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syslog-ng Open Source Edition 3.23 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng The syslog-ng OSE quick-start guide The syslog-ng OSE configuration file source: Read, receive, and collect log messages
How sources work default-network-drivers: Receive and parse common syslog messages internal: Collecting internal messages file: Collecting messages from text files wildcard-file: Collecting messages from multiple text files linux-audit: Collecting messages from Linux audit logs network: Collecting messages using the RFC3164 protocol (network() driver) nodejs: Receiving JSON messages from nodejs applications mbox: Converting local email messages to log messages osquery: Collect and parse osquery result logs pipe: Collecting messages from named pipes pacct: Collecting process accounting logs on Linux program: Receiving messages from external applications python: writing server-style Python sources python-fetcher: writing fetcher-style Python sources snmptrap: Read Net-SNMP traps sun-streams: Collecting messages on Sun Solaris syslog: Collecting messages using the IETF syslog protocol (syslog() driver) system: Collecting the system-specific log messages of a platform systemd-journal: Collecting messages from the systemd-journal system log storage systemd-syslog: Collecting systemd messages using a socket tcp, tcp6, udp, udp6: Collecting messages from remote hosts using the BSD syslog protocol— OBSOLETE unix-stream, unix-dgram: Collecting messages from UNIX domain sockets stdin: Collecting messages from the standard input stream
destination: Forward, send, and store log messages
amqp: Publishing messages using AMQP collectd: sending metrics to collectd elasticsearch2: Sending messages directly to Elasticsearch version 2.0 or higher (DEPRECATED) elasticsearch-http: Sending messages to Elasticsearch HTTP Bulk API file: Storing messages in plain-text files graphite: Sending metrics to Graphite Sending logs to Graylog hdfs: Storing messages on the Hadoop Distributed File System (HDFS) Posting messages over HTTP http: Posting messages over HTTP without Java kafka: Publishing messages to Apache Kafka (Java implementation) kafka: Publishing messages to Apache Kafka (C implementation, using the librdkafka client) loggly: Using Loggly logmatic: Using Logmatic.io mongodb: Storing messages in a MongoDB database network: Sending messages to a remote log server using the RFC3164 protocol (network() driver) osquery: Sending log messages to osquery's syslog table pipe: Sending messages to named pipes program: Sending messages to external applications pseudofile() python: writing custom Python destinations redis: Storing name-value pairs in Redis riemann: Monitoring your data with Riemann slack: Sending alerts and notifications to a Slack channel smtp: Generating SMTP messages (email) from logs snmp: Sending SNMP traps Splunk: Sending log messages to Splunk sql: Storing messages in an SQL database stomp: Publishing messages using STOMP syslog: Sending messages to a remote logserver using the IETF-syslog protocol syslog-ng(): Forward logs to another syslog-ng node tcp, tcp6, udp, udp6: Sending messages to a remote log server using the legacy BSD-syslog protocol (tcp(), udp() drivers) Telegram: Sending messages to Telegram unix-stream, unix-dgram: Sending messages to UNIX domain sockets usertty: Sending messages to a user terminal: usertty() destination Write your own custom destination in Java or Python Client-side failover
log: Filter and route log messages using log paths, flags, and filters Global options of syslog-ng OSE TLS-encrypted message transfer template and rewrite: Format, modify, and manipulate log messages parser: Parse and segment structured messages db-parser: Process message content with a pattern database (patterndb) Correlating log messages Enriching log messages with external data Statistics of syslog-ng Multithreading and scaling in syslog-ng OSE Troubleshooting syslog-ng Best practices and examples The syslog-ng manual pages Creative Commons Attribution Non-commercial No Derivatives (by-nc-nd) License

elasticsearch-http destination options

The elasticsearch-http destination of syslog-ng OSE can directly post log messages to an Elasticsearch deployment using the Elasticsearch Bulk API over the HTTP and Secure HTTP (HTTPS) protocols. The elasticsearch-http destination has the following options. The required options are: index(), type(), and url().

This destination is available in syslog-ng OSE version 3.21 and later.

batch-bytes()
Accepted values: number [bytes]
Default: none

Description: Sets the maximum size of payload in a batch. If the size of the messages reaches this value, syslog-ng OSE sends the batch to the destination even if the number of messages is less than the value of the batch-lines() option.

