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syslog-ng Premium Edition 7.0.30 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng PE The syslog-ng PE quick-start guide The syslog-ng PE configuration file Collecting log messages — sources and source drivers
How sources work default-network-drivers: Receive and parse common syslog messages internal: Collecting internal messages file: Collecting messages from text files google-pubsub: collecting messages from the Google Pub/Sub messaging service wildcard-file: Collecting messages from multiple text files linux-audit: Collecting messages from Linux audit logs mssql, oracle, sql: collecting messages from an SQL database network: Collecting messages using the RFC3164 protocol (network() driver) office365: Fetching logs from Office 365 osquery: Collect and parse osquery result logs pipe: Collecting messages from named pipes program: Receiving messages from external applications python: writing server-style Python sources python-fetcher: writing fetcher-style Python sources snmptrap: Read Net-SNMP traps syslog: Collecting messages using the IETF syslog protocol (syslog() driver) system: Collecting the system-specific log messages of a platform systemd-journal: Collecting messages from the systemd-journal system log storage systemd-syslog: Collecting systemd messages using a socket tcp, tcp6,udp, udp6: Collecting messages from remote hosts using the BSD syslog protocol udp-balancer: Receiving UDP messages at very high rate unix-stream, unix-dgram: Collecting messages from UNIX domain sockets windowsevent: Collecting Windows event logs
Sending and storing log messages — destinations and destination drivers
elasticsearch2>: Sending messages directly to Elasticsearch version 2.0 or higher (DEPRECATED) elasticsearch-http: Sending messages to Elasticsearch HTTP Event Collector file: Storing messages in plain-text files google_pubsub(): Sending logs to the Google Cloud Pub/Sub messaging service hdfs: Storing messages on the Hadoop Distributed File System (HDFS) http: Posting messages over HTTP kafka(): Publishing messages to Apache Kafka (Java implementation) (DEPRECATED) kafka-c(): Publishing messages to Apache Kafka using the librdkafka client (C implementation) logstore: Storing messages in encrypted files mongodb: Storing messages in a MongoDB database network: Sending messages to a remote log server using the RFC3164 protocol (network() driver) pipe: Sending messages to named pipes program: Sending messages to external applications python: writing custom Python destinations sentinel(): Sending logs to the Microsoft Azure Sentinel cloud snmp: Sending SNMP traps smtp: Generating SMTP messages (email) from logs splunk-hec: Sending messages to Splunk HTTP Event Collector sql(): Storing messages in an SQL database stackdriver: Sending logs to the Google Stackdriver cloud syslog: Sending messages to a remote logserver using the IETF-syslog protocol syslog-ng(): Forward logs to another syslog-ng node tcp, tcp6, udp, udp6: Sending messages to a remote log server using the legacy BSD-syslog protocol (tcp(), udp() drivers) unix-stream, unix-dgram: Sending messages to UNIX domain sockets usertty: Sending messages to a user terminal — usertty() destination Client-side failover
Routing messages: log paths, flags, and filters Global options of syslog-ng PE TLS-encrypted message transfer Advanced Log Transport Protocol Reliability and minimizing the loss of log messages Manipulating messages parser: Parse and segment structured messages Processing message content with a pattern database Correlating log messages Enriching log messages with external data Monitoring statistics and metrics of syslog-ng Multithreading and scaling in syslog-ng PE Troubleshooting syslog-ng Best practices and examples The syslog-ng manual pages Glossary

Limitations of the XML parser

The XML parser comes with certain limitations.

Using the list-handling functionality with vector-like structures

The XML parser uses the list-handling functionality to handle lists in the XML. The list-handling functionality has limitations when handling name-value pairs or quoting in SDATA as described below. Note that you can disable the list-handling functionality if needed.

The list-handling functionality of the XML parser separates vector-like structures by a comma as separate entries. Using the following structure as an example:

    <entry>value 2</entry>

After parsing, the entries are separated by a comma. If an entry has a space or is separated by a comma, for example, value 2 or Doe,John in the previous example, quoting is applied to the entry:

vector.entry = value1,"value 2","Doe,John",value3...valueN
Using the list-handling functionality with name-value pairs

As every value in name-value pairs can be quoted, One Identity recommends that you access name-values as lists as follows:

  • Use list-related template functions on the list created by the XML parser.
  • Use type-hinting using the format-json template function as shown in the example below:

    template("$(format-json --scope dot-nv-pairs LIST=list(${.xml.Event.EventData.Data}))\n")
Using the list-handling functionality with SDATA

According to RFC5424, SDATA parameter values must be quoted with double-quote ('"') characters. If the value contains double-quotes, they must be escaped with a backslash (\) character.

