A syslog-ng OSE destination recognizes a message as sent when the message has been sent to the Kafka client, not when the Kafka server confirms its delivery.
If the Kafka client collects too many unsent messages, it will not accept any more messages from syslog-ng OSE. The syslog-ng OSE application detects this and stops sending messages to the Kafka client. Also, syslog-ng OSE's flow control starts functioning in the direction of the sources (for example, syslog-ng OSE will not read from the sources in that specific logpath).
You can specify a "high water mark" limit for the Kafka client in the properties-file().
For more information about how the C implementation of the kafka() destination works with syslog-ng OSE, click here.
The C implementation of the kafka() destination of syslog-ng OSE can directly publish log messages to the Apache Kafka message bus, where subscribers can access them. The C implementation of the kafka() destination has the following options.
Required options:
The following options are required: bootstrap-servers(), topic(). Note that to use the C implementation of the kafka() destination, you must add the following lines to the beginning of your syslog-ng OSE configuration:
@define kafka-implementation kafka-c
NOTE: At least one of the config() and the properties_file() options is mandatory. While you can specify everything in the config() option if you want, the properties-file() is optional. If you have an option in both the config() and the properties-file() specified, the option specified later in the syslog-ng OSE configuration file will prevail.
batch-lines()
Description: Specifies how many lines are flushed to a destination in one batch. The syslog-ng OSE application waits for this number of lines to accumulate and sends them off in a single batch. Increasing this number increases throughput as more messages are sent in a single batch, but also increases message latency.
For example, if you set batch-lines() to 100, syslog-ng OSE waits for 100 messages.
If the batch-timeout() option is disabled, the syslog-ng OSE application flushes the messages if it has sent batch-lines() number of messages, or the queue became empty. If you stop or reload syslog-ng OSE or in case of network sources, the connection with the client is closed, syslog-ng OSE automatically sends the unsent messages to the destination.
Note that if the batch-timeout() option is enabled and the queue becomes empty, syslog-ng OSE flushes the messages only if batch-timeout() expires, or the batch reaches the limit set in batch-lines().
For optimal performance, make sure that the syslog-ng OSE source that feeds messages to this destination is configured properly: the value of the log-iw-size() option of the source must be higher than the batch-lines()*workers() of the destination. Otherwise, the size of the batches cannot reach the batch-lines() limit.
NOTE: The syslog-ng OSE configuration accepts this option with sync-send() set to both "yes" or "no", but the option will only take effect if you set sync-send() to "yes".
NOTE: If you set sync-send() to "yes", the number you specify for batch-lines() affects how many messages syslog-ng OSE packs into once transaction.
batch-timeout()
| Type: |
time in milliseconds |
| Default: |
-1 (disabled) |
Description: Specifies the time syslog-ng OSE waits for lines to accumulate in the output buffer. The syslog-ng OSE application sends batches to the destinations evenly. The timer starts when the first message arrives to the buffer, so if only few messages arrive, syslog-ng OSE sends messages to the destination at most once every batch-timeout() milliseconds.
NOTE: The syslog-ng OSE configuration accepts this option with sync-send() set to both "yes" or "no", but the option will only take effect if you set sync-send() to "yes".
NOTE: When setting batch-timeout(), consider the value of the transaction.timeout.ms Kafka property. If in case of timeout (that is, if syslog-ng OSE does not receive batch-lines() amount of messages) the value of batch-timeout() exceeds the value of transaction.timeout.ms, syslog-ng OSE will not send out messages in time.
For more information about the default values of the transaction.timeout.ms Kafka property, see the librdkafka documentation.
bootstrap-servers()
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, bootstrap-servers("127.0.0.1:2525,remote-server-hostname:6464")
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").
NOTE: Unlike in the Java implementation, the client-lib-dir() option has no significant role in the C implementation of the kafka() destination. The programming language accepts this option for better compatibility.
Description: You can use this option to expand or override the options of the properties-file().
NOTE: At least one of the config() and the properties_file() options is mandatory. While you can specify everything in the config() option if you want, the properties-file() is optional. If you have an option in both the config() and the properties-file() specified, the option specified later in the syslog-ng OSE configuration file will prevail.
The syslog-ng OSEkafka destination supports all properties of the official Kafka producer. For details, see the librdkafka documentation.
The syntax of the config() option is the following:
config(
“key1” => “value1”
“key2” => “value2”
)
disk-buffer()
Description: This option enables putting outgoing messages into the disk buffer of the destination to avoid message loss in case of a system failure on the destination side. It has the following options:
| reliable() |
| Type: |
yes|no |
| Default: |
no |
|
Description: If set to yes, syslog-ng OSE cannot lose logs in case of reload/restart, unreachable destination or syslog-ng OSE crash. This solution provides a slower, but reliable disk-buffer option. It is created and initialized at startup and gradually grows as new messages arrive. If set to no, the normal disk-buffer will be used. This provides a faster, but less reliable disk-buffer option.
