feat: Add expiresIn option

This allows users to override the default expiry behavior when using
DynamoDB TTL to expire sessions from the table. This would be useful,
for example, if they wanted to use a browser session scoped cookie as
the session cookie (with no maxAge attribute) but needed a shorter TTL
than the default '1 day from now'.

If this parameter is not provided then there will be no change to the
current behaviour.

Author: alex9smith

README.md

@@ -21,6 +21,7 @@ unless the `client` options is provided to override them.
   ☣️ Legacy reap behaviors use DynamoDB [`scan`](https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/clients/client-dynamodb/classes/scancommand.html)
   functionality that can incur significant costs. Should instead enable [DynamoDB TTL](http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html)
   and select the `expires` field. TODO should we just remove it since we're already making a breaking change?
+- `expiresIn` Optional set the number of seconds for DynamoDB TTL. Defaults to the cookie's maxAge.
 
 ## Usage
 
@@ -42,6 +43,8 @@ var options = {
   ],
   // Optional skip throw missing special keys in session, if set true
   skipThrowMissingSpecialKeys: true,
+  // Optional set the number of seconds for DynamoDB TTL
+  expiresIn: 3600,
 };
 ```
 

index.d.ts

@@ -37,6 +37,13 @@ declare namespace ConnectDynamoDB {
      * Useful if the table already exists or if you want to skip existence checks in a serverless environment such as AWS Lambda.
      */
     initialized?: boolean;
+    /**
+     * Set the number of seconds added to the item expiry time.
+     *
+     * Setting this to 0 will use the `maxAge` value from the session cookie.
+     * @default 0
+     */
+    expiresIn?: number;
   }
 
   interface DynamoDBStoreOptionsSpecialKey {

lib/connect-dynamodb.js

@@ -68,6 +68,7 @@ module.exports = function (connect) {
     if (this.reapInterval > 0) {
       this._reap = setInterval(this.reap.bind(this), this.reapInterval);
     }
+    this.expiresIn = null == options.expiresIn ? 0 : options.expiresIn
   }
 
   /*
@@ -344,11 +345,17 @@ module.exports = function (connect) {
    */
   DynamoDBStore.prototype.getExpiresValue = function (sess) {
     const now = Math.floor(Date.now() / 1000);
-    const expires =
+
+    if (this.expiresIn != 0) {
+      return now + this.expiresIn;
+    }
+    else {
+      const expires =
       typeof sess.cookie.maxAge === "number"
         ? now + (sess.cookie.maxAge / 1000)
         : now + oneDayInSeconds;
     return expires;
+    }
   };
 
   /**

test/test.js

@@ -5,6 +5,7 @@ const {
   DynamoDBClient,
   CreateTableCommand,
   DeleteTableCommand,
+  GetItemCommand,
   ScalarAttributeType,
 } = require("@aws-sdk/client-dynamodb");
 const ConnectDynamoDB = require(__dirname + "/../lib/connect-dynamodb.js");
@@ -231,6 +232,40 @@ describe("DynamoDBStore", () => {
         });
       });
     });
+
+    it("should set correct expiry when expiresIn option is set", async () => {
+      const storeWithExpiry = new DynamoDBStore({
+        client: client,
+        table: tableName,
+        expiresIn: 1000
+      });
+      const beforeTime = Math.floor(Date.now() / 1000);
+      
+      await new Promise((resolve, reject) => {
+        storeWithExpiry.set(
+          sessionId,
+          {
+            cookie: { maxAge: 2000 },
+            name: "test"
+          },
+          (err) => {
+            if (err) return reject(err);
+            resolve();
+          }
+        );
+      });
+
+      const result = await client.send(
+        new GetItemCommand({
+          TableName: tableName,
+          Key: { id: { S: "sess:" + sessionId } }
+        })
+      );
+      
+      const expiryValue = parseInt(result.Item.expires.N);
+      const expectedExpiry = beforeTime + 1000;
+      expiryValue.should.be.approximately(expectedExpiry, 2);
+    });
   });
 
   describe("Getting", () => {