Options of CSV parsers
The syslog-ng OSE application can separate parts of log messages (that is, the contents of the ${MESSAGE} macro) at delimiter characters or strings to named fields (columns). One way to achieve this is to use a csv (comma-separated-values) parser (for other methods and possibilities, see the other sections of parser: Parse and segment structured messages. The parsed fields act as user-defined macros that can be referenced in message templates, file- and tablenames, and so on.
Parsers are similar to filters: they must be defined in the syslog-ng OSE configuration file and used in the log statement. You can also define the parser inline in the log path.
NOTE: The order of filters, rewriting rules, and parsers in the log statement is important, as they are processed sequentially.
To create a csv-parser(), you have to define the columns of the message, the separator characters or strings (also called delimiters, for example, semicolon or tabulator), and optionally the characters that are used to escape the delimiter characters (quote-pairs()).
Declaration:
parser <parser_name> {
csv-parser(
columns(column1, column2, ...)
delimiters(chars("<delimiter_characters>"), strings("<delimiter_strings>"))
);
};Column names work like macros.
Names starting with a dot (for example, .example) are reserved for use by syslog-ng OSE. 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.)
columns()
| Synopsis: | columns("PARSER.COLUMN1", "PARSER.COLUMN2", ...) |
Description: Specifies the name of the columns to separate messages to. These names will be automatically available as macros. The values of these macros do not include the delimiters.
delimiters()
| Synopsis: |
delimiters(chars("<delimiter_characters>")) or delimiters("<delimiter_characters>") delimiters(strings("<delimiter_string1>", "<delimiter_string2>", ...)") delimiters(chars("<delimiter_characters>"), strings("<delimiter_string1>")) |
Description: The delimiter is the character or string that separates the columns in the message. If you specify multiple characters using the delimiters(chars("<delimiter_characters>")) option, every character will be treated as a delimiter. To separate the columns at the tabulator (tab character), specify \t. For example, to separate the text at every hyphen (-) and colon (:) character, use delimiters(chars("-:")), Note that the delimiters will not be included in the column values.
String delimiters:
If you have to use a string as a delimiter, list your string delimiters in the delimiters(strings("<delimiter_string1>", "<delimiter_string2>", ...)") format.
By default, syslog-ng OSE uses space as a delimiter. If you want to use only the strings as delimiters, you have to disable the space delimiter, for example: delimiters(chars(""), strings("<delimiter_string>"))
Otherwise, syslog-ng OSE will use the string delimiters in addition to the default character delimiter, so delimiters(strings("==")) actually equals delimiters(chars(" "), strings("==")), and not delimiters(chars(""), strings("=="))
Multiple delimiters:
If you use more than one delimiter, note the following points:
-
syslog-ng OSE will split the message at the nearest possible delimiter. The order of the delimiters in the configuration file does not matter.
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You can use both string delimiters and character delimiters in a parser.
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The string delimiters can include characters that are also used as character delimiters.
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If a string delimiter and a character delimiter both match at the same position of the message, syslog-ng OSE uses the string delimiter.
dialect()
| Synopsis: | escape-none|escape-backslash|escape-double-char |
Description: Specifies how to handle escaping in the parsed message. The following values are available. Default value: escape-none
-
escape-backslash: The parsed message uses the backslash (\) character to escape quote characters.
-
escape-double-char: The parsed message repeats the quote character when the quote character is used literally. For example, to escape a comma (,), the message contains two commas (,,).
-
escape-none: The parsed message does not use any escaping for using the quote character literally.
parser p_demo_parser {
csv-parser(
prefix(".csv.")
delimiters(" ")
dialect(escape-backslash)
flags(strip-whitespace, greedy)
columns("column1", "column2", "column3")
);
};flags()
| Synopsis: | drop-invalid, escape-none, escape-backslash, escape-double-char, greedy, strip-whitespace |
Description: Specifies various options for parsing the message. The following flags are available:
-
drop-invalid: When the drop-invalid option is set, the parser does not process messages that do not match the parser. For example, a message does not match the parser if it has less columns than specified in the parser, or it has more columns but the greedy flag is not enabled. Using the drop-invalid option practically turns the parser into a special filter, that matches messages that have the predefined number of columns (using the specified delimiters).
TIP: Messages dropped as invalid can be processed by a fallback log path. For details on the fallback option, see Log path flags.
-
escape-backslash: The parsed message uses the backslash (\) character to escape quote characters.
-
escape-double-char: The parsed message repeats the quote character when the quote character is used literally. For example, to escape a comma (,), the message contains two commas (,,).
-
escape-none: The parsed message does not use any escaping for using the quote character literally.
