Backend services and backend buckets in GCP - Step-by-Step Execution

Process Flow - Backend services and backend buckets

Client Request

↓

Load Balancer

↓

Backend Service

↓

Backend Bucket

↓

Backend VM Instances

↓

Serve Content or App Response

Client sends a request to the load balancer, which forwards it to a backend service. The backend service routes the request to either backend buckets (for static content) or backend VM instances (for dynamic content).

Execution Sample

GCP

gcloud compute backend-services create my-backend-service --global --protocol=HTTP

gcloud compute backend-buckets create my-backend-bucket --gcs-bucket-name=my-static-content

gcloud compute backend-services add-backend my-backend-service --backend-bucket=my-backend-bucket

This code creates a backend service, a backend bucket linked to a GCS bucket, and attaches the backend bucket to the backend service.

Process Table

Step	Action	Resource Created/Modified	Result
1	Create backend service with HTTP protocol	Backend Service: my-backend-service	Backend service ready to route HTTP requests
2	Create backend bucket linked to GCS bucket	Backend Bucket: my-backend-bucket	Backend bucket serves static content from GCS
3	Attach backend bucket to backend service	Backend Service: my-backend-service	Backend service now routes requests to backend bucket
4	Client sends HTTP request	Load Balancer forwards request	Request routed to backend service
5	Backend service routes request	To backend bucket	Static content served from GCS bucket
6	Request completed	Response sent to client	Client receives static content
7	End	No further action	Execution stops

💡 Request served and response sent; no more routing needed

Status Tracker

Resource	Initial State	After Step 1	After Step 2	After Step 3	Final State
Backend Service	None	Created with HTTP protocol	No change	Attached backend bucket	Routes requests to backend bucket
Backend Bucket	None	None	Created linked to GCS bucket	Attached to backend service	Serves static content from GCS
Client Request	None	Sent	Forwarded by load balancer	Routed by backend service	Response received

Key Moments - 3 Insights

Why do we need to create a backend bucket separately before attaching it to a backend service?

Because the backend bucket represents the static content source (GCS bucket) and must exist before the backend service can route requests to it, as shown in steps 2 and 3 of the execution_table.

What happens if the backend service has no backends attached?

The backend service cannot route requests anywhere, so client requests will fail or time out. This is why attaching a backend bucket or instance group is essential (step 3).

Can a backend service route requests to both backend buckets and VM instances?

Yes, a backend service can have multiple backends, including backend buckets for static content and VM instances for dynamic content, allowing flexible routing.

Visual Quiz - 3 Questions

Look at the execution_table, at which step is the backend bucket created?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Check the 'Resource Created/Modified' column for backend bucket creation.

According to variable_tracker, what is the state of the backend service after step 3?

A Attached backend bucket and routes requests

B Created with HTTP protocol only

C No backends attached

D Deleted

💡 Hint

Look at the 'Backend Service' row under 'After Step 3' and 'Final State'.

If the backend bucket was not attached to the backend service, what would happen to client requests?

A Requests would be routed to the backend bucket anyway

B Requests would be served from the load balancer directly

C Requests would fail or time out

D Requests would be redirected to another backend bucket automatically

💡 Hint

Refer to key_moments explanation about backend service without backends.

Concept Snapshot

Backend services route client requests to backends.
Backends can be backend buckets (static content) or VM instances (dynamic).
Create backend buckets linked to GCS buckets.
Attach backend buckets to backend services to serve static content.
Load balancer sends requests to backend services.
Backend services forward requests to attached backends.

Full Transcript

In Google Cloud Platform, backend services act like traffic managers that receive client requests from a load balancer and send them to backends. Backends can be backend buckets, which serve static content stored in Google Cloud Storage, or VM instances that run applications. First, you create a backend service specifying the protocol, such as HTTP. Then, you create a backend bucket linked to a GCS bucket containing your static files. After that, you attach the backend bucket to the backend service. When a client sends a request, the load balancer forwards it to the backend service, which routes it to the backend bucket. The backend bucket serves the static content back to the client. This setup allows efficient delivery of static content through the load balancer and backend service configuration.

Practice

1. What is the main purpose of a backend service in Google Cloud Load Balancing?

easy

A. To manage user authentication and authorization

B. To connect the load balancer to server groups for dynamic content

C. To monitor network traffic between regions

D. To store static files like images and videos

Solution

1. Step 1: Understand backend service role

   A backend service connects the load balancer to server groups that handle dynamic content like web apps.

2. Step 2: Differentiate from backend bucket

   Backend buckets connect to Cloud Storage for static content, not dynamic server groups.

