Kafka destination options
The kafka destination of syslog-ng OSE can directly publish log messages to the Apache Kafka message bus, where subscribers can access them. The kafka destination has the following options.
Required options:
The following options are required: kafka-bootstrap-servers(), topic(). Note that to use kafka, you must add the following lines to the beginning of your syslog-ng OSE configuration:
@module mod-java @include "scl.conf"
client-lib-dir()
| Type: | string |
| Default: | The syslog-ng OSE module directory: /opt/syslog-ng/lib/syslog-ng/java-modules/ |
Description: The list of the paths where the required Java classes are located. For example, class-path("/opt/syslog-ng/lib/syslog-ng/java-modules/:/opt/my-java-libraries/libs/"). If you set this option multiple times in your syslog-ng OSE configuration (for example, because you have multiple Java-based destinations), syslog-ng OSE will merge every available paths to a single list.
For the kafka destination, include the path to the directory where you copied the required libraries (see Prerequisites), for example, client-lib-dir("/opt/syslog-ng/lib/syslog-ng/java-modules/KafkaDestination.jar:/usr/share/kafka/lib/*.jar").
kafka-bootstrap-servers()
| Type: | list of hostnames |
| Default: |
Description: Specifies the hostname or IP address of the Kafka server. When specifying an IP address, IPv4 (for example, 192.168.0.1) or IPv6 (for example, [::1]) can be used as well. Use a colon (:) after the address to specify the port number of the server. When specifying multiple addresses, use a comma to separate the addresses, for example, kafka-bootstrap-servers("127.0.0.1:2525,remote-server-hostname:6464")
frac-digits()
| Type: | number |
| Default: | 0 |
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.
hook-commands()
Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.
NOTE: The syslog-ng OSE application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor or SELinux, you might have to modify your AppArmor or SELinux configuration to enable syslog-ng OSE to execute external applications.
Using the hook-commands() when syslog-ng OSE starts or stops
To execute an external program when syslog-ng OSE starts or stops, use the following options:
| startup() | |
| Type: | string |
| Default: | N/A |
|
Description: Defines the external program that is executed as syslog-ng OSE starts. | |
| shutdown() | |
| Type: | string |
| Default: | N/A |
|
Description: Defines the external program that is executed as syslog-ng OSE stops. | |
Using the hook-commands() when syslog-ng OSE reloads
To execute an external program when the syslog-ng OSE configuration is initiated or torn down, for example, on startup/shutdown or during a syslog-ng OSE reload, use the following options:
| setup() | |
| Type: | string |
| Default: | N/A |
|
Description: Defines an external program that is executed when the syslog-ng OSE configuration is initiated, for example, on startup or during a syslog-ng OSE reload. | |
| teardown() | |
| Type: | string |
| Default: | N/A |
|
Description: Defines an external program that is executed when the syslog-ng OSE configuration is stopped or torn down, for example, on shutdown or during a syslog-ng OSE reload. | |
Example: Using the hook-commands() with a network source
In the following example, the hook-commands() is used with the network() driver and it opens an iptables port automatically as syslog-ng OSE is started/stopped.
The assumption in this example is that the LOGCHAIN chain is part of a larger ruleset that routes traffic to it. Whenever the syslog-ng OSE created rule is there, packets can flow, otherwise the port is closed.
source {
network(transport(udp)
hook-commands(
startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
shutdown("iptables -D LOGCHAIN 1")
)
);
};jvm-options()
| Type: | list |
| Default: | N/A |
Description: Specify the Java Virtual Machine (JVM) settings of your Java destination from the syslog-ng OSE 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()
| Accepted values: |
drop-message|drop-property|fallback-to-string| silently-drop-message|silently-drop-property|silently-fallback-to-string |
| Default: | Use the global setting (which defaults to drop-message) |
Description: Controls what happens when type-casting fails and syslog-ng OSE cannot convert some data to the specified type. By default, syslog-ng OSE 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 OSE.
-
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.
key()
| Type: | template |
| Default: | N/A |
Description: The key of the partition under which the message is published. You can use templates to change the topic dynamically based on the source or the content of the message, for example, key("${PROGRAM}").
log-fifo-size()
| Type: | number |
| Default: | Use global setting. |
Description: The number of messages that the output queue can store.
properties-file()
| Type: | string (absolute path) |
| Default: | N/A |
Description: The absolute path and filename of the Kafka properties file to load. For example, properties-file("/opt/syslog-ng/etc/kafka_dest.properties"). The syslog-ng OSE application reads this file and passes the properties to the Kafka Producer. If a property is defined both in the syslog-ng OSE configuration file (syslog-ng.conf) and in the properties file, then syslog-ng OSE uses the definition from the syslog-ng OSE configuration file.
