Global Server Load Balancing (GSLB) — Advance

· What is GSLB, and how does it differ from a traditional load balancer?
∘ Key differences:
· How would GSLB be integrated with the Photogram codebase, and where would it fit in the overall architecture?
· How is GSLB integrated with DNS servers
· Ownership and responsibility for the authoritative nameservers and GSLB functionality
· How does GSLB handle IP addresses for servers, CDNs, etc.?
· To implement GSLB for Photogram, you’ll need to:
· Overview of Photogram and Key Requirements:
∘ Global Server Load Balancing (GSLB) Explanation:
· Key differences between GSLB and traditional load balancers:
∘ Global Server Load Balancing (GSLB) Explanation:
∘ Key differences between GSLB and traditional load balancers:
∘ Advantages of GSLB for Photogram:
· Image Upload and Rendering Flow for Photogram:
∘ Advantages of GSLB for Photogram:
· Step-by-step explanation of the image upload and rendering flow:
· Reference materials

*Photogram is an imaginary app like instagram

What is GSLB, and how does it differ from a traditional load balancer?

GSLB is an advanced load-balancing technique that distributes traffic across multiple data centers or server farms, which can be geographically dispersed. Unlike traditional load balancers that typically operate within a single data center, GSLB works globally.

Key differences:

• Scope: Traditional load balancers work within a single data center, while GSLB operates across multiple data centers worldwide.
• Decision factors: GSLB considers geographic location, network latency, and server health across different regions.
• Disaster recovery: GSLB can route traffic away from failed data centers, providing better disaster recovery capabilities.

How would GSLB be integrated with the Photogram codebase, and where would it fit in the overall architecture?

• GSLB would typically be implemented outside of your application code at the DNS level.
• It would sit at the entry point of your infrastructure, directing users to the most appropriate data center. Here’s a high-level overview of how it might fit into Photogram’s architecture:

1. User Layer: Mobile apps, web browsers
2. DNS Layer: GSLB implemented here
3. Global CDN Layer: For static content delivery
4. Regional Load Balancers: Within each data center
5. Application Servers: Your Photogram app instances
6. Database Layer: Distributed database system
7. Storage Layer: For user-uploaded photos and videos

Your application code wouldn’t directly interact with the GSLB. Instead, you’d need to ensure your app can run in multiple data centers and that your data is properly synchronized across regions.

How is GSLB integrated with DNS servers

let’s clarify the DNS resolution process:

1. When users type “photogram.com” into their browser, the request first goes to a recursive resolver.
2. The recursive resolver queries the root nameservers.
3. The root nameservers direct the resolver to the .com TLD nameservers.
4. The .com TLD nameservers provide the authoritative nameservers for photogram.com.
5. The recursive resolver then queries these authoritative nameservers.
6. The authoritative nameservers for photogram.com are where the GSLB functionality is typically implemented.

The .com TLD nameserver will resolve to the IP addresses of the authoritative nameservers for photogram.com. These authoritative nameservers are where the GSLB functionality is implemented.

Now, let’s break down the DNS resolution process for photogram.com in more detail:

1. User Query:

• The user enters “photogram.com” in their browser.
• The request is sent to the configured DNS recursive resolver (often provided by the ISP or a public DNS service like Google’s 8.8.8.8).

2. Recursive Resolver to Root Nameserver:

• The recursive resolver queries a root nameserver.
• The root nameserver responds with a referral to the .com TLD nameservers.

3. Recursive Resolver to TLD Nameserver:

• The recursive resolver queries a .com TLD nameserver.
• The .com TLD nameserver responds with the authoritative nameservers for photogram.com.

4. Recursive Resolver to Authoritative Nameserver:

• The recursive resolver queries the authoritative nameserver for photogram.com.
• This is where the GSLB functionality is implemented.

5. GSLB Decision:

• The authoritative nameserver, which has GSLB functionality, determines the best data center to route the user to based on factors like:
• User’s geographic location
• Current load on different data centers
• Health of data centers
• Network conditions

6. Response to User:

• The GSLB-enabled authoritative nameserver responds with the IP address of the chosen data center.
• This response goes back through the recursive resolver to the user.
• The user’s device then connects to this IP address to access Photogram.

Key Points:

• The .com TLD nameserver does not resolve directly to the GSLB. Instead, it provides the IP addresses of the authoritative nameservers for photogram.com.
• The authoritative nameservers for photogram.com are where the GSLB functionality is implemented.
• GSLB works by dynamically changing the IP address returned in the DNS response based on various factors to optimize routing.
• This process allows for global load balancing without changing the domain name that users interact with.

This setup allows Photogram to provide a globally distributed service while maintaining a single, easy-to-remember domain name. The GSLB functionality ensures that users are directed to the most appropriate data center, optimizing for factors like proximity and server load, which results in better application performance and reliability.

