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ring.go
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ring.go
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package ring
// Based on https://raw.githubusercontent.com/stathat/consistent/master/consistent.go
import (
"context"
"errors"
"flag"
"fmt"
"math"
"sort"
"sync"
"time"
"github.com/go-kit/kit/log/level"
"github.com/prometheus/client_golang/prometheus"
"github.com/cortexproject/cortex/pkg/ring/kv"
"github.com/cortexproject/cortex/pkg/util"
"github.com/cortexproject/cortex/pkg/util/services"
)
const (
unhealthy = "Unhealthy"
// IngesterRingKey is the key under which we store the ingesters ring in the KVStore.
IngesterRingKey = "ring"
// RulerRingKey is the key under which we store the rulers ring in the KVStore.
RulerRingKey = "ring"
// DistributorRingKey is the key under which we store the distributors ring in the KVStore.
DistributorRingKey = "distributor"
// CompactorRingKey is the key under which we store the compactors ring in the KVStore.
CompactorRingKey = "compactor"
)
// ReadRing represents the read interface to the ring.
type ReadRing interface {
prometheus.Collector
// Get returns n (or more) ingesters which form the replicas for the given key.
// buf is a slice to be overwritten for the return value
// to avoid memory allocation; can be nil.
Get(key uint32, op Operation, buf []IngesterDesc) (ReplicationSet, error)
GetAll() (ReplicationSet, error)
ReplicationFactor() int
IngesterCount() int
Subring(key uint32, n int) (ReadRing, error)
}
// Operation can be Read or Write
type Operation int
// Values for Operation
const (
Read Operation = iota
Write
Reporting // Special value for inquiring about health
)
// ErrEmptyRing is the error returned when trying to get an element when nothing has been added to hash.
var ErrEmptyRing = errors.New("empty ring")
// Config for a Ring
type Config struct {
KVStore kv.Config `yaml:"kvstore,omitempty"`
HeartbeatTimeout time.Duration `yaml:"heartbeat_timeout,omitempty"`
ReplicationFactor int `yaml:"replication_factor,omitempty"`
}
// RegisterFlags adds the flags required to config this to the given FlagSet with a specified prefix
func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
cfg.RegisterFlagsWithPrefix("", f)
}
// RegisterFlagsWithPrefix adds the flags required to config this to the given FlagSet with a specified prefix
func (cfg *Config) RegisterFlagsWithPrefix(prefix string, f *flag.FlagSet) {
cfg.KVStore.RegisterFlagsWithPrefix(prefix, "collectors/", f)
f.DurationVar(&cfg.HeartbeatTimeout, prefix+"ring.heartbeat-timeout", time.Minute, "The heartbeat timeout after which ingesters are skipped for reads/writes.")
f.IntVar(&cfg.ReplicationFactor, prefix+"distributor.replication-factor", 3, "The number of ingesters to write to and read from.")
}
// Ring holds the information about the members of the consistent hash ring.
type Ring struct {
services.Service
name string
key string
cfg Config
KVClient kv.Client
mtx sync.RWMutex
ringDesc *Desc
ringTokens []TokenDesc
memberOwnershipDesc *prometheus.Desc
numMembersDesc *prometheus.Desc
totalTokensDesc *prometheus.Desc
numTokensDesc *prometheus.Desc
oldestTimestampDesc *prometheus.Desc
}
// New creates a new Ring. Being a service, Ring needs to be started to do anything.
