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client.go
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client.go
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// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package client is an AgentCommunication client library.
package client
import (
"context"
"errors"
"fmt"
"io"
"log"
"os"
"sync"
"time"
"github.com/GoogleCloudPlatform/agentcommunication_client/gapic"
cm "cloud.google.com/go/compute/metadata"
"google.golang.org/api/option"
"github.com/google/uuid"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc"
"google.golang.org/grpc/keepalive"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/status"
acpb "github.com/GoogleCloudPlatform/agentcommunication_client/gapic/agentcommunicationpb"
)
func init() {
logger = log.New(os.Stderr, "", log.Ldate|log.Ltime|log.Lshortfile)
}
var (
// DebugLogging enables debug logging.
DebugLogging = false
// ErrConnectionClosed is an error indicating that the connection was closed by the caller.
ErrConnectionClosed = errors.New("connection closed")
// ErrMessageTimeout is an error indicating message send timed out.
ErrMessageTimeout = errors.New("timed out waiting for response")
// ErrResourceExhausted is an error indicating that the server responded to the send with
// ResourceExhausted.
ErrResourceExhausted = errors.New("resource exhausted")
logger *log.Logger
)
// Connection is an AgentCommunication connection.
type Connection struct {
client *agentcommunication.Client
stream acpb.AgentCommunication_StreamAgentMessagesClient
closed chan struct{}
streamReady chan struct{}
sends chan *acpb.StreamAgentMessagesRequest
closeErr error
resourceID string
channelID string
messages chan *acpb.MessageBody
responseSubs map[string]chan *status.Status
responseMx sync.Mutex
regional bool
timeToWaitForResp time.Duration
}
func loggerPrintf(format string, v ...any) {
if DebugLogging {
logger.Output(2, fmt.Sprintf(format, v...))
}
}
// Close the connection.
func (c *Connection) Close() {
c.close(ErrConnectionClosed)
}
func (c *Connection) close(err error) {
loggerPrintf("closing connection with err: %v", err)
st, _ := status.FromError(err)
loggerPrintf("closing connection with status: %+v", st)
select {
case <-c.closed:
return
default:
close(c.closed)
c.closeErr = err
c.client.Close()
}
}
func (c *Connection) waitForResponse(key string, channel chan *status.Status) error {
timer := time.NewTimer(c.timeToWaitForResp)
defer timer.Stop()
select {
case st := <-channel:
if st != nil {
switch st.Code() {
case codes.OK:
case codes.ResourceExhausted:
return fmt.Errorf("%w: %s", ErrResourceExhausted, st.Message())
default:
return fmt.Errorf("unexpected status: %+v", st)
}
}
case <-timer.C:
return fmt.Errorf("%w: timed out waiting for response, MessageID: %q", ErrMessageTimeout, key)
case <-c.closed:
return fmt.Errorf("connection closed with err: %w", c.closeErr)
}
c.responseMx.Lock()
delete(c.responseSubs, key)
c.responseMx.Unlock()
return nil
}
func (c *Connection) sendWithResp(req *acpb.StreamAgentMessagesRequest, channel chan *status.Status) error {
loggerPrintf("Sending message %+v", req)
select {
case <-c.closed:
return fmt.Errorf("connection closed with err: %w", c.closeErr)
case c.sends <- req:
}
return c.waitForResponse(req.GetMessageId(), channel)
}
// SendMessage sends a message to the client. Will automatically retry on message timeout (temporary
// disconnects) and in the case of ResourceExhausted with a backoff. Because retries are limited
// the returned error can in some cases be one of ErrMessageTimeout or ErrResourceExhausted, in
// which case send should be retried by the caller.
func (c *Connection) SendMessage(msg *acpb.MessageBody) error {
var err error
// Retry 4 times.
for i := 1; i <= 5; i++ {
err := c.sendMessage(msg)
if errors.Is(err, ErrResourceExhausted) {
// Start with 250ms sleep, then simply multiply by iteration.
time.Sleep(time.Duration(i*250) * time.Millisecond)
continue
} else if errors.Is(err, ErrMessageTimeout) {
continue
}
return err
}
return err
}
func (c *Connection) sendMessage(msg *acpb.MessageBody) error {
req := &acpb.StreamAgentMessagesRequest{
MessageId: uuid.New().String(),
Type: &acpb.StreamAgentMessagesRequest_MessageBody{MessageBody: msg},
}
channel := make(chan *status.Status)
c.responseMx.Lock()
c.responseSubs[req.GetMessageId()] = channel
c.responseMx.Unlock()
select {
case <-c.closed:
return fmt.Errorf("connection closed with err: %w", c.closeErr)
case c.streamReady <- struct{}{}: // Only sends if the stream is ready to send.
