Update dns-in-google-sheets.mdx to add caching in NSLookup

[beltofte]

Adding internal caching of the results on the NSLookup function to limit the number of the DNS resolver requests and speed up the results - especially in larger Google Sheets.

Summary

The NSLookup function for Google Sheets provided in the original documentation page does not support internal caching of the results. This can lead to issues in Google Sheets with many calls to the function - this includes error 400 from the https://cloudflare-dns.com/dns-query if you use it too much.

It is possible to disable caching and control the cache TTL via arguments in the NSLookup function.

Screenshots (optional)

Documentation checklist

• The documentation style guide has been adhered to.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• Files which have changed name or location have been allocated redirects.

[hunts]

Can be if (usecache) as usecache is validated to be boolean.

[hannes-cf]

The default value for usecache should be false, since correctness should be preferred over performance. Users who want to change that are free to do so.

[hunts]

Sorry for the confusing, I think our TTL calculation is still not right. This would be the changes I'd like to make before we can merge it.

Basically, use the minimal TTL from records, but clamp the lower bound at the minCacheTTL (which is 30 seconds). Also replaced var with const /let keywords by the way.

index df02454ac..480cd4be6 100644
--- a/src/content/docs/1.1.1.1/other-ways-to-use-1.1.1.1/dns-in-google-sheets.mdx
+++ b/src/content/docs/1.1.1.1/other-ways-to-use-1.1.1.1/dns-in-google-sheets.mdx
@@ -12,7 +12,7 @@ import { Details } from "~/components"
 1.1.1.1 works directly inside Google Sheets. To get started, create a [Google Function](https://developers.google.com/apps-script/guides/sheets/functions) with the following code:
 
 ```js
-function NSLookup(type, domain, usecache = false, cachettl = 30) {
+function NSLookup(type, domain, usecache = false, minCacheTTL = 30) {
 
   if (typeof type == 'undefined') {
     throw new Error('Missing parameter 1 dns type');
@@ -26,43 +26,44 @@ function NSLookup(type, domain, usecache = false, cachettl = 30) {
     throw new Error('Only boolean values allowed in 3 use cache');
   }
 
-  if (typeof cachettl != "number") {
-    throw new Error('Only numeric values allowed in 4 cache ttl');
+  if (typeof minCacheTTL != "number") {
+    throw new Error('Only numeric values allowed in 4 min cache ttl');
   }
 
   type = type.toUpperCase();
   domain = domain.toLowerCase();
 
+  let cache = null;
   if (usecache) {
     // Cache key and hash
     cacheKey = domain + "@" + type;
     cacheHash = Utilities.base64Encode(cacheKey);
     cacheBinKey = "nslookup-result-" + cacheHash;
 
-    var cache = CacheService.getScriptCache();
-    var cachedResult = cache.get(cacheBinKey);
+    cache = CacheService.getScriptCache();
+    const cachedResult = cache.get(cacheBinKey);
     if (cachedResult != null) {
       return cachedResult;
     }
   }
 
-  var url = 'https://cloudflare-dns.com/dns-query?name=' + encodeURIComponent(domain) + '&type=' + encodeURIComponent(type);
-  var options = {
+  const url = 'https://cloudflare-dns.com/dns-query?name=' + encodeURIComponent(domain) + '&type=' + encodeURIComponent(type);
+  const options = {
     muteHttpExceptions: true,
     headers: {
       accept: "application/dns-json"
     }
   };
 
-  var result = UrlFetchApp.fetch(url, options);
-  var rc = result.getResponseCode();
-  var resultText = result.getContentText();
+  const result = UrlFetchApp.fetch(url, options);
+  const rc = result.getResponseCode();
+  const resultText = result.getContentText();
 
   if (rc !== 200) {
     throw new Error(rc);
   }
 
-  var errors = [
+  const errors = [
     { name: "NoError", description: "No Error"}, // 0
     { name: "FormErr", description: "Format Error"}, // 1
     { name: "ServFail", description: "Server Failure"}, // 2
@@ -75,24 +76,25 @@ function NSLookup(type, domain, usecache = false, cachettl = 30) {
     { name: "NotAuth", description: "Not Authorized"} // 9
   ];
 
-  var response = JSON.parse(resultText);
+  const response = JSON.parse(resultText);
 
   if (response.Status !== 0) {
     return errors[response.Status].name;
   }
 
-  var outputData = [];
-  var minCacheTTL = cachettl;
+  const outputData = [];
+  let cacheTTL = 0;
 
-  for (var i in response.Answer) {
+  for (const i in response.Answer) {
     outputData.push(response.Answer[i].data);
-    minCacheTTL = Math.max(minCacheTTL, response.Answer[i].TTL);
+    const ttl = response.Answer[i].TTL;
+    cacheTTL = Math.min(cacheTTL || ttl, ttl);
   }
 
-  var outputString = outputData.join(',');
+  const outputString = outputData.join(',');
 
   if (usecache) {
-    cache.put(cacheBinKey, outputString, minCacheTTL);
+    cache.put(cacheBinKey, outputString, Math.max(cacheTTL, minCacheTTL));
   }
 
   return outputString;

[beltofte]

Thanks @hunts. I have committed the patch, and at the same time renamed usecache to useCache, so all variables / constants are following lowerCamelCase.

[hunts]

Thanks for the quick updates. Looks good to me now.

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