syslog-ng Premium Edition 7.0.12 - Administration Guide

How syslog-ng PE interacts with Apache Kafka

When stopping the syslog-ng PE application, syslog-ng PE will not stop until all Java threads are finished, including the threads started by the Kafka Producer. There is no way (except for the kill -9 command) to stop syslog-ng PE before the Kafka Producer stops. To change this behavior set the properties of the Kafka Producer in its properties file, and reference the file in the properties-file option.

The syslog-ng PE kafka destination tries to reconnect to the brokers in a tight loop. This can look as spinning, because of a lot of similar debug messages. To decrease the amount of such messages, set a bigger timeout using the following properties:

retry.backoff.ms=1000
reconnect.backoff.ms=1000

For details on using property files, see properties-file(). For details on the properties that you can set in the property file, see the Apache Kafka documentation.

Kafka destination options

The kafka destination of syslog-ng PE can directly publish log messages to the Apache Kafka message bus, where subscribers can access them. The kafka destination has the following options.

@module mod-java
@include "scl.conf"

frac-digits()

Description: The syslog-ng application can store fractions of a second in the timestamps according to the ISO8601 format. The frac-digits() parameter specifies the number of digits stored. The digits storing the fractions are padded by zeros if the original timestamp of the message specifies only seconds. Fractions can always be stored for the time the message was received. Note that syslog-ng can add the fractions to non-ISO8601 timestamps as well.

jvm-options()

Description: Specify the Java Virtual Machine (JVM) settings of your Java destination from the syslog-ng PE configuration file.

For example:

jvm-options("-Xss1M -XX:+TraceClassLoading")

You can set this option only as a global option, by adding it to the options statement of the syslog-ng configuration file.

on-error()

Description: Controls what happens when type-casting fails and syslog-ng PE cannot convert some data to the specified type. By default, syslog-ng PE drops the entire message and logs the error. Currently the value-pairs() option uses the settings of on-error().

• drop-message: Drop the entire message and log an error message to the internal() source. This is the default behavior of syslog-ng PE.

• drop-property: Omit the affected property (macro, template, or message-field) from the log message and log an error message to the internal() source.

• fallback-to-string: Convert the property to string and log an error message to the internal() source.

• silently-drop-message: Drop the entire message silently, without logging the error.

• silently-drop-property: Omit the affected property (macro, template, or message-field) silently, without logging the error.

• silently-fallback-to-string: Convert the property to string silently, without logging the error.

log-fifo-size()

Description: The number of messages that the output queue can store.

acks=all
compression.type=snappy

retries()

Description: The number of times syslog-ng PE attempts to send a message to this destination. If syslog-ng PE could not send a message, it will try again until the number of attempts reaches retries, then drops the message.

throttle()

Description: Sets the maximum number of messages sent to the destination per second. Use this output-rate-limiting functionality only when using disk-buffer as well to avoid the risk of losing messages. Specifying 0 or a lower value sets the output limit to unlimited.

time-zone()

Description: Convert timestamps to the timezone specified by this option. If this option is not set, then the original timezone information in the message is used. Converting the timezone changes the values of all date-related macros derived from the timestamp, for example, HOUR. For the complete list of such macros, see Date-related macros.

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.

ts-format()

Description: Override the global timestamp format (set in the global ts-format() parameter) for the specific destination. For details, see ts-format().

logstore: Storing messages in encrypted files

The syslog-ng PE application can store log messages securely in encrypted, compressed and timestamped binary files. Timestamps can be requested from an external Timestamping Authority (TSA).

Logstore files consist of individual chunks, every chunk can be encrypted, compressed, and timestamped separately. Chunks contain compressed log messages and header information needed for retrieving messages from the logstore file.

The syslog-ng PE application generates an SHA-1 hash for every chunk to verify the integrity of the chunk. The hashes of the chunks are chained together to prevent injecting chunks into the logstore file. The syslog-ng PE application can encrypt the logstore using various algorithms, using the aes128 encryption algorithm in CBC mode and the hmac-sha1 hashing (HMAC) algorithm as default. For other algorithms, see cipher() and digest().

The destination filename may include macros which get expanded when the message is written, thus a simple logstore() driver may create several files. For more information on available macros see Macros of syslog-ng PE.

If the expanded filename refers to a directory which does not exist, it will be created depending on the create-dirs() setting (both global and a per destination option).

The logstore() has a single required parameter that specifies the filename that stores the log messages. For the list of available optional parameters, see logstore() destination options.

logstore(filename options());

destination d_logstore { logstore("/var/log/messages.lgs" compress(5) ); };

destination d_logstore {
    logstore("/var/log/messages-logstore.lgs"
        encrypt-certificate("/opt/syslog-ng/etc/syslog-ng/keys/10-100-20-40/public-certificate-of-the-server.pem")
        owner("example")
        group("example")
        perm(0777)
    );
};

options {
        timestamp-url("http://10.50.50.50:8080/");
        timestamp-policy("0.4.0.2023.1.1");
};

Displaying the contents of logstore files

To display the contents of a logstore file, use the lgstool (formerly called logcat) command supplied with syslog-ng, for example, lgstool cat /var/log/messages.lgs. Log messages available in the journal file of the logstore (but not yet written to the logstore file itself) are displayed as well.

To display the contents of encrypted log files, specify the private key of the certificate used to encrypt the file, for example lgstool cat -k private.key /var/log/messages.lgs. The contents of the file are sent to the standard output, so it is possible to use grep and other tools to find particular log messages, for example, lgstool cat /var/log/messages.lgs |grep 192.168.1.1. For further details, see The logstore tool manual page.