Ownership and responsibility for the authoritative nameservers and GSLB functionality

1. Ownership of Authoritative Nameservers: The authoritative nameservers for photogram.com are owned and controlled by Photogram (the company), not by the .com registry or any other entity. When a company registers a domain, they have the right to specify which nameservers are authoritative for that domain.
2. Control of DNS Records: Photogram is responsible for managing the DNS records for its domain, including setting up and maintaining the authoritative nameservers.
3. Implementation of GSLB: The GSLB functionality is typically implemented by Photogram or a third-party service provider that Photogram contracts with. It’s not a service provided by the .com registry.
4. Payment for GSLB: Photogram (the company) would be responsible for paying for the GSLB service. This could be done in a few ways:
   → a. Self-managed: Photogram could implement GSLB on their own authoritative nameservers, in which case they’d bear the cost of the infrastructure and management.
   → b. Third-party service: Photogram could use a GSLB service from providers like AWS Route 53, Google Cloud DNS, Cloudflare, or Akamai. In this case, Photogram would pay these providers for the GSLB service. → c. Managed DNS service: Some DNS providers offer GSLB as part of their managed DNS services. Photogram would pay this provider for the entire DNS management service, including GSLB.
5. Role of .com TLD: The .com TLD (operated by Verisign) is only responsible for maintaining the NS (nameserver) records that point to Photogram’s authoritative nameservers. They do not provide or manage the GSLB functionality.

To clarify the process:

1. Photogram registers the domain photogram.com with a domain registrar.
2. Photogram establishes its authoritative nameservers (self-managed or through a DNS provider).
3. Photogram (or their DNS provider) implements GSLB on these authoritative nameservers.
4. Photogram informs the domain registrar of their authoritative nameservers.
5. The domain registrar communicates this information to the .com registry.
6. The .com TLD nameservers then direct queries for photogram.com to Photogram’s authoritative nameservers.

So, to directly answer your questions:

• The authoritative nameservers are owned/controlled by Photogram, not by .com.
• Photogram (the company) will pay for the GSLB service, either directly through their own implementation or as part of a service they purchase from a DNS or GSLB provider.

This setup allows companies like Photogram to have full control over their domain’s DNS management and to implement advanced features like GSLB to improve their service’s global performance and reliability.

How does GSLB handle IP addresses for servers, CDNs, etc.?

GSLB typically works by manipulating DNS responses. Here’s how it handles IP addresses:

1. The GSLB system maintains a list of IP addresses for all your data centers and CDN endpoints.
2. When users try to access photogram.com, their DNS request reaches your GSLB-enabled DNS server.
3. The GSLB system evaluates factors like user location, server health, and current load.
4. It then responds with the IP address of the most appropriate data center or CDN edge node.
5. The user’s device connects to this IP address.

This process allows GSLB to dynamically direct users to the best available resource without changing your application’s domain name.

This diagram illustrates how GSLB works in the context of Photogram:

1. The user makes a DNS query for photogram.com. The DNS server with GSLB functionality receives the query.
2. Based on factors like user location and server health, the GSLB system decides where to direct the user:
   a. It might direct them to Data Center 1
   b. Or to Data Center 2
   c. Or to the Global CDN for static content
3. The user then connects to the chosen destination.

This setup allows Photogram to efficiently serve users from multiple locations, improving performance and reliability.

To implement GSLB for Photogram, you’ll need to:

1. Set up multiple data centers in different geographic regions.
2. Implement a consistent data replication strategy across these data centers.
3. Choose a GSLB solution (many cloud providers offer this as a service).
4. Configure your DNS settings to work with the GSLB system.
5. Set up health checks and monitoring for all your data centers.
6. Test thoroughly to ensure traffic is being routed correctly.

Remember, while GSLB can significantly improve your app’s performance and reliability, it also adds complexity to your infrastructure. Start with a simpler setup and gradually implement GSLB as your user base grows and spreads geographically.

Overview of Photogram and Key Requirements:

Photogram is a photo-sharing application similar to Instagram, designed for global use. The key requirements for this application include:

1. Global scalability to serve users worldwide
2. High availability to ensure continuous service
3. Low latency for fast image uploads and rendering
4. Efficient content delivery across different geographic regions
5. Ability to handle sudden traffic spikes and viral content
6. Consistent user experience regardless of location

These requirements necessitate a globally distributed and highly scalable architecture.

Global Server Load Balancing (GSLB) Explanation:

GSLB is an advanced load-balancing technique that distributes traffic across multiple data centers or server farms located in different geographic regions. Unlike traditional load balancers that operate within a single data center, GSLB works on a global scale.

Key differences between GSLB and traditional load balancers:

1. Overview of Photogram and Key Requirements:
2. Photogram is a photo-sharing application similar to Instagram, designed for global use. The key requirements for this application include:
3. Global scalability to serve users worldwide
4. High availability to ensure continuous service
5. Low latency for fast image uploads and rendering
6. Efficient content delivery across different geographic regions
7. Ability to handle sudden traffic spikes and viral content
8. Consistent user experience regardless of location

These requirements necessitate a globally distributed and highly scalable architecture.

