[[cat-health]] == cat health `health` is a terse, one-line representation of the same information from `/_cluster/health`. It has one option `ts` to disable the timestamping. [source,sh] -------------------------------------------------- % curl localhost:9200/_cat/health 1384308967 18:16:07 foo green 3 3 3 3 0 0 0 % curl 'localhost:9200/_cat/health?v&ts=0' cluster status nodeTotal nodeData shards pri relo init unassign tasks foo green 3 3 3 3 0 0 0 0 -------------------------------------------------- A common use of this command is to verify the health is consistent across nodes: [source,sh] -------------------------------------------------- % pssh -i -h list.of.cluster.hosts curl -s localhost:9200/_cat/health [1] 20:20:52 [SUCCESS] es3.vm 1384309218 18:20:18 foo green 3 3 3 3 0 0 0 0 [2] 20:20:52 [SUCCESS] es1.vm 1384309218 18:20:18 foo green 3 3 3 3 0 0 0 0 [3] 20:20:52 [SUCCESS] es2.vm 1384309218 18:20:18 foo green 3 3 3 3 0 0 0 0 -------------------------------------------------- A less obvious use is to track recovery of a large cluster over time. With enough shards, starting a cluster, or even recovering after losing a node, can take time (depending on your network & disk). A way to track its progress is by using this command in a delayed loop: [source,sh] -------------------------------------------------- % while true; do curl localhost:9200/_cat/health; sleep 120; done 1384309446 18:24:06 foo red 3 3 20 20 0 0 1812 0 1384309566 18:26:06 foo yellow 3 3 950 916 0 12 870 0 1384309686 18:28:06 foo yellow 3 3 1328 916 0 12 492 0 1384309806 18:30:06 foo green 3 3 1832 916 4 0 0 ^C -------------------------------------------------- In this scenario, we can tell that recovery took roughly four minutes. If this were going on for hours, we would be able to watch the `UNASSIGNED` shards drop precipitously. If that number remained static, we would have an idea that there is a problem. [float] [[timestamp]] === Why the timestamp? You typically are using the `health` command when a cluster is malfunctioning. During this period, it's extremely important to correlate activities across log files, alerting systems, etc. There are two outputs. The `HH:MM:SS` output is simply for quick human consumption. The epoch time retains more information, including date, and is machine sortable if your recovery spans days.