syslog-ng Premium Edition 7.0.19 - Administration Guide

Adding metadata from an external file

In syslog-ng PE version 7.0 and later, you can use an external database file to add additional metadata to your log messages. For example, you can create a database (or export it from an existing tool) that contains a list of hostnames or IP addresses, and the department of your organization that the host belongs to, the role of the host (mailserver, webserver, and so on), or similar contextual information.

The database file is a simple text file in comma-separated value (CSV) format, where each line contains the following information:

• A selector or ID that appears in the log messages, or the name of a filter that matches the messages, for example, the hostname.

• The name of the name-value pair that syslog-ng PE adds to matching log messages.

• The value of the name-value pairs.

For example, the following csv-file contains three lines identified with the IP address, and adds the host-role field to the log message.

192.168.1.1,host-role,webserver
192.168.2.1,host-role,firewall
192.168.3.1,host-role,mailserver

192.168.1.1,host-role,webserver
192.168.1.1,contact-person,"John Doe"
192.168.1.1,contact-email,johndoe@example.com

parser p_add_context_data {
    add-contextual-data(
        selector("$HOST"),
        database("context-info-db.csv"),
    );
};

@include "scl.conf"

source s_network {
    network(port(5555));
};

destination d_local {
    file("/tmp/test-msgs.log"
    template("$MSG Additional metadata:[${.metadata.host-role}]")};

parser p_add_context_data {
    add-contextual-data(
        selector("$SOURCEIP"),
        database("context-info-db.csv"),
        default-selector("unknown"),
        prefix(".metadata.")
    );
};

log {
    source(s_network);
    parser(p_add_context_data);
    destination(d_local);
};

192.168.1.1,host-role,webserver
192.168.2.1,host-role,firewall
192.168.3.1,host-role,mailserver
unknown,host-role,unknown

Using filters as selector

To better control to which log messages you add contextual data, you can use filters as selectors. In this case, the first column of the CSV database file must contain the name of a filter. For each message, syslog-ng PE evaluates the filters in the order they appear in the database file. If a filter matches the message, syslog-ng PE adds the name-value pair related to the filter.

For example, the database file can contain the entries. (For details on the accepted CSV-format, see database().)

f_auth,domain,all
f_localhost,source,localhost
f_kern,domain,kernel

Note that syslog-ng PE does not evaluate other filters after the first match. For example, if you use the previous database file, and a message matches both the f_auth and f_localhost filters, syslog-ng PE adds only the name-value pair of f_auth to the message.

To add multiple name-value pairs to a message, include a separate line in the database for each name-value pair, for example:

f_localhost,host-role,firewall
f_localhost,contact-person,"John Doe"
f_localhost,contact-email,johndoe@example.com

You can also add data to messages that do not have a matching selector entry in the database using the default-selector() option.

You must store the filters you reference in a database in a separate file. This file is similar to a syslog-ng PE configuration file, but must contain only a version string and filters (and optionally comments). You can use the syslog-ng --syntax-only <filename> command to ensure that the file is valid. For example, the content of such a file can be:

@version: 7.0
filter f_localhost { host("mymachine.example.com") };
filter f_auth { facility(4) };
filter f_kern { facility(0) };

parser p_add_context_data_filter {
    add-contextual-data(
        selector(filters("filters.conf")),
        database("context-info-db.csv"),
        prefix(".metadata.")
    );
};

If you modify the database file, or the file that contains the filters, you have to reload syslog-ng PE for the changes to take effect. If reloading syslog-ng PE or the files fails for some reason, syslog-ng PE will keep using the last working version of the file.

Options add-contextual-data()

The add-contextual-data() has the following options.

unknown-hostname,host-role,unknown

add-contextual-data(
    selector("$HOST")
    database("context-info-db.csv")
    default-selector("unknown-hostname")
);

Looking up GeoIP2 data from IP addresses

The syslog-ng PE application can lookup IP addresses from an offline GeoIP2 database, and make the retrieved data available in name-value pairs. Depending on the database used, you can access country code, longitude, and latitude information and so on.

The syslog-ng PE application works with the Country and the City version of the GeoIP2 database, both free and the commercial editions. The syslog-ng PE application works with the mmdb (GeoIP2) format of these databases. Other formats, like csv are not supported.