Better caching during simulation

1 files changed, 23 insertions, 4 deletions

diff --git a/backend/src/simulation/robotMovementSimulator.ts b/backend/src/simulation/robotMovementSimulator.ts
index 2299f43..d3a2564 100644
--- a/backend/src/simulation/robotMovementSimulator.ts
+++ b/backend/src/simulation/robotMovementSimulator.ts
@@ -1,6 +1,7 @@
 import { QueryResult } from "pg";
 import { Server } from "socket.io";
 import db from "../database/postgres.js";
+import redisClient from "../database/redis.js";
 import {
     Robot,
     RobotPosition,
@@ -8,6 +9,9 @@ import {
     SimulationResponse,
 } from "../types/robot.js";
 
+const CACHE_TTL = 10;
+const ROBOTS_CACHE_KEY = "allMyRobots";
+
 // Coordinates for the boundaries of the frontend map
 const LEIPZIG_AREA = {
     WEST: 12.22,
@@ -70,10 +74,19 @@ async function updateRobotPositions(io: Server) {
     try {
         client = await db.connect();
 
-        const allRobotsQuery: QueryResult<Robot> = await client.query(
-            "SELECT * FROM robots ORDER BY id;"
-        );
-        const allRobots = allRobotsQuery.rows;
+	let allRobots;
+	const cachedData = await redisClient.get(ROBOTS_CACHE_KEY);
+
+	// Check Redis for cached data, otherwise query database
+	if (cachedData) {
+	    allRobots = JSON.parse(cachedData);
+	} else {
+	    const allRobotsQuery: QueryResult<Robot> = await client.query(
+		"SELECT * FROM robots ORDER BY id;"
+            );
+
+	    allRobots = allRobotsQuery.rows;
+	}
 
         // Update database
         await client.query("BEGIN");
@@ -142,6 +155,12 @@ async function updateRobotPositions(io: Server) {
 
         await client.query("COMMIT");
 
+	// Keep robots in Redis cache indefinitely while simulation is running to avoid db query on every tick
+	// Once the simulation stops, keep the cache alive for 10 seconds
+	await redisClient.set(ROBOTS_CACHE_KEY, JSON.stringify(updatedRobots), {
+	    EX: movingRobots.size === 0 ? CACHE_TTL : undefined,
+	});
+
         // Websocket broadcast, make sure robots stay in correct order
         updatedRobots.sort((a, b) => a.id - b.id);