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) };
Declaration
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.
The add-contextual-data() has the following options.
Required options
The following options are required: selector(), database().
database()
| Type: |
<path-to-file>.csv |
| Default: |
|
Description: Specifies the path to the CSV file, for example, /opt/syslog-ng/my-csv-database.csv. The extension of the file must be .csv, and can include Windows-style (CRLF) or UNIX-style (LF) linebreaks. You can use absolute path, or relative to the syslog-ng PE binary.
default-selector()
| Synopsis: |
default-selector() |
Description: Specifies the ID of the entry (line) that is corresponds to log messages that do not have a selector that matches an entry in the database. For example, if you add name-value pairs from the database based on the hostname from the log message (selector("${HOST}")), then you can include a line for unknown hosts in the database, and set default-selector() to the ID of the line for unknown hosts. In the CSV file:
unknown-hostname,host-role,unknown
In the syslog-ng PE configuration file:
add-contextual-data(
selector("$HOST")
database("context-info-db.csv")
default-selector("unknown-hostname")
);
prefix()
Description: Insert a prefix before the name part of the added name-value pairs (including the pairs added by the default-selector()) to help further processing.
selector()
Description: Specifies the string or macro that syslog-ng PE evaluates for each message, and if its value matches the ID of an entry in the database, syslog-ng PE adds the name-value pair of every matching database entry to the log message. Currently, you can use strings and a single macro (for example, ${HOST}) in the selector() option, templates are not supported. To use filters as selectors, see Using filters as selector.
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.
NOTE: To access longitude and latitude information, download the City version of the GeoIP2 database.
There are two types of GeoIP2 databases available.
-
GeoLite2 City:
-
free of charge
-
less accurate
-
GeoIP2 City:
-
has to be purchased
-
more accurate
Unzip the downloaded database (for example, to the /usr/share/GeoIP2/GeoIP2City.mmdb file). This path will be used later in the configuration.
Starting with version 7.0.17, syslog-ng PE tries to automatically detect the location of the database. If that is successful, the database() option is not mandatory.
The geoip2 parser has the following options.
prefix()
Description: Insert a prefix before the name part of the parsed name-value pairs to help further processing. For example:
-
To insert the my-parsed-data. prefix, use the prefix(my-parsed-data.) option.
-
To refer to a particular data that has a prefix, use the prefix in the name of the macro, for example, ${my-parsed-data.name} .
-
If you forward the parsed messages using the IETF-syslog protocol, you can insert all the parsed data into the SDATA part of the message using the prefix(.SDATA.my-parsed-data.) option.
Names starting with a dot (for example,
.example) are reserved for use by syslog-ng PE. If you use such a macro name as the name of a parsed value, it will attempt to replace the original value of the macro (note that only soft macros can be overwritten, see
Hard versus soft macros for details). To avoid such problems, use a prefix when naming the parsed values, for example,
prefix(my-parsed-data.)
For example, to insert the .geoip2 prefix, use the prefix(.geoip2) option. To refer to a particular data when using a prefix, use the prefix in the name of the macro, for example, ${geoip2.country_code}.
database()
| Synopsis: |
database() |
| Default: |
|
Description: Path to the GeoIP2 database to use. This works with absolute and relative paths as well. Note that syslog-ng PE must have the required privileges to read this file. Do not modify or delete this file while syslog-ng PE is running, it can crash syslog-ng PE.
Starting with version 7.0.17, syslog-ng PE tries to automatically detect the location of the database. If that is successful, the database() option is not mandatory.
