From 42837c18cf8d82bb9e5053d5d71f4fcb9f8124fb Mon Sep 17 00:00:00 2001
From: Icebob <mereg.norbert@gmail.com>
Date: Sun, 23 Apr 2023 17:25:17 +0200
Subject: [PATCH] support Redis capped streams

---
 .vscode/launch.json      |  4 ++--
 README.md                | 18 ++++++++++++++++++
 examples/simple/index.js |  4 ++--
 src/adapters/redis.js    | 22 +++++++++++++++++-----
 4 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/.vscode/launch.json b/.vscode/launch.json
index 68b327f..27f86cf 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -8,11 +8,11 @@
 		{
 			"type": "node",
 			"request": "launch",
-			"name": "Launch selected demo",
+			"name": "Launch demo",
 			"program": "examples/index.js",
 			"cwd": "${workspaceRoot}",
 			"args": [
-				"context"
+				"simple"
 			],
 			"console": "integratedTerminal",
 			"env": {
diff --git a/README.md b/README.md
index 6b4609f..4178832 100644
--- a/README.md
+++ b/README.md
@@ -271,6 +271,7 @@ Use the `broker.sendToChannel(channelName, payload, opts)` method to send a mess
 | `acks`                                  | `Number`             | Kafka                         | Control the number of required acks.                                                                                                                                                          |
 | `timeout`                               | `Number`             | Kafka                         | The time to await a response in ms. Default: `30000`                                                                                                                                          |
 | `compression`                           | `any`                | Kafka                         | Compression codec. Default: `CompressionTypes.None`                                                                                                                                           |
+| `xaddMaxLen`                           | `Number` or `String`  | Redis                         | Define `MAXLEN` for `XADD` command                                                                                                                                         |
 
 ## Middleware hooks
 
@@ -621,6 +622,23 @@ module.exports = {
 };
 ```
 
+#### Capped Streams
+
+To support Redis ["capped streams"](https://redis.io/docs/data-types/streams-tutorial/#capped-streams), you can define the `MAXLEN` value in `sendToChannel` options as `xaddMaxLen`. It can be a number or a string with `~` prefix like `~1000`. It will be transformed to `...MAXLEN ~ 1000 ...`
+
+**Example**
+
+```js
+broker.sendToChannel("order.created", {
+    id: 1234,
+    items: [
+        /*...*/
+    ]
+},{
+    xaddMaxLen: "~1000"
+});
+```
+
 ### AMQP (RabbitMQ)
 
 The AMQP adapter uses the exchange-queue logic of RabbitMQ for creating consumer groups. It means the `sendToChannel` method sends the message to the exchange and not for a queue.
diff --git a/examples/simple/index.js b/examples/simple/index.js
index 106ec36..7bbd20d 100644
--- a/examples/simple/index.js
+++ b/examples/simple/index.js
@@ -14,7 +14,7 @@ const broker = new ServiceBroker({
 	},
 	middlewares: [
 		ChannelsMiddleware({
-			adapter: process.env.ADAPTER || "Fake"
+			adapter: process.env.ADAPTER || "redis://localhost:6379"
 		})
 	],
 	replCommands: [
@@ -33,7 +33,7 @@ const broker = new ServiceBroker({
 						count: ++c,
 						pid: process.pid
 					},
-					{ key: "" + c, headers: { a: "something" } }
+					{ key: "" + c, headers: { a: "something" }, xaddMaxLen: "~10" }
 				);
 			}
 		},
diff --git a/src/adapters/redis.js b/src/adapters/redis.js
index d2956e9..3f24754 100644
--- a/src/adapters/redis.js
+++ b/src/adapters/redis.js
@@ -688,15 +688,27 @@ class RedisAdapter extends BaseAdapter {
 
 		try {
 			let args = [
-				channelName, // Stream name
-				"*", // Auto ID
-				"payload", // Entry
-				opts.raw ? payload : this.serializer.serialize(payload) // Actual payload
+				channelName // Stream name
 			];
 
+			// Support Capped Streams. More info: https://redis.io/docs/data-types/streams-tutorial/#capped-streams
+			if (opts && opts.xaddMaxLen) {
+				const maxLen = "" + opts.xaddMaxLen;
+				if (maxLen.startsWith("~")) {
+					args.push("MAXLEN", "~", maxLen.substring(1));
+				} else {
+					args.push("MAXLEN", maxLen);
+				}
+			}
+
+			// Auto ID
+			args.push("*");
+			// Add payload
+			args.push("payload", opts.raw ? payload : this.serializer.serialize(payload));
+
 			// Add headers
 			if (opts.headers) {
-				args.push(...["headers", this.serializer.serialize(opts.headers)]);
+				args.push("headers", this.serializer.serialize(opts.headers));
 			}
 
 			// https://redis.io/commands/XADD