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-bytes().

Available in syslog-ng OSE version 3.19 and later.

For details on how this option influences batch mode, see Batch mode and load balancing

batch-lines()
Type: number
Default: 25

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.

For details on how this option influences batch mode, see Batch mode and load balancing

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.

For details on how this option influences batch mode, see Batch mode and load balancing

ca-dir()
Accepted values: Directory name
Default: none

Description: Name of a directory, that contains a set of trusted CA certificates in PEM format. The CA certificate files have to be named after the 32-bit hash of the subject's name. This naming can be created using the c_rehash utility in openssl. For an example, see Configuring TLS on the syslog-ng clients. The syslog-ng OSE application uses the CA certificates in this directory to validate the certificate of the peer.

An alternative way to specify this option is to put it into a tls() block, together with any other TLS options. This allows you to separate these options and ensure better readability.

Make sure that you specify TLS options either using their own dedicated option (ca-dir(), ca-file(), cert-file(), cipher-suite(), key-file(), peer-verify(), and ssl-version()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

Declaration:
destination d_elasticsearch-http {
	elasticsearch-http(
		url("http://your-elasticsearch-server:9200/_bulk")
		type("")
		index("example-index")
		tls(
			ca-dir("dir")
			ca-file("ca")
			cert-file("cert")
			cipher-suite("cipher")
			key-file("key")
			peer-verify(yes|no)
			ssl-version(<the permitted SSL/TLS version>)
		)
	);
};
ca-file()
Accepted values: Filename
Default: none

Description: Name of a file that contains an X.509 CA certificate (or a certificate chain) in PEM format. The syslog-ng OSE application uses this certificate to validate the certificate of the HTTPS server. If the file contains a certificate chain, the file must begin with the certificate of the host, followed by the CA certificate that signed the certificate of the host, and any other signing CAs in order.

An alternative way to specify this option is to put it into a tls() block, together with any other TLS options. This allows you to separate these options and ensure better readability.

Make sure that you specify TLS options either using their own dedicated option (ca-dir(), ca-file(), cert-file(), cipher-suite(), key-file(), peer-verify(), and ssl-version()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

Declaration:
destination d_elasticsearch-http {
	elasticsearch-http(
		url("http://your-elasticsearch-server:9200/_bulk")
		type("")
		index("example-index")
		tls(
			ca-dir("dir")
			ca-file("ca")
			cert-file("cert")
			cipher-suite("cipher")
			key-file("key")
			peer-verify(yes|no)
			ssl-version(<the permitted SSL/TLS version>)
		)
	);
};
cert-file()
Accepted values: Filename
Default: none

Description: Name of a file, that contains an X.509 certificate (or a certificate chain) in PEM format, suitable as a TLS certificate, matching the private key set in the key-file() option. The syslog-ng OSE application uses this certificate to authenticate the syslog-ng OSE client on the destination server. If the file contains a certificate chain, the file must begin with the certificate of the host, followed by the CA certificate that signed the certificate of the host, and any other signing CAs in order.

An alternative way to specify this option is to put it into a tls() block, together with any other TLS options. This allows you to separate these options and ensure better readability.

Make sure that you specify TLS options either using their own dedicated option (ca-dir(), ca-file(), cert-file(), cipher-suite(), key-file(), peer-verify(), and ssl-version()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

Declaration:
destination d_elasticsearch-http {
	elasticsearch-http(
		url("http://your-elasticsearch-server:9200/_bulk")
		type("")
		index("example-index")
		tls(
			ca-dir("dir")
			ca-file("ca")
			cert-file("cert")
			cipher-suite("cipher")
			key-file("key")
			peer-verify(yes|no)
			ssl-version(<the permitted SSL/TLS version>)
		)
	);
};
cipher-suite()
Accepted values: Name of a cipher, or a colon-separated list
Default: Depends on the OpenSSL version that syslog-ng OSE uses

Description: Specifies the cipher, hash, and key-exchange algorithms used for the encryption, for example, ECDHE-ECDSA-AES256-SHA384. The list of available algorithms depends on the version of OpenSSL used to compile syslog-ng OSE. To specify multiple ciphers, separate the cipher names with a colon, and enclose the list between double-quotes, for example:

cipher-suite("ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384")

For a list of available algorithms, execute the openssl ciphers -v command. The first column of the output contains the name of the algorithms to use in the cipher-suite() option, the second column specifies which encryption protocol uses the algorithm (for example, TLSv1.2). That way, the cipher-suite() also determines the encryption protocol used in the connection: to disable SSLv3, use an algorithm that is available only in TLSv1.2, and that both the client and the server supports. You can also specify the encryption protocols using ssl-options().

