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resolver.go
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resolver.go
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/*
* Copyright (c) 2022, 2024 Oracle and/or its affiliates.
* Licensed under the Universal Permissive License v 1.0 as shown at
* https://oss.oracle.com/licenses/upl.
*/
package coherence
import (
"errors"
"fmt"
"github.com/oracle/coherence-go-client/coherence/discovery"
"google.golang.org/grpc/resolver"
"log"
"strings"
"sync"
)
const (
nsLookupScheme = "coherence"
)
var (
emptyAddresses = make([]string, 0)
resolverDebug = func(v ...any) {
// noop as default debug mode
}
)
type nsLookupResolverBuilder struct {
}
func (b *nsLookupResolverBuilder) Build(target resolver.Target, cc resolver.ClientConn, _ resolver.BuildOptions) (resolver.Resolver, error) {
r := &nsLookupResolver{
target: target,
cc: cc,
addrStore: map[string][]string{
nsLookupScheme: generateNSAddresses(target.Endpoint()),
},
}
checkResolverDebug()
r.start()
return r, nil
}
func (*nsLookupResolverBuilder) Scheme() string { return nsLookupScheme }
type nsLookupResolver struct {
target resolver.Target
cc resolver.ClientConn
mutex sync.Mutex
addrStore map[string][]string
}
func (r *nsLookupResolver) resolve() {
r.mutex.Lock()
defer r.mutex.Unlock()
grpcEndpoints := generateNSAddresses(r.target.Endpoint())
if len(grpcEndpoints) == 0 {
msg := "resolver produced zero addresses"
resolverDebug(msg)
r.cc.ReportError(errors.New(msg))
return
}
addresses := make([]resolver.Address, len(grpcEndpoints))
for i, s := range grpcEndpoints {
addresses[i] = resolver.Address{Addr: s}
}
resolverDebug(fmt.Sprintf("resolver produced the following addresses: %v", addresses))
_ = r.cc.UpdateState(resolver.State{Addresses: addresses})
}
func (r *nsLookupResolver) start() {
r.resolve()
}
func (r *nsLookupResolver) ResolveNow(_ resolver.ResolveNowOptions) {
r.resolve()
}
func (*nsLookupResolver) Close() {
}
func generateNSAddresses(endpoint string) []string {
addresses, err := NsLookupGrpcAddresses(endpoint)
if err != nil {
resolverDebug(fmt.Sprintf("NSlookup returned error: %v", err))
return emptyAddresses
}
return addresses
}
// NsLookupGrpcAddresses looks up grpc proxy server addresses based upon the provided
// name service address provided as host:port, e.g. localhost:7574[/cluster].
func NsLookupGrpcAddresses(address string) ([]string, error) {
var (
addrString string
_ []string
foreignCluster string
)
// check to see a cluster is provided for lookup
if strings.Contains(address, "/") {
s := strings.Split(address, "/")
address = s[0]
foreignCluster = s[1]
// retrieve the foreign clusters actual name service address
nsF, err := discovery.Open(address, discovery.DefaultTimeout)
if err != nil {
return emptyAddresses, err
}
defer nsF.Close()
query := discovery.NSPrefix + discovery.ClusterForeignLookup + "/" + foreignCluster + discovery.NSLocalPort
resolverDebug(fmt.Sprintf("lookup for foreign cluster NS port using %s", query))
port, err := nsF.Lookup(query)
if err != nil {
return emptyAddresses, fmt.Errorf("unable to lookup foreign clsuter NS port: %v", err)
}
// get the IP address portion
s1 := strings.Split(address, ":")
address = fmt.Sprintf("%s:%v", s1[0], port)
resolverDebug(fmt.Sprintf("actualy NS port for %s is %s", foreignCluster, address))
// fall through and do the actual lookup using new address
}
ns, err := discovery.Open(address, discovery.DefaultTimeout)
if err != nil {
return emptyAddresses, err
}
defer ns.Close()
addrString, err = ns.Lookup(discovery.NSPrefix + discovery.GrpcProxyLookup)
if err != nil {
return emptyAddresses, err
}
// parse the addresses which should be in the format of
// [127.0.0.1, 58193, 127.0.0.1, 58192, 127.0.0.1, 58194]
// and will be returned in array of 127.0.0.1:58193, 127.0.0.1:58192, 127.0.0.1:58194
return parseNsLookupString(addrString)
}
func parseNsLookupString(addresses string) ([]string, error) {
errInvalid := fmt.Errorf("invalid nslookup response of [%s]", addresses)
if addresses == "" {
return emptyAddresses, errInvalid
}
if addresses == "[]" {
return emptyAddresses, nil
}
if !strings.HasPrefix(addresses, "[") || !strings.HasSuffix(addresses, "]") {
return emptyAddresses, errInvalid
}
// split the addresses
addresses = strings.ReplaceAll(addresses, "[", "")
addresses = strings.ReplaceAll(addresses, "]", "")
s := strings.Split(addresses, ",")
l := len(s)
// should not be zero or an odd number of values, it should be even with IP/ host
if l == 0 || l%2 != 0 {
return emptyAddresses, errInvalid
}
results := make([]string, l/2)
for i := 0; i < l/2; i++ {
results[i] = fmt.Sprintf("%s:%s", strings.TrimSpace(s[i*2]), strings.TrimSpace(s[i*2+1]))
}
return results, nil
}
func checkResolverDebug() {
if getBoolValueFromEnvVarOrDefault(envResolverDebug, false) {
// enable session debugging
resolverDebug = func(v ...any) {
log.Println("RESOLVER DEBUG:", v)
}
}
}