What is 'salt' in graphite?

Question

http://thisthatserver/render/?width=586&height=308&_salt=1385043488.854&target=carbon.agents.ip-10-0-0-111-a.metricsReceived

&_salt=1385043488.854

and

http://thisthatserver/render/?width=586&height=308&_salt=1385043505.897&target=carbon.agents.ip-10-0-0-111-a.metricsReceived&areaMode=all

&_salt=1385043505.897

What is this salt parameter? i have noticed it since i upgraded to v0.9.12

Answer 1

It looks like it is a "cache buster". So "salt" is a bit of a misnomer -IMO-, as it is usually used in a cryptographic context.

In this case, the "salt" (i.e. cache buster) prevents the browser (or a proxy) from caching the graph/data, because the URL is always unique. Because of this we can be sure that the browser/proxy is always requesting graphs of the server (at the cost of additional round trips when perhaps the aren't needed -because the data may not have changed-).