You can also use the following command to automatically list only ciphers permitted in a specific encryption protocol, for example, TLSv1.2:

echo "cipher-suite(\"$(openssl ciphers -v | grep TLSv1.2 | awk '{print $1}' | xargs echo -n | sed 's/ /:/g' | sed -e 's/:$//')\")"

Note that starting with version 3.10, when syslog-ng OSE receives TLS-encrypted connections, the order of ciphers set on the syslog-ng OSE server takes precedence over the client settings.

An alternative way to specify this option is to put it into a tls() block, together with any other TLS options. This allows you to separate these options and ensure better readability.

Make sure that you specify TLS options either using their own dedicated option (ca-dir(), ca-file(), cert-file(), cipher-suite(), key-file(), peer-verify(), and ssl-version()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

Declaration:
destination d_elasticsearch-http {
	elasticsearch-http(
		url("http://your-elasticsearch-server:9200/_bulk")
		type("")
		index("example-index")
		tls(
			ca-dir("dir")
			ca-file("ca")
			cert-file("cert")
			cipher-suite("cipher")
			key-file("key")
			peer-verify(yes|no)
			ssl-version(<the permitted SSL/TLS version>)
		)
	);
};
custom-id()
Accepted values: string
Default: empty string

Description: Sets the specified value as the ID of the Elasticsearch index (_id).

delimiter()
Accepted values: string
Default: newline character

Description: By default, syslog-ng OSE separates the log messages of the batch with a newline character. You can specify a different delimiter by using the delimiter() option.

For details on how this option influences batch mode, see Batch mode and load balancing

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.

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.

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")
        )
    );
};
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")
        )
     );
};
index()
Accepted values: string or template
Default: None

Description: The name of the Elasticsearch index where Elasticsearch will store the messages received from syslog-ng OSE. This option is mandatory for this destination.

You can use macros and template functions, but you must ensure that the resolved template contains only characters that Elasticsearch permits in the name of the index. The syslog-ng OSE application does not validate the name of the index. For details on the characters permitted in the name of Elasticsearch indices, see the documentation of Elasticsearch.

log-fifo-size()
Type: number
Default: Use global setting.

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

key-file()
Accepted values: Filename
Default: none

Description: The name of a file that contains an unencrypted private key in PEM format, suitable as a TLS key. If properly configured, the syslog-ng OSE application uses this private key and the matching certificate (set in the cert-file() option) to authenticate the syslog-ng OSE client on the destination server.

This destination supports only unencrypted key files (that is, the private key cannot be password-protected).

An alternative way to specify this option is to put it into a tls() block, together with any other TLS options. This allows you to separate these options and ensure better readability.

Make sure that you specify TLS options either using their own dedicated option (ca-dir(), ca-file(), cert-file(), cipher-suite(), key-file(), peer-verify(), and ssl-version()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

Declaration:
destination d_elasticsearch-http {
	elasticsearch-http(
		url("http://your-elasticsearch-server:9200/_bulk")
		type("")
		index("example-index")
		tls(
			ca-dir("dir")
			ca-file("ca")
			cert-file("cert")
			cipher-suite("cipher")
			key-file("key")
			peer-verify(yes|no)
			ssl-version(<the permitted SSL/TLS version>)
		)
	);
};
password()
Type: string
Default:

Description: The password that syslog-ng OSE uses to authenticate on the server where it sends the messages.

peer-verify()
Accepted values: yes | no
Default: yes

Description: Verification method of the peer. The following table summarizes the possible options and their results depending on the certificate of the peer.

The remote peer has:
no certificate invalid certificate valid certificate
Local peer-verify() setting no (optional-untrusted) TLS-encryption TLS-encryption TLS-encryption
yes (required-trusted) rejected connection rejected connection TLS-encryption

For untrusted certificates only the existence of the certificate is checked, but it does not have to be valid — syslog-ng accepts the certificate even if it is expired, signed by an unknown CA, or its CN and the name of the machine mismatches.

