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 auto-generated 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
|add||Start an adaptor.||See below|
|close||Close socket connection to agent.||None|
|help||Display a list of available commands||None|
|list||List currently running adaptors||None|
|reloadcollectors||Re-read list of collectors (deprecated)||None|
|stop||Stop adaptor, abruptly||Adaptor name|
|stopall||Stop all adaptors, abruptly||Adaptor name|
|shutdown||Stop adaptor, gracefully||Adaptor name|
|stopagent||Stop agent process||None|
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 '='. Chukwa Adaptor names all start with "adaptor_". If you specify an adaptor name which does not start with that prefix, it will be added automatically.
Adaptor parameters aren't required by the Chukwa agent, but each class of adaptor may itself specify 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 pipeline writers. This option is intended for testing and debugging, not for production use.
bin/chukwa agent 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 FileAdaptor FooData /tmp/foo 0
This pushes file /tmp/foo as one chunk, with datatype FooData.
- filetailer.LWFTAdaptor 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. If log file is rotated while there is unread data, this adaptor will not attempt to recover it.
add filetailer.LWFTAdaptor BarData /foo/bar 0
This pushes /foo/bar in a sequence of Chunks of type BarData
- filetailer.FileTailingAdaptor Repeatedly tails a file, again ignoring content and with unspecified Chunk boundaries. Takes one mandatory parameter; a path to the file to tail. Keeps a file handle open in order to detect log file rotation.
add filetailer.FileTailingAdaptor BarData /foo/bar 0
This pushes /foo/bar in a sequence of Chunks of type BarData
- filetailer.RCheckFTAdaptor An experimental modification of the above, which avoids the need to keep a file handle open. Same parameters and usage as the above.
- filetailer.CharFileTailingAdaptorUTF8 The same as the base FileTailingAdaptor, 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.
- filetailer.FileTailingAdaptorPreserveLines Similar to CharFileTailingAdaptorUTF8. The difference with the latter is mainly seen in the Demux Chukwa process: CharFileTailingAdaptorUTF8 will process every line one by one whereas FileTailingAdaptorPreserveLines will process all the lines of a same Chunk in a same go which makes the Demux jobs faster. Same parameters and usage as the above.
- DirTailingAdaptor Takes a directory path and an 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 with an adaptor that keeps file handles open, it is possible to exceed your system's limit on open files. A file pattern can be specified as an optional second parameter.
add DirTailingAdaptor logs /var/log/ *.log filetailer.CharFileTailingAdaptorUTF8 0
- ExecAdaptor Takes a frequency (in milliseconds) 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, labeling output as Df.
- UDPAdaptor Takes a port number as mandatory parameter. Binds to the indicated UDP port, and emits one Chunk for each received packet.
add UdpAdaptor Packets 1234 0
This adaptor will listen for incoming traffic on port 1234, labeling output as Packets.
- edu.berkeley.chukwa_xtrace.XtrAdaptor (available in contrib) Takes an Xtrace ReportSource class name [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.
- sigar.SystemMetrics This adaptor collects CPU, disk, network utilization as well as model and specifications of the machine, and emits data as one Chunk periodically.
add sigar.SystemMetrics SystemMetrics 60 0
This adaptor will take snapshots of system state every minute, labeling output as SystemMetrics.
- SocketAdaptor This adaptor binds to a port and listen for Log4J SocketAppender traffic. Each logging entry is converted to one chunk.
add SocketAdaptor JobSummary 9098 0
This adaptor will bind to port 9098, and label output as JobSummary.