- Hasura GraphQL engine
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Action handlers¶
Table of contents
Introduction¶
Actions need to be backed by custom business logic. This business logic can be defined in a handler which is an HTTP webhook.
HTTP handler¶
When the action is executed i.e. when the query or the mutation is called, Hasura makes a POST request to the
handler with the action arguments and the session variables.
The request payload is of the format:
{
"action": {
"name": "<action-name>"
},
"input": {
"arg1": "<value>",
"arg2": "<value>"
},
"session_variables": {
"x-hasura-user-id": "<session user id>",
"x-hasura-role": "<session user role>"
}
}
Returning a success response¶
To return a success response, you must send back a response payload of action’s
response type. The HTTP status code must be 2xx for a successful response.
Returning an error response¶
To return an error response, you must send back an error object. An error object looks like:
{
"message": "<mandatory error message>",
"code": "<optional error code>"
}
The HTTP status code must be 4xx for an error response.
Example¶
For example, consider the following mutation.
extend type Mutation {
UserLogin (username: String!, email: String!): UserInfo
}
type UserInfo {
accessToken: String!
userId: Int!
}
Let’s say, the following mutation is executed:
mutation {
UserLogin (username: "jake", password: "secretpassword") {
accessToken
userId
}
}
Hasura will call the handler with the following payload:
{
"action": "UserLogin",
"input": {
"username": "jake",
"password": "secretpassword"
},
"session_variables": {
"x-hasura-user-id": "423",
"x-hasura-role": "user"
}
}
To return a success response, you must send the response of the action’s output
type (in this case, UserInfo) with a status code 2xx. So a sample
response would be:
{
"accessToken": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVC",
"userId": 4829
}
To throw an error, you must a response payload of the following type while
setting the status code as 4xx.
{
"message": "invalid credentials"
}