|
|
Caution:
Hazard of data loss! If you change the value of reliable() option when there are messages in the disk-buffer, the messages stored in the disk-buffer will be lost. | |
| compaction() |
| Type: |
yes|no |
| Default: |
no |
|
Description: If set to yes, syslog-ng OSE prunes the unused space in the LogMessage representation, making the disk queue size smaller at the cost of some CPU time. Setting the compaction() argument to yes is recommended when numerous name-value pairs are unset during processing, or when the same names are set multiple times. |
NOTE: Simply unsetting these name-value pairs by using the unset() rewrite operation is not enough, as due to performance reasons that help when syslog-ng OSE is CPU bound, the internal representation of a LogMessage will not release the memory associated with these name-value pairs. In some cases, however, the size of this overhead becomes significant (the raw message size can grow up to four times its original size), which unnecessarily increases the disk queue file size. For these cases, the compaction will drop unset values, making the LogMessage representation smaller at the cost of some CPU time required to perform compaction.
| dir() |
| Type: |
string |
| Default: |
N/A |
|
Description: Defines the folder where the disk-buffer files are stored.
|
|
Caution:
When creating a new dir() option for a disk buffer, or modifying an existing one, make sure you delete the persist file.
syslog-ng OSE creates disk-buffer files based on the path recorded in the persist file. Therefore, if the persist file is not deleted after modifying the dir() option, then following a restart, syslog-ng OSE will look for or create disk-buffer files in their old location. To ensure that syslog-ng OSE uses the new dir() setting, the persist file must not contain any information about the destinations which the disk-buffer file in question belongs to. |
NOTE: If the dir() path provided by the user does not exist, syslog-ng OSE creates the path with the same permission as the running instance. |
| disk-buf-size() |
| Type: |
number (bytes) |
| Default: |
|
| Description: This is a required option. The maximum size of the disk-buffer in bytes. The minimum value is 1048576 bytes. If you set a smaller value, the minimum value will be used automatically. It replaces the old log-disk-fifo-size() option. |
| mem-buf-length() |
| Type: |
number (messages) |
| Default: |
10000 |
| Description: Use this option if the option reliable() is set to no. This option contains the number of messages stored in overflow queue. It replaces the old log-fifo-size() option. It inherits the value of the global log-fifo-size() option if provided. If it is not provided, the default value is 10000 messages. Note that this option will be ignored if the option reliable() is set to yes. |
| mem-buf-size() |
| Type: |
number (bytes) |
| Default: |
163840000 |
| Description: Use this option if the option reliable() is set to yes. This option contains the size of the messages in bytes that is used in the memory part of the disk buffer. It replaces the old log-fifo-size() option. It does not inherit the value of the global log-fifo-size() option, even if it is provided. Note that this option will be ignored if the option reliable() is set to no. |
| qout-size() |
| Type: |
number (messages) |
| Default: |
64 |
| Description: The number of messages stored in the output buffer of the destination. Note that if you change the value of this option and the disk-buffer already exists, the change will take effect when the disk-buffer becomes empty. |
Options reliable() and disk-buf-size() are required options.
Example: Examples for using disk-buffer()
In the following case reliable disk-buffer() is used.
destination d_demo {
network(
"127.0.0.1"
port(3333)
disk-buffer(
mem-buf-size(10000)
disk-buf-size(2000000)
reliable(yes)
dir("/tmp/disk-buffer")
)
);
};
In the following case normal disk-buffer() is used.
destination d_demo {
network(
"127.0.0.1"
port(3333)
disk-buffer(
mem-buf-length(10000)
disk-buf-size(2000000)
reliable(no)
dir("/tmp/disk-buffer")
)
);
};
|
truncate-size-ratio() |
| Type: |
number (between 0 and 1) |
| Default: |
0.1 (10%) |
|
Description: Limits the truncation of the disk-buffer file. Truncating the disk-buffer file can slow down the disk IO operations, but it saves disk space, so syslog-ng only truncates the file, if the possible disk gain is more than truncate-size-ratio() times disk-buf-size().
|
|
Caution:
One Identity does not recommend you to change truncate-size-ratio(). Only change its value if you know the performance implications of doing so. | |
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: The syslog-ng OSE application can add the fractions to non-ISO8601 timestamps as well.
NOTE: As syslog-ng OSE is precise up to the microsecond, when the frac-digits() option is set to a value higher than 6, syslog-ng OSE will truncate the fraction seconds in the timestamps after 6 digits.
flush-timeout-on-reload()
| Type: |
integer in msec |
| Default: |
1000 |
Description: When syslog-ng reloads, the Kafka client will also reload. The flush-timeout-on-reload() option specifies the number of milliseconds syslog-ng waits for the Kafka client to send the unsent messages. The unsent messages will be retained in syslog-ng's own queue and syslog-ng will continue sending them after reload. This works without disk-buffering, too.
flush-timeout-on-shutdown()
| Type: |
integer in msec |
| Default: |
60000 |
Description: When syslog-ng shuts down, the Kafka client will also shut down. The flush-timeout-on-shutdown() option specifies the number of milliseconds syslog-ng waits for the Kafka client to send the unsent messages. Any messages not sent after the specified time will be lost. To avoid losing messages, we recommend you use the disk-buffer option.
