Set up server-side tagging with App Engine

This guide explains how to:

Provision a tagging server on Google Cloud Platform (GCP) App Engine.
Upgrade the tagging server to handle live traffic.
Increase or decrease the number of servers that are running your Google Tag Manager container.
Keep your tagging server version updated after provisioning the server.

Prerequisites

You need a GCP account. If you don't have one, create a new GCP account.
You need a GCP billing account. If you don't have one, create a GCP billing account (requires the Billing Account Creator role).
You need the Project Creator and the Billing Account User role. Learn more about adding roles.

1. Provision a server

To create a new tagging server on an App Engine instance, you need to:

Create a new server container in Tag Manager
Create a new Google Cloud Project (GCP)
Provision a new App Engine tagging server
Add the new tagging server's URL to the Tag Manager server container

Create a Google Tag Manager server container

Open Google Tag Manager.
In the account row, click on the overflow menu > Create Container.
Create a new server container.
Click the "Manually provision tagging server" radio button. Note the container config. You'll need it to provision your server.

Create a new GCP project

To create a new GCP project for your tagging server:

Open Google Cloud Console.
Create a new GCP project.
Name your project. We recommend using your container ID for convenience. This name is used only within GCP.
Note the GCP project ID, because you will need it to create your tagging server.

Provision a new tagging server

To create your tagging server:

Open the Cloud Shell.
Set the GCP project in the Cloud Shell. Replace project ID with the GCP project ID that you noted earlier:
```
gcloud config set project project ID
```
Create your tagging server by following the shell script. Set the deployment type to testing.

Tip: If you are not sure what to enter at any of the prompts, enter ? to get help.
```
bash -c "$(curl -fsSL https://googletagmanager.com/static/serverjs/setup.sh)"
```

Add the tagging server URL to Tag Manager

Open Google Tag Manager.
In Admin > Container Settings, click Add URL. If you don't know your server's URL, run the following command in the Cloud Shell:
```
gcloud app browse
```
Result: You've set up a tagging server and provisioned it with a testing configuration. You can now test server-side tagging.

Initial server configuration (`testing`)

The testing configuration is appropriate for exploring the product by sending small amounts of test traffic and using the Preview feature in Tag Manager. This configuration is an App Engine F1 instance class in the Standard environment and in most cases, you will not incur any costs.

2. Using App Engine in production

In production configuration, each server costs approximately $40 / month (USD). Each server is an App Engine instance with 1 vCPU, 0.5 GB memory, 10 GB disk in the Flexible environment.

See Managing App Engine costs to understand App Engine billing and how to configure billing alerts. We strongly recommend setting up a billing alert.

Recommended production settings

We recommend running a minimum of 3 servers to reduce the risk of data loss in case of a server outage. However, you may choose to run fewer (or more) servers. We expect that autoscaling 3-6 servers (the default) will handle 50-200 requests per second. The performance depends on the number of tags, and what those tags do.

To configure your tagging server:

Open the Google Cloud Platform Cloud Shell.
Set the Cloud Platform project in the Cloud Shell. Replace project ID with the GCP project ID that you noted earlier:
```
gcloud config set project project ID
```
To reconfigure the tagging server for a production environment, run the setup script below. Perform the following tasks:
```
bash -c "$(curl -fsSL https://googletagmanager.com/static/serverjs/setup.sh)"
```
1. Change the deployment type to production.
2. Set up additional servers to serve production traffic. We recommend a minimum of three servers.

Optional: Disable logging

Request logging

By default, App Engine logs information about every single request (e.g. request path, query parameters, etc) that it receives. If your tagging server handles a lot of requests per month (e.g. greater than 1 million), those log messages may incur significant logging charges. To reduce or eliminate the logging charges, we recommend disabling the App Engine request logging.

To disable App Engine request logging:

In Google Cloud platform, open the Logs Router. Make sure you're in the project that matches your container ID:
For the Type: Cloud Logging bucket, Name: _Default line, select the overflow menu, then click Edit Sink.
Under Sink destination, select logs bucket _Default.
Under Choose logs to include in sink, add a new line. Enter the following rule to the existing inclusion filter:
```
NOT LOG_ID("appengine.googleapis.com/nginx.request") AND NOT
LOG_ID("appengine.googleapis.com/request_log")
```
To also disable logging from the load balancer, add a new line and enter the following rule to the existing inclusion filter:
```
NOT LOG_ID("requests")
```
Note: This will disable all logging from the load balancer, including requests that are not sent to the server container.
Update Sink to apply the changes. Now the App Engine requests will be excluded from logging.
Verify that no new requests are appearing in the Logs Explorer logs.

Console logging

The tagging server, clients, or tags in a container can log messages to console that may incur logging charges. To reduce or eliminate the logging charges, you can disable unwanted console log messages.

