fix: alert when no vehicle states written for an agency (fixes #31)

src/index.js

@@ -3,6 +3,7 @@ const fs = require('fs');
 const s3Helper = require('./s3Helper');
 
 const interval = 15000; // ms
+const ALERT_THRESHOLD_MS = 5 * 60 * 1000; // 5 minutes
 
 const configPath = process.env.ORION_CONFIG_PATH;
 const configJson = process.env.ORION_CONFIG_JSON;
@@ -37,6 +38,9 @@ const providerNames = [
 const s3Bucket = config.s3_bucket;
 console.log("S3 bucket: " + s3Bucket);
 
+// Track last successful S3 write per agency
+const lastSuccessfulWrite = {};
+
 var agenciesInfo = config.agencies.map((agencyConfig) => {
     const providerName = agencyConfig.provider;
     if (!providerNames.includes(providerName)) {
@@ -52,31 +56,64 @@ var agenciesInfo = config.agencies.map((agencyConfig) => {
 
     console.log("Agency: " + agencyId + " (" + providerName + ")");
 
+    // Initialize timestamp so alert doesn't fire immediately on startup
+    lastSuccessfulWrite[agencyId] = Date.now();
+
     return {
         provider: provider,
         id: agencyId,
         config: agencyConfig
     };
 });
 
-// wait until the next multiple of 15 seconds
+// Alert function — uses Slack webhook if configured, else logs to stderr
+function sendAlert(agencyId) {
+    const message = `Orion Alert: No vehicle states written for agency "${agencyId}" in the last ${ALERT_THRESHOLD_MS / 60000} minutes. Provider may be down.`;
+    console.error(`ALERT: ${message}`);
+
+    const webhookUrl = process.env.ALERT_WEBHOOK_URL;
+    if (webhookUrl) {
+        axios.post(webhookUrl, { text: `🚨 ${message}` })
+            .catch((err) => console.error(`Failed to send alert webhook for ${agencyId}:`, err.message));
+    }
+}
+
+// Periodically check if any agency has stopped writing states
+setInterval(() => {
+    const now = Date.now();
+    agenciesInfo.forEach((agencyInfo) => {
+        const last = lastSuccessfulWrite[agencyInfo.id];
+        if (!last || (now - last) > ALERT_THRESHOLD_MS) {
+            sendAlert(agencyInfo.id);
+        }
+    });
+}, ALERT_THRESHOLD_MS);
+
+// Wait until the next multiple of 15 seconds
 setTimeout(function() {
     setInterval(saveVehicles, interval);
     saveVehicles();
 }, interval - Date.now() % interval);
 
 function saveVehicles() {
-  const currentTime = Date.now();
-
-  const promises = agenciesInfo.map((agencyInfo) => {
-    return agencyInfo.provider.getVehicles(agencyInfo.config)
-      .then((vehicles) => {
-        return s3Helper.writeToS3(s3Bucket, agencyInfo.id, currentTime, vehicles);
-      })
-      .catch((err) => {
-        console.log(err);
-      });
-  });
-
-  Promise.all(promises);
-}
+    const currentTime = Date.now();
+
+    const promises = agenciesInfo.map((agencyInfo) => {
+        return agencyInfo.provider.getVehicles(agencyInfo.config)
+            .then((vehicles) => {
+                return s3Helper.writeToS3(s3Bucket, agencyInfo.id, currentTime, vehicles)
+                    .then((result) => {
+                        // ✅ Update timestamp on successful write
+                        lastSuccessfulWrite[agencyInfo.id] = Date.now();
+                        return result;
+                    });
+            })
+            .catch((err) => {
+                // Log error but don't update lastSuccessfulWrite so alert can trigger
+                console.error(`Error saving vehicles for agency "${agencyInfo.id}":`, err.message || err);
+            });
+    });
+
+    // Return the Promise so errors are traceable
+    return Promise.all(promises);
+}