rabbah commented on a change in pull request #2360: Choose target invoker based
on specific invoker load.
URL:
https://github.com/apache/incubator-openwhisk/pull/2360#discussion_r122568453
##########
File path:
core/controller/src/main/scala/whisk/core/loadBalancer/LoadBalancerService.scala
##########
@@ -277,14 +277,44 @@ class LoadBalancerService(config: WhiskConfig,
entityStore: EntityStore)(implici
case _ => false
}
val invokers = if (isBlackbox) blackboxInvokers else managedInvokers
- val (hash, count) = hashAndCountSubjectAction(msg)
+ val hash = hashSubjectAction(msg).abs
invokers.flatMap { invokers =>
val numInvokers = invokers.length
if (numInvokers > 0) {
- val hashCount = math.abs(hash + count /
activationCountBeforeNextInvoker)
- val invokerIndex = hashCount % numInvokers
- Future.successful(invokers(invokerIndex))
+ val nextInvokerThreshold =
config.loadbalancerInvokerBusyThreshold
+ val homeInvoker = hash % numInvokers
+
+ val stepSizes = coprimePrimeNumbersUntil(numInvokers)
+ val step = stepSizes(hash % stepSizes.size)
+
+ /*
+ * Scans through all invokers and searches for an invoker,
which's queue is below
+ * the defined threshold. Iff no "underloaded" container was
found it will default
+ * to the least loaded invoker in the list.
+ *
+ * @param targetInvoker index of the invoker-candidate.
+ * @return name of the target invoker
+ */
+ @tailrec
+ def search(targetInvoker: Int): String = {
+ val invokerName = invokers(targetInvoker)
+
+ if
(activationByInvoker.get(invokerName).map(_.size).getOrElse(0) <
nextInvokerThreshold) {
Review comment:
how about some comments
```
+ // send the request to the target invoker if it has
capacity...
if
(activationByInvoker.get(invokerName).map(_.size).getOrElse(0) <
nextInvokerThreshold) {
invokerName
} else {
+ // ... otherwise look for a less loaded invoker by
stepping through a pre computed
+ // list of invokers; there are two possible
outcomes:
+ // 1. the search lands on a new invoker that has
capacity, choose it
+ // 2. walked through the entire list and found no
better invoker than the "home invoker", choose the least loaded invoker
```
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