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")
)
);
};
key()
| Type: |
template |
| Default: |
empty string |
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.
local-time-zone()
| Type: |
name of the timezone, or the timezone offset |
| Default: |
The local timezone. |
Description: Sets the timezone used when expanding filename and tablename templates.
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.
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.
persist-name()
| Type: |
string |
| Default: |
N/A |
Description:If you receive the following error message during syslog-ng OSE startup, set the persist-name() option of the duplicate drivers:
Error checking the uniqueness of the persist names, please override it with persist-name option. Shutting down.
This error happens if you use identical drivers in multiple sources, for example, if you configure two file sources to read from the same file. In this case, set the persist-name() of the drivers to a custom string, for example, persist-name("example-persist-name1").
poll-timeout()
| Type: |
integer in msec |
| Default: |
1000 |
Description: Specifies the frequency your syslog-ng queries the Kafka client about the amount of messages sent since the last poll-timeout (). In case of multithreading, the first syslog-ng worker is responsible for poll-timeout().
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.
The syslog-ng OSEkafka destination supports all properties of the official Kafka producer. For details, see the librdkafka documentation.
The 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.
NOTE: At least one of the config() and the properties_file() options is mandatory. While you can specify everything in the config() option if you want, the properties-file() is optional. If you have an option in both the config() and the properties-file() specified, the option specified later in the syslog-ng OSE configuration file will prevail.
retries()
| Type: |
number (of attempts) |
| Default: |
3 |
Description: If syslog-ng OSE cannot send a message, it will try again until the number of attempts reaches retries().
If the number of attempts reaches retries(), syslog-ng OSE will wait for time-reopen() time, then tries sending the message again.
send-time-zone()
| Accepted values: |
name of the timezone, or the timezone offset |
| Default: |
local timezone |
Description: Specifies the time zone associated with the messages sent by syslog-ng, if not specified otherwise in the message or in the destination driver. For details, see Timezones and daylight saving.
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.
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.
NOTE: If you want to use the sync-send() option set to "yes", One Identity recommends that you use librdkafka version 1.4.0 or higher, and a Kafka server with version number 0.11.0 or higher.
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()
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()
| 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.
topic()
| Type: |
string |
| Default: |
N/A |
Description: The Kafka topic under which the message is published.
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().
NOTE: 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.
workers()
Description: The workers are only responsible for formatting the messages that need to be delivered to the Kafka clients. Configure this option only if your Kafka clients have many threads and they do not receive enough messages.
NOTE: Kafka clients have their own threadpool, entirely independent from any syslog-ng settings. The workers() option has no effect on this threadpool.
The loggly() destination sends log messages to the Loggly Logging-as-a-Service provider. You can send log messages over TCP, or encrypted with TLS.
Declaration:
loggly(token());
Example: Using the loggly() driver
To use the loggly() destination, the only mandatory parameter is your user token. The following example sends every log from the system() source to your Loggly account.
log {
source { system(); };
destination { loggly(token("<USER-TOKEN-AS-PROVIDED-BY-LOGGLY>")); };
};
The following example uses TLS encryption. Before using it, download the CA certificate of Loggly and copy it to your hosts (for example, into the /etc/ssl/certs/ directory.
log {
destination {
loggly(token("<USER-TOKEN-AS-PROVIDED-BY-LOGGLY>") port(6514)
tls(peer-verify(required-trusted) ca-dir('/etc/ssl/certs'))
);
};
};
The following example parses the access logs of an Apache webserver from a file and sends them to Loggly in JSON format.
log {
source { file("/var/log/apache2/access.log" flags(no-parse)); };
parser { apache-accesslog-parser(); };
destination {
loggly(token("<USER-TOKEN-AS-PROVIDED-BY-LOGGLY>")
tag(apache)
template("$(format-json .apache.* timestamp=${ISODATE})"));
};
}
To use the loggly() driver, the scl.conf file must be included in your syslog-ng OSE configuration:
@include "scl.conf"
The loggly() driver is actually a reusable configuration snippet configured to send log messages using the tcp() driver using a template. For details on using or writing such configuration snippets, see Reusing configuration blocks. You can find the source of this configuration snippet on GitHub.
The loggly() destination has the following options. You can also set other options of the underlying tcp() driver (for example, port number or TLS-encryption).
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")
)
);
};
tls()
| Type: |
tls options |
| Default: |
n/a |
Description: This option sets various options related to TLS encryption, for example, key/certificate files and trusted CA locations. TLS can be used only with tcp-based transport protocols. For details, see TLS options.
token()
Description: Your Customer Token that you received from Loggly.
transport()
| Type: |
udp, tcp, or tls |
| Default: |
tcp |
Description: Specifies the protocol used to send messages to the destination server.
If you use the udp transport, syslog-ng OSE automatically sends multicast packets if a multicast destination address is specified. The tcp transport does not support multicasting.
