trying to be clever in error handling didn't work.... will fix later

functions/send_view.js

@@ -2,79 +2,82 @@ const axios = require("axios");
 
 exports.handler = function (event, context, callback) {
   try {
-    // if triggered as an image without JS (i.e. from AMP pages) set `?noscript=true`
-    const noScript = event.queryStringParameters["noscript"] === "true";
+    // attach a timer to axios to debug response time from endpoint
+    // https://stackoverflow.com/questions/62186171/measure-network-latency-in-react-native/62257712#62257712
+    (function (instance) {
+      instance.interceptors.request.use((request) => {
+        request.startTime = Date.now();
+        return request;
+      });
 
-    // https://docs.simpleanalytics.com/without-javascript
-    const endpointHost = "queue.simpleanalyticscdn.com";
-    const endpointPath = noScript ? "noscript.gif" : "simple.gif";
-    const endpointUrl = "https://" + endpointHost + "/" + endpointPath;
+      instance.interceptors.response.use((response) => {
+        response.elapsedTime = Number(Date.now() - response.config.startTime).toFixed();
+        return response;
+      });
+    })(axios);
 
-    // pass these headers along to SA
+    // pass these URL parameters along to endpoint
+    const reqQuery = event.queryStringParameters;
+    reqQuery["ignore-dnt"] = "true"; // this isn't nefarious, we're not tracking in the first place!
+
+    // pass these optional headers along to endpoint
     const reqHeaders = {
       referer: event.headers["referer"] || "",
       "user-agent": event.headers["user-agent"] || "",
     };
 
-    // pass these URL parameters along to SA
-    const reqQuery = event.queryStringParameters;
-    reqQuery["ignore-dnt"] = "true"; // this isn't nefarious, we're not tracking in the first place!
-
-    const reqConfig = {
-      method: "GET",
-      url: endpointUrl,
-      headers: reqHeaders,
-      params: reqQuery,
-      responseType: "arraybuffer",
-      timeout: 2000,
-    };
-
-    console.info(`Proxying ${reqQuery["type"]} to ${endpointPath} ...`);
+    // if triggered as an image without JS (i.e. from AMP pages) set `?noscript=true`
+    // https://docs.simpleanalytics.com/without-javascript
+    const endpointHost = "queue.simpleanalyticscdn.com";
+    const endpointPath = reqQuery["noscript"] === "true" ? "noscript.gif" : "simple.gif";
+    const endpointUrl = "https://" + endpointHost + "/" + endpointPath;
 
     axios
-      .request(reqConfig)
+      .request({
+        method: "GET",
+        url: endpointUrl,
+        headers: reqHeaders,
+        params: reqQuery,
+        responseType: "arraybuffer",
+        timeout: 2000,
+      })
       .then(function (response) {
-        // parse the feedback message from SA
+        console.info(
+          `${response.status} ${response.statusText} | ${response.elapsedTime}ms | ${response.headers["simple-analytics-feedback"]}`
+        );
+
+        // parse the feedback message from endpoint
         const apiFeedback = response.headers["simple-analytics-feedback"] || "No feedback from Simple Analytics.";
-        const shortFeedback = apiFeedback.toLowerCase().includes("thanks for sending") ? "OK" : `ERROR: ${apiFeedback}`;
-
-        console.info(response.status, apiFeedback);
-
-        // imitate the headers that would normally be sent back from SA's pixel
-        const resHeaders = {
-          "Content-Type": "image/gif",
-          "Cache-Control": "private, no-cache, no-store, must-revalidate",
-          Expires: "0",
-          Pragma: "no-cache",
-          "X-API-Response": shortFeedback,
-          "X-API-Endpoint": endpointHost,
-        };
+        const shortFeedback = apiFeedback.toLowerCase().includes("thanks for sending ")
+          ? "OK"
+          : `ERROR: ${apiFeedback}`;
 
         // reasoning for base64 encoding:
         // https://community.netlify.com/t/debugging-a-function-returns-502/429/12
         callback(null, {
           statusCode: response.status,
-          headers: resHeaders,
+          headers: {
+            "Content-Type": "image/gif",
+            "Cache-Control": "private, no-cache, no-store, must-revalidate",
+            Expires: "0",
+            Pragma: "no-cache",
+            "x-api-response": shortFeedback,
+            "x-api-latency": response.elapsedTime,
+          },
           body: response.data.toString("base64"),
           isBase64Encoded: true,
         });
       })
       .catch(function (error) {
-        // this indicates a function error, NOT an error returned from SA
-        throw error;
+        // this indicates a request error, NOT an error in the endpoint's reponse
+        console.error(error.message);
+
+        callback(Error(error));
       });
   } catch (error) {
     // something went VERY wrong...
-    console.log(error.message);
+    console.error(error.message);
 
-    callback(null, {
-      statusCode: 500,
-      headers: {
-        "Content-Type": "application/json",
-      },
-      body: JSON.stringify({
-        error: error.message,
-      }),
-    });
+    callback(Error(error));
   }
 };