Upstream

An Upstream in Sushi Gateway represents a backend service or server to which API requests are forwarded. Upstreams are part of a service configuration and help distribute traffic across multiple instances.

Fields in an Upstream

An Upstream configuration consists of the following fields:

Field	Type	Description
id	String	A unique identifier for the upstream.
host	String	The hostname or IP address of the backend server.
port	Number	The port number on which the backend server is listening.

TIP

Each upstream must have a unique id to avoid conflicts during configuration.

Example Configuration

Here’s an example of an upstream definition in config.json:

{
  "id": "upstream_1",
  "host": "example-upstream",
  "port": 3000
}

Key Fields Explained

1. id:

   • A unique identifier for the upstream.
   • Example: "upstream_1".

2. host:

   • Specifies the hostname or IP address of the backend service.
   • Example: "example-upstream".

3. port:

   • Defines the port number where the backend service is running.
   • Example: 3000.

Relationships with Other Entities

Upstreams are closely associated with the following entities:

• Service: Services define the upstreams used for routing traffic.
• Route: Routes determine how requests are directed to upstreams within a service.

Load Balancing

Upstreams are a critical component in load balancing strategies, such as:

• Round Robin: Distributes traffic equally across all upstreams.
• Weighted (in progress): Routes traffic based on predefined weights for each upstream.
• IP Hash (in progress): Routes traffic based on the client IP address, ensuring consistent upstream selection.

TIP

Learn more about load balancing strategies in the Load Balancing Concepts page.

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The Upstream entity is essential for connecting Sushi Gateway to backend services. To understand other entities, see:

• Service
• Route
• Plugin