source-flags.md

flags()

|Accepted values:| assume-utf8, empty-lines, expect-hostname, kernel, no-hostname, no-multi-line, no-parse, sanitize-utf8, store-legacy-msghdr, store-raw-message, syslog-protocol, threaded, validate-utf8, no-piggyback-errors| |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 the validate-utf8 flag.

• empty-lines: Use the empty-lines flag to keep the empty lines of the messages. By default, {{ site.product.short_name }} removes empty lines automatically.

• expect-hostname: If the expect-hostname flag is enabled, syslog-ng OSE 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 the no-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.

• ignore-aux-data: This flag enables the source to ignore auxiliary data.

• kernel: The kernel flag makes the source default to the LOG_KERN | LOG_NOTICE priority if not specified otherwise.

• no-header: The no-header flag triggers {{ site.product.short_name }} to parse only the PRI 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 the no-header flag does not skip the PRI field.

  NOTE: Essentially, the no-header flag signals {{ site.product.short_name }} that the syslog header is not present (or does not adhere to the conventions / RFCs), so the entire message (except from the PRI field) is put into ${MSG}. {: .notice--info}

  Example: using the no-header flag with the syslog-parser() parser

  The following example illustrates using the no-header flag with the syslog-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 {{ site.product.short_name }} 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 the file() and pipe() drivers support multi-line messages.

• no-parse: By default, {{ site.product.short_name }} 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 {{ site.product.short_name }} 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, {{ site.product.short_name }} generates a new syslog header (timestamp, host, and so on) automatically. Note that even though flags(no-parse) disables message parsing, some flags can still be used, for example, the no-multi-line flag.

• dont-store-legacy-msghdr: By default, {{ site.product.short_name }} 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 ({{ site.product.short_name }} 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 the dont-store-legacy-msghdr flag.

• sanitize-utf8: When using the sanitize-utf8 flag, {{ site.product.short_name }} converts non-UTF-8 input to an escaped form, which is valid UTF-8.

• 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 {{ site.product.short_name }} node using the [[syslog-ng() destination|adm-dest-syslogng]], 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 (RFC-5424), but without the frame header. Note that this flag is not needed for the syslog driver, which handles only messages that have a frame header.

• threaded: The threaded flag enables multithreading for the destination. For details on multithreading, see Multithreading and scaling in {{ site.product.short_name }}.

  If a parsing or syntax error occurs, use "threaded" nested in quotation marks.

  flags(
      validate-utf8
      "threaded"
      store-raw-message
  )
  

  NOTE: The file destination uses multiple threads only if the destination filename contains macros. {: .notice--info}

• validate-utf8: The validate-utf8 flag enables encoding-verification for messages formatted according to the new IETF syslog standard (for details, see IETF-syslog messages. If the BOM¹ character is missing, but the message is otherwise UTF-8 compliant, {{ site.product.short_name }} automatically adds the BOM character to the message.

• no-piggyback-errors: On failure, the original message will be left as it was before parsing, the value of $MSGFORMAT will be set to syslog:error, and a tag (see Tagging messages) will be placed on the message corresponding to the parser's failure.

• piggyback-errors: On failure, the old behaviour is used (clearing the entire message then syslog-ng will generate a new message in place of the old one describing the parser's error).

Footnotes

1. The byte order mark (BOM) is a Unicode character used to signal the byte-order of the message text. ↩