8:12 a.m.
Can you explain to me what's the big picture of the command
gateway? What's
the chain of calls when, for instance, there's a new deployment in Wildfly?
Joel asked this question - I figured it is good to post to h-dev, too, since I'm sure
others don't know this.
The "big picture" is:
First, remember the MiQ UI is connected to Hawkular-Services server via websocket. The
agents all connect to some Hawkular-Services server via a websocket. There can be more
than one Hawkular-Services server running and the UI may be talking to a server that is
different than the server the agent is talking to:
UI <---websocket---> Server A
^
|
(message bus)
|
V
Server B <---websocket---> agent
1) MiQ sends a JSON message over the websocket to a Hawkular-Services server (Server A in
the diagram above).
2) Hawkular-Services server A looks at the ResourcePath in the message to determine what
agent is responsible for managing that resource.
3) Hawkular-Services server A addresses the message to the proper agent and puts the JSON
message on the agent's queue on the message bus.
3b) At this point the Hawkular-Services server A sends back a JSON message to the UI over
the websocket that says "message forwarded to the bus".
4) The Hawkular-Services server that has a websocket connection to the targeted agent
picks off that message from the bus (Server B in the diagram)
5) That Hawkular-Services server B forwards the message to the agent via its websocket
connection.
6) Agent looks the the message's ResourcePath and the rest of the JSON to determine
what it needs to do. It does the action.
// now the process goes in reverse
7) Agent sends back a response to the server B over websocket (either a success or fail
message)
8) Server B takes response, figures out which UI the response should go to, and puts it on
message bus addressed to the correct UI
9) The Server A takes the response message off the bus
10) Server A sends the response message to the UI over its websocket connection.
Tell me if I'm correct, for what I've seen it's MIQ
which, though the ruby
client, sends a websocket event, caught by the WF agent through the command
gateway. In the end, the WF agent will perform a full sync of affected root
resources in inventory. Is that correct?
In the case of a "Deployment" JSON message, yes, the agent will trigger a full
discovery scan so it can quickly discover the new deployment you just added to WildFly.
If that's correct, there's no direct interaction between
inventory and the
command gateway. I'm asking because I hope we can keep the command gateway
messages unchanged, and change only places where there's direct calls to
the inventory rest api.
Most of the time, its just using ResourcePath API (just that simple inventory POJO).
HOWEVER, I believe Jay added some code that does interact with Inventory to do things like
create relationships in inventory when new cluster entities are added. That is why (I
think) he did this commit. Though I can't remember where this code is that builds
inventory relationships - he'll have to point that out. But I'm pretty sure there
is some inventory stuff going on under the covers for that stuff - more than just using
the canonical ResourcePath stuff.