Parsing dates and timestamps

1: Options of date-parser() parsers

The date parser can extract dates from non-syslog messages. It operates by default on the ${MESSAGE} part of the log message, but can operate on any template or field provided. The parsed date will be available as the sender date (that is, the ${S_DATE}, ${S_ISODATE}, ${S_MONTH}, and so on, and related macros). (To store the parsed date as the received date, use the time-stamp(recvd) option.)

Note Note that parsing will fail if the format string does not match the entire template or field. Since by default AxoSyslog uses the ${MESSAGE} part of the log message, parsing will fail, unless the log message contains only a date, but that is unlikely, so practically you will have to segment the message (for example, using a csv-parser()) before using the date-parser(). You can also use date-parser() to parse dates received in a JSON or key-value-formatted log message.

Declaration

   parser parser_name {
        date-parser(
            format("<format-string-for-the-date>")
            template("<field-to-parse>")
        );
    };

Example: Using the date-parser()

In the following example, AxoSyslog parses dates like 01/Jan/2016:13:05:05 PST from a field called MY_DATE using the following format string: format("%d/%b/%Y:%H:%M:%S %Z") (how you create this field from the incoming message is not shown in the example). In the destination template every message will begin with the timestamp in ISODATE format. Since the syslog parser is disabled, AxoSyslog will include the entire original message (including the original timestamp) in the ${MESSAGE} macro.

   source s_file {
        file("/tmp/input" flags(no-parse));
    };
    
    destination d_file {
        file(
            "/tmp/output"
            template("${S_ISODATE} ${MESSAGE}\n")
        );
    };
    
    log {
        source(s_file);
        parser { date-parser(format("%d/%b/%Y:%H:%M:%S %Z") template("${MY_DATE}")); };
        destination(d_file);
    };

In the template option, you can use template functions to specify which part of the message to parse with the format string. The following example selects the first 24 characters of the ${MESSAGE} macro.

   date-parser(format("%d/%b/%Y:%H:%M:%S %Z") template("$(substr ${MESSAGE} 0 24)") );

In AxoSyslog version 3.23 and later, you can specify a comma-separated list of formats to parse multiple date formats with a single parser. For example:

   date-parser(format(
        "%FT%T.%f",
        "%F %T,%f",
        "%F %T"
    ));

If you need to modify or correct the timezone of the message after parsing, see Rewrite the timezone of a message.

1 - Options of date-parser() parsers

The date-parser() parser has the following options.

format()


Synopsis:	format(string)
Default:

Description: Specifies the format how AxoSyslog should parse the date. You can use the following format elements:

%%      PERCENT
%a      day of the week, abbreviated
%A      day of the week
%b      month abbr
%B      month
%c      MM/DD/YY HH:MM:SS
%C      ctime format: Sat Nov 19 21:05:57 1994
%d      numeric day of the month, with leading zeros (eg 01..31)
%e      like %d, but a leading zero is replaced by a space (eg  1..31)
%f      microseconds, leading 0's, extra digits are silently discarded
%D      MM/DD/YY
%G      GPS week number (weeks since January 6, 1980)
%h      month, abbreviated
%H      hour, 24 hour clock, leading 0's)
%I      hour, 12 hour clock, leading 0's)
%j      day of the year
%k      hour
%l      hour, 12 hour clock
%L      month number, starting with 1
%m      month number, starting with 01
%M      minute, leading 0's
%n      NEWLINE
%o      ornate day of month -- "1st", "2nd", "25th", etc.
%p      AM or PM
%P      am or pm (Yes %p and %P are backwards :)
%q      Quarter number, starting with 1
%r      time format: 09:05:57 PM
%R      time format: 21:05
%s      seconds since the Epoch, UCT
%S      seconds, leading 0's
%t      TAB
%T      time format: 21:05:57
%U      week number, Sunday as first day of week
%w      day of the week, numerically, Sunday == 0
%W      week number, Monday as first day of week
%x      date format: 11/19/94
%X      time format: 21:05:57
%y      year (2 digits)
%Y      year (4 digits)
%Z      timezone in ascii format (for example, PST), or in format -/+0000
%z      timezone in ascii format (for example, PST), or in format -/+0000  (Required element)

Warning

When using the %z and %Z format codes, consider that while %z strictly expects a specified timezone, and triggers a warning if the timezone is missing, %Z does not trigger a warning if the timezone is not specified.

For further information about the %z and %Z format codes, see the ‘DESCRIPTION’ section on the srtptime(3) - NetBSD Manual Pages.

For example, for the date 01/Jan/2016:13:05:05 PST use the following format string: "%d/%b/%Y:%H:%M:%S %Z"

In AxoSyslog version 3.23 and later, you can specify a comma-separated list of formats to parse multiple date formats with a single parser. For example:

   date-parser(format(
        "%FT%T.%f",
        "%F %T,%f",
        "%F %T"
    ));

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}).

flags()


Type:	guess-timezone
Default:	empty string

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. For example:

   date-parser(flags(guess-timezone));

time-stamp()


Synopsis:	`stamp` or `recvd`
Default:	stamp

Description: Determines if the parsed date values are treated as sent or received date. If you use time-stamp(stamp), AxoSyslog adds the parsed date to the S_ macros (corresponding to the sent date). If you use time-stamp(recvd), AxoSyslog adds the parsed date to the R_ macros (corresponding to the received date).

time-zone()


Synopsis:	time-zone(string)
Default:

Description: If this option is set, AxoSyslog assumes that the parsed timestamp refers to the specified timezone. The timezone set in the time-zone() option overrides any timezone information parsed from the timestamp.

The timezone can be specified by using the name, for example, time-zone("Europe/Budapest")), or as the timezone offset in +/-HH:MM format, for example, +01:00). On Linux and UNIX platforms, the valid timezone names are listed under the /usr/share/zoneinfo directory.

value()


Synopsis:	string
Default:

Available in AxoSyslog 4.1 and later.

Description: Instruct date-parser() to store the resulting timestamp in a name-value pair specified in value(), instead of changing the timestamp value of the LogMessage.