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request_manager.go
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/
request_manager.go
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/***************************************************************
*
* Copyright (C) 2024, Pelican Project, Morgridge Institute for Research
*
* 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
*
* http://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 broker
import (
"context"
"errors"
"math/rand"
"sync"
"time"
)
type (
reversalRequest struct {
CallbackUrl string `json:"callback_url,omitempty"`
PrivateKey string `json:"private_key,omitempty"`
RequestId string `json:"request_id,omitempty"`
Prefix string `json:"prefix,omitempty"`
OriginName string `json:"origin,omitempty"`
}
requestInfo struct {
channel chan reversalRequest
prefix string
}
requestKey struct {
origin string
prefix string
}
)
var (
errRetrieveTimeout error = errors.New("retrieve request timed out")
errRequestTimeout error = errors.New("reverse request timed out")
requestsLock sync.Mutex = sync.Mutex{}
requests map[requestKey]requestInfo = make(map[requestKey]requestInfo)
)
func getOriginQueue(prefix, origin string) chan reversalRequest {
requestsLock.Lock()
defer requestsLock.Unlock()
if req, ok := requests[requestKey{origin: origin, prefix: prefix}]; ok {
return req.channel
} else {
newChan := make(chan reversalRequest)
requests[requestKey{origin: origin, prefix: prefix}] = requestInfo{channel: newChan, prefix: prefix}
return newChan
}
}
// Send a request to a given origin's queue.
// Return a requestTimeout error if no origin retrieved the request before the context timed out.
func handleRequest(ctx context.Context, origin string, req reversalRequest, timeout time.Duration) (err error) {
queue := getOriginQueue(req.Prefix, origin)
maxTime := timeout - 500*time.Millisecond - time.Duration(rand.Intn(500))*time.Millisecond
if maxTime <= 0 {
maxTime = time.Millisecond
}
tick := time.NewTicker(maxTime)
defer tick.Stop()
select {
case queue <- req:
break
case <-tick.C:
err = errRequestTimeout
break
case <-ctx.Done():
err = errRequestTimeout
break
}
return
}
// Handle the origin's request to retrieve any pending reversals.
func handleRetrieve(appCtx context.Context, ginCtx context.Context, prefix, origin string, timeout time.Duration) (req reversalRequest, err error) {
// Return randomly short of the timeout.
maxTime := timeout - 500*time.Millisecond - time.Duration(rand.Intn(500))*time.Millisecond
if maxTime <= 0 {
maxTime = time.Millisecond
}
tick := time.NewTicker(maxTime)
defer tick.Stop()
select {
case req = <-getOriginQueue(prefix, origin):
break
case <-tick.C:
err = errRetrieveTimeout
case <-ginCtx.Done():
err = errRetrieveTimeout
case <-appCtx.Done():
err = errRetrieveTimeout
}
return
}