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topic.go
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topic.go
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package config
import (
"errors"
"fmt"
"github.com/ghodss/yaml"
"github.com/hashicorp/go-multierror"
"github.com/segmentio/kafka-go"
"github.com/segmentio/topicctl/pkg/admin"
log "github.com/sirupsen/logrus"
)
// PlacementStrategy is a string type that stores a replica placement strategy for a topic.
type PlacementStrategy string
const (
// PlacementStrategyAny allows any partition placement.
PlacementStrategyAny PlacementStrategy = "any"
// PlacementStrategyBalancedLeaders is a strategy that ensures the leaders of
// each partition are balanced by rack, but does not care about the placements
// of the non-leader replicas.
PlacementStrategyBalancedLeaders PlacementStrategy = "balanced-leaders"
// PlacementStrategyInRack is a strategy in which the leaders are balanced
// and the replicas for each partition are in the same rack as the leader.
PlacementStrategyInRack PlacementStrategy = "in-rack"
// PlacementStrategyStatic uses a static placement defined in the config. This is for
// testing only and should generally not be used in production.
PlacementStrategyStatic PlacementStrategy = "static"
// PlacementStrategyStaticInRack is a strategy in which the replicas in each partition
// are chosen from the rack in a static list, but the specific replicas within each partition
// aren't specified.
PlacementStrategyStaticInRack PlacementStrategy = "static-in-rack"
)
var allPlacementStrategies = []PlacementStrategy{
PlacementStrategyAny,
PlacementStrategyBalancedLeaders,
PlacementStrategyInRack,
PlacementStrategyStatic,
PlacementStrategyStaticInRack,
}
// PickerMethod is a string type that stores a picker method for breaking ties when choosing
// the replica placements for a topic.
type PickerMethod string
const (
// PickerMethodClusterUse uses broker frequency in the topic, breaking ties by
// looking at the total number of replicas across the entire cluster that each broker
// appears in.
PickerMethodClusterUse PickerMethod = "cluster-use"
// PickerMethodLowestIndex uses broker frequency in the topic, breaking ties by
// choosing the broker with the lowest index.
PickerMethodLowestIndex PickerMethod = "lowest-index"
// PickerMethodRandomized uses broker frequency in the topic, breaking ties by
// using a repeatably random choice from the options.
PickerMethodRandomized PickerMethod = "randomized"
)
var allPickerMethods = []PickerMethod{
PickerMethodClusterUse,
PickerMethodLowestIndex,
PickerMethodRandomized,
}
// TopicConfig represents the desired configuration of a topic.
type TopicConfig struct {
Meta TopicMeta `json:"meta"`
Spec TopicSpec `json:"spec"`
}
// TopicMeta stores the (mostly immutable) metadata associated with a topic.
// Inspired by the meta structs in Kubernetes objects.
type TopicMeta struct {
Name string `json:"name"`
Cluster string `json:"cluster"`
Region string `json:"region"`
Environment string `json:"environment"`
Description string `json:"description"`
// Consumers is a list of consumers who are expected to consume from this
// topic.
Consumers []string `json:"consumers,omitempty"`
}
// TopicSpec stores the (mutable) specification for a topic.
type TopicSpec struct {
Partitions int `json:"partitions"`
ReplicationFactor int `json:"replicationFactor"`
RetentionMinutes int `json:"retentionMinutes,omitempty"`
Settings TopicSettings `json:"settings,omitempty"`
PlacementConfig TopicPlacementConfig `json:"placement"`
MigrationConfig *TopicMigrationConfig `json:"migration,omitempty"`
}
// TopicPlacementConfig describes how the partition replicas in a topic
// should be chosen.
type TopicPlacementConfig struct {
Strategy PlacementStrategy `json:"strategy"`
Picker PickerMethod `json:"picker,omitempty"`
// StaticAssignments is a list of lists of desired replica assignments. It's used
// for the "static" strategy only.
StaticAssignments [][]int `json:"staticAssignments,omitempty"`
// StaticRackAssignments is a list of list of desired replica assignments. It's used
// for the "static-in-rack" strategy only.
StaticRackAssignments []string `json:"staticRackAssignments,omitempty"`
}
// TopicMigrationConfig configures the throttles and batch sizes used when
// running a partition migration. If these are left unset, resonable defaults
// will be used instead.
type TopicMigrationConfig struct {
ThrottleMB int64 `json:"throttleMB"`
PartitionBatchSize int `json:"partitionBatchSize"`
}
// ToNewTopicConfig converts a TopicConfig to a kafka.TopicConfig that can be
// used by kafka-go to create a new topic.
func (t TopicConfig) ToNewTopicConfig() (kafka.TopicConfig, error) {
config := kafka.TopicConfig{
Topic: t.Meta.Name,
NumPartitions: t.Spec.Partitions,
ReplicationFactor: t.Spec.ReplicationFactor,
}
if len(t.Spec.Settings) > 0 {
entries, err := t.Spec.Settings.ToConfigEntries(nil)
if err != nil {
return config, err
}
config.ConfigEntries = entries
}
if t.Spec.RetentionMinutes > 0 {
config.ConfigEntries = append(
config.ConfigEntries,
kafka.ConfigEntry{
ConfigName: admin.RetentionKey,
ConfigValue: fmt.Sprintf("%d", t.Spec.RetentionMinutes*60*1000),
},
)
}
return config, nil
}
// SetDefaults sets the default migration and placement settings in a topic config
// if these aren't set.
