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syslog-ng Premium Edition 6.0.24 - Administration Guide

Preface Chapter 1. Introduction to syslog-ng Chapter 2. The concepts of syslog-ng Chapter 3. Installing syslog-ng Chapter 4. The syslog-ng PE quick-start guide Chapter 5. The syslog-ng PE configuration file Chapter 6. Collecting log messages — sources and source drivers Chapter 7. Sending and storing log messages — destinations and destination drivers Chapter 8. Routing messages: log paths, reliability, and filters Chapter 9. Global options of syslog-ng PE Chapter 10. TLS-encrypted message transfer Chapter 12.  Reliable Log Transfer Protocol™ Chapter 13. Reliability and minimizing the loss of log messages Chapter 14. Manipulating messages Chapter 15. Parsing and segmenting structured messages Chapter 16. Processing message content with a pattern database Chapter 17. Statistics and metrics of syslog-ng Chapter 18. Multithreading and scaling in syslog-ng PE Chapter 19. Troubleshooting syslog-ng Chapter 20. Best practices and examples GNU General Public License v2

Message size and encoding

Internally, syslog-ng PE represents every message as UTF-8. The maximal length of the log messages is limited by the log-msg-size() option: if a message is longer than this value, syslog-ng PE truncates the message at the location it reaches the log-msg-size() value, and discards the rest of the message.

When encoding is set in a source (using the encoding() option) and the message is longer (in bytes) than log-msg-size() in UTF-8 representation, syslog-ng PE splits the message at an undefined location (because the conversion between different encodings is not trivial).

Structuring macros, metadata, and other value-pairs

Available in syslog-ng PE5.1 and later.

The syslog-ng PE application allows you to select and construct name-value pairs from any information already available about the log message, or extracted from the message itself. You can directly use this structured information, for example, in the following places:

When using value-pairs, there are three ways to specify which information (that is, macros or other name-value pairs) to include in the selection.

  • Select groups of macros using the scope() parameter, and optionally remove certain macros from the group using the exclude() parameter.

  • List specific macros to include using the key() parameter.

  • Define new name-value pairs to include using the pair() parameter.

These parameters are detailed in the section called “value-pairs()”.

Structuring macros, metadata, and other value-pairs

By default, syslog-ng PE handles every data as strings. However, certain destinations and data formats (for example, SQL, MongoDB, JSON) support other types of data as well, for example, numbers or dates. The syslog-ng PE application allows you to specify the data type in templates (this is also called type-hinting). If the destination driver supports data types, it converts the incoming data to the specified data type. For example, this allows you to store integer numbers as numbers in MongoDB, instead of strings.

 Caution:

Hazard of data loss! If syslog-ng PE cannot convert the data into the specified type, an error occurs, and syslog-ng PE drops the message by default. To change how syslog-ng PE handles data-conversion errors, see the section called “on-error()”.

To use type-hinting, enclose the macro or template containing the data with the type: <datatype>("<macro>"), for example: int("$PID").

Currently the mongodb() destination and the format-json template function supports data types.

Example 2.6. Using type-hinting

The following example stores the MESSAGE, PID, DATE, and PROGRAM fields of a log message in a MongoDB database. The DATE and PID parts are stored as numbers instead of strings.

						mongodb(
						value-pairs(pair("date", datetime("$UNIXTIME"))
						pair("pid", int64("$PID"))
						pair("program", "$PROGRAM"))
						pair("message", "$MESSAGE"))
						)
						);

The following example formats the same fields into JSON.

$(format-json date=datetime("$UNIXTIME") pid=int64("$PID") program="$PROGRAM" message="$MESSAGE")

The syslog-ng PE application currently supports the following data-types.

  • boolean: Converts the data to a boolean value. Anything that begins with a t or 1 is converted to true, anything that begins with an f or 0 is converted to false.

  • datetime: Use it only with UNIX timestamps, anything else will likely result in an error. This means that currently you can use only the $UNIXTIME macro for this purpose.

