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host_filter.go
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/
host_filter.go
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package instance
import (
"context"
"fmt"
"net"
"sync"
"github.com/prometheus/common/model"
"github.com/prometheus/prometheus/config"
"github.com/prometheus/prometheus/discovery/kubernetes"
"github.com/prometheus/prometheus/discovery/targetgroup"
"github.com/prometheus/prometheus/pkg/labels"
"github.com/prometheus/prometheus/pkg/relabel"
)
// HostFilterLabelMatchers are the set of labels that will be used to match
// against an incoming target.
var HostFilterLabelMatchers = []string{
// Consul
"__meta_consul_node",
// Dockerswarm
"__meta_dockerswarm_node_id",
"__meta_dockerswarm_node_hostname",
"__meta_dockerswarm_node_address",
// Kubernetes node labels. Labels for `role: service` are omitted as
// service targets have labels merged with discovered pods.
"__meta_kubernetes_pod_node_name",
"__meta_kubernetes_node_name",
// Generic (applied by host_filter_relabel_configs)
"__host__",
}
// DiscoveredGroups is a set of groups found via service discovery.
type DiscoveredGroups = map[string][]*targetgroup.Group
// GroupChannel is a channel that provides discovered target groups.
type GroupChannel = <-chan DiscoveredGroups
// HostFilter acts as a MITM between the discovery manager and the
// scrape manager, filtering out discovered targets that are not
// running on the same node as the agent itself.
type HostFilter struct {
ctx context.Context
cancel context.CancelFunc
host string
inputCh GroupChannel
outputCh chan map[string][]*targetgroup.Group
relabelMut sync.Mutex
relabels []*relabel.Config
}
// NewHostFilter creates a new HostFilter.
func NewHostFilter(host string, relabels []*relabel.Config) *HostFilter {
ctx, cancel := context.WithCancel(context.Background())
f := &HostFilter{
ctx: ctx,
cancel: cancel,
host: host,
relabels: relabels,
outputCh: make(chan map[string][]*targetgroup.Group),
}
return f
}
// PatchSD patches services discoveries to optimize performance for host
// filtering. The discovered targets will be pruned to as close to the set
// that HostFilter will output as possible.
func (f *HostFilter) PatchSD(scrapes []*config.ScrapeConfig) {
for _, sc := range scrapes {
for _, d := range sc.ServiceDiscoveryConfigs {
switch d := d.(type) {
case *kubernetes.SDConfig:
if d.Role == kubernetes.RolePod {
d.Selectors = []kubernetes.SelectorConfig{{
Role: kubernetes.RolePod,
Field: fmt.Sprintf("spec.nodeName=%s", f.host),
}}
}
}
}
}
}
// SetRelabels updates the relabeling rules used by the HostFilter.
func (f *HostFilter) SetRelabels(relabels []*relabel.Config) {
f.relabelMut.Lock()
defer f.relabelMut.Unlock()
f.relabels = relabels
}
// Run starts the HostFilter. It only exits when the HostFilter is stopped.
// Run will continually read from syncCh and filter groups discovered down to
// targets that are colocated on the same node as the one the HostFilter is
// running in.
func (f *HostFilter) Run(syncCh GroupChannel) {
f.inputCh = syncCh
for {
select {
case <-f.ctx.Done():
return
case data := <-f.inputCh:
f.relabelMut.Lock()
relabels := f.relabels
f.relabelMut.Unlock()
f.outputCh <- FilterGroups(data, f.host, relabels)
}
}
}
// Stop stops the host filter from processing more target updates.
func (f *HostFilter) Stop() {
f.cancel()
}
// SyncCh returns a read only channel used by all the clients to receive
// target updates.
func (f *HostFilter) SyncCh() GroupChannel {
return f.outputCh
}
// FilterGroups takes a set of DiscoveredGroups as input and filters out
// any Target that is not running on the host machine provided by host.
//
// This is done by looking at HostFilterLabelMatchers and __address__.
//
// If the discovered address is localhost or 127.0.0.1, the group is never
// filtered out.
func FilterGroups(in DiscoveredGroups, host string, configs []*relabel.Config) DiscoveredGroups {
out := make(DiscoveredGroups, len(in))
for name, groups := range in {
groupList := make([]*targetgroup.Group, 0, len(groups))
for _, group := range groups {
newGroup := &targetgroup.Group{
Targets: make([]model.LabelSet, 0, len(group.Targets)),
Labels: group.Labels,
Source: group.Source,
}
for _, target := range group.Targets {
allLabels := mergeSets(target, group.Labels)
processedLabels := relabel.Process(toLabelSlice(allLabels), configs...)
if !shouldFilterTarget(processedLabels, host) {
newGroup.Targets = append(newGroup.Targets, target)
}
}
groupList = append(groupList, newGroup)
}
out[name] = groupList
}
return out
}
// shouldFilterTarget returns true when the target labels (combined with the set of common
// labels) should be filtered out by FilterGroups.
func shouldFilterTarget(lbls labels.Labels, host string) bool {
shouldFilterTargetByLabelValue := func(labelValue string) bool {
if addr, _, err := net.SplitHostPort(labelValue); err == nil {
labelValue = addr
}
// Special case: always allow localhost/127.0.0.1
if labelValue == "localhost" || labelValue == "127.0.0.1" {
return false
}
return labelValue != host
}
lset := labels.New(lbls...)
addressLabel := lset.Get(model.AddressLabel)
if addressLabel == "" {
// No address label. This is invalid and will generate an error by the scrape
// manager, so we'll pass it on for now.
return false
}
// If the __address__ label matches, we can quit early.
if !shouldFilterTargetByLabelValue(addressLabel) {
return false
}
// Fall back to checking metalabels as long as their values are nonempty.
for _, check := range HostFilterLabelMatchers {
// If any of the checked labels match for not being filtered out, we can
// return before checking any of the other matchers.
if addr := lset.Get(check); addr != "" && !shouldFilterTargetByLabelValue(addr) {
return false
}
}
// Nothing matches, filter it out.
return true
}
// mergeSets merges the sets of labels together. Earlier sets take priority for label names.
func mergeSets(sets ...model.LabelSet) model.LabelSet {
sz := 0
for _, set := range sets {
sz += len(set)
}
result := make(model.LabelSet, sz)
for _, set := range sets {
for labelName, labelValue := range set {
if _, exist := result[labelName]; exist {
continue
}
result[labelName] = labelValue
}
}
return result
}
func toLabelSlice(set model.LabelSet) labels.Labels {
slice := make(labels.Labels, 0, len(set))
for name, value := range set {
slice = append(slice, labels.Label{Name: string(name), Value: string(value)})
}
return slice
}