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Manual Reference Pages  -  RWFLOWAPPEND (8)

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rwflowappend - Append incremental SiLK Flow files to hourly files



  rwflowappend --incoming-directory=DIR_PATH --root-directory=DIR_PATH
        --error-directory=DIR_PATH [--archive-directory=DIR_PATH]
        [--flat-archive] [--post-command=COMMAND]
        [--hour-file-command=COMMAND] [--threads=N]
        [--reject-hours-past=NUM] [--reject-hours-future=NUM]
        [--no-file-locking] [--polling-interval=NUM]
        [--byte-order=ENDIAN] [--pad-header]
        { --log-destination=DESTINATION
          | --log-pathname=FILE_PATH
          | --log-directory=DIR_PATH [--log-basename=LOG_BASENAME]
            [--log-post-rotate=COMMAND] }
        [--log-level=LEVEL] [--log-sysfacility=NUMBER]
        [--pidfile=FILE_PATH] [--no-chdir] [--no-daemon]

  rwflowappend --help

  rwflowappend --version


rwflowappend is a daemon that watches a directory for files that contain small numbers of SiLK Flow records---these files are called incremental files---as generated by rwflowpack(8) when it is run with --output-mode=incremental-files or --output-mode=sending. rwflowappend appends these SiLK Flow records to the hourly files stored in the SiLK data repository whose directory tree root is specified by the --root-directory switch.

The directory that rwflowappend watches for incremental files is specified by --incoming-directory. Once rwflowappend processes an incremental file, the file is deleted unless the --archive-directory switch is specified, in which case the incremental file is moved to that directory.

If a fatal write error occurs (for example, the disk containing the data repository becomes full), rwflowappend exits. Before exiting, rwflowappend attempts to truncate the hourly file to the size it had when it was opened, and rwflowappend moves the incremental file it was reading to the directory specified by --error-directory.

Running rwflowappend separately from rwflowpack is used when you wish to copy the packed SiLK Flow records from the machine doing the packing to multiple machines for use by analysts. Almost any network file transport protocol may be used to move the files from the packing machine to the destination machine where rwflowappend is running, though we have written the rwsender(8) and rwreceiver(8) to perform this task.

Separate rwflowpack and rwflowappend processes are also recommended if you want another process (such as the Analysis Pipeline <>) to process the SiLK Flow records as they are generated.


Option names may be abbreviated if the abbreviation is unique or is an exact match for an option. A parameter to an option may be specified as --arg=param or --arg param, though the first form is required for options that take optional parameters.