}
return c.sendWithResp(req, channel)
}
// Receive messages, Receive should be called continuously for the life of the stream connection,
// any delay (>500ms) in Receive when there are queued messages will cause the server to disconnect the
// stream. This means handling the MessageBody from Receive should not be blocking, offload message
// handling to another goroutine and immediately call Receive again.
func (c *Connection) Receive() (*acpb.MessageBody, error) {
select {
case msg := <-c.messages:
return msg, nil
case <-c.closed:
return nil, fmt.Errorf("connection closed with err: %w", c.closeErr)
}
}
func (c *Connection) streamSend(req *acpb.StreamAgentMessagesRequest, streamClosed chan struct{}) error {
if err := c.stream.Send(req); err != nil {
if err != io.EOF && !errors.Is(err, io.EOF) {
// Something is very broken, just close the stream here.
loggerPrintf("Unexpected send error, closing connection: %v", err)
c.close(err)
return err
}
// EOF error means the stream is closed, this should be picked up by recv, but that could be
// blocked, close our sends for now and just allow the caller handle it, SendMessage will wait
// for response which will never come and auto retry. acknowledgeMessage will fail and prevent
// the message from being passed on to message handlers, allowing recv to handle the stream
// close error.
loggerPrintf("Error sending message, stream closed.")
select {
case <-streamClosed:
default:
close(streamClosed)
}
return ErrConnectionClosed
}
return nil
}
func (c *Connection) send(streamClosed chan struct{}) {
for {
select {
case req := <-c.sends:
if err := c.streamSend(req, streamClosed); err != nil {
return
}
case <-c.closed:
c.stream.CloseSend()
return
case <-streamClosed:
return
}
}
}
// recv keeps receiving and acknowledging new messages.
func (c *Connection) recv(ctx context.Context, streamClosed chan struct{}) {
loggerPrintf("Receiving messages")
var unavailableRetries int
for {
resp, err := c.stream.Recv()
if err != nil {
select {
case <-streamClosed:
default:
close(streamClosed)
}
select {
case <-c.closed:
return
default:
}
st, ok := status.FromError(err)
if ok && st.Code() == codes.ResourceExhausted {
loggerPrintf("Resource exhausted, sleeping before reconnect: %v", err)
time.Sleep(1000 * time.Millisecond)
} else if ok && st.Code() == codes.Unavailable {
// Retry max 5 times (2s total).
if unavailableRetries > 5 {
loggerPrintf("Stream returned Unavailable, exceeded max number of reconnects, closing connection: %v", err)
c.close(err)
return
}
loggerPrintf("Stream returned Unavailable, will reconnect: %v", err)
// Sleep for 200ms * num of unavailableRetries, first retry is immediate.
time.Sleep(time.Duration(unavailableRetries*200) * time.Millisecond)
unavailableRetries++
} else if err != io.EOF && !errors.Is(err, io.EOF) && (ok && st.Code() != codes.Canceled) && (ok && st.Code() != codes.DeadlineExceeded) {
// EOF is a normal stream close, Canceled will be set by the server when stream timeout is
// reached, DeadlineExceeded would be because of the client side deadline we set.
loggerPrintf("Unexpected error, closing connection: %v", err)
c.close(err)
return
}
loggerPrintf("Creating new stream")
if err := c.createStream(ctx); err != nil {
loggerPrintf("Error creating new stream: %v", err)
c.close(err)
}
return
}
// Reset unavailable retries.
unavailableRetries = 0
switch resp.GetType().(type) {
case *acpb.StreamAgentMessagesResponse_MessageBody:
// Acknowledge message first, if this ack fails dont forward the message on to the handling
// logic since that indicates a stream disconnect.