Caution:

When validating a certificate, the entire certificate chain must be valid, including the CA certificate. If any certificate of the chain is invalid, syslog-ng OSE will reject the connection.

An alternative way to specify this option is to put it into a tls() block, together with any other TLS options. This allows you to separate these options and ensure better readability.

Make sure that you specify TLS options either using their own dedicated option (ca-dir(), ca-file(), cert-file(), cipher-suite(), key-file(), peer-verify(), and ssl-version()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

Declaration:
destination d_elasticsearch-http {
	elasticsearch-http(
		url("http://your-elasticsearch-server:9200/_bulk")
		type("")
		index("example-index")
		tls(
			ca-dir("dir")
			ca-file("ca")
			cert-file("cert")
			cipher-suite("cipher")
			key-file("key")
			peer-verify(yes|no)
			ssl-version(<the permitted SSL/TLS version>)
		)
	);
};
persist-name()
Type: string
Default:

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").

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.

To handle HTTP error responses, if the HTTP server returns 5xx codes, syslog-ng OSE will attempt to resend messages until the number of attempts reaches retries. If the HTTP server returns 4xx codes, syslog-ng OSE will drop the messages.

ssl-version()
Type: string
Default: None, uses the libcurl default

Description: Specifies the permitted SSL/TLS version. Possible values: sslv2, sslv3, tlsv1, tlsv1_0, tlsv1_1, tlsv1_2.

An alternative way to specify this option is to put it into a tls() block, together with any other TLS options. This allows you to separate these options and ensure better readability.

Make sure that you specify TLS options either using their own dedicated option (ca-dir(), ca-file(), cert-file(), cipher-suite(), key-file(), peer-verify(), and ssl-version()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

Declaration:
destination d_elasticsearch-http {
	elasticsearch-http(
		url("http://your-elasticsearch-server:9200/_bulk")
		type("")
		index("example-index")
		tls(
			ca-dir("dir")
			ca-file("ca")
			cert-file("cert")
			cipher-suite("cipher")
			key-file("key")
			peer-verify(yes|no)
			ssl-version(<the permitted SSL/TLS version>)
		)
	);
};
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.

type()
Type: string or template
Default: N/A

Description: The type of the Elasticsearch index.

Use an empty string to omit the type from the index: type(""). For example, you need to do that when using Elasticsearch 7 or newer, and you use a mapping in Elasticsearch to modify the type of the data.

timeout()
Type: number [seconds]
Default: 10

Description: The value (in seconds) to wait for an operation to complete, and attempt to reconnect the server if exceeded.

url()
Type: URL or list of URLs, for example, url("site1", "site2")
Default: N/A

Description: Specifies the hostname or IP address and optionally the port number of the Elasticsearch indexer. Use a colon (:) after the address to specify the port number of the server. For example: http://your-elasticsearch-indexer.server:8088/_bulk

This option is mandatory for this destination.

Make sure that the URL ends with _bulk, this is the Elasticsearch API endpoint that properly parses the messages sent by syslog-ng OSE.

In case the server on the specified URL returns a redirect request, syslog-ng OSE automatically follows maximum 3 redirects. Only HTTP and HTTPS based redirections are supported.

Starting with version 3.19, you can specify multiple URLs, for example, url("site1", "site2"). In this case, syslog-ng OSE sends log messages to the specified URLs in a load-balance fashion. This means that syslog-ng OSE sends each message to only one URL. For example, you can use this to send the messages to a set of ingestion nodes or indexers of your SIEM solution if a single node cannot handle the load. Note that the order of the messages as they arrive on the servers can differ from the order syslog-ng OSE has received them, so use load-balancing only if your server can use the timestamp from the messages. If the server uses the timestamp when it receives the messages, the order of the messages will be incorrect.

Caution:

If you set multiple URLs in the url() option, set the persist-name() option as well to avoid data loss.

