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// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build go1.13 && (linux || darwin)
// +build go1.13
// +build linux darwin
package pool
import (
"context"
"fmt"
"log"
"sort"
"sync"
"time"
"golang.org/x/build/internal/cloud"
)
// entry contains the resource usage of an instance as well as
// identifying information.
type entry struct {
createdAt time.Time
instanceID string
instanceName string
instanceType string
vCPUCount int64
}
// ledger contains a record of the instances and their resource
// consumption. Before an instance is created, a call to the ledger
// will ensure that there are available resources for the new instance.
type ledger struct {
mu sync.RWMutex
// cpuLimit is the limit of how many on-demand vCPUs can be created on EC2.
cpuLimit int64
// cpuUsed is the current count of vCPUs reserved for on-demand instances.
cpuUsed int64
// entries contains a mapping of instance name to entries for each instance
// that has resources allocated to it.
entries map[string]*entry
// instanceA1Limit is the limit of a1.metal instances which can be created on EC2.
instanceA1Limit int64
// instanceA1Used is the current count of a1.metal instances.
instanceA1Used int64
// types contains a mapping of instance type names to instance types for each
// ARM64 EC2 instance.
types map[string]*cloud.InstanceType
}
// newLedger creates a new ledger.
func newLedger() *ledger {
return &ledger{
entries: make(map[string]*entry),
instanceA1Limit: 1, // TODO(golang.org/issue/42604) query for limit once issue is resolved.
types: make(map[string]*cloud.InstanceType),
}
}
// ReserveResources attempts to reserve the resources required for an instance to be created.
// It will attempt to reserve the resourses that an instance type would require. This will
// attempt to reserve the resources until the context deadline is reached.
func (l *ledger) ReserveResources(ctx context.Context, instName, vmType string) error {
instType, err := l.PrepareReservationRequest(instName, vmType)
if err != nil {
return err
}
t := time.NewTicker(2 * time.Second)
defer t.Stop()
for {
if l.allocateResources(instType.CPU, instName, instType.Type) {
return nil
}
select {
case <-t.C:
case <-ctx.Done():
return ctx.Err()
}
}
}
// PrepareReservationRequest ensures all the preconditions necessary for a reservation request are
// met. If the conditions are met then an instance type for the requested VM type is returned. If
// not an error is returned.
func (l *ledger) PrepareReservationRequest(instName, vmType string) (*cloud.InstanceType, error) {
l.mu.RLock()
defer l.mu.RUnlock()
instType, ok := l.types[vmType]
if !ok {
return nil, fmt.Errorf("unknown EC2 vm type: %s", vmType)
}
_, ok = l.entries[instName]
if ok {
return nil, fmt.Errorf("quota has already been allocated for %s of type %s", instName, vmType)
}
return instType, nil
}
const a1MetalInstance = "a1.metal" // added for golang.org/issue/42604
// releaseResources deletes the entry associated with an instance. The resources associated with the
// instance will also be released. An error is returned if the instance entry is not found.
// Lock l.mu must be held by the caller.
func (l *ledger) releaseResources(instName string) error {
e, ok := l.entries[instName]
if !ok {
return fmt.Errorf("instance not found for releasing quota: %s", instName)
}
if e.instanceType == a1MetalInstance && l.instanceA1Used > 0 {
l.instanceA1Used--
}
l.deallocateCPU(e.vCPUCount)
return nil
}
// allocateResources ensures that there is enough CPU to allocate below the CPU Quota
// for the caller to create a resouce with the numCPU passed in. If there is enough
// then the ammount of used CPU will increase by the requested ammount. If there is
// not enough CPU available, then a false is returned. In the event that CPU is allocated
// an entry will be added in the entries map for the instance.
