glb stands for glb Load Balancer; no, it's not Generics Load Balancer.
I decided to practice generics in Go 1.18 and developed this in the process. The idea behind it was hugely inspired by bag. Kudos to the author...
The repo contains implementation of the following load balancing algorithms:
- RoundRobin
- LeastConns
There are two implementations of LeastConns strategy. They are only different in
how they internally choose the least used backend. LeastConns holds backends []backend[T]
and returns the index of least used backend through leastUsedBackendIdx. LeastConnsHeap,
on the other hand, contains backends []*backend[T] and returns the least used backend
as *backend[T] through leastUsedBackend. These algorithms are safe for concurrent
usage, meaning that instances of these structs can be used by several goroutines at the same time.
One ramification of this for LeastConnsHeap is that each *backend will be allocated on the
heap, and as a result in situations where many instances of the structs are being created, each load balancing amongst hundreds of backends (e.g. think of modern cloud native apps which are comprised of hundreds of pods)
LeastConns is more preferable.
Following is the output of escape analysis for examples of LeastConns and LeastConnsHeap where I've marked
heap allocation lines with arrows:
go build -gcflags="-m" ./examples/leastconns/...
examples/leastconns/main.go:28:41: []*url.URL{...} does not escape
examples/leastconns/main.go:28:30: make([]glb.backend[go.shape.*uint8_0], len(glb.backends)) escapes to heap
examples/leastconns/main.go:28:30: &glb.LeastConns[go.shape.*uint8_0]{...} escapes to heap
glb/leastconns.go:25:12: make([]glb.backend[go.shape.*uint8_0], len(glb.backends)) escapes to heap
glb/leastconns.go:32:8: &glb.LeastConns[go.shape.*uint8_0]{...} escapes to heapgo build -gcflags="-m" ./examples/leastconnsheap/...
examples/leastconnsheap/main.go:28:45: []*url.URL{...} does not escape
examples/leastconnsheap/main.go:28:34: make([]*glb.backend[go.shape.*uint8_0], len(glb.backends)) escapes to heap
examples/leastconnsheap/main.go:28:34: &glb.backend[go.shape.*uint8_0]{...} escapes to heap <== **allocs**
examples/leastconnsheap/main.go:28:34: &glb.LeastConnsHeap[go.shape.*uint8_0]{...} escapes to heap
glb/leastconnsheap.go:20:12: make([]*glb.backend[go.shape.*uint8_0], len(glb.backends)) escapes to heap
glb/leastconnsheap.go:22:11: &glb.backend[go.shape.*uint8_0]{...} escapes to heap <== **allocs**
glb/leastconnsheap.go:27:8: &glb.LeastConnsHeap[go.shape.*uint8_0]{...} escapes to heap