    General Configuration

The following switches are required:
--incoming-directory=DIR_PATH Watch this directory for new incremental files to append to the hourly files. rwflowappend ignores any files in this directory that are empty or whose names begin with a dot (.). In addition, new files are only considered when their size is constant for one polling-interval after they are first noticed.
--root-directory=DIR_PATH Append to existing hourly files and create new hourly files in the directory tree rooted at this location. The directory tree has the same subdirectory structure as that created by rwflowpack.
--error-directory=DIR_PATH Store in this directory incremental files that were NOT successfully appended to an hourly file.
The following switches are optional:
--archive-directory=DIR_PATH Move each incremental file to DIR_PATH or a subdirectory of it after rwflowappend has successfully appended the incremental file to an hourly file. If this switch is not provided, the incremental files are deleted once they are successfully appended to an hourly file. When the --flat-archive switch is also provided, incremental files are moved into the top of DIR_PATH; when --flat-archive is not given, each incremental file is moved to a subdirectory of DIR_PATH that mirrors the path of the hourly file to which the incremental file was appended. Removing files from the archive-directory is not the job of rwflowappend; the system administrator should implement a separate process to clean this directory. This switch is required when the --post-command switch is present.
--flat-archive When archiving incremental files via --archive-directory, move the files into the top of the archive-directory, not into subdirectories of it. This switch has no effect if --archive-directory is not also specified. This switch can be used to allow another process to watch for new files appearing in the archive-directory.
--post-command=COMMAND Run COMMAND on each incremental file after rwflowappend has successfully appended it to an hourly file and moved it into the archive-directory. Each occurrence of the string %s in COMMAND is replaced with the full path to the incremental file in the archive-directory, and each occurrence of %% is replaced with %. If any other character follows %, rwflowappend exits with an error. When using this feature, the --archive-directory must be specified. See also the rwpollexec(8) daemon.
--hour-file-command=COMMAND Run COMMAND upon creation of a new hourly file. The string %s in COMMAND is replaced with the full path to the hourly file, and the string %% is replaced with %. If any other character follows %, rwflowappend exits with an error.
--threads=N Invoke rwflowappend with N threads reading the incremental files and writing to the repository. When this switch is not provided, rwflowappend runs with a single thread. Since SiLK 3.8.2.
--reject-hours-past=NUM Reject incremental files containing records whose starting hour occurs more than this number of hours in the past relative to the current hour. Incremental files that violate this value are moved into the error directory. Times are compared using the starting hour of the flow record and the current hour. For example, flow records that start at 18:02:56 and 18:58:04 are considered 1 hour in the past whether the current time is 19:01:47 or 19:59:33. When performing live data collection, it is not uncommon to get flows one to two hours in the past due to the flow generator’s active timeout (often 30 minutes) and the time to transfer the flow records through the collection system. The default is to accept all incremental files.
--reject-hours-future=NUM Similar to --reject-hours-past, but reject incremental files containing records whose starting hour occurs more than this number of hours in the future relative to the current hour. Future dated flow records are rare, but can occur due to time drift at the sensor. The default is to accept all incremental files.
--no-file-locking Do not use advisory write locks. Normally, rwflowappend obtains a write lock on an hourly file prior to writing records to it. The write lock prevents two instances of rwflowappend from writing to the same hourly file simultaneously. However, attempting to use a write lock on some file systems causes rwflowappend to exit with an error, and this switch can be use when writing data to these file systems.
--polling-interval=NUM Check the incoming directory for new incremental files every NUM seconds. The default polling interval is 15 seconds.
--byte-order=ENDIAN Set the byte order for newly created SiLK Flow files. When appending records to an existing file, the byte order of the file is maintained. The argument is one of the following:
as-is Maintain the byte order of the incremental files (i.e., the byte order specified to rwflowpack). This is the default.
native Use the byte order of the machine where rwflowappend is running.
big Use network byte order (big endian) for the flow files.
little Write the flow files in little endian format.
--compression-method=COMP_METHOD Specify how to compress newly created hourly files. When this switch is not given, newly created hourly files maintain the compression method used by the incremental file (i.e., the compression method specified to rwflowpack). When appending to an existing hourly file, the compression method of the file is maintained. The valid values for COMP_METHOD are determined by which external libraries were found when SiLK was compiled. To see the available compression methods and the default method. use the --help or --version switch. SiLK can support the following COMP_METHOD values when the required libraries are available.
none Do not compress the output using an external library.
zlib Use the zlib(3) library for compressing the output. Using zlib produces the smallest output files at the cost of speed.
lzo1x Use the lzo1x algorithm from the LZO real time compression library for compression. This compression provides good compression with less memory and CPU overhead.
best Use lzo1x if available, otherwise use zlib.
--site-config-file=FILENAME Read the SiLK site configuration from the named file FILENAME. When this switch is not provided, rwflowappend searches for the site configuration file in the locations specified in the FILES section.

    Logging and Daemon Configuration

One of the following mutually-exclusive switches is required:
--log-destination=DESTINATION Specify the destination where logging messages are written. When DESTINATION begins with a slash /, it is treated as a file system path and all log messages are written to that file; there is no log rotation. When DESTINATION does not begin with /, it must be one of the following strings:
none Messages are not written anywhere.
stdout Messages are written to the standard output.
stderr Messages are written to the standard error.
syslog Messages are written using the syslog(3) facility.
both Messages are written to the syslog facility and to the standard error (this option is not available on all platforms).
--log-directory=DIR_PATH Use DIR_PATH as the directory where the log files are written. DIR_PATH must be a complete directory path. The log files have the form


where YYYYMMDD is the current date and LOG_BASENAME is the application name or the value passed to the --log-basename switch when provided. The log files are rotated: At midnight local time, a new log is opened, the previous file is closed, and the command specified by --log-post-rotate is invoked on the previous day’s log file. (Old log files are not removed by rwflowappend; the administrator should use another tool to remove them.) When this switch is provided, a process-ID file (PID) is also written in this directory unless the --pidfile switch is provided.