3. Final Answer:

   To connect the load balancer to server groups for dynamic content -> Option B

4. Quick Check:

   Backend service = dynamic content connection [OK]

Hint: Backend service = dynamic servers, backend bucket = static storage [OK]

Common Mistakes:

• Confusing backend service with backend bucket
• Thinking backend service stores static files
• Assuming backend service manages authentication

2. Which of the following is the correct way to specify a backend bucket in a Google Cloud Load Balancer configuration?

easy

A. "backendService": "projects/my-project/global/backendBuckets/my-bucket"

B. "backendService": "projects/my-project/global/backendServices/my-service"

C. "backendBucket": "projects/my-project/global/backendServices/my-service"

D. "backendBucket": "projects/my-project/global/backendBuckets/my-bucket"

Solution

1. Step 1: Identify correct field for backend bucket

   The field to specify a backend bucket is "backendBucket" with the bucket's full path.

2. Step 2: Verify resource path matches backend bucket

   The resource path must include "backendBuckets" for a bucket, not "backendServices".

3. Final Answer:

   "backendBucket": "projects/my-project/global/backendBuckets/my-bucket" -> Option D

4. Quick Check:

   backendBucket field + backendBuckets path = correct [OK]

Hint: backendBucket key + backendBuckets path = backend bucket config [OK]

Common Mistakes:

• Using backendService key for backend bucket
• Mixing backendServices and backendBuckets in path
• Incorrect resource path format

3. Given this backend service configuration snippet, what will happen if the health check fails for all instances in the backend?

{
  "name": "my-backend-service",
  "healthChecks": ["projects/my-project/global/healthChecks/my-check"],
  "backends": [{"group": "projects/my-project/zones/us-central1-a/instanceGroups/my-group"}]
}

medium

A. The load balancer will stop sending traffic to this backend service

B. The load balancer will continue sending traffic to the backend service regardless

C. The load balancer will delete the backend service automatically

D. The load balancer will redirect traffic to the backend bucket

Solution

1. Step 1: Understand health check role

   Health checks monitor backend instances. If all fail, the backend is unhealthy.

2. Step 2: Effect on load balancer traffic

   Load balancer stops sending traffic to unhealthy backends to avoid errors.

3. Final Answer:

   The load balancer will stop sending traffic to this backend service -> Option A

4. Quick Check:

   Health check fail = no traffic sent [OK]

Hint: Failed health checks stop traffic to backend service [OK]

Common Mistakes:

• Assuming traffic continues despite health check failure
• Thinking backend service is deleted automatically
• Confusing backend service with backend bucket behavior

4. You configured a backend bucket for your load balancer but users report 403 errors when accessing static content. What is the most likely cause?

medium

A. The load balancer is not attached to any instance group

B. The backend service health check is failing

C. The backend bucket is missing the correct Cloud Storage permissions

D. The backend bucket name is misspelled in the load balancer config

Solution

1. Step 1: Check backend bucket access

   Backend buckets serve static content from Cloud Storage, which requires proper permissions.

2. Step 2: Identify cause of 403 errors

   Missing or incorrect permissions cause 403 errors because content cannot be accessed.

3. Final Answer:

   The backend bucket is missing the correct Cloud Storage permissions -> Option C

4. Quick Check:

   Missing permissions cause 403 on static content [OK]

Hint: 403 on static content usually means permission issues [OK]

Common Mistakes:

• Confusing backend bucket with backend service health checks
• Assuming instance groups affect backend buckets
• Overlooking spelling errors as cause

5. You want to serve a website with both dynamic content from Compute Engine instances and static content from Cloud Storage using a single HTTP(S) load balancer. How should you configure the backend services and backend buckets?

hard

A. Create a backend service for the instance group and a backend bucket for the Cloud Storage bucket, then configure URL map to route requests accordingly

B. Create only a backend bucket and upload dynamic content to Cloud Storage

C. Create multiple backend services for both static and dynamic content and ignore backend buckets

D. Use a backend service for static content and a backend bucket for dynamic content

Solution

1. Step 1: Understand content types and backends

   Dynamic content requires backend services connected to instance groups; static content uses backend buckets linked to Cloud Storage.

2. Step 2: Configure URL map routing

   Use URL map rules to route requests to backend service or backend bucket based on URL paths.

3. Final Answer:

   Create a backend service for the instance group and a backend bucket for the Cloud Storage bucket, then configure URL map to route requests accordingly -> Option A

4. Quick Check:

   Dynamic = backend service, static = backend bucket, route with URL map [OK]

Hint: Use URL map to route dynamic to backend service, static to backend bucket [OK]

Common Mistakes:

• Trying to serve dynamic content from backend bucket
• Ignoring URL map routing configuration
• Using backend service for static content