Use express ttl

CHANGELOG.md

@@ -1,5 +1,11 @@
 # bedrock-session-mongodb ChangeLog
 
+## 4.2.0 -
+
+### Changed
+- `config.session-mongodb.ttl` is now a computed property.
+- `config.session-mongodb.ttl` is now computed from config.express.session.ttl.
+
 ## 4.1.0 - 2020-07-07
 
 ### Changed

README.md

@@ -37,6 +37,9 @@ bedrock.start();
 
 For documentation on configuration, see [config.js](./lib/config.js).
 
+`config.session-mongodb.ttl` is a computed property that converts
+`config.express.session.ttl` to seconds. In order to change the ttl for sessions you will
+now need to change the `config.express.session.ttl` using milliseconds.
 
 [bedrock]: https://github.com/digitalbazaar/bedrock
 [bedrock-express]: https://github.com/digitalbazaar/bedrock-express

lib/config.js

@@ -5,10 +5,22 @@
  */
 'use strict';
 
-const {config} = require('bedrock');
-
+const {config, util} = require('bedrock');
+const cc = util.config.main.computer();
 config['session-mongodb'] = {
   collection: 'session',
-  // timeout is in seconds (time for session to live on the server)
-  ttl: 60 * 30
 };
+
+// MongoStore ttl defaults to thirtyMinutes expressed in seconds.
+const thirtyMinutes = 60 * 30;
+
+// timeout is in seconds (time for session to live on the server)
+cc('session-mongodb.ttl', () => {
+  if(config.express && config.express.session) {
+    // express session ttl is in milliseconds
+    const {ttl = thirtyMinutes * 1000} = config.express.session;
+    // round down to ensure session doesn't live beyond configured value
+    return Math.floor(ttl / 1000);
+  }
+  return thirtyMinutes;
+});

package.json

@@ -28,7 +28,7 @@
   },
   "peerDependencies": {
     "bedrock": "1.0.0 - 3.x",
-    "bedrock-express": "2.0.3 - 3.x",
+    "bedrock-express": "2.0.3 - 4.x",
     "bedrock-mongodb": "^7.1.0"
   },
   "directories": {