Starting with version syslog-ng OSE version 3.22, you can use any of the following formats to specify multiple URLs:

url("server1", "server2", "server3"); # comma-separated strings
url("server1" "server2" "server3"); # space-separated strings
url("server1 server2 server3"); # space-separated within a single string
url("server1,server2,server3"); # comma-separated within a single string
user()
Type: string
Default:

Description: The username that syslog-ng OSE uses to authenticate on the server where it sends the messages.

use-system-cert-store()
Type: yes | no
Default: no

Description: Use the certificate store of the system for verifying HTTPS certificates. For details, see the curl documentation.

workers()
Type: integer
Default: 4

Description: Specifies the number of worker threads (at least 1) that syslog-ng OSE uses to send messages to the server. Increasing the number of worker threads can drastically improve the performance of the destination.

Caution:

Hazard of data loss. When you use more than one worker threads together with disk-based buffering, syslog-ng OSE creates a separate disk buffer for each worker thread. This means that decreasing the number of workers can result in losing data currently stored in the disk buffer files. Do not decrease the number of workers when the disk buffer files are in use.

If you are using load-balancing (that is, you have configured multiple servers in the url() option), increase the number of worker threads at least to the number of servers. For example, if you have set three URLs (url("site1", "site2", "site3")), set the workers() option to 3 or more.


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file: Storing messages in plain-text files

The file driver is one of the most important destination drivers in syslog-ng. It allows to output messages to the specified text file, or to a set of files.

The destination filename may include macros which get expanded when the message is written, thus a simple file() driver may create several files: for example, syslog-ng OSE can store the messages of client hosts in a separate file for each host. For more information on available macros see Macros of syslog-ng OSE.

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

Declaration:
file(filename options());
Example: Using the file() driver
destination d_file { file("/var/log/messages"); };
Example: Using the file() driver with macros in the file name and a template for the message
destination d_file {
    file("/var/log/${YEAR}.${MONTH}.${DAY}/messages"
         template("${HOUR}:${MIN}:${SEC} ${TZ} ${HOST} [${LEVEL}] ${MESSAGE}\n")
         template-escape(no));
};

NOTE:

When using this destination, update the configuration of your log rotation program to rotate these files. Otherwise, the log files can become very large.

Also, after rotating the log files, reload syslog-ng OSE using the syslog-ng-ctl reload command, or use another method to send a SIGHUP to syslog-ng OSE.

Caution:

Since the state of each created file must be tracked by syslog-ng, it consumes some memory for each file. If no new messages are written to a file within 60 seconds (controlled by the time-reap() global option), it is closed, and its state is freed.

Exploiting this, a DoS attack can be mounted against the system. If the number of possible destination files and its needed memory is more than the amount available on the syslog-ng server.

The most suspicious macro is ${PROGRAM}, where the number of possible variations is rather high. Do not use the ${PROGRAM} macro in insecure environments.


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file() destination options

The file() driver outputs messages to the specified text file, or to a set of files. The file() destination has the following options:

Caution:

When creating several thousands separate log files, syslog-ng might not be able to open the required number of files. This might happen for example, when using the ${HOST} macro in the filename while receiving messages from a large number of hosts. To overcome this problem, adjust the --fd-limit command-line parameter of syslog-ng or the global ulimit parameter of your host. For setting the --fd-limit command-line parameter of syslog-ng see the The syslog-ng manual page manual page. For setting the ulimit parameter of the host, see the documentation of your operating system.

create-dirs()
Type: yes or no
Default: no

Description: Enable creating non-existing directories.

dir-group()
Type: string
Default: Use the global settings

Description: The group of the directories created by syslog-ng. To preserve the original properties of an existing directory, use the option without specifying an attribute: dir-group().

dir-owner()
Type: string
Default: Use the global settings

Description: The owner of the directories created by syslog-ng. To preserve the original properties of an existing directory, use the option without specifying an attribute: dir-owner().

Starting with version 3.16, the default value of this option is -1, so syslog-ng OSE does not change the ownership, unless explicitly configured to do so.

dir-perm()
Type: number
Default: Use the global settings

Description: The permission mask of directories created by syslog-ng. Log directories are only created if a file after macro expansion refers to a non-existing directory, and directory creation is enabled (see also the create-dirs() option). For octal numbers prefix the number with 0, for example, use 0755 for rwxr-xr-x.

To preserve the original properties of an existing directory, use the option without specifying an attribute: dir-perm(). Note that when creating a new directory without specifying attributes for dir-perm(), the default permission of the directories is masked with the umask of the parent process (typically 0022).

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.

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.

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")
        )
    );
};
flags()
Type: no-multi-line, syslog-protocol, threaded
Default: empty set

Description: Flags influence the behavior of the destination driver.

