High-Performance HTTP Traffic Management for LLMs

Question

Pulumi · Accepted Answer

To achieve high-performance HTTP traffic management for Large Language Models (LLMs), it's crucial to utilize cloud resources that can handle the significant load and optimize the routing of traffic. This ensures lower latency, improved reliability, and a better user experience. In this context, we will discuss the use of a Global HTTP(S) Load Balancer on Google Cloud Platform (GCP), as it's designed to provide these benefits at a global scale.

In Google Cloud, a Global HTTP(S) Load Balancer uses a global external IP address to route user requests to the nearest backend service based on the user's geographical location, the load on backend services, and other factors. Backend services are typically auto-scaled groups of virtual machines or containers that run your application.

Here's a rundown of what you'd typically implement:

1. **Global HTTP(S) Load Balancer**: This forwards traffic to the backend service that's best suited to serve the request, again, based on conditions like proximity and load.
2. **Backend Services**: These are the actual resources handling the requests. In most advanced use cases like LLMs, these would ideally be autoscaling, ensuring they can handle the load.
3. **Autoscaler**: This automatically adjusts the number of instances in a managed instance group based on the load.
4. **Instance Group**: A group of virtual machine instances that you manage as a single entity.
5. **URL Map**: This defines rules for routing HTTP(S) requests to backend services based on paths and hostnames in the request URLs.

Let's look at a simple Pulumi program that provision a hypothetical LLM service's infrastructure, focusing on the traffic management aspect using GCP.

```python
import pulumi
from pulumi_gcp import compute

# Define the instance template, which determines what each VM will be like
instance_template = compute.InstanceTemplate("llm-instance-template",
    machine_type="n1-standard-4",  # Choose an appropriate machine type for your LLM
    disk=[{
        "boot": True,
        "autoDelete": True,
        "type": "PERSISTENT",
        "device_name": "local-disk",
        "initialize_params": [{
            "image": compute.get_image_latest_from_family("debian-9", project="debian-cloud").then(lambda family: family.self_link)
        }]
    }],
    network_interfaces=[{
        "network": "default",
        "access_configs": [{}]
    }]
)

# Create a managed instance group using the instance template
managed_instance_group = compute.InstanceGroupManager("llm-instance-group",
    base_instance_name="llm",
    instance_template=instance_template.id,
    target_size=2,  # Start with 2 instances and let the Autoscaler scale as needed
    zone="us-central1-a",  # Choose an appropriate zone for your LLM
)

# Create a Backend Service to associate with the Instance Group
backend = compute.BackendService("llm-backend",
    backends=[{
        "group": managed_instance_group.instance_group,
    }],
    port_name="http",
    protocol="HTTP",
    health_checks=[compute.HealthCheck("health-check",
        http_health_check={
            "port": 80
        }
    ).id]
)

# Set up an Autoscaler to scale the Instance Group based on load
autoscaler = compute.Autoscaler("llm-autoscaler",
    target=managed_instance_group.id,
    autoscaling_policy={
        "max_replicas": 10,
        "min_replicas": 2,
        "cpu_utilization": {
            "target": 0.6  # Target utilisation at which to scale (60% CPU usage in this case)
        },
        "cooldown_period": 45
    },
    zone=managed_instance_group.zone,
)

# Define the URL map to route the incoming requests
url_map = compute.URLMap("llm-url-map",
    default_service=backend.id
)

# Create a Target HTTP Proxy to use with the URL Map
target_proxy = compute.TargetHttpProxy("llm-target-proxy",
    url_map=url_map.id
)

# Allocate a Global IP for the Load Balancer
ip_address = compute.GlobalAddress("llm-ip")

# Define the forwarding rule that connects the IP to the Target Proxy
forwarding_rule = compute.GlobalForwardingRule("llm-forwarding-rule",
    ip_address=ip_address.id,
    port_range="80",
    target=target_proxy.id
)

# Export the IP address so that we can easily access it to connect to our LLM
pulumi.export("llm_ip_address", ip_address.address)
```

In this program, we've set up the following:
- An **Instance Template** to define the VMs in our managed instance group.
- A **Managed Instance Group**, which uses the template, and specifies the number of instances.
- A **Backend Service** to manage these groups and define health checks.
- An **Autoscaler** to automatically scale the instances in our Instance Group.
- A **URL Map** to define how HTTP requests should be routed to the Backend Services.
- A **Target HTTP Proxy** to pair the URL Map with a global external IP address.
- A **Forwarding Rule** to forward traffic from the IP address to the Target Proxy using HTTP protocol.
- And finally, exporting the Global IP address to know where to point our DNS or know where our service is exposed.

These resources together provide high-performance HTTP traffic management suited for an LLM running in the cloud, ensuring that incoming traffic is efficiently distributed across available resources to maintain performance and reliability at scale.

Remember to replace placeholders like the project ID, region, and machine types with suitable values that match your requirements and also check other properties you might set for increased security or performance like HTTPS, SSL certificates, etc.