func New(cfg Config, name, key string) (*Ring, error) {
if cfg.ReplicationFactor <= 0 {
return nil, fmt.Errorf("ReplicationFactor must be greater than zero: %d", cfg.ReplicationFactor)
}
codec := GetCodec()
store, err := kv.NewClient(cfg.KVStore, codec)
if err != nil {
return nil, err
}
r := &Ring{
name: name,
key: key,
cfg: cfg,
KVClient: store,
ringDesc: &Desc{},
memberOwnershipDesc: prometheus.NewDesc(
"cortex_ring_member_ownership_percent",
"The percent ownership of the ring by member",
[]string{"member", "name"}, nil,
),
numMembersDesc: prometheus.NewDesc(
"cortex_ring_members",
"Number of members in the ring",
[]string{"state", "name"}, nil,
),
totalTokensDesc: prometheus.NewDesc(
"cortex_ring_tokens_total",
"Number of tokens in the ring",
[]string{"name"}, nil,
),
numTokensDesc: prometheus.NewDesc(
"cortex_ring_tokens_owned",
"The number of tokens in the ring owned by the member",
[]string{"member", "name"}, nil,
),
oldestTimestampDesc: prometheus.NewDesc(
"cortex_ring_oldest_member_timestamp",
"Timestamp of the oldest member in the ring.",
[]string{"state", "name"}, nil,
),
}
r.Service = services.NewBasicService(nil, r.loop, nil)
return r, nil
}
func (r *Ring) loop(ctx context.Context) error {
r.KVClient.WatchKey(ctx, r.key, func(value interface{}) bool {
if value == nil {
level.Info(util.Logger).Log("msg", "ring doesn't exist in consul yet")
return true
}
ringDesc := value.(*Desc)
ringTokens := ringDesc.getTokens()
r.mtx.Lock()
defer r.mtx.Unlock()
r.ringDesc = ringDesc
r.ringTokens = ringTokens
return true
})
return nil
}
// Get returns n (or more) ingesters which form the replicas for the given key.
func (r *Ring) Get(key uint32, op Operation, buf []IngesterDesc) (ReplicationSet, error) {
r.mtx.RLock()
defer r.mtx.RUnlock()
if r.ringDesc == nil || len(r.ringTokens) == 0 {
return ReplicationSet{}, ErrEmptyRing
}
var (
n = r.cfg.ReplicationFactor
ingesters = buf[:0]
distinctHosts = map[string]struct{}{}
start = r.search(key)
iterations = 0
)
for i := start; len(distinctHosts) < n && iterations < len(r.ringTokens); i++ {
iterations++
// Wrap i around in the ring.
i %= len(r.ringTokens)
// We want n *distinct* ingesters.
token := r.ringTokens[i]
if _, ok := distinctHosts[token.Ingester]; ok {
continue
}
distinctHosts[token.Ingester] = struct{}{}
ingester := r.ringDesc.Ingesters[token.Ingester]
// We do not want to Write to Ingesters that are not ACTIVE, but we do want
// to write the extra replica somewhere. So we increase the size of the set
// of replicas for the key. This means we have to also increase the
// size of the replica set for read, but we can read from Leaving ingesters,
// so don't skip it in this case.
// NB dead ingester will be filtered later (by replication_strategy.go).
if op == Write && ingester.State != ACTIVE {
n++
} else if op == Read && (ingester.State != ACTIVE && ingester.State != LEAVING) {
n++
}
ingesters = append(ingesters, ingester)
}
liveIngesters, maxFailure, err := r.replicationStrategy(ingesters, op)
if err != nil {
return ReplicationSet{}, err
}
return ReplicationSet{
Ingesters: liveIngesters,
MaxErrors: maxFailure,
}, nil
}
// GetAll returns all available ingesters in the ring.
func (r *Ring) GetAll() (ReplicationSet, error) {
r.mtx.RLock()
defer r.mtx.RUnlock()
if r.ringDesc == nil || len(r.ringTokens) == 0 {
return ReplicationSet{}, ErrEmptyRing
}
ingesters := make([]IngesterDesc, 0, len(r.ringDesc.Ingesters))
maxErrors := r.cfg.ReplicationFactor / 2
for _, ingester := range r.ringDesc.Ingesters {
if !r.IsHealthy(&ingester, Read) {
maxErrors--
continue
}
ingesters = append(ingesters, ingester)
}
if maxErrors < 0 {
return ReplicationSet{}, fmt.Errorf("too many failed ingesters")
}
return ReplicationSet{
Ingesters: ingesters,
MaxErrors: maxErrors,
}, nil
}
func (r *Ring) search(key uint32) int {
i := sort.Search(len(r.ringTokens), func(x int) bool {
return r.ringTokens[x].Token > key
})
if i >= len(r.ringTokens) {
i = 0
}
return i
}
// Describe implements prometheus.Collector.
