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prefix_lookup.go
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/
prefix_lookup.go
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package shard
import (
"encoding/json"
"errors"
"strings"
"github.com/gojektech/weaver"
)
const (
defaultBackendKey = "default"
defaultPrefixSplitter = "-"
)
type prefixLookupConfig struct {
PrefixSplitter string `json:"prefix_splitter"`
Backends map[string]BackendDefinition `json:"backends"`
}
func (plg prefixLookupConfig) Validate() error {
if len(plg.Backends) == 0 {
return errors.New("no backends specified")
}
return nil
}
func NewPrefixLookupStrategy(data json.RawMessage) (weaver.Sharder, error) {
prefixLookupConfig := &prefixLookupConfig{}
if err := json.Unmarshal(data, &prefixLookupConfig); err != nil {
return nil, err
}
if err := prefixLookupConfig.Validate(); err != nil {
return nil, err
}
backends, err := toBackends(prefixLookupConfig.Backends)
if err != nil {
return nil, err
}
prefixSplitter := prefixLookupConfig.PrefixSplitter
if prefixSplitter == "" {
prefixSplitter = defaultPrefixSplitter
}
return &PrefixLookupStrategy{
backends: backends,
prefixSplitter: prefixSplitter,
}, nil
}
type PrefixLookupStrategy struct {
backends map[string]*weaver.Backend
prefixSplitter string
}
func (pls *PrefixLookupStrategy) Shard(key string) (*weaver.Backend, error) {
prefix := strings.SplitAfter(key, pls.prefixSplitter)[0]
if pls.backends[prefix] == nil {
return pls.backends[defaultBackendKey], nil
}
return pls.backends[prefix], nil
}