README
¶
#jobd
Jobd implements cron as a 9p file system. 9p is a simple file protocol to build sane distributed systems. It's the cornerstone of the Styx Architecture for Distributed Systems which represents the system's resources as a form of file system. Jobd illustrates this approach to system design using the go9p library.
##Installation
jobd uses godep to capture its dependencies. To install it just
$ go get github.com/wkharold/jobd
To build it, make sure you have godep installed and then
$ godep go install
##Usage
jobd --help
Usage of jobd:
-alsologtostderr=false: log to standard error as well as files
-dbdir="/var/lib/jobd": Location of the jobd jobs database
-debug=false: 9p debugging to stderr
-fsaddr="0.0.0.0:5640": Address where job file service listens for connections
-log_backtrace_at=:0: when logging hits line file:N, emit a stack trace
-log_dir="": If non-empty, write log files in this directory
-logtostderr=false: log to standard error instead of files
-stderrthreshold=0: logs at or above this threshold go to stderr
-v=0: log level for V logs
-vmodule=: comma-separated list of pattern=N settings for file-filtered logging
Once jobd is started the file system it provides can be mounted via
$ mount -t 9p -o protocol=tcp,port=5640 <addr> <mountpoint>
Where addr is the IP address of the box running jobd. Note that it needn't be mounted on the machine running jobd, any box running a Linux 3.x kernel should suffice.
##Design
cron is a time-based job scheduler, it has two primary concerns: jobs which are commands to be executed, and schedules that determine when a job is run. The design of a 9p-based application or system service generally begins with the creation of a name space, think file system subtree, that represents the application's resources in terms of files and directories.
Jobd represents jobs as subdirectories of a jobs directory. Each job subdirectory contains four files:
- the ctl file which is used to start and stop the job
- the cmd file that records the command the job executes
- the log file that is used to retrieve the job's execution history
- the schedule file that records the job's schedule and its next scheduled execution time
To start a job, write the string start to the ctl file
$ echo -n start > <mountpoint>/jobs/<job>/ctl
Similarly to stop it write the string stop to the ctl file
$ echo -n stop > <mountpoint>/jobs/<job>/ctl
Read from the cmd, log, or schedule file to retrieve the information they provide
$ cat <mountpoint>/jobs/<job>/cmd
echo hello world
$ cat <mountpoint>/jobs/<job>/schedule
0 0/5 * * * ? *
$ cat <mountpoint>/jobs/<job>/log
2014-02-11 09:42:33.454707331 -0600 CST:started
2014-02-11 09:42:35.004655691 -0600 CST:hello world
2014-02-11 09:42:40.003579265 -0600 CST:hello world
2014-02-11 09:42:45.003220637 -0600 CST:hello world
2014-02-11 09:42:50.00294003 -0600 CST:hello world
...
Jobd jobs are created via the clone file. The clone file is a peer of the jobs directory in the jobd name space. To create a job write a string of the form: :: to the clone file
$ echo -n 'hello:0 0/5 * * * ? *:echo hello world' > <mountpoint>/clone
##TODO
- support deleting jobs
Documentation
¶
Overview ¶
jobd is a 9p server that executes jobs - standard Unix command lines a'la cron.
Source Files
Directories
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| Path | Synopsis |
|---|---|
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Godeps
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_workspace/src/code.google.com/p/go9p/p
The p9 package provides the definitions and functions used to implement the 9P2000 protocol.
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The p9 package provides the definitions and functions used to implement the 9P2000 protocol. |
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_workspace/src/code.google.com/p/go9p/p/clnt
The clnt package provides definitions and functions used to implement a 9P2000 file client.
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The clnt package provides definitions and functions used to implement a 9P2000 file client. |
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_workspace/src/code.google.com/p/go9p/p/clnt/examples/tls
Connects to a server over TLS and lists the specified directory
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Connects to a server over TLS and lists the specified directory |
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_workspace/src/code.google.com/p/go9p/p/srv
The srv package provides definitions and functions used to implement a 9P2000 file server.
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The srv package provides definitions and functions used to implement a 9P2000 file server. |
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_workspace/src/code.google.com/p/go9p/p/srv/examples/tlsramfs
Listen on SSL connection, can be used as an example with p/clnt/examples/tls.go Sample certificate was copied from the Go source code
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Listen on SSL connection, can be used as an example with p/clnt/examples/tls.go Sample certificate was copied from the Go source code |
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_workspace/src/github.com/golang/glog
Package glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup.
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Package glog implements logging analogous to the Google-internal C++ INFO/ERROR/V setup. |
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_workspace/src/github.com/gorhill/cronexpr
Package cronexpr parses cron time expressions.
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Package cronexpr parses cron time expressions. |