400 Bad Request while sending data to Google Tag Manager

Question

I have setup GTM server side following this guide: https://aws-solutions-library-samples.github.io/advertising-marketing/using-google-tag-manager-for-server-side-website-analytics-on-aws.html

Now I have two links to access my GTM server:

Primary Server-Side Container (analytics.example.com)

Preview Server Container (preview-analytics.example.com)

I am using these parameters in the aws_ecs_task_definition setup:

PreviewContainer:

  container_definitions    = <<TASK_DEFINITION
  [
  {
    "name": "preview",
    "image": "gcr.io/cloud-tagging-10302018/gtm-cloud-image",
    "environment": [
      {
        "name": "PORT",
        "value": "80"
      },
      {
        "name": "RUN_AS_PREVIEW_SERVER",
        "value": "true"
      },
      {
        "name": "CONTAINER_CONFIG",
        "value": "${var.CONTAINER_CONFIG}"
      }
    ],

PrimaryContainer:

{
    "name": "primary",
    "image": "gcr.io/cloud-tagging-10302018/gtm-cloud-image",
    "environment": [
      {
        "name": "PORT",
        "value": "80"
      },
      {
        "name": "PREVIEW_SERVER_URL",
        "value": "${var.PREVIEW_SERVER_URL}"
      },
      {
        "name": "CONTAINER_CONFIG",
        "value": "${var.CONTAINER_CONFIG}"
      }
    ]

Now I am trying to send data to GTM using Snowbridge, which runs using a docker container on an Ec2 instance. Snowbridge reads data from a Kinesis data stream and forwards it to GTM.

https://docs.snowplow.io/docs/destinations/forwarding-events/snowbridge/configuration/targets/http/google-tag-manager/

config.hcl.tmpl

source {
  use "kinesis" {
    stream_name = "${stream_name}"
    region      = "${region}"
    app_name    = "${app_name}"

    role_arn = "${role_arn}"
    read_throttle_delay_ms = 500

    # Maximum concurrent goroutines (lightweight threads) for message processing (default: 50)
    concurrent_writes = 50
  }
}

target {
  use "http" {
    url                        = "https://analytics.xx/com.snowplowanalytics.snowplow/enriched"
    request_timeout_in_seconds = 60
    content_type               = "application/json"

    # this line is optional, in case you want to send events to GTM Preview Mode
    headers                    = "{\"x-gtm-server-preview\": \"AAAAAAAXXXX==\"}"
  }
}

transform {
  use "spEnrichedToJson" {}
}

This works as expected and I am able to see incoming data in the preview mode. From my understanding, data is still being sent to the original mode but it is just being forwarded to the preview mode when this option is enabled.

As soon as I remove the optional header (i.e., the x-gtm-server-preview parameter), I get errors on Cloudwatch while sending data:

level=warning msg="Retrying func (attempts: 2): target.Write: Error sending http requests: 1 error occurred:\n\t* Got response status: 400 Bad Request\n\n"

I also changed the environment variable for the PreviewContainer here to false:

 {
        "name": "RUN_AS_PREVIEW_SERVER",
        "value": "true"
 },

It appears that I am able to send data to the Preview Mode but not otherwise. What could be possible reasons for this?

Does the error comes from the source (snowbridge) or target (gtm)?

Answer 1

400 Bad Request is an error response generated by the Google Tag Manager server application when an incoming HTTP request has no "Client" to claim it.

Each HTTP request to the Server container needs a Client to claim the request, or the Server container will respond with the 400 error.

To avoid the error, make sure your Server container has a Client in place that claims the incoming requests you are sending to it.

More information about Clients: https://developers.google.com/tag-platform/tag-manager/server-side/intro#how_clients_work