REST API troubleshooting

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When working with the REST API, you might encounter an issue.

To troubleshoot, refer to the REST API status codes. It might also help to include the HTTP response headers and exit code.

Status codes

The GitLab REST API returns a status code with every response, according to context and action. The status code returned by a request can be useful when troubleshooting.

The following table gives an overview of how the API functions generally behave.

Request type	Description
`GET`	Access one or more resources and return the result as JSON.
`POST`	Returns `201 Created` if the resource is successfully created and return the newly created resource as JSON.
`GET` / `PUT` / `PATCH`	Returns `200 OK` if the resource is accessed or modified successfully. The (modified) result is returned as JSON.
`DELETE`	Returns `204 No Content` if the resource was deleted successfully or `202 Accepted` if the resource is scheduled to be deleted.

The following table shows the possible return codes for API requests.

Return values	Description
`200 OK`	The `GET`, `PUT`, `PATCH` or `DELETE` request was successful, and the resource itself is returned as JSON.
`201 Created`	The `POST` request was successful, and the resource is returned as JSON.
`202 Accepted`	The `GET`, `PUT` or `DELETE` request was successful, and the resource is scheduled for processing.
`204 No Content`	The server has successfully fulfilled the request, and there is no additional content to send in the response payload body.
`301 Moved Permanently`	The resource has been definitively moved to the URL given by the `Location` headers.
`304 Not Modified`	The resource hasn't been modified since the last request.
`400 Bad Request`	A required attribute of the API request is missing. For example, the title of an issue is not given.
`401 Unauthorized`	The user isn't authenticated. A valid user token is necessary.
`403 Forbidden`	The request isn't allowed. For example, the user isn't allowed to delete a project.
`404 Not Found`	A resource couldn't be accessed. For example, an ID for a resource couldn't be found, or the user isn't authorized to access the resource.
`405 Method Not Allowed`	The request isn't supported.
`409 Conflict`	A conflicting resource already exists. For example, creating a project with a name that already exists.
`412 Precondition Failed`	The request was denied. This can happen if the `If-Unmodified-Since` header is provided when trying to delete a resource, which was modified in between.
`422 Unprocessable`	The entity couldn't be processed.
`429 Too Many Requests`	The user exceeded the application rate limits.
`500 Server Error`	While handling the request, something went wrong on the server.
`503 Service Unavailable`	The server cannot handle the request because the server is temporarily overloaded.

Status code 400

When working with the API you may encounter validation errors, in which case the API returns an HTTP 400 error.

Such errors appear in the following cases:

A required attribute of the API request is missing (for example, the title of an issue isn't given).
An attribute did not pass the validation (for example, the user bio is too long).

When an attribute is missing, you receive something like:

HTTP/1.1 400 Bad Request
Content-Type: application/json
{
    "message":"400 (Bad request) \"title\" not given"
}

When a validation error occurs, error messages are different. They hold all details of validation errors:

HTTP/1.1 400 Bad Request
Content-Type: application/json
{
    "message": {
        "bio": [
            "is too long (maximum is 255 characters)"
        ]
    }
}

This makes error messages more machine-readable. The format can be described as follows:

{
    "message": {
        "<property-name>": [
            "<error-message>",
            "<error-message>",
            ...
        ],
        "<embed-entity>": {
            "<property-name>": [
                "<error-message>",
                "<error-message>",
                ...
            ],
        }
    }
}

Include HTTP response headers

The HTTP response headers can provide extra information when troubleshooting.

To include HTTP response headers in the response, use the --include option:

curl --include "https://gitlab.example.com/api/v4/projects"
HTTP/2 200
...

Include HTTP exit code

The HTTP exit code in the API response can provide extra information when troubleshooting.

To include the HTTP exit code, include the --fail option:

curl --fail "https://gitlab.example.com/api/v4/does-not-exist"
curl: (22) The requested URL returned error: 404

Requests detected as spam

REST API requests can be detected as spam. If a request is detected as spam and:

A CAPTCHA service is not configured, an error response is returned. For example:

{"message":{"error":"Your snippet has been recognized as spam and has been discarded."}}

A CAPTCHA service is configured, you receive a response with:

needs_captcha_response set to true.
The spam_log_id and captcha_site_key fields set.

For example:

{"needs_captcha_response":true,"spam_log_id":42,"captcha_site_key":"REDACTED","message":{"error":"Your snippet has been recognized as spam. Please, change the content or solve the reCAPTCHA to proceed."}}

Use the captcha_site_key to obtain a CAPTCHA response value using the appropriate CAPTCHA API. Only Google reCAPTCHA v2 is supported.

Resubmit the request with the X-GitLab-Captcha-Response and X-GitLab-Spam-Log-Id headers set.

export CAPTCHA_RESPONSE="<CAPTCHA response obtained from CAPTCHA service>"
export SPAM_LOG_ID="<spam_log_id obtained from initial REST response>"
curl --request POST --header "PRIVATE-TOKEN: $PRIVATE_TOKEN" --header "X-GitLab-Captcha-
Response: $CAPTCHA_RESPONSE" --header "X-GitLab-Spam-Log-Id: $SPAM_LOG_ID"
"https://gitlab.example.com/api/v4/snippets?
title=Title&file_name=FileName&content=Content&visibility=public"