My logstash server has been working fine for weeks. No-one has touched it. All of a sudden, it has lost connectivity to ElasticSearch.
The log is filled with "Marking url as dead. Last error: [LogStash::Outputs::ElasticSearch::HttpClient::Pool::HostUnreachableError] Elasticsearch Unreachable: "
However, issuing a curl command (e.g. to list all indices) from the same machine, with the same user, works fine.
How can I debug this?