How to use Introspection

In this example we take you through how to use introspection using the Seller API

3 minute read

What you’ll learn

In this article we look at the concept of GraphQL introspection, specifically:

What is introspection & why you’d use it
How to run an introspection query
How to use the query results to render documentation

What is Introspection?

In the context of GraphQL, introspection is simply the ability ask for (query) the current capabilities of the GraphQL API endpoint. In other words, the result of an introspection query is a view of all fields, objects, queries and mutations that you can perform with the API.

3rd party tools, (like Insomnia and GraphQL Voyager), can then ingest the schema and use it for some practical purpose, e.g.:

Render in-line documentation
Provide query tool tips and suggestions

A Personalized View

It’s worth noting the results of an introspection query (on the same API endpoint) may differ depending on who is running that query, and more importantly, what level of authorization they have. For example it’s possible, (and indeed likely), that running an introspection query without an API Key will render a different result when compared with the result of a query run when an API key was provided.

Further Reading: For a more in depth discussion on introspection you can refer to the official docs here, or do some Googling.

Running an introspection query

Running an introspection query is no different from executing any other type of GraphQL query, you will need:

The endpoint url of the GraphQL API
A tool to query the endpoint (e.g. Insomnia or Postman)
An example GraphQL query
[Optional] an API Key / Credentials

The API Key / Credentials has been tagged as optional as many GraphQL endpoints (including the Marketplacer GraphQL API) provide some degree of anonymous functionality, (e.g. the ability to query Products / Adverts). Therefore running an introspection query anonymously may still render a result set, (albeit a subset of the complete range of functionality).

Example

Follow the steps below to execute an introspection query with Postman.

Example Query

You can find a copy of the introspection query in both our Postman and Insomnia collections which can be found here.

Download the Marketplacer GraphQL Postman Collection
Import into Postman

Import Postman Collection

Expand the Introspection folder and select the query

Select Query

Click Send to execute the query

Execute Query

Configuring Variables

The Postman collection works with variables, that allow you to set values for things like the base_url, api_key etc., you’ll need to configure these as required by editing the Postman collection variable set.

Assuming everything works as expected you should get a HTTP 200 OK status, and JSON result set. This result set is a JSON representation of the entire GraphQL API schema that you have access to.

Query result

In the final section of this article, we’re going to take that result set and copy it into GraphQL Voyager.

Using our schema

We can now use the result of our introspection query and plug it into GraphQL Voyager. GraphQL Voyager takes a GraphQL schema and renders it as a “graph”, detailing fields, objects and their relationships.

Browse to: https://graphql-kit.com/graphql-voyager/
Click Change Schema

Change Schema

Select “Introspection” from the list of options

Select Introspection

Copy the introspection result from Postman and paste into GraphQL Voyager

Paste Schema

Finally click “Display” and GraphQL Voyager will render the schema

GraphQL Voyager