feta/manager.go

package feta

import "sync"
import "time"
import "fmt"
import "runtime"

//import "github.com/gin-gonic/gin"
import "github.com/rs/zerolog/log"

const HOST_DISCOVERY_PARALLELISM = 10

type InstanceBackend interface {
	//FIXME
}

type InstanceManager struct {
	mu                       sync.Mutex
	instances                map[InstanceHostname]*Instance
	newInstanceNotifications chan InstanceHostname
	startup                  time.Time
	hostAdderSemaphore       chan bool
}

func NewInstanceManager() *InstanceManager {
	i := new(InstanceManager)
	i.hostAdderSemaphore = make(chan bool, HOST_DISCOVERY_PARALLELISM)
	i.instances = make(map[InstanceHostname]*Instance)
	return i
}

func (self *InstanceManager) logCaller(msg string) {
	fpcs := make([]uintptr, 1)
	// Skip 2 levels to get the caller
	n := runtime.Callers(3, fpcs)
	if n == 0 {
		log.Debug().Msg("MSG: NO CALLER")
	}

	caller := runtime.FuncForPC(fpcs[0] - 1)
	if caller == nil {
		log.Debug().Msg("MSG CALLER WAS NIL")
	}

	// Print the file name and line number
	filename, line := caller.FileLine(fpcs[0] - 1)
	function := caller.Name()

	log.Debug().
		Str("filename", filename).
		Int("linenum", line).
		Str("function", function).
		Msg(msg)
}

func (self *InstanceManager) Lock() {
	//self.logCaller("instancemanager attempting to lock")
	self.mu.Lock()
	//self.logCaller("instancemanager locked")
}

func (self *InstanceManager) Unlock() {
	self.mu.Unlock()
	//self.logCaller("instancemanager unlocked")
}

func (self *InstanceManager) AddInstanceNotificationChannel(via chan InstanceHostname) {
	self.Lock()
	defer self.Unlock()
	self.newInstanceNotifications = via
}

func (self *InstanceManager) Manage() {
	log.Info().Msg("InstanceManager starting")
	go func() {
		self.receiveNewInstanceHostnames()
	}()
	self.startup = time.Now()
	for {
		log.Info().Msg("InstanceManager tick")
		self.managerLoop()
		time.Sleep(1 * time.Second)
	}
}

func (self *InstanceManager) managerLoop() {
	self.Lock()
	il := make([]*Instance, 0)
	for _, v := range self.instances {
		il = append(il, v)
	}
	self.Unlock()

	for _, v := range il {
		if v.dueForFetch() {
			go func(i *Instance) {
				i.Fetch()
			}(v)
		}
	}

}

func (self *InstanceManager) hostnameExists(newhn InstanceHostname) bool {
	self.Lock()
	defer self.Unlock()
	for k, _ := range self.instances {
		if newhn == k {
			return true
		}
	}
	return false
}

func (self *InstanceManager) addInstanceByHostname(newhn InstanceHostname) {
	if self.hostnameExists(newhn) {
		return
	}

	// this blocks on the channel size, limiting concurrency
	self.hostAdderSemaphore <- true

	i := NewInstance(newhn)
	// we do node detection under the addLock to avoid thundering
	// on startup
	i.detectNodeTypeIfNecessary()

	// pop an item from the buffered channel
	<-self.hostAdderSemaphore

	// lock the map to insert
	self.Lock()
	self.instances[newhn] = i
	self.Unlock()

}

func (self *InstanceManager) receiveNewInstanceHostnames() {
	var newhn InstanceHostname
	for {
		newhn = <-self.newInstanceNotifications
		// receive them fast out of the channel, let the adding function lock to add
		// them one at a time
		go self.addInstanceByHostname(newhn)
	}
}

func (self *InstanceManager) logInstanceReport() {
	r := self.instanceSummaryReport()
	log.Info().
		Uint("up", r.up).
		Uint("total", r.total).
		Uint("identified", r.identified).
		Msg("instance report")
}

type InstanceSummaryReport struct {
	up         uint
	identified uint
	total      uint
}

func (r *InstanceSummaryReport) String() string {
	return fmt.Sprintf("up=%d identified=%d total=%d", r.up, r.identified, r.total)
}

func (self *InstanceManager) NumInstances() uint {
	return self.instanceSummaryReport().total
}

type InstanceListReport []*InstanceDetail

type InstanceDetail struct {
	hostname  string
	up        bool
	nextFetch string
}

func (self *InstanceManager) listInstances() []*Instance {
	var out []*Instance
	self.Lock()
	defer self.Unlock()
	for _, v := range self.instances {
		out = append(out, v)
	}
	return out
}

func (self *InstanceManager) instanceSummaryReport() *InstanceSummaryReport {
	self.Lock()
	defer self.Unlock()
	r := new(InstanceSummaryReport)

	r.total = uint(len(self.instances))

	for _, elem := range self.instances {
		if elem.identified == true {
			r.identified = r.identified + 1
		}

		if elem.status == InstanceStatusAlive {
			r.up = r.up + 1
		}
	}

	return r
}