Measures reported by AlibabaSLBTest

SLB (Server Load Balancer) distributes inbound network traffic across multiple Elastic Compute Service (ECS) instances that act as backend servers based on forwarding rules. You can use SLB to improve the responsiveness and availability of your applications.

After you add ECS instances that are deployed in the same region to a SLB instance, SLB uses virtual IP addresses (VIPs) to virtualize these ECS instances into backend servers in a highperformance server pool that ensures high availability. Client requests are distributed to the ECS instances based on forwarding rules.

SLB checks the health status of the ECS instances and automatically removes unhealthy ones from the server pool to eliminate single points of failure (SPOFs). This enhances the resilience of your applications. You can also use SLB to defend your applications against distributed denial of service (DDoS) attacks.

If an SLB instance is inaccessible to clients, then applications that overlay the backend ECS instances will be unable to receive or process requests, thereby impacting user productivity and damaging user experience with the Alibaba cloud. Similarly, if many backend ECS instances are unhealthy, then the healthy servers will be overloaded with requests, thereby affecting application responsiveness. To avoid this, administrators need to track the status of each SLB instance and the health of ECS instances managed by each instance. Additionally, the administrators also need to study the incoming and outgoing traffic of every SLB instance to ascertain whether a single SLB instance would suffice to cater to the availability and load requirements of the application, or whether multiple SLB instances are required. Likewise, the connection load on an instance, its responsiveness to requests, and the quality of these responses should also be monitored, so that overload conditions and processing latencies can be captured and addressed rapidly. The AlibabaSLBTest test helps administrators perform all of the above!

For an SLB instance, this test reports the status of that instance and the count of healthy and unhealthy servers managed by that instance. This way, administrators can figure out if too many unhealthy instances exist, diagnose the reason for the ‘bad health’ of the instances, and restore those instances to normalcy, so that they can be added back to the SLB server pool to ensure the high availability and responsiveness of the applications they support. Additionally, the test also tracks the request and response traffic to and from the SLB instance and the time taken by the instance to service the requests; in the process, the test draws administrator attention to potential bottlenecks in request processing. Administrators are also alerted if data, packets, and connections are dropped frequently. These metrics prompt administrators to figure out how the capacity of the SLB instance can be optimized, so it can handle additional load without dropping them.

Outputs of the test : One set of results for each SLB instance.

The measures made by this test are as follows: