/
client.go
313 lines (294 loc) · 7.12 KB
/
client.go
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package service
import (
"context"
"encoding/json"
"io"
"reflect"
"sync"
"golang.org/x/sync/errgroup"
"golang.org/x/xerrors"
)
type serviceInvoke struct {
req serviceRequest
reply serviceResponse
err error
doneCh chan struct{}
}
type serviceClient struct {
ctx context.Context
invokeCh chan *serviceInvoke
}
func (s *serviceClient) runReaderThread(
r io.ReadCloser, readerCh chan<- serviceResponse,
) error {
defer func() { _ = r.Close() }()
d := json.NewDecoder(r)
for {
var response serviceResponse
if err := d.Decode(&response); err != nil {
if err == io.EOF {
err = nil
}
return err
}
select {
case <-s.ctx.Done():
return nil
case readerCh <- response:
}
}
}
func (s *serviceClient) runMasterThread(
w io.WriteCloser, readerCh <-chan serviceResponse,
) (rerr error) {
defer func() { _ = w.Close() }()
var current uint64
pending := make(map[uint64]*serviceInvoke)
defer func() {
err := rerr
if err == nil {
err = xerrors.New("client closed")
}
for _, invoke := range pending {
invoke.err = err
close(invoke.doneCh)
}
}()
e := json.NewEncoder(w)
for {
select {
case <-s.ctx.Done():
return nil
case invoke := <-s.invokeCh:
if err := func() error {
allocated := false
for next := current + 1; next != current; next++ {
if _, ok := pending[next]; !ok {
current = next
allocated = true
break
}
}
if !allocated {
invoke.err = xerrors.New("cannot allocate sequence")
close(invoke.doneCh)
return nil
}
invoke.req.Sequence = current
pending[current] = invoke
return e.Encode(invoke.req)
}(); err != nil {
return err
}
case reply := <-readerCh:
if invoke, ok := pending[reply.Sequence]; ok {
delete(pending, reply.Sequence)
invoke.reply = reply
if reply.ErrMsg != nil {
invoke.err = xerrors.New(*reply.ErrMsg)
}
close(invoke.doneCh)
}
}
}
}
func (s *serviceClient) call(
ns, name string, data json.RawMessage,
) (json.RawMessage, error) {
invoke := &serviceInvoke{
req: serviceRequest{
Namespace: ns,
Type: serviceTypeCall,
Name: name,
Args: data,
},
doneCh: make(chan struct{}),
}
select {
case <-s.ctx.Done():
return nil, s.ctx.Err()
case s.invokeCh <- invoke:
<-invoke.doneCh
return invoke.reply.Reply, invoke.err
}
}
func (s *serviceClient) getManifest(ns string) (json.RawMessage, error) {
invoke := &serviceInvoke{
req: serviceRequest{
Namespace: ns,
Type: serviceTypeGetManifest,
},
doneCh: make(chan struct{}),
}
select {
case <-s.ctx.Done():
return nil, s.ctx.Err()
case s.invokeCh <- invoke:
<-invoke.doneCh
return invoke.reply.Reply, invoke.err
}
}
func (s *serviceClient) listServices(ns string) ([]string, error) {
invoke := &serviceInvoke{
req: serviceRequest{
Namespace: ns,
Type: serviceTypeListServices,
},
doneCh: make(chan struct{}),
}
select {
case <-s.ctx.Done():
return nil, s.ctx.Err()
case s.invokeCh <- invoke:
<-invoke.doneCh
return invoke.reply.Services, invoke.err
}
}
func (s *serviceClient) hasNamespace(ns string) (bool, error) {
invoke := &serviceInvoke{
req: serviceRequest{
Namespace: ns,
Type: serviceTypeHasNamespace,
},
doneCh: make(chan struct{}),
}
select {
case <-s.ctx.Done():
return false, s.ctx.Err()
case s.invokeCh <- invoke:
<-invoke.doneCh
return invoke.reply.Ok, invoke.err
}
}
func newServiceClient(ctx context.Context) (*serviceClient, error) {
r, w, err := openHostFiles()
if err != nil {
return nil, err
}
grp, errCtx := errgroup.WithContext(ctx)
client := &serviceClient{
ctx: errCtx,
invokeCh: make(chan *serviceInvoke),
}
readerCh := make(chan serviceResponse)
grp.Go(func() error {
return client.runReaderThread(r, readerCh)
})
grp.Go(func() error {
return client.runMasterThread(w, readerCh)
})
return client, nil
}
var (
getOnce sync.Once
clientObj *serviceClient
clientErr error
)
func getServiceClient(ctx context.Context) (*serviceClient, error) {
getOnce.Do(func() {
clientObj, clientErr = newServiceClient(ctx)
})
return clientObj, clientErr
}
// InitServiceClient attempts to initialize the service
// client when it is executed from a plugin.
//
// Though it is dispensible, it is the only chance for
// setting up context for service client, so it should be
// executed before any service has been called.
func InitServiceClient(ctx context.Context) error {
_, err := getServiceClient(ctx)
return err
}
// GetService will attempt to retrieve a service from host.
//
// The service argument must be a pointer to function, and a
// common usage for it might be shown as below:
//
// var target func(x, y int) (z int, err error)
// plugin.GetService("my-package", "add", &target)
// target(1, 2) // returns (3, nil) on success
//
// This function panics when the provided service argument
// is not acceptable. While other errors should be returned
// as the error in provided function.
func GetService(namespace, name string, service Service) {
val := reflect.ValueOf(service)
panicPointerToFunc := func() {
panic("service must be pointer to function")
}
if val.Type().Kind() != reflect.Ptr {
panicPointerToFunc()
}
typ := val.Type().Elem()
if typ.Kind() != reflect.Func {
panicPointerToFunc()
}
numOut := typ.NumOut()
if numOut < 0 || typ.Out(numOut-1) != typeError {
panic("service must have error as last argument")
}
f := func(args []reflect.Value) []reflect.Value {
result := make([]reflect.Value, numOut)
for i := 0; i < numOut-1; i++ {
result[i] = reflect.New(typ.Out(i)).Elem()
}
result[numOut-1] = reflect.Zero(typeError)
if err := func() error {
client, err := getServiceClient(context.Background())
if err != nil {
return err
}
input := make([]interface{}, typ.NumIn())
for i := 0; i < len(input); i++ {
input[i] = args[i].Interface()
}
inputData, err := json.Marshal(&input)
if err != nil {
return err
}
outputData, err := client.call(
namespace, name, inputData)
if err != nil {
return err
}
output := make([]interface{}, numOut-1)
for i := 0; i < len(output); i++ {
output[i] = result[i].Addr().Interface()
}
return json.Unmarshal(outputData, &output)
}(); err != nil {
result[numOut-1] = reflect.ValueOf(err)
}
return result
}
val.Elem().Set(reflect.MakeFunc(typ, f))
}
// GetManifest attempt to retrieve manifest for namespace.
func GetManifest(namespace string, v interface{}) error {
client, err := getServiceClient(context.Background())
if err != nil {
return err
}
data, err := client.getManifest(namespace)
if err != nil {
return err
}
return json.Unmarshal(data, v)
}
// ListServices attempt to list services in a namespace.
func ListServices(namespace string) ([]string, error) {
client, err := getServiceClient(context.Background())
if err != nil {
return nil, err
}
return client.listServices(namespace)
}
// HasNamespace attempt to verify whether namespace exists.
func HasNamespace(namespace string) (bool, error) {
client, err := getServiceClient(context.Background())
if err != nil {
return false, err
}
return client.hasNamespace(namespace)
}