Identify unwanted console logs:

In GCP, open the Logs Explorer.
Look for any unwanted log messages that originate from your tags. For example:

A tag might send the following logs:
```
const logToConsole = require('logToConsole');

logToConsole('Custom message: ' + data.param1);
logToConsole('An important message to keep around!');
data.gtmOnSuccess()
```
Look for the corresponding log messages in the textPayload field:

To disable console log message:

In Google Cloud platform, open the Logs Router. Make sure you're in the project that matches your container ID:
For the Type: Cloud Logging bucket, Name: _Default line, select the overflow menu, then click Edit Sink.
Under Sink destination, select logs bucket _Default.
Under Choose logs to include in sink, add a new line. Enter the following rule to the existing inclusion filter:
```
NOT textPayload:"Custom message:"
```
For your console logs, replace the Custom message: text with a substring from console log you wish to disable. For more elaborate filters, utilize the logging query language.
Update Sink to apply the changes. The matching logToConsole message should be excluded from logging.
Verify that no new console log messages are appearing in the Logs Explorer.

3. Map the deployment to your custom domain

The default server-side tagging deployment is hosted on an App Engine domain. We recommend that you modify the deployment to use a subdomain of your website.

Map your website subdomain to your tagging server.

4. Add the server URL to Google Tag Manager

Now that you have a server, you need to make sure that Google Tag Manager knows it should use your server.

Open Google Tag Manager.
Click on the server container you want to point to your tagging server.
Open your server container settings in the Admin tab > Container Settings.
Click Add URL and paste your server URL.
Save and go back to your workspace.

5. Validation

Now that you've set up your tagging server, make sure that it works as intended. In your Tag Manager workspace, click the Preview button. If the preview page loads, then everything is set up correctly.

Previewing multiple URLs

If you have mapped multiple domains to a single tagging server, make sure each URL is added to the container settings.

If you provided multiple URLs, all paths (the string after the domain name) must match.

Works	Does not work
URL 1: `example.com/abc` URL 2: `example2.com/abc`	URL 1: `example.com/abc` URL 2: `example2.com/def`

If multiple URLs are added, you will see an icon next to the Preview button that allows you to select the URL to preview.

Update the tagging server version

New tagging server updates contain security vulnerability fixes and new features. We recommend at least updating your tagging server for each major version release (e.g. upgrading from version 1.x.x to 2.x.x) when Tag Manager notifies you to update.

To update your tagging server, re-run the setup script using the same settings you used previously. The existing settings are set by default.

To update your tagging server:

Open the Google Cloud Platform Cloud Shell.
Set the Cloud Platform project in the Cloud Shell. Replace project ID with the GCP project ID that you noted earlier:
```
gcloud config set project project ID
```
Run the setup script using the same settings you used previously. The existing settings are set by default.
```
bash -c "$(curl -fsSL https://googletagmanager.com/static/serverjs/setup.sh)"
```

To verify that the update was successful:

In your server container, click the Preview button to start a new debug session and send a request on a separate tab.
In the Summary, select the Console tab and make sure there are no messages asking you to update the tagging server.

Tag Manager may show messages asking you to update your tagging server for up to a day after the server has been updated successfully. However, the preview page will show an up to date message about the tagging server version.

Troubleshoot production deployment timeouts

When you run the setup script to create or reconfigure the tagging server, the script may time out. There are several reasons this could happen. The two most common are:

Service accounts have incorrect permissions - The Compute Engine and App Engine service accounts are responsible for deploying and maintaining the production deployment. By default, they are preconfigured with the appropriate permissions. However, in some cases, an organization's policy may cause them to be incorrect.
1. Navigate to the IAM & Admin page in the left-hand navigation bar in the Google Cloud console.
2. Find the Compute Engine service account <project_number>-compute@developer.gserviceaccount.com and the App Engine service account <project_name>@appspot.gserviceaccount.com.
3. Both service accounts must have the Editor role. If either account does not have the Editor role, update the role by clicking the pencil icon on the right of the account, clicking the dropdown of the existing role, scrolling up to the top and clicking Project, then Editor.
Insufficient quota - The production deployment consumes Compute Engine quota. If the project does not have enough quota, the deployment may time out while trying to provision resources.
1. Navigate to the IAM & Admin page in the left-hand navigation bar in the Google Cloud console, then click the Quotas tab in the left-hand navigation bar.
2. Near the top of the page, click the text box that says Filter table and type in Compute Engine API. Click the only result.
3. Verify that all the quota statuses are within limit or have a green checkmark.
4. Find and click into CPUs. Verify that the current usage plus the number of instances being deployed will still be below the limit for the deployment region.