The AxoSyslog application can separate a message consisting of whitespace or comma-separated key=value pairs (for example, Postfix log messages) into name-value pairs. You can also specify other separator character instead of the equal sign, for example, colon (:) to parse MySQL log messages. The AxoSyslog application automatically trims any leading or trailing whitespace characters from the keys and values, and also parses values that contain unquoted whitespace. For details on using value-pairs in AxoSyslog see Structuring macros, metadata, and other value-pairs.
You can refer to the separated parts of the message using the key of the value as a macro. For example, if the message contains KEY1=value1,KEY2=value2, you can refer to the values as ${KEY1} and ${KEY2}.
Note
If a log message contains the same key multiple times (for example,key1=value1, key2=value2, key1=value3, key3=value4, key1=value5), then AxoSyslog stores only the last (rightmost) value for the key. Using the previous example, AxoSyslog will store the following pairs: key1=value5, key2=value2, key3=value4.
Warning
If the names of keys in the message is the same as the names of AxoSyslog soft macros, the value from the parsed message will overwrite the value of the macro. For example, the PROGRAM=value1, MESSAGE=value2 content will overwrite the ${PROGRAM} and ${MESSAGE} macros. To avoid overwriting such macros, use the prefix() option.
Hard macros cannot be modified, so they will not be overwritten. For details on the macro types, see Hard versus soft macros.
The parser discards message sections that are not key=value pairs, even if they appear between key=value pairs that can be parsed.
The names of the keys can contain only the following characters: numbers (0-9), letters (a-z,A-Z), underscore (_), dot (.), hyphen (-). Other special characters are not permitted.
To parse key=value pairs, define a parser that has the kv-parser() option. Defining the prefix is optional. By default, the parser will process the ${MESSAGE} part of the log message. You can also define the parser inline in the log path.
Declaration:
parser parser_name {
kv-parser(
prefix()
);
};
Example: Using a key=value parser
In the following example, the source is a log message consisting of comma-separated key=value pairs, for example, a Postfix log message:
Jun 20 12:05:12 mail.example.com <info> postfix/qmgr[35789]: EC2AC1947DA: from=<[email protected]>, size=807, nrcpt=1 (queue active)
The kv-parser inserts the “.kv.” prefix before all extracted name-value pairs. The destination is a file, that uses the format-json template function. Every name-value pair that begins with a dot (".") character will be written to the file (dot-nv-pairs). The log line connects the source, the destination and the parser.
source s_kv {
network(port(21514));
};
destination d_json {
file("/tmp/test.json"
template("$(format-json --scope dot-nv-pairs)\n"));
};
parser p_kv {
kv-parser (prefix(".kv."));
};
log {
source(s_kv);
parser(p_kv);
destination(d_json);
};
You can also define the parser inline in the log path.
source s_kv {
network(port(21514));
};
destination d_json {
file("/tmp/test.json"
template("$(format-json --scope dot-nv-pairs)\n"));
};
log {
source(s_kv);
parser {
kv-parser (prefix(".kv."));
};
destination(d_json);
};
You can set the separator character between the key and the value to parse for example, key:value pairs, like MySQL logs:
Mar 7 12:39:25 myhost MysqlClient[20824]: SYSTEM_USER:'oscar', MYSQL_USER:'my_oscar', CONNECTION_ID:23, DB_SERVER:'127.0.0.1', DB:'--', QUERY:'USE test;'
parser p_mysql {
kv-parser(value-separator(":") prefix(".mysql."));
};