Add short-term caching header to list-devices and list-devices-near.

README.md

@@ -4,7 +4,7 @@
 
 This project contains the web interface for the ConnectedHumber sensor system. Despite being called _Air Quality Web_, it is designed to display any kind of sensor data - not just air quality sensor readings.
 
- It is composed of 2 parts:
+It is composed of 2 parts:
 
  - A PHP-based JSON API server (entry point: api.php) that's backed by a MariaDB server
  - A Javascript client application that runs in the browser

logic/Actions/ListDevices.php

@@ -83,8 +83,11 @@ class ListDevices implements IAction {
 		
 		// 4: Send response
 		
-		// Don't a cache control header, because new devices might get added at any time
-		// TODO: Investigate adding a short-term (~10mins?) cache-control header here
+		// Don't cache for ages, because new devices might get added at any time
+		// FUTURE: Move last-seen to a different API call if caching becomes critically important?
+		if($this->settings->get("env.mode") == "production") {
+			header("cache-control: public, max-age=" . $this->settings->get("cache.max-age-supershort"));
+		}
 		
 		header("content-length: " . strlen($response));
 		header("content-type: $response_type");

logic/Actions/ListDevicesNear.php

@@ -83,8 +83,9 @@ class ListDevicesNear implements IAction {
 		// 4: Send response
 		
 		// Send a cache-control header, but only in production mode
+		// FUTURE: Move last-seen to a different API call if caching becomes critically important?
 		if($this->settings->get("env.mode") == "production") {
-			header("cache-control: public, max-age=" . $this->settings->get("cache.max-age"));
+			header("cache-control: public, max-age=" . $this->settings->get("cache.max-age-supershort"));
 		}
 		
 		header("content-length: " . strlen($response));

settings.default.toml

@@ -34,6 +34,9 @@ default-action = "index"
 # Note also that cache headers are only sent in production mode - see env.mode above
 max-age = 2592000 # 30 days
 
+# The max-age for time-sensitive data (e.g. last_seen values). Defaults to 30 seconds, which should yield some benefit).
+max-age-supershort = 30 # 30 seconds
+
 [data]
 # Settings relating to the data returned by the API.