Chukwa Agent Setup Guide

In a normal Chukwa installation, an Agent process runs on every machine being monitored. This process is responsible for all the data collection on that host. Data collection might mean periodically running a Unix command, or tailing a file, or listening for incoming UDP packets.

Each particular data source corresponds to a so-called Adaptor. Adaptors are dynamically loadable modules that run inside the Agent process. There is generally one Adaptor for each data source: for each file being watched or for each Unix command being executed. Each adaptor has a unique name. If you do not specify a name, one will be autogenerated by hashing the Adaptor type and parameters.

There are a number of Adaptors built into Chukwa, and you can also develop your own. Chukwa will use them if you add them to the Chukwa library search path (e.g., by putting them in a jarfile in $CHUKWA_HOME/lib.)

Once an Agent process is running, there are a number of commands that you can use to inspect and control it. By default, Agents listen for incoming commands on port 9093. Commands are case-insensitive

The add command is by far the most complex; it takes several mandatory and optional parameters. The general form is as follows:

add [name =] <adaptor_class_name> <datatype> <adaptor 
specific params> <initial offset>. 

There are four mandatory fields: The word add, the class name for the Adaptor, the datatype of the Adaptor's output, and the sequence number for the first byte. There are two optional fields; the adaptor instance name, and the adaptor parameters.

The adaptor name, if specified, should go after the add command, and be followed with an equals sign. It should be a string of printable characters, without whitespace or '='.

Adaptor parameters aren't required by the add command, but adaptor implementations may have both mandatory and optional parameters. See below.

Normally, agents are configured via the file conf/chukwa-agent-conf.xml. However, there are a few command-line options that are sometimes useful in troubleshooting. If you specify "local" as an option, then the agent will print chunks to standard out, rather than to a collector. If you specify a URI, then that will be used as collector, overriding the collectors specified in conf/collectors. These options are intended for testing and debugging, not for production use.

bin/agent.sh local

This section lists the standard adaptors, and the arguments they take.

• FileAdaptor: Pushes a whole file, as one Chunk, then exits. Takes one mandatory parameter; the file to push.

  add FileTailer FooData /tmp/foo 0

  This pushes file /tmp/foo as one chunk, with datatype FooData.
• filetailer.FileTailingAdaptor Repeatedly tails a file, treating the file as a sequence of bytes, ignoring the content. Chunk boundaries are arbitrary. This is useful for streaming binary data. Takes one mandatory parameter; a path to the file to tail.

  add filetailer.FileTailingAdaptor BarData /foo/bar 0

  This pushes /foo/bar in a sequence of Chunks of type BarData
• filetailer.CharFileTailingAdaptorUTF8 The same, except that chunks are guaranteed to end only at carriage returns. This is useful for most ASCII log file formats.
• filetailer.CharFileTailingAdaptorUTF8NewLineEscaped The same, except that chunks are guaranteed to end only at non-escaped carriage returns. This is useful for pushing Chukwa-formatted log files, where exception stack traces stay in a single chunk.
• DirTailingAdaptor Takes a directory path and a second adaptor name as mandatory parameters; repeatedly scans that directory and all subdirectories, and starts the indicated adaptor running on each file. Since the DirTailingAdaptor does not, itself, emit data, the datatype parameter is applied to the newly-spawned adaptors. Note that if you try this on a large directory, it is possible to exceed your system's limit on open files.

  add DirTailingAdaptor logs /var/log/ filetailer.CharFileTailingAdaptorUTF8 0

• ExecAdaptor Takes a frequency (in miliseconds) as optional parameter, and then program name as mandatory parameter. Runs that program repeatedly at a rate specified by frequency.

  add ExecAdaptor Df 60000 /bin/df -x nfs -x none 0

  This adaptor will run df every minute, labelling output as Df.
• edu.berkeley.chukwa_xtrace.XtrAdaptor (available in contrib) Takes an Xtrace ReportSource classname [without package] as mandatory argument, and no optional parameters. Listens for incoming reports in the same way as that ReportSource would.

  add edu.berkeley.chukwa_xtrace.XtrAdaptor Xtrace UdpReportSource 0

  This adaptor will create and start a UdpReportSource, labeling its output datatype as Xtrace.