The syslog-ng OSE kafka destination supports all properties of the official Kafka producer. For details, see the Apache Kafka documentation.
The kafka-bootstrap-servers option is translated to the bootstrap.servers property.
For example, the following properties file defines the acknowledgment method and compression:
acks=all compression.type=snappy
retries()
| Type: | number (of attempts) |
| Default: | 3 |
Description: The number of times syslog-ng OSE attempts to send a message to this destination. If syslog-ng OSE could not send a message, it will try again until the number of attempts reaches retries, then drops the message.
sync-send()
| Type: | true | false |
| Default: | false |
Description: When sync-send is set to true, syslog-ng OSE sends the message reliably: it sends a message to the Kafka server, then waits for a reply. In case of failure, syslog-ng OSE repeats sending the message, as set in the retries() parameter. If sending the message fails for retries() times, syslog-ng OSE drops the message.
This method ensures reliable message transfer, but is very slow.
When sync-send is set to false, syslog-ng OSE sends messages asynchronously, and receives the response asynchronously. In case of a problem, syslog-ng OSE cannot resend the messages.
This method is fast, but the transfer is not reliable. Several thousands of messages can be lost before syslog-ng OSE recognizes the error.
template()
| Type: | template or template function |
| Default: | $ISODATE $HOST $MSGHDR$MSG\n |
Description: The message as published to Apache Kafka. You can use templates and template functions (for example, format-json()) to format the message, for example, template("$(format-json --scope rfc5424 --exclude DATE --key ISODATE)").
For details on formatting messages in JSON format, see format-json.
throttle()
| Type: | number |
| Default: | 0 |
Description: Sets the maximum number of messages sent to the destination per second. Use this output-rate-limiting functionality only when using disk-buffer as well to avoid the risk of losing messages. Specifying 0 or a lower value sets the output limit to unlimited.
topic()
| Type: | template |
| Default: | N/A |
Description: The Kafka topic under which the message is published. You can use templates to change the topic dynamically based on the source or the content of the message, for example, topic("${HOST}").
time-zone()
| Type: | name of the timezone, or the timezone offset |
| Default: | unspecified |
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 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.
ts-format()
| Type: | rfc3164, bsd, rfc3339, iso |
| Default: | rfc3164 |
Description: Override the global timestamp format (set in the global ts-format() parameter) for the specific destination. For details, see ts-format().
This option applies only to file and file-like destinations. Destinations that use specific protocols (for example, network(), or syslog()) ignore this option. For protocol-like destinations, use a template locally in the destination, or use the proto-template option.
kafka: Publishing messages to Apache Kafka (C implementation, using the librdkafka client)
Starting with version
As of syslog-ng OSE version
How the C implementation of the kafka destination works with syslog-ng OSE
Figure 11: How the C implementation of the kafka destination works with syslog-ng OSE
Shifting from Java implementation to C implementation
If you were using the Java implementation of the kafka destination and want to shift to its C implementation, the following changes to the configuration file and considerations are necessary.
- Unlike the old one, the new topic() option can not handle templates. It must be a string.
-
The template() option has been renamed message().
- The kafka-bootstrap-servers() option has been renamed bootstrap-servers().
- The properties-file() is a Java properties file with options that are similar to, but not identical with, the options in the old, Java implementation's properties-file(). For more information, click here.
- The sync-send() option has been deprecated. Remove it from the configuration file.
- The client_lib_dir() option has been deprecated. Remove it from the configuration file.
-
The old implementation's option() option has been removed and replaced by the config() option, which has a different syntax.
For more information, see Options of the kafka destination's C implementation .
Before you begin
This section describes the prerequisites and restrictions for using the kafka destination in the new C implementation, and important information about the declaration of the destination.
Prerequisites and restrictions
-
This destination is only supported on the Linux platform.
-
Since the new C implementation uses the librdkafka client library, the kafka destination has less memory usage than the previous Java implementation (which uses the official Java Kafka producer).
-
The log messages of the underlying client libraries are available in the internal() source of syslog-ng OSE.
- If you used the Java implementation before, see Shifting from Java implementation to C implementation .
-
The syslog-ng OSE kafka destination supports all properties of the official Kafka producer. For details, see the librdkafka documentation.
-
For the list of options, see Options of the kafka destination's C implementation .
Declaration:
@define kafka-implementation kafka-c
kafka(
bootstrap-servers("1.2.3.4:9092,192.168.0.2:9092")
topic("{MYTOPIC}")
);Example: Sending log data to Apache Kafka
The following example defines a kafka destination in the new C implementation, using only the required parameters.
@define kafka-implementation kafka-c
@include "scl.conf"
destination d_kafka {
kafka(
bootstrap-servers("1.2.3.4:9092,192.168.0.2:9092")
topic("{MYTOPIC}")
);
};