Bernd Mathiske created MESOS-3785:
-------------------------------------
Summary: Use URI content modification time to trigger fetcher
cache updates.
Key: MESOS-3785
URL: https://issues.apache.org/jira/browse/MESOS-3785
Project: Mesos
Issue Type: Improvement
Components: fetcher
Reporter: Bernd Mathiske
Assignee: Benjamin Bannier
Instead of using checksums to trigger fetcher cache updates, we can for
starters use the content modification time (mtime), which is available for a
number of download protocols, e.g. HTTP and HDFS.
Proposal: Instead of just fetching the content size, we fetch both size and
mtime together. As before, if there is no size, then caching fails and we fall
back on direct downloading to the sandbox.
Assuming a size is given, we compare the mtime from the fetch URI with the
mtime known to the cache. If it differs, we update the cache. (As a defensive
measure, a difference in size should also trigger an update.)
Not having an mtime available at the fetch URI is simply treated as a unique
valid mtime value that differs from all others. This means that when initially
there is no mtime, cache content remains valid until there is one. Thereafter,
anew lack of an mtime invalidates the cache once. In other words: any change
from no mtime to having one or back is the same as encountering a new mtime.
Note that this scheme does not require any new protobuf fields.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