--log-pathname=FILE_PATH Use FILE_PATH as the complete path to the log file. The log file is not rotated.
The following set of switches is optional:
--log-level=LEVEL Set the severity of messages that will be logged. The levels from most severe to least are: emerg, alert, crit, err, warning, notice, info, debug. The default is info.
--log-sysfacility=NUMBER Set the facility that syslog(3) uses for logging messages. This switch takes a number as an argument. The default is a value that corresponds to LOG_USER on the system where rwflowappend is running. This switch produces an error unless --log-destination=syslog is specified.
--log-basename=LOG_BASENAME Use LOG_BASENAME in place of the application name in the name of log files in the log directory. See the description of the --log-directory switch. This switch does not affect the name of the process-ID file.
--log-post-rotate=COMMAND Run COMMAND on the previous day’s log file after log rotation. When this switch is not specified, the previous day’s log file is compressed with gzip(1). When the switch is specified and COMMAND is the empty string, no action is taken on the log file. Each occurrence of the string %s in COMMAND will be replaced with the full path to the log file, and each occurrence of %% will be replaced with %. If any other character follows %, rwflowappend exits with an error. Specifying this switch without also using --log-directory is an error.
--pidfile=FILE_PATH Set the complete path to the file in which rwflowappend writes its process ID (PID) when it is running as a daemon. No PID file is written when --no-daemon is given. When this switch is not present, no PID file is written unless the --log-directory switch is specified, in which case the PID is written to LOGPATH/
--no-chdir Do not change directory to the root directory. When rwflowappend becomes a daemon process, it changes its current directory to the root directory so as to avoid potentially running on a mounted file system. Specifying --no-chdir prevents this behavior, which may be useful during debugging. The application does not change its directory when --no-daemon is given.
--no-daemon Force rwflowappend to run in the foreground---it does not become a daemon process. This may be useful during debugging.
--help Print the available options and exit.
--version Print the version number and information about how SiLK was configured, then exit the application.


SILK_CONFIG_FILE This environment variable is used as the value for the --site-config-file when that switch is not provided.
SILK_PATH This environment variable gives the root of the install tree. When searching for configuration files, rwflowappend may use this environment variable. See the FILES section for details.


/usr/local/share/silk.conf Possible locations for the SiLK site configuration file which are checked when the --site-config-file switch is not provided, where ROOT_DIRECTORY/ is the directory specified to the --root-directory switch.


rwflowpack(8), rwreceiver(8), rwsender(8), rwpollexec(8), rwfilter(1), silk(7), gzip(1), syslog(3), zlib(3), The SiLK Installation Handbook


rwflowappend does not check the integrity of an hourly file before appending records to it.

Prior to SiLK 3.6.0 when a write error occurred, rwflowappend could leave a partially written record or compressed block in the hourly file. If a partially written compressed block remained and additional compressed blocks were appended, these compressed blocks could not be read by other SiLK tools. If a partially written record remained and additional records were appended, SiLK tools would read the unaligned data as if it were aligned and produce garbage records. Although SiLK 3.6.0 works around the issue on write errors, similar issues can occur if rwflowappend is suddenly killed (e.g., by kill -9).

When a write error occurs, rwflowappend may leave a zero byte file in the data repository. Such files do affect the exit status of rwfilter(1), though rwfilter warns about being unable to read the header from the file.

As of SiLK 3.1.0, rwflowappend obtains an advisory write lock on the hourly file it is writing, allowing multiple rwflowappend processes to write to the same hourly file. File locking may be disabled by using the --no-file-locking switch. If this switch is enabled, the administrator must ensure that multiple rwflowappend processes do not attempt to write to the same hourly file simultaneously.

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SiLK RWFLOWAPPEND (8) 2016-04-05

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