Jonathan Hurley created AMBARI-15324:
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Summary: Kerberos Tickets Expire Too Frequently For Alerts
Key: AMBARI-15324
URL: https://issues.apache.org/jira/browse/AMBARI-15324
Project: Ambari
Issue Type: Bug
Components: ambari-agent
Affects Versions: 2.1.0
Reporter: Jonathan Hurley
Assignee: Jonathan Hurley
Priority: Critical
Fix For: 2.2.2
When a cluster has been Kerberized, alerts use the {{curl_krb_request}} module
in order to make requests using SPNEGO negotiation.
Normally this would involve calling {{kinit}} and then invoking the {{curl}}
command to use the acquired ticket. However, because alerts run often on fixed
intervals, this would mean that the KDC would be flooded with requests every
minute.
To alleviate this problem, {{curl_krb_request}} uses {{klist}} to inspect the
{{KRB5CCNAME}} cache. Only if an invalid ticket is found is {{kinit}} invoked.
Additionally, {{kinit}} is invoked with a fixed ticket lifetime of 5 minutes.
Since many alerts run on 5-minute intervals, this causes boundary issues.
To workaround these problems while continuing to leverage the cache,
{{curl_krb_request}} should be changed to:
- Use the default ticket expiry configured for Kerberos in {{krb5.conf}}
- Employ in-memory tracking of the last time {{kinit}} was called so that it
can be invoked before hitting the boundary of the ticket's expiration time
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