Briefly, this error occurs when an unsupported grant type is used during the OAuth2 authentication process in Elasticsearch. The grant type is a parameter that defines the method used to obtain the access tokens. To resolve this issue, ensure that you are using a supported grant type such as ‘password’, ‘client_credentials’, ‘refresh_token’, or ‘authorization_code’. Also, check your Elasticsearch version as some grant types may not be supported in older versions.
This guide will help you check for common problems that cause the log ” the grant type [{}] is not supported ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin.
Log Context
Log “the grant type [{}] is not supported” class name is TransportGrantAction.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
try (ThreadContext.StoredContext ignore = threadContext.stashContext()) {
final AuthenticationToken authenticationToken = request.getGrant().getAuthenticationToken();
assert authenticationToken != null : "authentication token must not be null";
if (authenticationToken == null) {
listener.onFailure(
new ElasticsearchSecurityException("the grant type [{}] is not supported"; request.getGrant().getType())
);
return;
} final String runAsUsername = request.getGrant().getRunAsUsername();