  • literal: The data as a literal string, without adding any quotes or escape characters.

  • int or int32: 32-bit integer.

  • int64: 64-bit integer.

  • string: The data as a string.

value-pairs()
Type: parameter list of thevalue-pairs() option
Default: 
empty string

Description: The value-pairs() option allows you to select specific information about a message easily using predefined macro groups. The selected information is represented as name-value pairs and can be used formatted to JSON format, or directly used in a mongodb() destination.

Example 2.7. Using thevalue-pairs() option

The following example selects every available information about the log message, except for the date-related macros (R_* and S_*), selects the .SDATA.meta.sequenceId macro, and defines a new value-pair called MSGHDR that contains the program name and PID of the application that sent the log message. 

						value-pairs(
						scope(nv_pairs core syslog all_macros selected_macros everything)
						exclude("R_*")
						exclude("S_*")
						key(".SDATA.meta.sequenceId")
						pair("MSGHDR" "$PROGRAM[$PID]: ")
						)

The following example selects the same information as the previous example, but converts it into JSON format.

						$(format-json --scope nv_pairs,core,syslog,all_macros,selected_macros,everything \
						--exclude R_* --exclude S_* --key .SDATA.meta.sequenceId \
						--pair MSGHDR="$PROGRAM[$PID]: ")

NOTE: Every macro is included in the selection only once, but redundant information may appear if multiple macros include the same information (for example, including several date-related macros in the selection).

The value-pairs() option has the following parameters. The parameters are evaluated in the following order:

  1. scope()

  2. exclude()

  3. key()

  4. pair()

  5. subkeys()

exclude()
Type: Space-separated list of macros to remove from the selection created using thescope() option.
Default: empty string

Description: This option removes the specified macros from the selection. Use it to remove unneeded macros selected using the scope() parameter.

For example, the following example removes the SDATA macros from the selection.

									value-pairs(
									scope(rfc5424 selected_macros)
									exclude(".SDATA*")
									)

The name of the macro to remove can include wildcards (*, ?). Regular expressions are not supported.

key()
Type: Space-separated list of macros to be included in selection
Default: empty string

Description: This option selects the specified macros. The selected macros will be included as MACRONAME = MACROVALUE, that is using key("HOST") will result in HOST = $HOST. You can use wildcards (*, ?) to select multiple macros. For example: 

									value-pairs(
									scope(rfc3164)
									key("HOST"))
pair()
Type: name value pairs in "<NAME>" "<VALUE>" format
Default: empty string

Description: This option defines a new name-value pair to be included in the message. The value part can include macros, templates, and template functions as well. For example: 

									value-pairs(
									scope(rfc3164)
									pair("TIME" "$HOUR:$MIN")
									pair("MSGHDR" "$PROGRAM[$PID]: "))
rekey()
Type: <pattern-to-select-names>, <list of transformations>
Default: empty string

Description: This option allows you to manipulate and modify the name of the value-pairs. You can define transformations, which are are applied to the selected name-value pairs. The first parameter of the rekey() option is a glob pattern that selects the name-value pairs to modify. If you omit the pattern, the transformations are applied to every key of the scope. For details on globs, see the section called “glob”.

  • If rekey() is used within a key() option, the name-value pairs specified in the glob of the key() option are transformed.

  • If rekey() is used outside the key() option, every name-value pair of the scope() is transformed.

The following transformations are available:

add-prefix("<my-prefix>")

Adds the specified prefix to every name. For example, rekey( add-prefix("my-prefix."))

replace-prefix("<prefix-to-replace>", "<new-prefix>")

Replaces a substring at the beginning of the key with another string. Only prefixes can be replaced. For example, replace-prefix(".class", ",patterndb") changes the beginning tag .class to .patterndb

shift("<number>")

Cuts the specified number of characters from the beginning of the name.

