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.

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

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"

Error: 404 Not Found when using a reverse proxy

If your GitLab instance uses a reverse proxy, you might see 404 Not Found errors when using a GitLab editor extension, the GitLab CLI, or API calls with URL-encoded parameters.

This problem occurs when your reverse proxy decodes characters like /, ?, and @ before passing the parameters on to GitLab.

To resolve this problem, edit the configuration for your reverse proxy:

• In the VirtualHost section, add AllowEncodedSlashes NoDecode.
• In the Location section, edit ProxyPass and add the nocanon flag.

For example:

::Tabs

:::TabTitle Apache configuration

<VirtualHost *:443>
  ServerName git.example.com

  SSLEngine on
  SSLCertificateFile     /etc/letsencrypt/live/git.example.com/fullchain.pem
  SSLCertificateKeyFile  /etc/letsencrypt/live/git.example.com/privkey.pem
  SSLVerifyClient None

  ProxyRequests     Off
  ProxyPreserveHost On
  AllowEncodedSlashes NoDecode

  <Location />
     ProxyPass http://127.0.0.1:8080/ nocanon
     ProxyPassReverse http://127.0.0.1:8080/
     Order deny,allow
     Allow from all
  </Location>
</VirtualHost>

:::TabTitle NGINX configuration

server {
  listen       80;
  server_name  gitlab.example.com;
  location / {
     proxy_pass    http://ip:port;
     proxy_set_header        X-Forwarded-Proto $scheme;
     proxy_set_header        Host              $http_host;
     proxy_set_header        X-Real-IP         $remote_addr;
     proxy_set_header        X-Forwarded-For   $proxy_add_x_forwarded_for;
     proxy_read_timeout    300;
     proxy_connect_timeout 300;
  }
}

::EndTabs

For more information, see issue 18775.