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[Launchpad Bug Tracker <1788518@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package landscape-client -
16.03-0ubuntu2.16.04.7

---------------
landscape-client (16.03-0ubuntu2.16.04.7) xenial; urgency=medium

  * d/p/product-name-vminfo-1828217.patch: Add product_name to things scanned
    for vm_info (LP: #1828217)
  * d/landscape-client.postinst: Set default value if data_path is
    missing. (LP: #1728681)
  * d/p/stagger-launch-1788518.patch: Add option to stagger launch of broker
    plugins. (LP: #1788518)
  * d/landscape-client.init: Fix init script stop action (LP: #1833137)

 -- Simon Poirier <simon.poirier@xxxxxxxxxxxxx>  Fri, 28 Jun 2019
12:18:32 -0400

** Changed in: landscape-client (Ubuntu Xenial)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1788518

Title:
  Intervals should be staggered

Status in Landscape Client:
  Fix Committed
Status in landscape-client package in Ubuntu:
  Fix Released
Status in landscape-client source package in Xenial:
  Fix Released
Status in landscape-client source package in Bionic:
  Fix Released
Status in landscape-client source package in Disco:
  Fix Released

Bug description:
  [Impact]

   * Restarting hosts/clouds of multiple VMs or containers managed by
     landscape leads to synchronized monitoring tasks. This can generate
     significant recurring load.

   * The fix adds a configurable randomized interval to scheduled tasks.

  [Test Case]

  sudo landscape-config --stagger-launch 0.5 --log-level debug
  # accept client in server interface
  sudo tail -f /var/log/landscape/monitor.log
  # Check for debug log entries mentioning monitors getting delayed

  [Regression Potential]

   * Although changing the scheduler for non-fixed loop intervals could
     have been slightly better at avoid load peaks on shared hosts, the
     current approach has been deemed safer as it simply adds an initial
     delay to tasks. The current logic of scheduling is unchanged. 

   * External scripts expecting monitors to run instantly on
     landscape-client restart could be affected. I'm not aware of
     any such case, as the async nature of the code never made that
     guarantee.

   * The stagger interval is configurable with a flag and a configuration
     entry to work around regressions.

  [Original Description]

  The various intervals appear to be statically determined from program
  start.  As a practical example, a rebooted VM host with a large number
  of guests means all the guests start landscape-client at about the
  same time.  Then every 30 minutes, package-monitor runs (which is a
  rather heavy operation).  Multiply by a hundred or so and you've got a
  large flood on the host.

  When the client starts up, it would be good to have the initial
  schedule for each timer be ((interval / 2) + random(interval)), so the
  collective load is spread out over the entire interval.

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