How to use the gorgone pull mode

Centreon offers the possibility to reverse the connection flow of the Gorgone process through the Gorgone Pull mode.

Context

Many situations can lead us to implement this feature. Consider a context in which a client has a distributed architecture with a Central server accessible from a public IP adresse (for example in a public Cloud) and many Pollers configured on different LANs. Of course, you cannot contact your remote Pollers from your Central because the Pollers' IPs are not accessible from the Internet and therefore not accessible from the Central server either. In this case, we will ask each Poller to initiate a connection to the public IP of the Central in order to recover its configuration.

Architecture

Consider the distributed architecture:

To identify incoming and outgoing connections between the two servers, we can run the ss command with the -plantu option:

[root@Centreon_Central centos]# ss -plantu | grep 5669
tcp    LISTEN     0      128       *:5669                  *:*                   users:(("cbd",pid=4635,fd=9))
tcp    ESTAB      0      0      10.25.10.88:5669               10.25.15.237:60486               users:(("cbd",pid=4635,fd=18))
tcp    ESTAB      0      0      127.0.0.1:5669               127.0.0.1:53592               users:(("cbd",pid=4635,fd=17))
tcp    ESTAB      0      0      127.0.0.1:53592              127.0.0.1:5669                users:(("centengine",pid=4673,fd=16))

[root@Centreon_Central centos]# ss -plantu | grep 5556
tcp    ESTAB      0      0      10.25.10.88:47216              10.25.15.237:5556                users:(("gorgone-proxy",pid=4774,fd=76))

We have two important network flows between the two Centreon servers:

• In order to transfer the collected data, the connection is made by Centreon Engine from the Poller to the Central Server on port 5669.
• In order to export the Centreon configuration and to transfer external commands, the connection is made by Centreon Gorgone from the Central Server to the Poller on port 5556.

Let's go back to our context: the connection from the Central Server to the Poller is not possible. We have then to start the Gorgone connection from the Poller. We will have the following network flows:

Prerequisite

The Remote Poller is already installed and Gorgone also ( it may not be possible to perform the Register the server step, but don't worry)

In our case, we have the following configuration:

• Central server:
  • address: 10.25.10.88
• Poller:
  • address: 10.25.15.237

Configuration on Poller side

• In the menu Configuration > Poller > Poller, edit the Poller configuration, select ZMQ as Gorgone connection protocol and define the suitable port (port 5556 is recommended).

• From the Pollers listing, click on the Display Gorgone configuration action icon on the line corresponding to the Poller

• A pop-in will show the configuration to copy into the Poller terminal. Click on Copy to clipboard

• Paste the content of the clipboard directly into the Poller terminal and hit the Enter key for the command to be applied.
• Edit the file /etc/centreon-gorgone/config.d/40-gorgoned.yaml, modify the section gorgonecore and add the pull module after replacing the IP address in the target_path column with the IP address of the Central server

name:  distant-server
description: Configuration for distant server
gorgone:
  gorgonecore:
    id: 3
    privkey: "/var/lib/centreon-gorgone/.keys/rsakey.priv.pem"
    pubkey: "/var/lib/centreon-gorgone/.keys/rsakey.pub.pem"

  modules:
    - name: action
      package: gorgone::modules::core::action::hooks
      enable: true

    - name: engine
      package: gorgone::modules::centreon::engine::hooks
      enable: true
      command_file: "/var/lib/centreon-engine/rw/centengine.cmd"

    - name: pull
      package: "gorgone::modules::core::pull::hooks"
      enable: true
      target_type: tcp
      target_path: 10.25.10.88:5556
      ping: 1

• Run the following command to restart the Gorgone service:

systemctl restart gorgoned

• Make sure it is started by running the following command:

systemctl status gorgoned

• Retrieve the gorgone_key_thumbprint.pl 

[root@poller tmp]# wget https://github.com/centreon/centreon-gorgone/blob/develop/contrib/gorgone_key_thumbprint.pl

• Edit the file and replace /etc/pki/gorgone/pubkey.pem by  /var/lib/centreon-gorgone/.keys/rsakey.pub.pem
• Run perl gorgone_key_thumbprint.pl

It should result as follows:

[root@poller ~]# perl gorgone_key_thumbprint.pl
2022-03-03 14:59:53 - INFO - File '/var/lib/centreon-gorgone/.keys/rsakey.pub.pem' JWK thumbprint: f1QbOx92vskVps1TGxxLOf8JS4Yc3Tak43jgRmSFL3U

• keep the rsa public keythumbprint:  f1QbOx92vskVps1TGxxLOf8JS4Yc3Tak43jgRmSFL3U

Configuration on Central side 

• Edit the Gorgone configuration file /etc/centreon-gorgone/config.d/40-gorgoned.yaml and add the following line (key refers to the rsa public keythumbprint )

...
gorgone:
  gorgonecore:
    ...
    external_com_type: tcp
    external_com_path: "*:5556"
    authorized_clients:
      - key: f1QbOx92vskVps1TGxxLOf8JS4Yc3Tak43jgRmSFL3U
    ...
  modules:
    ...
    - name: register
      package: "gorgone::modules::core::register::hooks"
      enable: true
      config_file: /etc/centreon-gorgone/nodes-register-override.yml
    ...

• Then create a new /etc/centreon-gorgone/nodes-register-override.yml file with the following content:

nodes:
  - id: 3
    type: pull
    prevail: 1

          The parameter ID correspond to the Poller ID (retrieve in the Gorgone configuration file of the Poller)

•  Run the following command to restart the Gorgone service:

systemctl restart gorgoned

• Make sure it is started by running the following command:

systemctl status gorgoned

• From the Pollers listing, select the Poller and click on Export configuration. Then check the four first boxes, select the Restart method and click on Export:

The Poller's engine will then start and connect to the Central Broker.

We got the following network flows:

As expected, we have:

tcp    ESTAB      0      0      10.25.10.88:5556               10.25.15.237:60376 

tcp    ESTAB      0      0      10.25.10.88:5669               10.25.15.237:54180