hasn't been cached yet// cache an undefined value$LLIAPI.MemcachedUtil.SetValue(prgCtx, namespace, key, Undefined)results = $LLIAPI.MemcachedUtil.GetValue(prgCtx, namespace, key)echo(results.found)// still false, although the Undefined value was stored and returned from memcached

I think Undefined should be a valid cache value since it has application in, say, caching database values that are null.

Thanks!

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Comments

Jacopo Malnati

Good to know, thanks for sharing

Chris Meyer

I have another bug with $LLIAPI.CacheUtil I'd like to report. Consider the following code snippet:

Object prgCtx = $RHCore.Utils.GetPrgCtx()// Write "Value 1" to the cacheAssoc results = $LLIAPI.CacheUtil.New(prgCtx, "Value 1")if results.OK    // Get the cache id    Integer objectID = results.objectID    // Start a database transaction    if prgCtx.fDbConnect.StartTrans()        // Update the cache value for the given cache id        $LLIAPI.CacheUtil.Update(prgCtx, objectID, "Value 2")        // rollback the transaction, which should rollback the cache update        prgCtx.fDbConnect.EndTrans( false )    end    echo( $LLIAPI.CacheUtil.Load(prgCtx, objectID) )end

The output of this is "Value 2" when it should be "Value 1" due to the transaction rollback. The reason it fails is because memcache is updated with the new value in $LLIAPI.CacheUtil.Update() and ignores and database rollback. The fix is to delete the memcache key in the Update() call (with error handling, of course) and lazy load the memcache value on the next Load() call. Thanks!