how to use vars_combination

[huang-x-h]

When we use upstream use chash balancer, then choose hash on vars_combination, but how to config? No document find 😢

[soulbird]

reference： https://github.com/apache/apisix/blob/master/docs/en/latest/admin-api.md#upstream

Related Instructions：

The following should be considered when setting the hash_on value:

• When set to vars, a key is required. The value of the key can be any of the Nginx variables without the $ prefix.
• When set to header, a key is required. This is equal to "http_key".
• When set to cookie, a key is required. This key is equal to "cookie_key". The cookie name is case-sensitive.
• When set to consumer, the key is optional and the key is set to the consumer_name captured from the authentication Plugin.
• When set to vars_combinations, the key is required. The value of the key can be a combination of any of the Nginx variables like $request_uri$remote_addr.
• When no value is set for either hash_on or key, the key defaults to remote_addr.