Hey Jeremy!
We occasionally see a node disconnect from the cluster (not disappear from the
cluster) so I’m building this flow just to reconnect a disconnected node. The
cluster still shows the node, but just that it is in a disconnected state.
As far as the API call to /nifi-api/controller/cluster, yes I get the same
result if I call the API on one of the connected nodes. If I call the API of a
disconnected node, I get “Only a node connected to a cluster can process the
request.” And since the flowfile is sometimes run and processed on the
disconnected node, using ${hostname(true)} in the API to
/nifi-api/controller/cluster won’t work.
I am also using NiFi 1.8.0 for reference as well.
-Chad
From: Jeremy Dyer <jdy...@gmail.com>
Reply-To: "users@nifi.apache.org" <users@nifi.apache.org>
Date: Monday, December 10, 2018 at 9:12 AM
To: "users@nifi.apache.org" <users@nifi.apache.org>
Subject: Re: How to get Node ID of disconnected node to be used in a
cluster/node monitoring flow
*External Message* - Use caution before opening links or attachments
Chad - The API call to /nifi-api/controller/cluster will return all of the
nodes even if they are disconnected. The JSON response will indicate which node
is "disconnected". I have included a screenshot of a simple environment I have
setup for this where I just tested it. However I'm thinking since you are
performing monitoring here you might have a deeper issue you are trying to work
to monitor for. Are you experiencing situations where you are seeing nodes
completely disappear from the cluster and not just be in the "disconnected"
state? If so that is a different issue but if they are just "disconnected" you
should be able to see that as the screenshot below illustrates. I am using NiFi
1.8.0 just for reference.
On Mon, Dec 10, 2018 at 8:47 AM Woodhead, Chad
<chad.woodh...@ncr.com<mailto:chad.woodh...@ncr.com>> wrote:
I am working on a cluster/node monitoring flow and was looking for some
guidance.
I currently have a working flow that monitors if a node gets disconnected from
the cluster and sends an email if a node disconnects.
Here is the flow:
(A SiteToSiteBulletinReportingTask sends to the ClusterMonitoring input port)
[cid:image001.png@01D49064.FF6A8F90]
The CheckAPIForDisconnectedNode process group makes an API call to NiFi confirm
the node is still disconnected before sending the email.
This flow works as expected. I am now wanting to update the flow to
automatically attempt to reconnect the node itself. When a node disconnects, I
capture the server name of that node. To reconnect a node, you can call the API
with PUT /nifi-api/controller/cluster/nodes/{id}, but the problem is I don’t
know the Node ID. The only place I have found I can get the Node ID is via a
GET /nifi-api/controller/cluster, but that API only works on a node that is
connected to the cluster and the way this flow works, the processing can and
sometimes does actually run on the node that has been disconnected. Is there a
way to force it so the processing is only done on a cluster connected node and
then use ${hostname(true)} in the API call, or is there another way I can get
the Node ID, even on a disconnected node? I don’t want to have to hard code all
of my Node ID’s somewhere.
Thanks,
Chad Woodhead