func (t *TopicConfig) SetDefaults() {
if t.Spec.MigrationConfig == nil {
t.Spec.MigrationConfig = &TopicMigrationConfig{}
}
if t.Spec.MigrationConfig.PartitionBatchSize == 0 {
// Migration partitions one at a time
t.Spec.MigrationConfig.PartitionBatchSize = 1
}
if t.Spec.PlacementConfig.Picker == "" {
t.Spec.PlacementConfig.Picker = PickerMethodRandomized
}
}
// Validate evaluates whether the topic config is valid.
func (t TopicConfig) Validate(numRacks int) error {
var err error
if t.Meta.Name == "" {
err = multierror.Append(err, errors.New("Name must be set"))
}
if t.Meta.Cluster == "" {
err = multierror.Append(err, errors.New("Cluster must be set"))
}
if t.Meta.Region == "" {
err = multierror.Append(err, errors.New("Region must be set"))
}
if t.Meta.Environment == "" {
err = multierror.Append(err, errors.New("Environment must be set"))
}
if t.Spec.Partitions <= 0 {
err = multierror.Append(err, errors.New("Partitions must be a positive number"))
}
if t.Spec.ReplicationFactor <= 0 {
err = multierror.Append(err, errors.New("ReplicationFactor must be > 0"))
}
if settingsErr := t.Spec.Settings.Validate(); settingsErr != nil {
err = multierror.Append(err, settingsErr)
}
if t.Spec.RetentionMinutes < 0 {
err = multierror.Append(err, errors.New("RetentionMinutes must be >= 0"))
}
if t.Spec.RetentionMinutes > 0 && t.Spec.Settings["retention.ms"] != nil {
err = multierror.Append(
err,
errors.New("Cannot set both RetentionMinutes and retention.ms in settings"),
)
}
placement := t.Spec.PlacementConfig
strategyIndex := -1
for s, strategy := range allPlacementStrategies {
if strategy == placement.Strategy {
strategyIndex = s
break
}
}
if strategyIndex == -1 {
err = multierror.Append(
err,
fmt.Errorf(
"PlacementStrategy must in %+v",
allPlacementStrategies,
),
)
}
pickerIndex := -1
for p, pickerMethod := range allPickerMethods {
if pickerMethod == placement.Picker {
pickerIndex = p
break
}
}
if pickerIndex == -1 {
err = multierror.Append(
err,
fmt.Errorf(
"PickerMethod must in %+v",
allPickerMethods,
),
)
}
switch placement.Strategy {
case PlacementStrategyBalancedLeaders:
if numRacks > 0 && t.Spec.Partitions%numRacks != 0 {
// The balanced-leaders strategy requires that the
// partitions be a multiple of the number of racks, otherwise it's impossible
// to find a placement that satisfies the strategy.
err = multierror.Append(
err,
fmt.Errorf(
"Number of partitions (%d) is not a multiple of the number of racks (%d)",
t.Spec.Partitions,
numRacks,
),
)
}
case PlacementStrategyInRack:
case PlacementStrategyStatic:
if len(placement.StaticAssignments) != t.Spec.Partitions {
err = multierror.Append(
err,
errors.New("Static assignments must be same length as partitions"),
)
} else {
for _, replicas := range placement.StaticAssignments {
if len(replicas) != t.Spec.ReplicationFactor {
err = multierror.Append(
err,
errors.New("Static assignment rows must match replication factor"),
)
break
}
}
}
case PlacementStrategyStaticInRack:
if len(placement.StaticRackAssignments) != t.Spec.Partitions {
err = multierror.Append(
err,
errors.New("Static rack assignments must be same length as partitions"),
)
}
}
// Warn about the partition count in the non-balanced-leaders case
if numRacks > 0 &&
placement.Strategy != PlacementStrategyBalancedLeaders &&
t.Spec.Partitions%numRacks != 0 {
log.Warnf("Number of partitions (%d) is not a multiple of the number of racks (%d)",
t.Spec.Partitions,
numRacks,
)
}
return err
}
// ToYAML converts the current TopicConfig to a YAML string.
func (t TopicConfig) ToYAML() (string, error) {
outBytes, err := yaml.Marshal(t)
if err != nil {
return "", err
}
return string(outBytes), nil
}
// TopicConfigFromTopicInfo generates a TopicConfig from a ClusterConfig and admin.TopicInfo
// struct generated from the cluster state.
func TopicConfigFromTopicInfo(
clusterConfig ClusterConfig,
topicInfo admin.TopicInfo,
) TopicConfig {
topicConfig := TopicConfig{
Meta: TopicMeta{
Name: topicInfo.Name,
Cluster: clusterConfig.Meta.Name,
Region: clusterConfig.Meta.Region,
Environment: clusterConfig.Meta.Environment,
Description: "Bootstrapped via topicctl bootstrap",
},
Spec: TopicSpec{
Partitions: len(topicInfo.Partitions),
ReplicationFactor: len(topicInfo.Partitions[0].Replicas),
PlacementConfig: TopicPlacementConfig{
Strategy: PlacementStrategyAny,
},
},
}
topicConfig.Spec.Settings = FromConfigMap(topicInfo.Config)
retentionMinutes := topicInfo.Retention().Minutes()
if retentionMinutes >= 1.0 && float64(int(retentionMinutes)) == retentionMinutes {
topicConfig.Spec.RetentionMinutes = int(retentionMinutes)
delete(topicConfig.Spec.Settings, admin.RetentionKey)
}
return topicConfig
}