Safety Policies

While Akamas leverages similar AI methods for both live optimizations and optimization studies, the way these methods are applied is radically different. Indeed, for optimization studies running in pre-production environments, the approach is to explore the configuration space by also accepting potential failed experiments, to identify regions that do not correspond to viable configurations. Of course, this approach cannot be accepted for live optimization running in production environments. For this purpose, Akamas live optimization uses observations of configuration changes combined with the automatic detection of workload contexts and provides several customizable safety policies when recommending configurations to be approved, revisited, and applied.

Akamas provides a few customizable optimizer options (refer to the options described on the Optimize step page of the reference guide) that should be configured so as to make configurations recommended in live optimization and applied to production environments as safe as possible.

Exploration factor

Akamas provides an optimizer option known as the exploration factor that only allows gradual changes to the parameters. This gradual optimization allows Akamas to observe how these changes impact the system behavior before applying the following gradual changes.

By properly configuring the optimizer, Akamas can gradually explore regions of the configuration space and slowly approach any potentially risky regions, thus avoiding recommending any configurations that may negatively impact the system. Gradual optimization takes into account the maximum recommended change for each parameter. This is defined as a percentage (default is 5%) with respect to the baseline value. For example, in the case of a container whose CPU limit is 1000 millicores, the corresponding maximum allowed change is 50 millicores. It is important to notice that this does not represent an absolute cap, as Akamas also takes into account any good configurations observed. For example, in the event of a traffic peak, Akamas would recommend a good configuration that was observed working fine for a similar workload in the past, even if the change is higher than 5% of the current configuration value.

Notice that this feature would not work for categorical parameters (e.g. JVM GC Type) as their values do not change incrementally. Therefore, when it comes to these parameters, Akamas by default takes a conservative approach of only recommending configurations with categorical parameters taking already observed before values. This still allows some never-observed values to be recommended as users are allowed to modify values also for categorical parameters when operating in human-in-the-loop mode. Once Akamas has observed that that specific configuration is working fine, the corresponding value can then be recommended. For example, a user might modify the recommended configuration for GC Type from Serial to Parallel. Once Parallel has been observed as working fine, Akamas would consider it for future recommendations of GC Type, while other values (e.g. G1) would not be considered until verified as safe recommendations.

The exploration factor can be customized for each live optimization individually and changed while live optimizations are running.

Safety factor

Akamas provides an optimizer option known as the safety factor designed to prevent Akamas from selecting configurations (even if slowly approaching them) that may impact the ability to match defined SLOs. For example, when optimizing container CPU limits, lower and lower CPU limits might be recommended, up to the point that the limit becomes too low that the application performance degrades.

Akamas takes into account the magnitude of constraint breaches: a severe breach is considered more negative than a minor breach. For example, in the case of an SLO of 200 ms on response time, a configuration causing a 1 sec response time is assigned a very different penalty than a configuration causing a 210 ms response time. Moreover, Akamas leverages the smart constraint evaluation feature that takes into account if a configuration is causing constraints to approach their corresponding thresholds. For example, in the case of an SLO of 200 ms on response time, a configuration changing response time from 170 ms to 190 ms is considered more problematic than one causing a change from 100 ms to 120 ms. The first one is considered by Akamas as corresponding to a gray area that should not be explored.

The safety factor is also used when starting the study in order to validate the behavior of the baseline to identify the safety of exploring configurations close to the baseline. If the baseline presents some constraint violations, then even exploring configurations close to the baseline might cause a risk. If Akamas identifies that, in the baseline configuration, more than (safety_factor*number_of_trials) manifest constraint violations then the optimization is stopped.

If your baseline has some trials failing constraint validation we suggest you analyze them before proceeding with the optimization

The safety factor is set by default to 0.5 and can be customized for each live optimization individually and changed while live optimizations are running.

Outlier detection

It is also worth mentioning that Akamas also features an outlier detection capability to compensate for production environments typically being noisy and much less stable than staging environments, thus displaying highly fluctuating performance metrics. As a consequence, constraints may fail from time to time, even for perfectly good configurations. This may be due to a variety of causes, such as shared infrastructure on the cloud, slowness of external systems, etc.

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