# The TTL Of Kyuubi Engines For a multi-tenant cluster, its overall resource utilization is a KPI that measures how effectively its resource is utilized against its availability or capacity. To better improve the overall resource utilization of the cluster, - At cluster layer, we leverage the capabilities, such as [Capacity Scheduler](https://hadoop.apache.org/docs/stable/hadoop-yarn/hadoop-yarn-site/CapacityScheduler.html), of resource scheduling management services, such as YARN and K8s. - At application layer, we'd be better to acquire and release resources according to the real workloads. ## The Big Contributors Of Resource Waste - The time to wait for the resource to be allocated, such as the scheduling delay, the start/stop cost. - A longer time-to-live(TTL) for allocated resources can significantly reduce such time costs within an application. - The time being idle of the resource. - A shorter time to live for allocated resources can make all resources in rapid turnarounds across applications. ## TTL Types In Kyuubi Engines
- Engine TTL - The TTL of engines describes how long an engine will be cached after all sessions are disconnected. - Executor TTL - The TTL of the executor describes how long an executor will be cached when no tasks come. ## Configurations ### Engine TTL | Key | Default | Meaning | Type | Since | |----------------------------------------------|--------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------|--------------------------------------| | kyuubi\.session\.engine