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package main
import (
"context"
"log"
"strconv"
"strings"
"time"
"github.com/aws/aws-sdk-go-v2/aws"
"github.com/aws/aws-sdk-go-v2/service/sqs"
"github.com/aws/aws-sdk-go-v2/service/sqs/types"
"gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/messages"
"gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/sqsclient"
)
const (
cleanupThreshold = -2 * time.Minute
)
type sqsHandler struct {
SQSClient sqsclient.SQSClient
SQSQueueURL *string
IPC *IPC
cleanupInterval time.Duration
}
func (r *sqsHandler) pollMessages(ctx context.Context, chn chan<- *types.Message) {
for {
select {
case <-ctx.Done():
// if context is cancelled
return
default:
res, err := r.SQSClient.ReceiveMessage(ctx, &sqs.ReceiveMessageInput{
QueueUrl: r.SQSQueueURL,
MaxNumberOfMessages: 10,
WaitTimeSeconds: 15,
MessageAttributeNames: []string{
string(types.QueueAttributeNameAll),
},
})
if err != nil {
log.Printf("SQSHandler: encountered error while polling for messages: %v\n", err)
continue
}
for _, message := range res.Messages {
chn <- &message
}
}
}
}
func (r *sqsHandler) cleanupClientQueues(ctx context.Context) {
for range time.NewTicker(r.cleanupInterval).C {
// Runs at fixed intervals to clean up any client queues that were last changed more than 2 minutes ago
select {
case <-ctx.Done():
// if context is cancelled
return
default:
queueURLsList := []string{}
var nextToken *string
for {
res, err := r.SQSClient.ListQueues(ctx, &sqs.ListQueuesInput{
QueueNamePrefix: aws.String("snowflake-client-"),
MaxResults: aws.Int32(1000),
NextToken: nextToken,
})
if err != nil {
log.Printf("SQSHandler: encountered error while retrieving client queues to clean up: %v\n", err)
// client queues will be cleaned up the next time the cleanup operation is triggered automatically
break
}
queueURLsList = append(queueURLsList, res.QueueUrls...)
if res.NextToken == nil {
break
} else {
nextToken = res.NextToken
}
}
numDeleted := 0
cleanupCutoff := time.Now().Add(cleanupThreshold)
for _, queueURL := range queueURLsList {
if !strings.Contains(queueURL, "snowflake-client-") {
continue
}
res, err := r.SQSClient.GetQueueAttributes(ctx, &sqs.GetQueueAttributesInput{
QueueUrl: aws.String(queueURL),
AttributeNames: []types.QueueAttributeName{types.QueueAttributeNameLastModifiedTimestamp},
})
if err != nil {
// According to the AWS SQS docs, the deletion process for a queue can take up to 60 seconds. So the queue
// can be in the process of being deleted, but will still be returned by the ListQueues operation, but
// fail when we try to GetQueueAttributes for the queue
log.Printf("SQSHandler: encountered error while getting attribute of client queue %s. queue may already be deleted.\n", queueURL)
continue
}
lastModifiedInt64, err := strconv.ParseInt(res.Attributes[string(types.QueueAttributeNameLastModifiedTimestamp)], 10, 64)
if err != nil {
log.Printf("SQSHandler: encountered invalid lastModifiedTimetamp value from client queue %s: %v\n", queueURL, err)
continue
}
lastModified := time.Unix(lastModifiedInt64, 0)
if lastModified.Before(cleanupCutoff) {
_, err := r.SQSClient.DeleteQueue(ctx, &sqs.DeleteQueueInput{
QueueUrl: aws.String(queueURL),
})
if err != nil {
log.Printf("SQSHandler: encountered error when deleting client queue %s: %v\n", queueURL, err)
continue
} else {
numDeleted += 1
}
}
}
log.Printf("SQSHandler: finished running iteration of client queue cleanup. found and deleted %d client queues.\n", numDeleted)
}
}
}
func (r *sqsHandler) handleMessage(context context.Context, message *types.Message) {
var encPollReq []byte
var response []byte
var err error
clientID := message.MessageAttributes["ClientID"].StringValue
if clientID == nil {
log.Println("SQSHandler: got SDP offer in SQS message with no client ID. ignoring this message.")
return
}
res, err := r.SQSClient.CreateQueue(context, &sqs.CreateQueueInput{
QueueName: aws.String("snowflake-client-" + *clientID),
})
if err != nil {
log.Printf("SQSHandler: error encountered when creating answer queue for client %s: %v\n", *clientID, err)
return
}
answerSQSURL := res.QueueUrl
encPollReq = []byte(*message.Body)
arg := messages.Arg{
Body: encPollReq,
RemoteAddr: "",
RendezvousMethod: messages.RendezvousSqs,
}
err = r.IPC.ClientOffers(arg, &response)
if err != nil {
log.Printf("SQSHandler: error encountered when handling message: %v\n", err)
return
}
r.SQSClient.SendMessage(context, &sqs.SendMessageInput{
QueueUrl: answerSQSURL,
MessageBody: aws.String(string(response)),
})
}
func (r *sqsHandler) deleteMessage(context context.Context, message *types.Message) {
r.SQSClient.DeleteMessage(context, &sqs.DeleteMessageInput{
QueueUrl: r.SQSQueueURL,
ReceiptHandle: message.ReceiptHandle,
})
}
func newSQSHandler(context context.Context, client sqsclient.SQSClient, sqsQueueName string, region string, i *IPC) (*sqsHandler, error) {
// Creates the queue if a queue with the same name doesn't exist. If a queue with the same name and attributes
// already exists, then nothing will happen. If a queue with the same name, but different attributes exists, then
// an error will be returned
res, err := client.CreateQueue(context, &sqs.CreateQueueInput{
QueueName: aws.String(sqsQueueName),
Attributes: map[string]string{
"MessageRetentionPeriod": strconv.FormatInt(int64((5 * time.Minute).Seconds()), 10),
},
})
if err != nil {
return nil, err
}
return &sqsHandler{
SQSClient: client,
SQSQueueURL: res.QueueUrl,
IPC: i,
cleanupInterval: time.Second * 30,
}, nil
}
func (r *sqsHandler) PollAndHandleMessages(ctx context.Context) {
log.Println("SQSHandler: Starting to poll for messages at: " + *r.SQSQueueURL)
messagesChn := make(chan *types.Message, 2)
go r.pollMessages(ctx, messagesChn)
go r.cleanupClientQueues(ctx)
for message := range messagesChn {
select {
case <-ctx.Done():
// if context is cancelled
return
default:
r.handleMessage(ctx, message)
r.deleteMessage(ctx, message)
}
}
}
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