value-pairs()

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: Using the value-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]: ")

value-pairs() parameters

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

1. scope()
2. exclude()
3. key()
4. pair()

exclude()

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()

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")
    )

   value-pairs(
        scope(rfc3164)
        key("HOST", "PROGRAM")
    )

omit-empty-values()

Description: If this option is specified, AxoSyslog does not include value-pairs with empty values in the output. For example: $(format-json --scope none --omit-empty-values) or

   value-pairs(
        scope(rfc3164 selected-macros)
        omit-empty-values()
    )

Available in AxoSyslog version 3.21 and later.

pair()

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()

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 glob.

If you want to modify the names of several message fields, see also map-value-pairs: Rename value-pairs to normalize logs.

• 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

  This option was called replace() in AxoSyslog version 3.4.

• lower

  Convert all keys to lowercase. Only supports US ASCII.

• shift("<number>")

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

• shift-levels("<number>")

  Similar to –shift, but instead of cutting characters, it cuts dot-delimited “levels” in the name (including the initial dot). For example, --shift-levels 2 deletes the prefix up to the second dot in the name of the key: .iptables.SRC becomes SRC

• upper

  Convert all keys to uppercase. Only supports US ASCII.

Example: 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()

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 AxoSyslog 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 AxoSyslog 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, $R_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 also has the following alias: syslog-proto. Note that the value of $R_DATE will be listed under the DATE key.

  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).

• none: Reset previously added scopes, for example, to delete automatically-added name-value pairs. The following example deletes every value-pair from the scope, and adds only the ones starting with iptables: $(format-welf --scope none .iptables.*)

For example:

   value-pairs(
        scope(rfc3164 selected-macros)
    )