This allows plugins to add controls to nodes that already have some
controls set by other plugin. Previously only the last plugin that
sets the controls in the node would have its controls visible. That
was because of NodeControls' Merge function that actually weren't
merging data from two inputs, but rather returning data that was newer
and discarding the older one.
It exposes a button that allows switching between showing an iowait
statistics and an idle statistics. When the button is pressed it
should be replaced with other button. The button is shown in the host
node.
This is a rather nasty case as it shows several problems:
- Button control races
- The way the NodeControl currently works creates races between
plugins adding buttons to the same node. This is because
NodeControls are not really merged, but rather one of the two are
chosen based on a NodeControls' timestamps, so the older one is
thrown away entirely. In the end GUI can switch randomly between
showing controls from one plugin or from another.
- Showing outdated statistics
- When pressing the button to switch to show the other statistics,
the old ones are still shown for several seconds.
- Slowness of the updates in GUI
- Pressing the button yields no immediate reaction. Changes happen
after several seconds. Probably related to the previous point.
Squash of:
* Include plugins in the report
* show plugin list in the UI
* moving metric and metadata templates into the probe reports
* update js for prime -> priority
* added retry to plugin handshake
* added iowait plugin
* review feedback
* plugin documentation