-
greedy: The greedy option assigns the remainder of the message to the last column, regardless of the delimiter characters set. You can use this option to process messages where the number of columns varies.
Example: Adding the end of the message to the last column
If the greedy option is enabled, the syslog-ng application adds the not-yet-parsed part of the message to the last column, ignoring any delimiter characters that may appear in this part of the message.
For example, you receive the following comma-separated message: example 1, example2, example3, and you segment it with the following parser:
csv-parser(columns("COLUMN1", "COLUMN2", "COLUMN3") delimiters(","));The COLUMN1, COLUMN2, and COLUMN3 variables will contain the strings example1, example2, and example3, respectively. If the message looks like example 1, example2, example3, some more information, then any text appearing after the third comma (that is, some more information) is not parsed, and possibly lost if you use only the variables to reconstruct the message (for example, to send it to different columns of an SQL table).
Using the greedy flag will assign the remainder of the message to the last column, so that the COLUMN1, COLUMN2, and COLUMN3 variables will contain the strings example1, example2, and example3, some more information.
csv-parser(columns("COLUMN1", "COLUMN2", "COLUMN3") delimiters(",") flags(greedy)); -
strip-whitespace: The strip-whitespace flag removes leading and trailing whitespaces from all columns.
null()
| Synopsis: | string |
Description: If the value of a column is the value of the null() parameter, syslog-ng OSE changes the value of the column to an empty string. For example, if the columns of the message contain the "N/A" string to represent empty values, you can use the null("N/A") option to change these values to empty stings.
prefix()
| Synopsis: | 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, ${my-parsed-data.name}.
-
If you forward the parsed messages using the IETF-syslog protocol, you can insert all the parsed data into the SDATA part of the message using the prefix(.SDATA.my-parsed-data.) option.
Names starting with a dot (for example, .example) are reserved for use by syslog-ng OSE. If you use such a macro name as the name of a parsed value, it will attempt to replace the original value of the macro (note that only soft macros can be overwritten, see Hard versus soft macros for details). To avoid such problems, use a prefix when naming the parsed values, for example, prefix(my-parsed-data.)
quote-pairs()
| Synopsis: | quote-pairs('<quote_pairs>') |
Description: List quote-pairs between single quotes. Delimiter characters or strings enclosed between quote characters are ignored. Note that the beginning and ending quote character does not have to be identical, for example, [} can also be a quote-pair. For an example of using quote-pairs() to parse Apache log files, see Example: Parsing Apache log files.
template()
| Synopsis: | template("${<macroname>}") |
Description: The macro that contains the part of the message that the parser will process. It can also be a macro created by a previous parser of the log path. By default, the parser processes the entire message (${MESSAGE}).
For examples, see Example: Segmenting hostnames separated with a dash and Example: Segmenting a part of a message.
Parsing key=value pairs
The syslog-ng OSE 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 syslog-ng OSE 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 syslog-ng OSE 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 syslog-ng OSE stores only the last (rightmost) value for the key. Using the previous example, syslog-ng OSE will store the following pairs: key1=value5, key2=value2, key3=value4.
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Caution:
If the names of keys in the message is the same as the names of syslog-ng OSE 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 ${MESSAGE} part of the log message. You can also define the parser inline in the log path.
Declaration:
parser parser_name {
kv-parser(
prefix()
);
};
Example: Using a key=value parser
In the following example, the source is a log message consisting of comma-separated key=value pairs, for example, a Postfix log message:
Jun 20 12:05:12 mail.example.com <info> postfix/qmgr[35789]: EC2AC1947DA: from=<me@example.com>, size=807, nrcpt=1 (queue active)
The kv-parser inserts the ".kv." prefix before all extracted name-value pairs. The destination is a file, that uses the format-json template function. Every name-value pair that begins with a dot (".") character will be written to the file (dot-nv-pairs). The log line connects the source, the destination and the parser.
source s_kv {
network(port(21514));
};
destination d_json {
file("/tmp/test.json"
template("$(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."));
};Options of key=value parsers
The kv-parser has the following options.
extract-stray-words-into()
| Synopsis: | extract-stray-words-into("<name-value-pair>") |
Description: Specifies the name-value pair where syslog-ng OSE stores any stray words that appear before or between the parsed key-value pairs (mainly when the pair-separator() option is also set). If multiple stray words appear in a message, then syslog-ng OSE stores them as a comma-separated list. Note that the prefix() option does not affect the name-value pair storing the stray words. Default value: N/A
Example: Extracting stray words in key-value pairs
For example, consider the following message:
VSYS=public; Slot=5/1; protocol=17; source-ip=10.116.214.221; source-port=50989; destination-ip=172.16.236.16; destination-port=162;time=2016/02/18 16:00:07; interzone-emtn_s1_vpn-enodeb_om; inbound; policy=370;
This is a list of key-value pairs, where the value separator is = and the pair separator is ;. However, before the last key-value pair (policy=370), there are two stray words: interzone-emtn_s1_vpn-enodeb_om inbound. If you want to store or process these, specify a name-value pair to store them in the extract-stray-words-into() option, for example, extract-stray-words-into("my-stray-words"). The value of ${my-stray-words} for this message will be interzone-emtn_s1_vpn-enodeb_om, inbound
prefix()
| Synopsis: | 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, ${my-parsed-data.name}.
