Supply API key to avoid Hit Limit error from Maps Service in Apps Script

Question

I have a Google Sheet where we are fetching the driving distance between two Lat/Lng via the Maps Service . The function below works, but the matrix is 4,500 cells, so I'm getting the "Hit Limit" error.

How can I supply my paid account's API key here?

Custom Function

function drivingMeters(origin, destination) {
  if (origin=='' || destination==''){return ''}
  var directions = Maps.newDirectionFinder()
  .setOrigin(origin)
  .setDestination(destination)
  .getDirections();
  return directions.routes[0].legs[0].distance.value ;
}

Example use:

A1: =drivingMeters($E10,G$9)

Where E10 = 42.771328,-91.902281
  and G9  = 42.490390,-91.1626620

Answer 1

Per documentation, you should initialize the Maps service with your authentication details prior to calling other methods:

Your client ID and signing key can be obtained from the Google Enterprise Support Portal. Set these values to null to go back to using the default quota allowances.

I recommend storing these values in PropertiesService and using CacheService , to provide fast access. Using this approach, rather than writing them in the body of your script project, means they will not be inadvertently copied by other editors, pushed to a shared code repository, or visible to other developers if your script is published as a library.

Furthermore, I recommend rewriting your custom function to accept array inputs and return the appropriate array output - this will help speed up its execution. Google provides an example of this on the custom function page: https://developers.google.com/apps-script/guides/sheets/functions#optimization

Example with use of props/cache:

function authenticateMaps_() {
  // Try to get values from cache:
  const cache = CacheService.getScriptCache();
  var props = cache.getAll(['mapsClientId', 'mapsSigningKey']);
  // If it wasn't there, read it from PropertiesService.
  if (!props || !props.mapsClientId || !props.mapsSigningKey) {
    const allProps = PropertiesService.getScriptProperties().getProperties();
    props = {
      'mapsClientId': allProps.mapsClientId,
      'mapsSigningKey': allProps.mapsSigningKey
    };
    // Cache these values for faster access (max 6hrs)
    cache.putAll(props, 21600);
  }
  // Apply these keys to the Maps Service. If they don't exist, this is the
  // same as being a default user (i.e. no paid quota).
  Maps.setAuthentication(props.mapsClientId, props.mapsSigningKey);
}
function deauthMaps_() {
  Maps.setAuthentication(null, null);
}

// Your called custom function. First tries without authentication,
// and then if an error occurs, assumes it was a quota limit error
// and retries. Other errors do exist (like no directions, etc)...
function DRIVINGMETERS(origin, dest) {
  if (!origin || !destination)
    return;
  try {
    return drivingMeters_(origin, dest);
  } catch (e) {
    console.error({
      message: "Error when computing directions: " + e.message,
      error: e
    });
    // One of the possible errors is a quota limit, so authenticate and retry:
    // (Business code should handle other errors instead of simply assuming this :) )
    authenticateMaps_();
    var result = drivingMeters_(origin, dest);
    deauthMaps_();
    return result;
  }
}

// Your implementation function.
function drivingMeters_(origin, dest) {
  var directions = Maps.newDirectionFinder()
  ...
}