The SP Proxy (https://login.terena.org/wayf) uses metadata that is generated by another host: https://pioneer.terena.org/mr.
This host polls various metadata sources from cron, using SimpleSAMLphp's metarefresh module.
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During the SimpleSAMLphp hackathon on 27 May 2015 a an attempt has been made to add some form of monitoring capabilities to metarefresh.
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- Write any custom Nagios checks and let the Nagios server poll the URLs. This option was rejected because the network checks should be done from the same host that does the metarefresh process. Otherwise subtle changes in network access lists, firewall, OS and library versions might yield different results.
- Runs separate Nagios checks through/from the same host that does the metarefresh process. This approach was rejected because with dozens of URLs, any non-responsive URLs would significantly increase the time it takes to run the Nagios plugin. blah blah
In the end the follow approach was chosen. The metarefresh process already logs all possible errors, and also stores any Conditional GET values for each URL in a state file.
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