-
If you forward the parsed messages using the IETF-syslog protocol, you can insert all the parsed data into the SDATA part of the message using the prefix(.SDATA.my-parsed-data.) option.
Names starting with a dot (for example, .example) are reserved for use by syslog-ng OSE. If you use such a macro name as the name of a parsed value, it will attempt to replace the original value of the macro (note that only soft macros can be overwritten, see Hard versus soft macros for details). To avoid such problems, use a prefix when naming the parsed values, for example, prefix(my-parsed-data.)
For example, to insert the postfix prefix when parsing Postfix log messages, use the prefix(.postfix.) option.
pair-separator()
| Synopsis: | pair-separator("<separator-string>") |
Description: Specifies the character or string that separates the key-value pairs from each other. Default value: , (a comma followed by a whitespace)
For example, to parse key1=value1;key2=value2 pairs, use kv-parser(pair-separator(";"));
template()
| Synopsis: | template("${<macroname>}") |
Description: The macro that contains the part of the message that the parser will process. It can also be a macro created by a previous parser of the log path. By default, the parser processes the entire message (${MESSAGE}).
value-separator()
| Synopsis: | value-separator("<separator-character>") |
Description: Specifies the character that separates the keys from the values. Default value: =
For example, to parse key:value pairs, use kv-parser(value-separator(":"));
JSON parser
JavaScript Object Notation (JSON) is a text-based open standard designed for human-readable data interchange. It is used primarily to transmit data between a server and web application, serving as an alternative to XML. It is described in RFC 4627. The syslog-ng OSE application can separate parts of incoming JSON-encoded log messages to name-value pairs. For details on using value-pairs in syslog-ng OSE see Structuring macros, metadata, and other value-pairs.
You can refer to the separated parts of the JSON message using the key of the JSON object as a macro. For example, if the JSON contains {"KEY1":"value1","KEY2":"value2"}, you can refer to the values as ${KEY1} and ${KEY2}. If the JSON content is structured, syslog-ng OSE converts it to dot-notation-format. For example, to access the value of the following structure {"KEY1": {"KEY2": "VALUE"}}, use the ${KEY1.KEY2} macro.
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Caution:
If the names of keys in the JSON content are the same as the names of syslog-ng OSE soft macros, the value from the JSON content will overwrite the value of the macro. For example, the {"PROGRAM":"value1","MESSAGE":"value2"} JSON 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. |
NOTE: The JSON parser currently supports only integer, double and string values when interpreting JSON structures. As syslog-ng does not handle different data types internally, the JSON parser converts all JSON data to string values. In case of boolean types, the value is converted to 'TRUE' or 'FALSE' as their string representation.
The JSON parser discards messages if it cannot parse them as JSON messages, so it acts as a JSON-filter as well.
To create a JSON parser, define a parser that has the json-parser() option. Defining the prefix and the marker are optional. By default, the parser will process the ${MESSAGE} part of the log message. To process other parts of a log message with the JSON parser, use the template() option. You can also define the parser inline in the log path.
Declaration:
parser parser_name {
json-parser(
marker()
prefix()
);
};Example: Using a JSON parser
In the following example, the source is a JSON encoded log message. The syslog parser is disabled, so that syslog-ng OSE does not parse the message: flags(no-parse). The json-parser inserts ".json." prefix before all extracted name-value pairs. The destination is a file that uses the format-json template function. Every name-value pair that begins with a dot (".") character will be written to the file (dot-nv-pairs). The log line connects the source, the destination and the parser.
source s_json {
network(
port(21514
flags(no-parse)
);
};
destination d_json {
file(
"/tmp/test.json"
template("$(format-json --scope dot-nv-pairs)\n")
);
};
parser p_json {
json-parser (prefix(".json."));
};
log {
source(s_json);
parser(p_json);
destination(d_json);
};
You can also define the parser inline in the log path.
source s_json {
network(
port(21514)
flags(no-parse)
);
};
destination d_json {
file(
"/tmp/test.json"
template("$(format-json --scope dot-nv-pairs)\n")
);
};
log {
source(s_json);
parser {
json-parser (prefix(".json."));
};
destination(d_json);
};