// numNewHostsForDistro determine how many new hosts should be spun up for an
// individual distro
func (self *DeficitBasedHostAllocator) numNewHostsForDistro(
hostAllocatorData *HostAllocatorData, distro distro.Distro, settings *evergreen.Settings) int {
cloudManager, err := providers.GetCloudManager(distro.Provider, settings)
if err != nil {
evergreen.Logger.Logf(slogger.ERROR, "Couldn't get cloud manager for distro %v with provider %v: %v",
distro.Id, distro.Provider, err)
return 0
}
can, err := cloudManager.CanSpawn()
if err != nil {
evergreen.Logger.Logf(slogger.ERROR, "Couldn't check if cloud provider %v is spawnable: %v",
distro.Provider, err)
return 0
}
if !can {
return 0
}
existingDistroHosts := hostAllocatorData.existingDistroHosts[distro.Id]
runnableDistroTasks := hostAllocatorData.
taskQueueItems[distro.Id]
freeHosts := make([]host.Host, 0, len(existingDistroHosts))
for _, existingDistroHost := range existingDistroHosts {
if existingDistroHost.RunningTask == "" {
freeHosts = append(freeHosts, existingDistroHost)
}
}
numNewHosts := util.Min(
// the deficit of available hosts vs. tasks to be run
len(runnableDistroTasks)-len(freeHosts),
// the maximum number of new hosts we're allowed to spin up
distro.PoolSize-len(existingDistroHosts),
)
// cap to zero as lower bound
if numNewHosts < 0 {
numNewHosts = 0
}
return numNewHosts
}
// numNewDistroHosts computes the number of new hosts needed as allowed by
// poolSize. if the duration based estimate (durNewHosts) is too large, e.g.
// when there's a small number of very long running tasks, utilize the deficit
// of available hosts vs. tasks to be run
func numNewDistroHosts(poolSize, numExistingHosts, numFreeHosts, durNewHosts,
taskQueueLength int) (numNewHosts int) {
numNewHosts = util.Min(
// the maximum number of new hosts we're allowed to spin up
poolSize-numExistingHosts,
// the duration based estimate for the number of new hosts needed
durNewHosts,
// the deficit of available hosts vs. tasks to be run
taskQueueLength-numFreeHosts,
)
// cap to zero as lower bound
if numNewHosts < 0 {
numNewHosts = 0
}
return
}