This manual is for the Pipe NodeBrain Module (version 0.1, August 2014) used to accept commands via named pipe.
Copyright © 2014 Ed Trettevik <eat@nodebrain.org>
Permission is granted to copy, distribute and/or modify this document under the terms of either the MIT License (Expat) or NodeBrain License. See the Licenses section at the end of this document for details.Short Table Of Contents
The Pipe module provides a simple unauthenticated method of communication between NodeBrain and external programs running on the same system. A pipe server node is used to accept input from other programs while a pipe node is used to write output to another program. You must use file permissions on the pipe (FIFO) file for security. An identity is associated with input commands to enable restrictions on the input commands.
To listen closely and reply well is the highest perfection we are able to attain in the art of conversation. —Francois de La Rochefoucauld (1613–1680)
To construct a successful NodeBrain application, you must configure NodeBrain to listen closely and respond well. The Operating Mode tutorial" illustrates how NodeBrain can listen for input commands from stdin and both input commands and error messages from servant scripts. NodeBrain's ability to listen is controlled by a component called the medulla. Node modules interface with the medulla to extend NodeBrain's ability to listen to include other sources of input.
A pipe node is perhaps the simplest of listening nodes. It listens to a FIFO (named pipe) file, and you can write to the pipe using any program you like, including an echo command.
To begin this tutorial, createan agent script called smokey.nb with two pipe server nodes as shown here.
#!/usr/local/bin/nb -d
# File: tutorial/Pipe/smokey.nb
-rm smokey.log
setlog="smokey.log",out=".";
declare jed identity guest;
declare chief identity owner;
define corncob node pipe.server("jed@corncob");
corncob.define r1 on(a=1 and b=2);
define peace node pipe.server("chief@peace");
peace.define r1 on(a=1 and b=2);
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The argument to a pipe.server is of the form "identity@pipe".
Identities are associated with listening nodes to limit the types of commands the interpreter will accept from the node. In this example, you associate the identity jed with the corncob pipe, and the identity chief with the peace pipe.
You have declared jed to be a guest and chief to be an owner. A guest can only connect and issue show commands—like read only access.
An owner can issue any command, including shell commands, which means they have all permissions of the user that started the agent. For this reason, pipes are created with owner-only read/write permissions.
However, if you declare the associated identity to be a "peer," you can give other user's write permission on the pipe.
They will be able to issue assertions and alerts but not modify your rules or issue shell commands.
You must still think through how the agent will respond to their assertions.
For example, if you create a rule that reboots the system when a=1, then letting someone assert a=1 is the same as letting them reboot the system.
Now let's start the agent. This script is executable because the -d (daemon) option is specificied on the she-bang line. So you can just execute it like any executable and it will load the rules and go into the background (daemonize).
$ ./smokey.nb
2008/06/1017:09:16 NB000I Argument [1] -d
2008/06/1017:09:16 NB000I Argument [2] ./smokey.nb
> #!/usr/local/bin/nb -d
> # File: smokey.nb
> -rm smokey.log
[13993]Started: -rm smokey.log
[13993]Exit(0)
> set log="smokey.log",out=".";
2008/06/1017:09:16 NB000I NodeBrain nb will log to smokey.log
> declare jed identity guest;
> declare chief identity owner;
> define corncob node pipe.server("jed@corncob");
> corncob. define r1 on(a=1 and b=2);
> define peace node pipe.server("chief@peace");
> peace. define r1 on(a=1 and b=2);
2008/06/1017:09:16 NB000I Source file "./smokey.nb" included. size=323
2008/06/1017:09:16 NB000I NodeBrain nb[13992,4118] daemonizing
$
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Use the echo command to send NodeBrain commands to the pipe servers.
$ echo stop > corncob
$ echo stop > peace
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The log file shows you what happened.
$ cat smokey.log
N o d e B r a i n 0.8.17 (Dopey) 2014-04-10
Compiled Jul 6 2014 21:00:54 x86_64-unknown-linux-gnu
Copyright (C) 2014 Ed Trettevik <eat@nodebrain.org>
MIT or NodeBrain License
----------------------------------------------------------------
/usr/local/bin/nb -d ./smokey.nb
Date Time Message
---------- ----------------------------------------------------
2014/06/10 17:09:16 NB000I NodeBrain nb[13994:1] myuser@myhost
2014/06/10 17:09:16 NB000I Agent log is smokey.log
2014/06/10 17:09:16 NM000I pipe.server peace: Listening for FIFO connections as chief@peace
2014/06/10 17:09:16 NM000I pipe.server corncob: ...
... Listening for FIFO connections as jed@corncob
2014/06/10 17:41:11 NM000I pipe.server corncob: FIFO jed@corncob
> corncob. stop
2014/06/10 17:41:11 NB000E Identity "jed" does not have authority to issue stop command.
2014/06/10 17:41:19 NM000I pipe.server peace: FIFO chief@peace
> peace. stop
2014/06/10 17:41:19 NB000I NodeBrain nb[13994] terminating - exit code=0
$
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Notice that when you sent a stop command to the corncob pipe, you didn't have the needed authority, but when you sent the same stop command to the peace pipe it worked.
Run smokey.nb again with the following commands to see what happens.
$ ./smokey.nb
$ echo "common. define r1 on(a=1 and b=2);" > peace
$ echo "common. assert a=1,b=3;" > peace
$ echo "common. assert b=2;" > peace
$ echo "common. show -t" > peace
$ echo "stop" > peace
$ cat smokey.log
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This sections describes commands used with the Pipe module.
The identity must be declared prior to pipe server definition. The FIFO identified by fileName must exist when a pipe server is enabled.
declare fred identity ... ;
define mypipe node pipe(”fred@pipe/myhose”);
... include rules here...
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The ENABLE and DISABLE commands are supported. Node commands and assertions are not currently supported.
Commands read from the pipe file are interpreted in the context of the pipe server node. Rules defined in this context must be designed for compatibility with the commands written to the pipe by the external program.
The FIFO identified by fileName must exist when a command is issued to the pipe node.
define mypipe node pipe("pipe/myhose");
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Commands directed to a pipe node are simply written to the pipe (FIFO) file.
node:... any text... |
The ENABLE and DISABLE commands and assertions are not supported.
This module does not implement triggers. Each line received on a pipe is passed to the interpretter.
NodeBrain is free software; you can modify and/or redistribute it, including this document, under the terms of either the MIT License (Expat) or the NodeBrain License.
MIT License
Copyright © 2014 Ed Trettevik <eat@nodebrain.org>
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NodeBrain License
Copyright © 2014 Ed Trettevik <eat@nodebrain.org>
Permission to use and redistribute with or without fee, in source and binary forms, with or without modification, is granted free of charge to any person obtaining a copy of this software and included documentation, provided that the above copyright notice, this permission notice, and the following disclaimer are retained with source files and reproduced in documention included with source and binary distributions.
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