Global Server Load Balancing (GSLB) Explanation:

GSLB is an advanced load-balancing technique that distributes traffic across multiple data centers or server farms located in different geographic regions. Unlike traditional load balancers that operate within a single data center, GSLB works on a global scale.

Key differences between GSLB and traditional load balancers:

1. Scope: GSLB operates across multiple global data centers, while traditional load balancers work within a single data center.
2. Decision factors: GSLB considers factors like user geographic location, network latency, and server health across different regions.
3. DNS-level operation: GSLB often works at the DNS level, directing users to the most appropriate data center before they even connect to your application.
4. Disaster recovery: GSLB can route traffic away from failed data centers, providing better disaster recovery capabilities.

Advantages of GSLB for Photogram:

1. Improved user experience: Users are directed to the nearest or best-performing data center.
2. Reduced latency: By serving content from geographically closer locations, GSLB minimizes network travel time.
3. Higher availability: If one data center fails, traffic can be automatically rerouted to other operational centers.
4. Better load distribution: Traffic is spread across multiple data centers, preventing any single point of overload.
5. Geo-targeting: Content can be served based on user location, which is useful for region-specific features or compliance.

Image Upload and Rendering Flow for Photogram:

Now, let’s walk through the step-by-step process of how an image upload and rendering would work in Photogram using GSLB and other relevant technologies.GSLB operates across multiple global data centers, while traditional load balancers work within a single data center.

1. Decision factors: GSLB considers factors like user geographic location, network latency, and server health across different regions.
2. DNS-level operation: GSLB often works at the DNS level, directing users to the most appropriate data center before they even connect to your application.
3. Disaster recovery: GSLB can route traffic away from failed data centers, providing better disaster recovery capabilities.

Advantages of GSLB for Photogram:

1. Improved user experience: Users are directed to the nearest or best-performing data center.
2. Reduced latency: By serving content from geographically closer locations, GSLB minimizes network travel time.
3. Higher availability: If one data center fails, traffic can be automatically rerouted to other operational centers.
4. Better load distribution: Traffic is spread across multiple data centers, preventing any single point of overload.
5. Geo-targeting: Content can be served based on user location, useful for region-specific features or compliance.

Image Upload and Rendering Flow for Photogram:

Now, let’s walk through the step-by-step process of how an image upload and rendering would work in Photogram using GSLB and other relevant technologies.

Step-by-step explanation of the image upload and rendering flow:

1. DNS Query:

• The user initiates a request to upload an image to Photogram.
• A DNS query is sent to resolve photogram.com.

2. GSLB Routing:

• The DNS server with GSLB functionality receives the query.
• Based on factors like user location and data center health, GSLB decides which data center to route the user to.
• It returns the IP address of the chosen data center (either 2a or 2b in the diagram).

3. Image Upload:

• The user’s request is routed to the chosen data center.
• The application server in that data center receives the image upload request.
• The server processes the image (e.g., resizing, format conversion) and generates any necessary metadata.

4. Storage:

• The processed image is stored in a distributed object storage system (e.g., Amazon S3, Google Cloud Storage).
• This system ensures the image is replicated across multiple geographic regions for redundancy and faster access.

5. CDN Push:

• Once the image is stored, it’s pushed to a Content Delivery Network (CDN).
• The CDN distributes the image to edge locations around the world, closer to end-users.

6. Database Update:

• The application server updates the database with metadata about the new image (e.g., user ID, timestamp, CDN URL).
• This update is propagated to database replicas in other data centers to maintain consistency.

7. Rendering (Image View):

• When another user wants to view the image, they also go through the GSLB process (steps 1–2).
• The application server in the chosen data center receives the request to view the image.
• It retrieves the image metadata from the database.
• The server constructs a response with the CDN URL for the image.

8. Content Delivery:

• The user’s device requests the image from the CDN URL.
• The CDN serves the image from the nearest edge location, ensuring fast delivery.

9. Final Rendering:

• The user’s device receives the image data and renders it in the Photogram app or web interface.

This architecture leverages GSLB, globally distributed data centers, object storage, and CDN to achieve the key objectives:

• Global Scalability: Multiple data centers and CDN allow serving users worldwide.
• High Availability: Redundancy at every level (GSLB, multiple data centers, distributed storage) ensures the service remains available even if some components fail.
• Low Latency: GSLB routes users to nearby data centers, and CDN serves images from edge locations, minimizing latency.

By implementing this architecture, Photogram can provide a fast, reliable, and consistent experience to users around the globe, handling high traffic and large volumes of image uploads and views efficiently.

Reference materials

• “Global Server Load Balancing Fundamentals” by Citrix
• “What is Global Server Load Balancing (GSLB)?” by A10 Networks
• “Understanding Global Server Load Balancing” by F5
• “Implement Global Server Load Balancing” by Amazon Web Services
• “Global Server Load Balancing (GSLB) Overview” by Cloudflare