  • no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line.

  • syslog-protocol: The syslog-protocol flag instructs the driver to format the messages according to the new IETF syslog protocol standard (RFC5424), but without the frame header. If this flag is enabled, macros used for the message have effect only for the text of the message, the message header is formatted to the new standard. Note that this flag is not needed for the syslog driver, and that the syslog driver automatically adds the frame header to the messages.

  • threaded: The threaded flag enables multithreading for the destination. For details on multithreading, see Multithreading and scaling in syslog-ng OSE.

    NOTE:

    The file destination uses multiple threads only if the destination filename contains macros.

flush-lines()
Type: number
Default: Use global setting (exception: for http() destination, the default is 1).

Description: Specifies how many lines are flushed to a destination at a time. 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.

The syslog-ng OSE application flushes the messages if it has sent flush-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.

For optimal performance when sending messages to an syslog-ng OSE server, make sure that the value of flush-lines() is smaller than the window size set in the log-iw-size() option in the source of your server.

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.

fsync()
Type: yes or no
Default: no

Description: Forces an fsync() call on the destination fd after each write.

NOTE: Enabling this option may seriously degrade performance.

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")
        )
     );
};
group()
Type: string
Default: Use the global settings

Description: Set the group of the created file to the one specified. To preserve the original properties of an existing file, use the option without specifying an attribute: group().

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.

log-fifo-size()
Type: number
Default: Use global setting.

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

mark-freq()
Accepted values: number [seconds]
Default: 1200

Description: An alias for the obsolete mark() option, retained for compatibility with syslog-ng version 1.6.x.

The number of seconds between two MARK messages. MARK messages are generated when there was no message traffic to inform the receiver that the connection is still alive. If set to zero (0), no MARK messages are sent. The mark-freq() can be set for global option and/or every MARK capable destination driver if mark-mode() is periodical or dst-idle or host-idle. If mark-freq() is not defined in the destination, then the mark-freq() will be inherited from the global options. If the destination uses internal mark-mode(), then the global mark-freq() will be valid (does not matter what mark-freq() set in the destination side).

mark-mode()
Accepted values: internal | dst-idle | host-idle | periodical | none | global
Default:

internal for pipe, program drivers

none for file, unix-dgram, unix-stream drivers

global for syslog, tcp, udp destinations

host-idle for global option

Description: The mark-mode() option can be set for the following destination drivers: file(), program(), unix-dgram(), unix-stream(), network(), pipe(), syslog() and in global option.

  • internal: When internal mark mode is selected, internal source should be placed in the log path as this mode does not generate mark by itself at the destination. This mode only yields the mark messages from internal source. This is the mode as syslog-ng OSE 3.3 worked. MARK will be generated by internal source if there was NO traffic on local sources:

    file(), pipe(), unix-stream(), unix-dgram(), program()

  • dst-idle: Sends MARK signal if there was NO traffic on destination drivers. MARK signal from internal source will be dropped.

    MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().

  • host-idle: Sends MARK signal if there was NO local message on destination drivers. for example, MARK is generated even if messages were received from tcp. MARK signal from internal source will be dropped.

    MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().

  • periodical: Sends MARK signal perodically, regardless of traffic on destination driver. MARK signal from internal source will be dropped.

    MARK signal can be sent by the following destination drivers: network(), syslog(), program(), file(), pipe(), unix-stream(), unix-dgram().

  • none: Destination driver drops all MARK messages. If an explicit mark-mode() is not given to the drivers where none is the default value, then none will be used.

  • global: Destination driver uses the global mark-mode() setting. Note that setting the global mark-mode() to global causes a syntax error in syslog-ng OSE.

NOTE:

In case of dst-idle, host-idle and periodical, the MARK message will not be written in the destination, if it is not open yet.