func (r *Ring) Describe(ch chan<- *prometheus.Desc) {
ch <- r.memberOwnershipDesc
ch <- r.numMembersDesc
ch <- r.totalTokensDesc
ch <- r.numTokensDesc
}
func countTokens(ringDesc *Desc, tokens []TokenDesc) (map[string]uint32, map[string]uint32) {
owned := map[string]uint32{}
numTokens := map[string]uint32{}
for i, token := range tokens {
var diff uint32
if i+1 == len(tokens) {
diff = (math.MaxUint32 - token.Token) + tokens[0].Token
} else {
diff = tokens[i+1].Token - token.Token
}
numTokens[token.Ingester] = numTokens[token.Ingester] + 1
owned[token.Ingester] = owned[token.Ingester] + diff
}
for id := range ringDesc.Ingesters {
if _, ok := owned[id]; !ok {
owned[id] = 0
numTokens[id] = 0
}
}
return numTokens, owned
}
// Collect implements prometheus.Collector.
func (r *Ring) Collect(ch chan<- prometheus.Metric) {
r.mtx.RLock()
defer r.mtx.RUnlock()
numTokens, ownedRange := countTokens(r.ringDesc, r.ringTokens)
for id, totalOwned := range ownedRange {
ch <- prometheus.MustNewConstMetric(
r.memberOwnershipDesc,
prometheus.GaugeValue,
float64(totalOwned)/float64(math.MaxUint32),
id,
r.name,
)
ch <- prometheus.MustNewConstMetric(
r.numTokensDesc,
prometheus.GaugeValue,
float64(numTokens[id]),
id,
r.name,
)
}
numByState := map[string]int{}
oldestTimestampByState := map[string]int64{}
// Initialised to zero so we emit zero-metrics (instead of not emitting anything)
for _, s := range []string{unhealthy, ACTIVE.String(), LEAVING.String(), PENDING.String(), JOINING.String()} {
numByState[s] = 0
oldestTimestampByState[s] = 0
}
for _, ingester := range r.ringDesc.Ingesters {
s := ingester.State.String()
if !r.IsHealthy(&ingester, Reporting) {
s = unhealthy
}
numByState[s]++
if oldestTimestampByState[s] == 0 || ingester.Timestamp < oldestTimestampByState[s] {
oldestTimestampByState[s] = ingester.Timestamp
}
}
for state, count := range numByState {
ch <- prometheus.MustNewConstMetric(
r.numMembersDesc,
prometheus.GaugeValue,
float64(count),
state,
r.name,
)
}
for state, timestamp := range oldestTimestampByState {
ch <- prometheus.MustNewConstMetric(
r.oldestTimestampDesc,
prometheus.GaugeValue,
float64(timestamp),
state,
r.name,
)
}
ch <- prometheus.MustNewConstMetric(
r.totalTokensDesc,
prometheus.GaugeValue,
float64(len(r.ringTokens)),
r.name,
)
}
// Subring returns a ring of n ingesters from the given ring
// Subrings are meant only for ingestor lookup and should have their data externalized.
func (r *Ring) Subring(key uint32, n int) (ReadRing, error) {
r.mtx.RLock()
defer r.mtx.RUnlock()
if r.ringDesc == nil || len(r.ringTokens) == 0 || n <= 0 {
return nil, ErrEmptyRing
}
var (
ingesters = make(map[string]IngesterDesc, n)
distinctHosts = map[string]struct{}{}
start = r.search(key)
iterations = 0
)
// Subring exceeds number of ingesters, set to total ring size
if n > len(r.ringDesc.Ingesters) {
n = len(r.ringDesc.Ingesters)
}
for i := start; len(distinctHosts) < n && iterations < len(r.ringTokens); i++ {
iterations++
// Wrap i around in the ring.
i %= len(r.ringTokens)
// We want n *distinct* ingesters.
token := r.ringTokens[i]
if _, ok := distinctHosts[token.Ingester]; ok {
continue
}
distinctHosts[token.Ingester] = struct{}{}
ingester := r.ringDesc.Ingesters[token.Ingester]
ingesters[token.Ingester] = ingester
}
if n > len(ingesters) {
return nil, fmt.Errorf("too few ingesters found")
}
numTokens := 0
for _, ing := range ingesters {
numTokens += len(ing.Tokens)
}
sub := &Ring{
name: "subring",
cfg: r.cfg,
ringDesc: &Desc{
Ingesters: ingesters,
},
ringTokens: make([]TokenDesc, 0, numTokens),
}
// add tokens for the ingesters in the subring, they should already be sorted, so no need to re-sort
for _, t := range r.ringTokens {
if _, ok := ingesters[t.Ingester]; ok {
sub.ringTokens = append(sub.ringTokens, t)
}
}
return sub, nil
}