I have 50-60 aws instances running behind an ALB in AWS. I can get the total request count in the cloudwatch monitoring section, but is there anyway I can get to know how many requests are actually being directed to each instances from the ALB in real time.
SnapOverflow
What are you trying to accomplish? There isn't a simple way to do this with default metrics in Cloudwatch.
However, AWS now supports "Metric Math" if you wanted to use that to calculate a value. You could use that and a network in / out metric to estimate the traffic per instance, or you could use a custom metric from the instance.
If it doesn't need to be real-time, you could process the instance logs, push them into firehose or cloudwatch logs and build metrics off that.
For access logs it should be possible to enable ALB logs, and analyze them. The field target contains the information to which instance the request was routed.
https://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-access-logs.html#access-log-entry-format
Another way to find out the maximim amount of requests for an instance type is to setup a loadtest witb e.g. Apache Jmeter, build a set of requests from e.g. ALB logs, and run them against a single instance while monitoring the instance metrics. Doing so, make sure TLS is terminated the same way as in the production setup. TLS can have a major impact on test results with high request counts. In case you have a ALB / ELB in the test calls be aware that these need time to ramp up or "pre-heat" them as otherwise requests could be dropped there.