Load Balancer
A load balancer is a component that, once invoked, it distributes incoming requests to a list of registered providers and return the value obtained from one of the registered providers to the original caller. For simplicity we will consider both the load balancer and the provider having a public method named get()
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Step 1 – Generate provider Generate a Provider that, once invoked on his get() method, retrieve an unique identifier (string) of the provider instance
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Step 2 – Register a list of providers Register a list of provider instances to the Load Balancer - the maximum number of providers accepted from the load balancer is 10
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Step 3 – Random invocation Develop an algorithm that, when invoking multiple times the Load Balancer on its get() method, should cause the random invocation of the get() method of any registered provider instance.
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Step 4 – Round Robin invocation Develop an algorithm that, when invoking multiple times the Load Balancer on its get() method, should cause the round-robin (sequential) invocation of the get() method of the registered providers.
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Step 5 – Manual node exclusion / inclusion Develop the possibility to exclude / include a specific provider into the balancer
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Step 6 – Heart beat checker The load balancer should invoke every X seconds each of its registered providers on a special method called check() to discover if they are alive – if not, it should exclude the provider node from load balancing.
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Step 7 – Improving Heart beat checker If a node has been previously excluded from the balancing it should be re-included if it has successfully been “heartbeat checked” for 2 consecutive times
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Step 8 – Cluster Capacity Limit Assuming that each provider can handle a maximum number of Y parallel requests, the Balancer should not accept any further request when it has (Y*aliveproviders) incoming requests running simultaneously