Example 2.8. Using the rekey() option

The following sample selects every value-pair that begins with .cee., deletes this prefix by cutting 4 characters from the names, and adds a new prefix (events.). 

											value-pairs(
											key(".cee.*"
											rekey(
											shift(4)
											add-prefix("events.")
											)
											)
											)

The rekey() option can be used with the format-json template-function as well, using the following syntax: 

$(format-json --rekey .cee.* --add-prefix events.)

scope()
Type: space-separated list of macro groups to include in selection
Default: empty string

Description: This option selects predefined groups of macros. The following groups are available:

  • nv-pairs: Every soft macro (name-value pair) associated with the message, except the ones that start with a dot (.) character. Macros starting with a dot character are generated within syslog-ng PE and are not originally part of the message, therefore are not included in this group.

  • dot-nv-pairs: Every soft macro (name-value pair) associated with the message which starts with a dot (.) character. For example, .classifier.rule_id and .sdata.*. Macros starting with a dot character are generated within syslog-ng PE and are not originally part of the message.

  • all-nv-pairs: Include every soft macro (name-value pair). Equivalent to using both nv-pairs and dot-nv-pairs.

  • rfc3164: The macros that correspond to the RFC3164 (legacy or BSD-syslog) message format: $FACILITY, $PRIORITY, $HOST, $PROGRAM, $PID, $MESSAGE, and $DATE.

  • rfc5424: The macros that correspond to the RFC5424 (IETF-syslog) message format: $FACILITY, $PRIORITY, $HOST, $PROGRAM, $PID, $MESSAGE, $MSGID, $DATE, and the metadata from the structured-data (SDATA) part of RFC5424-formatted messages, that is, every macro that starts with .SDATA..

    The rfc5424 group does not contain any metadata about the message, only information that was present in the original message. To include the most commonly used metadata (for example, the $SOURCEIP macro), use the selected-macros group instead.

  • all-macros: Include every hard macro. This group is mainly useful for debugging, as it contains redundant information (for example, the date-related macros include the date-related information several times in various formats).

  • selected-macros: Include the macros of the rfc3164 groups, and the most commonly used metadata about the log message: the $TAGS, $SOURCEIP, and $SEQNUM macros.

  • sdata: The metadata from the structured-data (SDATA) part of RFC5424-formatted messages, that is, every macro that starts with .SDATA.

  • everything: Include every hard and soft macros. This group is mainly useful for debugging, as it contains redundant information (for example, the date-related macros include the date-related information several times in various formats).

For example:

									value-pairs(
									scope(rfc3164 selected-macros))
subkeys()
Type: name value pairs to select
Default: empty string

Description: This option selects every value-pair that has a name beginning with the specified prefix, but removes the prefix when formatting the message. For example: 

									value-pairs(
									scope(rfc3164)
									subkeys(".cef.")
									)

Things to consider when forwarding messages between syslog-ng PE hosts

When you send your log messages from a syslog-ng PE client through the network to a syslog-ng PE server, you can use different protocols and options. Every combination has its advantages and disadvantages. The most important thing is to use matching protocols and options, so the server handles the incoming log messages properly.

In syslog-ng PE you can change many aspects of the network communication. First of all, there is the structure of the messages itself. Currently, syslog-ng PE supports two standard syslog protocols: the BSD (RFC3164) and the syslog (RFC5424) message format.

These RFCs describe the format and the structure of the log message, and add a (lightweight) framing around the messages. You can set this framing/structure by selecting the appropriate driver in syslog-ng PE. There are two drivers you can use: the network() driver and the syslog() driver. The syslog() driver is for the syslog (RFC5424) protocol and the network() driver is for the BSD (RFC3164) protocol.

The tcp() and udp() drivers are now deprecated, they are essentially equivalent with the network(transport(tcp)) and network(transport(udp)) drivers.

In addition to selecting the driver to use, both drivers allow you to use different transport-layer protocols: TCP and UDP, and optionally also higher-level transport protocols: TLS (over TCP, and RLTP (optionally using TLS). To complicate things a bit more, you can configure the network() driver (corresponding to the BSD (RFC3164) protocol) to send the messages in the syslog (RFC5424) format (but without the framing used in RFC5424) using the flag(syslog-protocol) option.