if err := c.acknowledgeMessage(resp.GetMessageId(), streamClosed); err != nil {
loggerPrintf("Error acknowledging message %q: %v", resp.GetMessageId(), err)
continue
}
c.messages <- resp.GetMessageBody()
case *acpb.StreamAgentMessagesResponse_MessageResponse:
st := resp.GetMessageResponse().GetStatus()
c.responseMx.Lock()
for key, sub := range c.responseSubs {
if key != resp.GetMessageId() {
continue
}
select {
case sub <- status.FromProto(st):
default:
}
}
c.responseMx.Unlock()
}
}
}
func (c *Connection) acknowledgeMessage(messageID string, streamClosed chan struct{}) error {
ackReq := &acpb.StreamAgentMessagesRequest{
MessageId: messageID,
Type: &acpb.StreamAgentMessagesRequest_MessageResponse{},
}
select {
case <-c.closed:
return fmt.Errorf("connection closed with err: %w", c.closeErr)
default:
return c.streamSend(ackReq, streamClosed)
}
}
func (c *Connection) createStream(ctx context.Context) error {
loggerPrintf("Creating stream.")
token, err := cm.Get("instance/service-accounts/default/identity?audience=agentcommunication.googleapis.com&format=full")
if err != nil {
return fmt.Errorf("error getting instance token: %v", err)
}
ctx = metadata.NewOutgoingContext(ctx, metadata.New(map[string]string{
"authentication": "Bearer " + token,
"agent-communication-resource-id": c.resourceID,
"agent-communication-channel-id": c.channelID,
}))
loggerPrintf("Using ResourceID %q", c.resourceID)
loggerPrintf("Using ChannelID %q", c.channelID)
// Set a timeout for the stream, this is well above service side timeout.
cnclCtx, cancel := context.WithTimeout(ctx, 60*time.Minute)
c.stream, err = c.client.StreamAgentMessages(cnclCtx)
if err != nil {
cancel()
return fmt.Errorf("error creating stream: %v", err)
}
streamClosed := make(chan struct{})
go c.recv(ctx, streamClosed)
go c.send(streamClosed)
req := &acpb.StreamAgentMessagesRequest{
MessageId: uuid.New().String(),
Type: &acpb.StreamAgentMessagesRequest_RegisterConnection{
RegisterConnection: &acpb.RegisterConnection{ResourceId: c.resourceID, ChannelId: c.channelID}}}
channel := make(chan *status.Status)
c.responseMx.Lock()
c.responseSubs[req.GetMessageId()] = channel
c.responseMx.Unlock()
if err := c.sendWithResp(req, channel); err != nil {
cancel()
return err
}
go func() {
defer cancel()
for {
select {
case <-c.streamReady:
case <-streamClosed:
return
}
}
}()
loggerPrintf("Stream established.")
return nil
}
// CreateConnection creates a new connection.
func CreateConnection(ctx context.Context, channelID string, regional bool, opts ...option.ClientOption) (*Connection, error) {
conn := &Connection{
regional: regional,
channelID: channelID,
closed: make(chan struct{}),
messages: make(chan *acpb.MessageBody),
responseSubs: make(map[string]chan *status.Status),
streamReady: make(chan struct{}),
sends: make(chan *acpb.StreamAgentMessagesRequest),
timeToWaitForResp: 2 * time.Second,
}
zone, err := cm.Zone()
if err != nil {
return nil, err
}
projectNum, err := cm.NumericProjectID()
if err != nil {
return nil, err
}
instanceID, err := cm.InstanceID()
if err != nil {
return nil, err
}
conn.resourceID = fmt.Sprintf("projects/%s/zones/%s/instances/%s", projectNum, zone, instanceID)
location := zone
if conn.regional {
location = location[:len(location)-2]
}
defaultOpts := []option.ClientOption{
option.WithoutAuthentication(), // Do not use oauth.
option.WithGRPCDialOption(grpc.WithTransportCredentials(credentials.NewTLS(nil))), // Because we disabled Auth we need to specifically enable TLS.
option.WithGRPCDialOption(grpc.WithKeepaliveParams(keepalive.ClientParameters{Time: 60 * time.Second, Timeout: 10 * time.Second})),
option.WithEndpoint(fmt.Sprintf("%s-agentcommunication.googleapis.com:443", location)),
}
opts = append(defaultOpts, opts...)
conn.client, err = agentcommunication.NewClient(ctx, opts...)
if err != nil {
return nil, err
}
if err := conn.createStream(ctx); err != nil {
return nil, err
}
return conn, nil
}