// It also enforces instance type limits.
func (l *ledger) allocateResources(numCPU int64, instName, instType string) bool {
// should never happen
if numCPU <= 0 {
log.Printf("invalid allocation requested: %d", numCPU)
return false
}
isA1Metal := instType == a1MetalInstance
l.mu.Lock()
defer l.mu.Unlock()
if isA1Metal && l.instanceA1Used >= l.instanceA1Limit {
return false
}
if numCPU+l.cpuUsed > l.cpuLimit {
return false
}
l.cpuUsed += numCPU
if isA1Metal {
l.instanceA1Used++
}
e, ok := l.entries[instName]
if ok {
e.vCPUCount = numCPU
} else {
l.entries[instName] = &entry{
instanceName: instName,
vCPUCount: numCPU,
instanceType: instType,
}
}
return true
}
// deallocateCPU releases the CPU allocated to an instance associated with an entry. When an instance
// is deleted, the CPU allocated for the instance should not be counted against the CPU quota reserved
// all on-demand instances. If an invalid CPU number is passed in the function will not lower the CPU count.
// Lock l.mu must be held by the caller.
func (l *ledger) deallocateCPU(numCPU int64) {
if numCPU <= 0 {
log.Printf("invalid deallocation requested: %d", numCPU)
return
}
if l.cpuUsed-numCPU < 0 {
log.Printf("attempting to deallocate more cpu than used: %d of %d", numCPU, l.cpuUsed)
return
}
l.cpuUsed -= numCPU
}
// UpdateReservation updates the entry for an instance with the id value for that instance. If
// an entry for the instance does not exist then an error will be returned. Another mechanism should
// be used to manage untracked instances. Updating the reservation acts as a signal that the instance
// has actually been created since the instance ID is known.
func (l *ledger) UpdateReservation(instName, instID string) error {
l.mu.Lock()
defer l.mu.Unlock()
e, ok := l.entries[instName]
if !ok {
return fmt.Errorf("unable to update reservation: instance not found %s", instName)
}
e.createdAt = time.Now()
e.instanceID = instID
return nil
}
// Remove releases any reserved resources for an instance and deletes the associated entry.
// An error is returned if and entry does not exist for the instance.
func (l *ledger) Remove(instName string) error {
l.mu.Lock()
defer l.mu.Unlock()
if err := l.releaseResources(instName); err != nil {
return fmt.Errorf("unable to remove instance: %w", err)
}
delete(l.entries, instName)
return nil
}
// InstanceID retrieves the instance ID for an instance by looking up the instance name.
// If an instance is not found, an empty string is returned.
func (l *ledger) InstanceID(instName string) string {
l.mu.RLock()
defer l.mu.RUnlock()
e, ok := l.entries[instName]
if !ok {
return ""
}
return e.instanceID
}
// SetCPULimit sets the vCPU limit used to determine if a CPU allocation would
// cross the threshold for available CPU for on-demand instances.
func (l *ledger) SetCPULimit(numCPU int64) {
l.mu.Lock()
defer l.mu.Unlock()
l.cpuLimit = numCPU
}
// UpdateInstanceTypes updates the map of instance types used to map instance
// type to the resources required for the instance.
func (l *ledger) UpdateInstanceTypes(types []*cloud.InstanceType) {
l.mu.Lock()
defer l.mu.Unlock()
for _, it := range types {
l.types[it.Type] = it
}
}
// resources contains the current limit and usage of instance related resources.
type resources struct {
// InstCount is the count of how many on-demand instances are tracked in the ledger.
InstCount int64
// CPUUsed is a count of the vCPU's for on-demand instances are currently allocated in the ledger.
CPUUsed int64
// CPULimit is the limit of how many vCPU's for on-demand instances can be allocated.
CPULimit int64
}
// Resources retrives the resource usage and limits for instances in the
// store.
func (l *ledger) Resources() *resources {
l.mu.RLock()
defer l.mu.RUnlock()
return &resources{
InstCount: int64(len(l.entries)),
CPUUsed: l.cpuUsed,
CPULimit: l.cpuLimit,
}
}
// ResourceTime give a ResourceTime entry for each active instance.
// The resource time slice is storted by creation time.
func (l *ledger) ResourceTime() []ResourceTime {
l.mu.RLock()
defer l.mu.RUnlock()
ret := make([]ResourceTime, 0, len(l.entries))
for name, data := range l.entries {
ret = append(ret, ResourceTime{
Name: name,
Creation: data.createdAt,
})
}
sort.Sort(ByCreationTime(ret))
return ret
}