Options of syslog-parser() parsers
The syslog-parser()
has the following options:
default-facility()
Type: | facility string |
Default: | kern |
Description: This parameter assigns a facility value to the messages received from the file source if the message does not specify one.
default-priority()
Type: | priority string |
Default: |
Description: This parameter assigns an emergency level to the messages received from the file source if the message does not specify one. For example, default-priority(warning)
.
drop-invalid()
Type: | yes or no |
Values: | `yes |
Default: | no |
Description: This option determines how the syslog-parser()
affects messages when parsing fails.
If you set drop-invalid()
to yes
, syslog-parser()
will drop the message if the parsing fails.
If you set drop-invalid()
to no
, the parsing error triggers syslog-parser()
to rewrite and extend the original log message with the following additional information:
- It prepends the following message to the contents of the
$MESSAGE
field:Error processing log message
. - It sets the contents of the
$PROGRAM
field tosyslog-ng
. - It sets the contents of the
facility
field tosyslog
. - It sets the contents of the
severity
field toerror
.
drop-invalid(no)
option syslog-parser()
will work in the same way as the sources which receive syslog-protocol/BSD-format messages.
Example: enabling the drop-invalid() option
parser p_syslog { syslog-parser(drop-invalid(yes)); };
flags()
Type: | assume-utf8, empty-lines, expect-hostname, kernel, no-hostname, no-multi-line, no-parse, sanitize-utf8, store-legacy-msghdr, store-raw-message, syslog-protocol, validate-utf8 |
Default: | empty set |
Description: Specifies the log parsing options of the source.
-
assume-utf8: The
assume-utf8
flag assumes that the incoming messages are UTF-8 encoded, but does not verify the encoding. If you explicitly want to validate the UTF-8 encoding of the incoming message, use thevalidate-utf8
flag. -
empty-lines: Use the
empty-lines
flag to keep the empty lines of the messages. By default, AxoSyslog removes empty lines automatically. -
expect-hostname: If the
expect-hostname
flag is enabled, AxoSyslog will assume that the log message contains a hostname and parse the message accordingly. This is the default behavior for TCP sources. Note that pipe sources use theno-hostname
flag by default. -
guess-timezone: Attempt to guess the timezone of the message if this information is not available in the message. Works when the incoming message stream is close to real time, and the timezone information is missing from the timestamp.
-
kernel: The
kernel
flag makes the source default to theLOG_KERN | LOG_NOTICE
priority if not specified otherwise. -
no-header: The
no-header
flag triggers AxoSyslog to parse only thePRI
field of incoming messages, and put the rest of the message contents into$MSG
.Its functionality is similar to that of the
no-parse
flag, except theno-header
flag does not skip thePRI
field.Note Essentially, theno-header
flag signals AxoSyslog that thesyslog
header is not present (or does not adhere to the conventions / RFCs), so the entire message (except from thePRI
field) is put into$MSG
.Example: using the no-header flag with the syslog-parser() parser
The following example illustrates using the
no-header
flag with thesyslog-parser()
parser:parser p_syslog { syslog-parser( flags(no-header) ); };
-
no-hostname: Enable the
no-hostname
flag if the log message does not include the hostname of the sender host. That way AxoSyslog assumes that the first part of the message header is ${PROGRAM} instead of ${HOST}. For example:source s_dell { network( port(2000) flags(no-hostname) ); };
-
no-multi-line: The
no-multi-line
flag disables line-breaking in the messages: the entire message is converted to a single line. Note that this happens only if the underlying transport method actually supports multi-line messages. Currently thefile()
andpipe()
drivers support multi-line messages. -
no-parse: By default, AxoSyslog parses incoming messages as syslog messages. The
no-parse
flag completely disables syslog message parsing and processes the complete line as the message part of a syslog message. The AxoSyslog application will generate a new syslog header (timestamp, host, and so on) automatically and put the entire incoming message into the MESSAGE part of the syslog message (available using the${MESSAGE}
macro). This flag is useful for parsing messages not complying to the syslog format.If you are using the
flags(no-parse)
option, then syslog message parsing is completely disabled, and the entire incoming message is treated as the ${MESSAGE} part of a syslog message. In this case, AxoSyslog generates a new syslog header (timestamp, host, and so on) automatically. Note that even thoughflags(no-parse)
disables message parsing, some flags can still be used, for example, theno-multi-line
flag. -
dont-store-legacy-msghdr: By default, AxoSyslog stores the original incoming header of the log message. This is useful if the original format of a non-syslog-compliant message must be retained (AxoSyslog automatically corrects minor header errors, for example, adds a whitespace before
msg
in the following message:Jan 22 10:06:11 host program:msg
). If you do not want to store the original header of the message, enable thedont-store-legacy-msghdr
flag. -
sanitize-utf8: When using the
sanitize-utf8
flag, AxoSyslog converts non-UTF-8 input to an escaped form, which is valid UTF-8.Prior to version 4.6, this flag worked only when parsing RFC3164 messages. Starting with version 4.6, it works also for RFC5424 and raw messages.
-
store-raw-message: Save the original message as received from the client in the
${RAWMSG}
macro. You can forward this raw message in its original form to another AxoSyslog node using thesyslog-ng()
destination, or to a SIEM system, ensuring that the SIEM can process it. Available only in 3.16 and later. -
syslog-protocol: The
syslog-protocol
flag specifies that incoming messages are expected to be formatted according to the new IETF syslog protocol standard (RFC5424), but without the frame header. Note that this flag is not needed for thesyslog
driver, which handles only messages that have a frame header. -
validate-utf8: The
validate-utf8
flag enables encoding-verification for messages.Prior to version 4.6, this flag worked only when parsing RFC3164 messages. Starting with version 4.6, it works also for RFC5424 and raw messages.
For RFC5424-formatted messages, if the BOM character is missing, but the message is otherwise UTF-8 compliant, AxoSyslog automatically adds the BOM character to the message.
The byte order mark (BOM) is a Unicode character used to signal the byte-order of the message text.
For the syslog-parser()
you can also set the check-hostname
flag, which is equivalent with the check-hostname()
global option, but only applies to this parser.
sdata-prefix()
Type: | string |
Default: | .SDATA. |
Available in AxoSyslog 4.1 and later.
Description: Adds a specific string before the names of the parsed SDATA fields to store the name-value pairs created from the SDATA fields separately. Note that unless the value of sdata-prefix
starts with .SDATA.
, using this option excludes the parsed fields from the sdata
and rfc5424
scopes of the value pairs.
template()
Synopsis: | template("${<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}
).