#   How to Fetch Metrics

These instructions describe the ways to collect metrics from a filtering node.

##  Exporting Metrics Directly From `collectd`

You can export the metrics collected by `collectd` directly to the tools that support working with `collectd` data streams.

!!! warning "Prerequisites"
    All further steps must be performed as a superuser (e.g., `root`).

### Exporting Metrics via the `collectd` Network Plugin

Configure and connect the [network plugin](https://collectd.org/wiki/index.php/Plugin:Network) to `collectd`:

**Docker image, cloud image, all-in-one installer:**

1.  Add the following configuration to the `/opt/wallarm/etc/collectd/wallarm-collectd.conf` file:

    ```
    LoadPlugin network

    <Plugin "network">
      Server "Server IPv4/v6 address or FQDN" "Server port"
    </Plugin>
    ```

    As stated in this configuration, the plugin will be loaded upon starting `collectd`, operate in the client mode, and send the filter node’s metrics data to the specified server.
1.  Configure a server that will receive data from the `collectd` client. The necessary configuration steps depend on the selected server (see examples for [`collectd`](https://collectd.org/wiki/index.php/Networking_introduction) and [InfluxDB](https://docs.influxdata.com/influxdb/v1.7/supported_protocols/collectd/)).


    !!! info "Working with the Network Plugin"
        The network plugin works over UDP (see the [plugin documentation](https://www.collectd.org/documentation/manpages/collectd.conf.html)). Make sure that the server allows communication over UDP for metrics collection to be operational.
1.  Restart the `wallarm` service by running the following command:

    ```bash
    sudo systemctl restart wallarm
    ```

**Other installations:**

1.  In the `/etc/collectd/collectd.conf.d/` directory, create a file with the `.conf` extension (e.g., `export-via-network.conf`) and the following content:

    ```
    LoadPlugin network

    <Plugin "network">
      Server "Server IPv4/v6 address or FQDN" "Server port"
    </Plugin>
    ```

    As stated in this file, the plugin will be loaded upon starting `collectd`, operate in the client mode, and send the filter node’s metrics data to the specified server.
1.  Configure a server that will receive data from the `collectd` client. The necessary configuration steps depend on the selected server (see examples for [`collectd`](https://collectd.org/wiki/index.php/Networking_introduction) and [InfluxDB](https://docs.influxdata.com/influxdb/v1.7/supported_protocols/collectd/)).


    !!! info "Working with the Network Plugin"
        The network plugin works over UDP (see the [plugin documentation](https://www.collectd.org/documentation/manpages/collectd.conf.html)). Make sure that the server allows communication over UDP for metrics collection to be operational.
1.  Restart the `collectd` service by executing the appropriate command:

    **Ubuntu 14.04 LTS:**

    ```bash
    sudo service collectd restart
    ```

    **Other supported distributions:**

    ```bash
    sudo systemctl restart collectd
    ```
!!! info "Example"
    Read an [example of exporting metrics](https://docs.wallarm.com/5.x/admin-en/monitoring/network-plugin-influxdb.md) to InfluxDB via the Network plugin with subsequent visualization of the metrics in Grafana.

### Exporting Metrics via the `collectd` Write Plugins

To configure export of metrics via the `collectd` [write plugins](https://collectd.org/wiki/index.php/Table_of_Plugins), refer to the documentation of the corresponding plugin.

!!! info "Example"
    To get basic information about using write plugins, read an [example of exporting metrics](https://docs.wallarm.com/5.x/admin-en/monitoring/write-plugin-graphite.md) to Graphite with subsequent visualization of the metrics in Grafana.

##  Exporting Metrics Using the `collectd-nagios` Utility

To export metrics using this method:

1.  Install the `collectd-nagios` utility on a host with a filter node by running the appropriate command (for a filter node installed on Linux):

    **DEB-based distributions:**

    ```bash
    sudo apt -y install --no-install-recommends collectd-utils
    ```

    **RPM-based distributions:**

    ```bash
    sudo yum install -y collectd-utils
    ```
    !!! info "Docker image"
        The filter node Docker image ships with a preinstalled `collectd-nagios` utility.