Available in syslog-ng OSE 3.4 and later.

overwrite-if-older()
Type: number (seconds)
Default: 0

Description: If set to a value higher than 0, syslog-ng OSE checks when the file was last modified before starting to write into the file. If the file is older than the specified amount of time (in seconds), then syslog-ng removes the existing file and opens a new file with the same name. In combination with for example, the ${WEEKDAY} macro, this can be used for simple log rotation, in case not all history has to be kept. (Note that in this weekly log rotation example if its Monday 00:01, then the file from last Monday is not seven days old, because it was probably last modified shortly before 23:59 last Monday, so it is actually not even six days old. So in this case, set the overwrite-if-older() parameter to a-bit-less-than-six-days, for example, to 518000 seconds.

owner()
Type: string
Default: Use the global settings

Description: Set the owner of the created file to the one specified. To preserve the original properties of an existing file, use the option without specifying an attribute: owner().

pad-size()
Type: number
Default: 0

Description: If set, syslog-ng OSE will pad output messages to the specified size (in bytes). Some operating systems (such as HP-UX) pad all messages to block boundary. This option can be used to specify the block size. (HP-UX uses 2048 bytes).

Caution:

Hazard of data loss! If the size of the incoming message is larger than the previously set pad-size() value, syslog-ng will truncate the message to the specified size. Therefore, all message content above that size will be lost.

perm()
Type: number
Default: Use the global settings

Description: The permission mask of the file if it is created by syslog-ng. For octal numbers prefix the number with 0, for example, use 0755 for rwxr-xr-x.

To preserve the original properties of an existing file, use the option without specifying an attribute: perm().

suppress()
Type: seconds
Default: 0 (disabled)

Description: If several identical log messages would be sent to the destination without any other messages between the identical messages (for example, an application repeated an error message ten times), syslog-ng can suppress the repeated messages and send the message only once, followed by the Last message repeated n times. message. The parameter of this option specifies the number of seconds syslog-ng waits for identical messages.

template()
Type: string
Default: A format conforming to the default logfile format.

Description: Specifies a template defining the logformat to be used in the destination. Macros are described in Macros of syslog-ng OSE. Please note that for network destinations it might not be appropriate to change the template as it changes the on-wire format of the syslog protocol which might not be tolerated by stock syslog receivers (like syslogd or syslog-ng itself). For network destinations make sure the receiver can cope with the custom format defined.

template-escape()
Type: yes or no
Default: no

Description: Turns on escaping for the ', ", and backspace characters in templated output files. This is useful for generating SQL statements and quoting string contents so that parts of the log message are not interpreted as commands to the SQL server.

time-reap()
Accepted values: number (seconds)
Default: 60 or 0, see description for details

Description: The time to wait in seconds before an idle destination file or pipe is closed. Note that only destination files having macros in their filenames are closed automatically.

Starting with version 3.23, the way how time-reap() works is the following.

  1. If the time-reap() option of the destination is set, that value is used, for example:

    destination d_fifo {
        pipe(
            "/tmp/test.fifo",
            time-reap(30)  # sets time-reap() for this destination only
        );
    };
  2. If the time-reap() option of the destination is not set, and the destination does not use a template or macro in its filename or path, time-reap() is automatically set to 0. For example:

    destination d_fifo {
        pipe(
            "/tmp/test.fifo",
        );
    };
  3. Otherwise, the value of the global time-reap() option is used, which defaults to 60 seconds.

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().

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.


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graphite: Sending metrics to Graphite

The graphite() destination can send metrics to a Graphite server to store numeric time-series data. There are many ways to feed the Graphite template function with name value pairs. The syslog-ng OSE CSV and PatternDB parsers (for details, see Using pattern parsers) can parse log messages and generate name value pairs based on message content. The CSV parser (for details, see Parsing messages with comma-separated and similar values) can be used for logs that have a constant field based structure, like the Apache web server access logs. The patterndb parser can parse information and can extract important fields from free form log messages, as long as patterns describing the log messages are available. Another way is to send JSON-based log messages (for details, see JSON parser) to syslog-ng OSE, like running a simple shell script collecting metrics and running it from cron regularly.

To see an example of how the graphite() destination is used to collect statistics coming from syslog-ng, see the blog post Collecting syslog-ng statistics to Graphite.

Declaration:
graphite(payload());
Example: Using the graphite() driver

To use the graphite() destination, the only mandatory parameter is payload, which specifies the value pairs to send to graphite. In the following example any value pairs starting with "monitor." are forwarded to graphite.

destination d_graphite { graphite(payload("--key monitor.*")); };

NOTE:

The graphite() destination is only a wrapper around the network() destination and the graphite-output template function. If you want to fine-tune the TCP parameters, use the network() destination instead, as described in graphite-output.


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