From 0830a60342b30c033c816d25a5518b2123e34ffc Mon Sep 17 00:00:00 2001
From: Nicolas Bigot <nicbigot@gmail.com>
Date: Sun, 3 Dec 2023 11:39:09 +0100
Subject: [PATCH] feat: handle long pooling for GetRecords request

---
 stream/streamiterator.go        | 53 +++++++++++++++++++++++----------
 types/istreamiteratorhandler.go | 11 +++----
 2 files changed, 44 insertions(+), 20 deletions(-)

diff --git a/stream/streamiterator.go b/stream/streamiterator.go
index 763c006..401d0a8 100644
--- a/stream/streamiterator.go
+++ b/stream/streamiterator.go
@@ -111,20 +111,23 @@ func (it *StreamIterator) GetRecords(c *fasthttp.RequestCtx, maxRecords uint) (*
 		recordId, record, foundRecord, canContinue, err = it.handler.GetNextRecord()
 
 		if !foundRecord {
-			// // TODO: ajouter un mécanisme comme dans aws sqs qui attend x secondes avant de retourner un résultat
-			// // on ne retourne pas immédiatement une réponse vide, on attend la fin du timeout (max 60 secs par exemple)
-			// // on peut imaginer utiliser un header http pour spécifier le délai d'attente maximal
-			// // long pooling
-			// if maxWaitTimeSeconds > 0 && response.Count == 0 {
-			// 	elaspedTime := int(time.Since(startTime).Seconds())
-			// 	if elaspedTime < maxWaitTimeSeconds {
-			// 		// has not timed out already
-			// 		time.Sleep()
-			// 		continue
-			// 	}
-			// }
-
-			// no record found, this is the end of the stream
+			// No record found, this is the end of the stream.
+			// Long polling is activated when the 'createIterator' request has
+			// the 'MaxWaitTimeSeconds' attribute set to a value greater than 0.
+			// Long polling addresses this issue by allowing the server to hold the response to a client's request
+			// until new information is available or a timeout occurs.
+			// Long polling reducing the occurrence of empty responses,
+			// which occur when there are no messages available for a GetRecords request.
+			if response.Count == 0 && it.request.MaxWaitTimeSeconds > 0 {
+				elaspedTime := int(time.Since(startTime).Seconds())
+				if elaspedTime < it.request.MaxWaitTimeSeconds {
+					// request has not reached its timeout yet
+					time.Sleep(time.Second)
+					// continue to search again
+					continue
+				}
+			}
+
 			err = nil
 			break
 		}
@@ -275,6 +278,11 @@ func init() {
 								"type": "string",
 								"minLength": 1,
 								"maxLength": 256
+						},
+						"maxWaitTimeSeconds": {
+							"type": "integer",
+							"minimum": 0,
+						  "maximum": 60
 						}
 					},
 					"required": ["iteratorType"],
@@ -299,6 +307,11 @@ func init() {
 								"type": "string",
 								"minLength": 1,
 								"maxLength": 256
+						},
+						"maxWaitTimeSeconds": {
+							"type": "integer",
+							"minimum": 0,
+						  "maximum": 60
 						}
 					},
 					"required": ["iteratorType", "messageId"],
@@ -323,6 +336,11 @@ func init() {
 								"type": "string",
 								"minLength": 1,
 								"maxLength": 256
+						},
+						"maxWaitTimeSeconds": {
+							"type": "integer",
+							"minimum": 0,
+						  "maximum": 60
 						}
 					},
 					"required": ["iteratorType", "timestamp"],
@@ -368,11 +386,16 @@ Valid iterator request examples:
 
 {
 	"iteratorType": "FIRST_MESSAGE"
-	"Name": "myApp"
+	"name": "myApp"
 }
 
 {
 	"iteratorType": "FIRST_MESSAGE"
 	"jqFilter": ".[0]"
 }
+
+{
+	"iteratorType": "FIRST_MESSAGE"
+	"maxWaitTimeSeconds": "20"
+}
 */
diff --git a/types/istreamiteratorhandler.go b/types/istreamiteratorhandler.go
index 8c2a67a..8744f4b 100644
--- a/types/istreamiteratorhandler.go
+++ b/types/istreamiteratorhandler.go
@@ -3,11 +3,12 @@ package types
 import "time"
 
 type StreamIteratorRequest struct {
-	IteratorType string    `json:"iteratorType" validate:"required,oneof=FIRST_MESSAGE LAST_MESSAGE AFTER_LAST_MESSAGE AT_MESSAGE_ID AFTER_MESSAGE_ID AT_TIMESTAMP"`
-	MessageId    MessageId `json:"messageId"`
-	Timestamp    time.Time `json:"timestamp"`
-	JqFilter     string    `json:"jqFilter"`
-	Name         string    `json:"name"`
+	IteratorType       string    `json:"iteratorType" validate:"required,oneof=FIRST_MESSAGE LAST_MESSAGE AFTER_LAST_MESSAGE AT_MESSAGE_ID AFTER_MESSAGE_ID AT_TIMESTAMP"`
+	MessageId          MessageId `json:"messageId"`
+	Timestamp          time.Time `json:"timestamp"`
+	JqFilter           string    `json:"jqFilter"`
+	MaxWaitTimeSeconds int       `json:"maxWaitTimeSeconds"`
+	Name               string    `json:"name"`
 }
 
 type IStreamIteratorHandler interface {