Overview

Working with Mesh means dealing with 4 main concepts: Sources, Handlers, Transforms and Unified Schema:

1. In Mesh, a sub-service (GraphQL API, REST API) is called a Source.
2. Sources are translated to GraphQL Schemas with the appropriate Handler.
3. All Sources’ GraphQL Schema are merged into a final Unified Schema.
4. Finally, if applicable, configured transformations, called Transforms, are applied to the Unified Schema.

The above GraphQL Mesh Gateway has 3 configured Sources:

1. The “City” Source configured with the @graphql-mesh/openapi Handler.
2. The “Population” Source configured with the @graphql-mesh/graphql Handler.
3. The “Weather” Source configured with the @graphql-mesh/raml Handler.

Sources, Handlers, Transforms are configured in a .mesh.yaml (or .json, .js, .ts) configuration file that defines:

• How to fetch the definition of the sub-services (GraphQL API, REST API, and more)
• What transformations should be applied to the unified schema (optional)
• The path to the declaration of custom resolvers (optional)
• Which cache strategy should be used? (optional)
• Which envelop plugins should be loaded and configured at the server level? (optional)

Let’s have a closer look to a .mesh.yaml configuration file by installing Mesh and building our first Gateway!