Due to the list-handling functionality of the XML parser, parsed XML text contents are also quoted using double-quote ('"') characters. As parsed XML text content are part of the message, they are quoted when used as SDATA parameter values.

Using the following structure as an example:

<Data>Testing testing</Data>

The expected name-value pair is as follows:

Event.Data = 42,"Testing testing"

In SDATA, this is quoted as shown below:

[Event Data="42,\"Testing testing\""]
Disabling the list-handling functionality

To disable the list-handling functionality, use the create_lists(yes/no) option as shown below. The default value is set to yes.

parser p_xml {

Note that if you disable the list-handling functionality, the XML parser cannot address each element of a vector-like structure individually. Using the following structure as an example:


After parsing, the entries are not addressed individually. Instead, the text of the entries are concatenated:

vector.entry = "value1value2...valueN"

The XML parser does not support CDATA. CDATA inside the XML input is ignored. This is true for the processing instructions as well.

Inherited limitations

The XML parser is based on the glib XML subset parser, called "GMarkup" parser, which is not a full-scale XML parser. It is intended to parse a simple markup format that is a subset of XML. Some limitations are inherited:

  • Do not use the XML parser if you expect to interoperate with applications generating full-scale XML. Instead, use it for application data files, configuration files, log files, and so on, where you know your application will be the only one writing the file.

  • The XML parser is not guaranteed to display an error message in the case of invalid XML. It may accept invalid XML. However, it does not accept XML input that is not well-formed (a condition that is weaker than requiring XML to be valid).

No support for long keys

If the key is longer than 255 characters, syslog-ng drops the entry and an error log is emitted. There is no chunking or any other way of recovering data, not even partial data. The entry will be replaced by an empty string.

Options of the XML parsers

The XML parser has the following options.

Synopsis: create-lists()
Format: yes|no
Default: yes
Mandatory: no

Description: If set, the list-handling functionality of the XML parser separates vector-like structures by a comma as separate entries. For more information, see Limitations of the XML parsers.

Synopsis: drop-invalid()
Format: yes|no
Default: no
Mandatory: no

Description: If set, messages with an invalid XML will be dropped entirely.

Synopsis: exclude-tags()
Format: list of globs


If not set, no filtering is done.

Mandatory: no

Description: The XML parser matches tags against the listed globs. If there is a match, the given subtree of the XML will be omitted.

Example: Using exclude_tags
parser xml_parser {
       xml(template("$MSG") exclude_tags("tag1", "tag2", "inner*"));

From this XML input:


The following output is generated:

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, ${} .

  • 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( option.

Names starting with a dot (for example, .example) are reserved for use by syslog-ng PE. 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.)

The prefix() option is optional and its default value is ".xml".

Synopsis: strip-whitespaces()
Format: yes|no
Default: no
Mandatory: no

Description: Strip the whitespaces from the XML text nodes before adding them to the message.

Example: Using strip-whitespaces
parser xml_parser {
       xml(template("$MSG") strip_whitespaces(yes));

From this XML input:

<tag1> Tag </tag1>

The following output is generated:

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}).

Parsing dates and timestamps

The date parser can extract dates from non-syslog messages. It operates by default on the ${MSG} 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 timestamp(recvd) option.)

NOTE: Note that parsing will fail if the format string does not match the entire template or field. Since by default syslog-ng Premium Edition (syslog-ng PE) 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.

parser parser_name {
Example: Using the date-parser()

In the following example, syslog-ng PE 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, syslog-ng PE 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 {
    parser { date-parser(format("%d/%b/%Y:%H:%M:%S %Z") template("${MY_DATE}")); };

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 ${MSG} 0 24)") );

In syslog-ng PE version 7.0.18 and later, you can specify a comma-separated list of formats to parse multiple date formats with a single parser. For example:

    "%F %T,%f",
    "%F %T"

Options ofdate-parser() parsers

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

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:

Synopsis: format(string)

Description: Specifies the format how syslog-ng PE 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. eg: PST
%z      timezone in format -/+0000

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

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}).

Synopsis: stamp | recvd
Default: stamp

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

Synopsis: timezone(string)

Description: If this option is set, syslog-ng PE 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 as using the name of the (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.

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