7.6.5. HDFS destination options

The hdfs destination stores the log messages in files on the Hadoop Distributed File System (HDFS). The hdfs destination has the following options.

The following options are required: hdfs-file(), hdfs-uri(). Note that to use hdfs, 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 hdfs destination, include the path to the directory where you copied the required libraries (see Procedure 7.6.1, Prerequisites), for example, client-lib-dir("/opt/syslog-ng/lib/syslog-ng/java-modules/*.jar:/opt/hadoop/libs/*.jar").

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.

Warning

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. This option has priority over --qdisk-dir=.
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.

Options reliable() and disk-buf-size() are required options.

Example 7.17. 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")
            )
        );
};

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.

hdfs-append-enabled()

Type: true | false
Default: false

Description: When hdfs-append-enabled is set to true, syslog-ng OSE will append new data to the end of an already existing HDFS file.

When hdfs-append-enabled is set to false, the syslog-ng OSE application always creates a new file if the previous has been closed. In that case, appending data to existing files is not supported.

When you choose to write data into an existing file, syslog-ng OSE does not extend the filename with a UUID suffix because there is no need to open a new file (a new unique ID would mean opening a new file and writing data into that).

Warning

Before enabling the hdfs-append-enabled option, ensure that your HDFS server supports the append operation and that it is enabled. Otherwise syslog-ng OSE will not be able to append data into an existing file, resulting in an error log.

hdfs-archive-dir()

Type: string
Default: N/A

Description: The path where syslog-ng OSE will move the closed log files. If syslog-ng OSE cannot move the file for some reason (for example, syslog-ng OSE cannot connect to the HDFS NameNode), the file remains at its original location. For example, hdfs-archive-dir("/usr/hdfs/archive/").

hdfs-file()

Type: string
Default: N/A

Description: The path and name of the log file. For example, hdfs-file("/usr/hdfs/mylogfile.txt"). syslog-ng OSE checks if the path to the logfile exists. If a directory does not exist syslog-ng OSE automatically creates it.

hdfs-file() supports the usage of macros. This means that syslog-ng OSE can create files on HDFS dynamically, using macros in the file (or directory) name.

Note

When a filename resolved from the macros contains a character that HDFS does not support, syslog-ng OSE will not be able to create the file. Make sure that you use macros that do not contain unsupported characters.

Example 7.18. Using macros in filenames

In the following example, a /var/testdb_working_dir/$DAY-$HOUR.txt file will be created (with a UUID suffix):

destination d_hdfs_9bf3ff45341643c69bf46bfff940372a {
    hdfs(client-lib-dir(/hdfs-libs)
 hdfs-uri("hdfs://hdp2.syslog-ng.balabit:8020")
 hdfs_file("/var/testdb_working_dir/$DAY-$HOUR.txt"));
};

As an example, if it is the 31st day of the month and it is 12 o'clock, then the name of the file will be 31-12.txt.

hdfs-max-filename-length()

Type: number
Default: 255

Description: The maximum length of the filename. This filename (including the UUID that syslog-ng OSE appends to it) cannot be longer than what the file system permits. If the filename is longer than the value of hdfs-max-filename-length, syslog-ng OSE will automatically truncate the filename. For example, hdfs-max-filename-length("255").

hdfs-resources()

Type: string
Default: N/A

Description: The list of Hadoop resources to load, separated by semicolons. For example, hdfs-resources("/home/user/hadoop/core-site.xml;/home/user/hadoop/hdfs-site.xml").

hdfs-uri()

Type: string
Default: N/A

Description: The URI of the HDFS NameNode is in hdfs://IPaddress:port or hdfs://hostname:port format. When using MapR-FS, the URI of the MapR-FS NameNode is in maprfs://IPaddress or maprfs://hostname format, for example: maprfs://10.140.32.80. The IP address of the node can be IPv4 or IPv6. For example, hdfs-uri("hdfs://10.140.32.80:8020"). The IPv6 address must be enclosed in square brackets ([]) as specified by RFC 2732, for example, hdfs-uri("hdfs://[FEDC:BA98:7654:3210:FEDC:BA98:7654:3210]:8020").

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.

kerberos-keytab-file()

Type: string
Default: N/A

Description: The path to the Kerberos keytab file that you received from your Kerberos administrator. For example, kerberos-keytab-file("/opt/syslog-ng/etc/hdfs.headless.keytab"). This option is needed only if you want to authenticate using Kerberos in Hadoop. You also have to set the hdfs-option-kerberos-principal() option. For details on the using Kerberos authentication with the hdfs() destination, see Section 7.6.4, Kerberos authentication with syslog-ng hdfs() destination.

destination d_hdfs {
    hdfs(client-lib-dir("/hdfs-libs/lib")
    hdfs-uri("hdfs://hdp-kerberos.syslog-ng.balabit:8020")
    kerberos-keytab-file("/opt/syslog-ng/etc/hdfs.headless.keytab")
    kerberos-principal("hdfs-hdpkerberos@MYREALM")
    hdfs-file("/var/hdfs/test.log"));
};

Available in syslog-ng OSE version 3.10 and later.

kerberos-principal()

Type: string
Default: N/A

Description: The Kerberos principal you want to authenticate with. For example, kerberos-principal("hdfs-user@MYREALM"). This option is needed only if you want to authenticate using Kerberos in Hadoop. You also have to set the hdfs-option-kerberos-keytab-file() option. For details on the using Kerberos authentication with the hdfs() destination, see Section 7.6.4, Kerberos authentication with syslog-ng hdfs() destination.

destination d_hdfs {
    hdfs(client-lib-dir("/hdfs-libs/lib")
    hdfs-uri("hdfs://hdp-kerberos.syslog-ng.balabit:8020")
    kerberos-keytab-file("/opt/syslog-ng/etc/hdfs.headless.keytab")
    kerberos-principal("hdfs-hdpkerberos@MYREALM")
    hdfs-file("/var/hdfs/test.log"));
};

Available in syslog-ng OSE version 3.10 and later.

log-fifo-size()

Type: number
Default: Use global setting.

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

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.

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.

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 Section 11.1.5, 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.

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.

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 Section 11.1.3, Date-related macros.

The timezone can be specified as using the name of the (for example time-zone("Europe/Budapest")), or as the timezone offset in +/-HH:MM format (for example +01:00). On Linux and UNIX platforms, the valid timezone names are listed under the /usr/share/zoneinfo directory.

ts-format()

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 Section 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.