2.  Make sure that you can run this utility with elevated privileges either on behalf of a superuser (for example, `root`) or as a regular user. In the latter case, add the user to the `sudoers` file with the `NOPASSWD` directive, and use the `sudo` utility.

    !!! info "Working with the Docker container"
        When executing the `collectd-nagios` utility in a Docker container with the filter node, elevation of privileges is not required.

3.  Connect and configure the [`UnixSock`](https://collectd.org/wiki/index.php/Plugin:UnixSock) plugin to transmit the `collectd` metrics via a Unix domain socket. To do this, create the file `/etc/collectd/collectd.conf.d/unixsock.conf` with the following content:

    ```
    LoadPlugin unixsock

    <Plugin unixsock>
        SocketFile "/var/run/wallarm-collectd-unixsock"
        SocketGroup "root"
        SocketPerms "0770"
        DeleteSocket true
    </Plugin>
    ```

4.  Restart the `collectd` service by executing the appropriate command:

    **Ubuntu 14.04 LTS:**

    ```bash
    sudo service collectd restart
    ```

    **Other supported distributions:**

    ```bash
    sudo systemctl restart collectd
    ```
5.  Get the value of the necessary metric by running the appropriate command:

    **Linux:**

    ```bash
    /usr/bin/collectd-nagios -s /var/run/wallarm-collectd-unixsock -n <metric name without host name> -H <FQDN of the host with the filter node on which the utility is running>
    ```

    **Docker:**

    ```bash
    docker exec <container name> /usr/bin/collectd-nagios -s /var/run/wallarm-collectd-unixsock -n <metric name without host name> -H <container ID>
    ```
    !!! info "Getting the Docker container's ID"
        You can find the value of the container identifier by running the `docker ps` command (see the “CONTAINER ID” column).

!!! info "Setting Thresholds for the `collectd-nagios` Utility"
    If necessary, you can specify a range of values for which the `collectd-nagios` utility will return the `WARNING` or `CRITICAL` status by using the corresponding `-w` and `-c` options (detailed information is available in the utility [documentation](https://www.collectd.org/documentation/manpages/collectd-nagios.html)).
   
**Examples of using the utility:**
*   To get the value of the `wallarm_nginx/gauge-abnormal` metric (at the time `collectd-nagios` was called) on the Linux host `node.example.local` with the filter node, run the following command:
  
    ```
    /usr/bin/collectd-nagios -s /var/run/wallarm-collectd-unixsock -n wallarm_nginx/gauge-abnormal -H node.example.local
    ```
       
*   To get the value of the `wallarm_nginx/gauge-abnormal` metric (at the time `collectd-nagios` was called) for the filter node running in the Docker container with the `wallarm-node` name and the `95d278317794` identifier, run the following command:
  
    ```
    docker exec wallarm-node /usr/bin/collectd-nagios -s /var/run/wallarm-collectd-unixsock -n wallarm_nginx/gauge-abnormal -H 95d278317794
    ```

!!! info "More examples"
    To get basic information about using the `collectd-nagios` utility, read examples of exporting metrics
    
    *   [to the Nagios monitoring system](https://docs.wallarm.com/5.x/admin-en/monitoring/collectd-nagios.md) and
    *   [to the Zabbix monitoring system](https://docs.wallarm.com/5.x/admin-en/monitoring/collectd-zabbix.md).

##  Sending Notifications from `collectd`

Notifications are configured in the following file:

**DEB-based distributions:**

```bash
/etc/collectd/conf.d/traps.conf
```

**RPM-based distributions:**

```bash
/etc/collectd.d/traps.conf
```
A general description of how notifications work is available [here](https://collectd.org/wiki/index.php/Notifications_and_thresholds).

More detailed information about how to set up notifications is available [here](https://www.collectd.org/documentation/manpages/collectd-threshold.html).

Possible methods of sending notifications:
*   NSCA and NSCA-ng
*   SNMP TRAP
*   email messages
*   custom scripts