Because some combination of drivers and options are invalid, you can use the following drivers and options as sources and as destinations:

  1. syslog(transport(tcp))

  2. syslog(transport(udp))

  3. syslog(transport(rltp))

  4. syslog(transport(tls))

  5. syslog(transport(rltp(tls-required(yes)))

  6. network(transport(tcp))

  7. network(transport(udp))

  8. network(transport(rltp))

  9. network(transport(tls))

  10. network(transport(rltp(tls-required(yes)))

  11. network(transport(tcp) flag(syslog-protocol))

  12. network(transport(udp) flag(syslog-protocol))

  13. network(transport(rltp)flag(syslog-protocol))

  14. network(transport(tls) flag(syslog-protocol))

  15. network(transport(rltp(tls-required(yes)) flag(syslog-protocol))

If you use the same driver and options in the destination of your syslog-ng PE client and the source of your syslog-ng PE server, everything should work as expected. Unfortunately there are some other combinations, that seem to work, but result in losing parts of the messages. The following table show the combinations:

Table 2.6. Source-destination driver combinations

S \ D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1 ✔ - - - - ! - - - - ! - - - -
2 - ✔ - - - - ! - - - - ! - - -
3 - - ✔ - - - - ! - - - - ! - -
4 - - - ✔ - - - - ! - - - - ! -
5 - - - - ✔ - - - - ! - - - - !
6 - - - - - ✔ - - - - ✔? - - - -
7 - ✔? - - - - ✔ - - - - ✔? - - -
8 - - ✔? - - - - ✔ - - - - ✔? - -
9 - - - - - - - - ✔ - - - - ✔? -
10 - - - - ✔? - - - - ✔ - - - - ✔?
11 ! - - - - ! - - - - ✔ - - - -
12 - ! - - - - ! - - - - ✔ - - -
13 - - ! - - - - ! - - - - ✔ - -
14 - - - ! - - - - ! - - - - ✔ -
15 - - - - ! - - - - ! - - - - ✔

  • - This method does not work. The logs will not get to the server.

  • ✔ This method works.

  • ! This method has some visible drawbacks. The logs go through, but some of the values are missing/misplaced/and so on.

  • ✔? This method seems to work, but it is not recommended because this can change in a future release.

The configuration options of the syslog-ng Agent for Windows application are much more limited. The configurable elements are:

  • Protocol: (Legacy BSD Syslog Protocol, Syslog Protocol, Snare Protocol)

  • Use SSL option

  • Use syslog-ng proprietary Reliable Log Transfer Protocol (RLTP) option

The protocol corresponds to the network() and syslog() drivers of syslog-ng PE, except that the syslog-ng PE server does not support the Snare protocol.

The Use syslog-ng proprietary Reliable Log Transfer Protocol (RLTP) option is equivalent to the transport(rltp) option.

The Use SSL option is the Windows equivalent of the transport(tls) option if RLTP is not set, and to the transport(rltp(tls-required(yes)) otherwise.

Therefore with syslog-ng Agent the following cases are possible:

Table 2.7. Source-destination driver combinations in syslog-ng Agent for Windows

The syslog-ng Agent for Windows setting Corresponding syslog-ng PE server setting
Protocol: Syslog Protocol syslog(transport(tcp))
Protocol: Syslog Protocol, Use RLTP on syslog(transport(rltp))
Protocol: Syslog Protocol, Use SSL on syslog(transport(tls))
Protocol: Syslog Protocol, Use RLTP on, Use SSL on syslog(transport(rltp(tls-required(yes)))
Protocol: Legacy BSD Syslog Protocol network(transport(tcp))
Protocol: Legacy BSD Syslog Protocol, Use RLTP on network(transport(rltp))
Protocol: Legacy BSD Syslog Protocol, Use SSL on network(transport(tls))
Protocol: Legacy BSD Syslog Protocol, Use RLTP on, Use SSL on network(transport(rltp(tls-required(yes)))

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