Krake

Krake provides health monitor functionality for servers.

Overview

Krake is a health monitor which can check the server's health status.

Feature List:

• Support health monitoring in:
• ICMP
• TCP
• HTTP/HTTPS
• Support callback mechanism that can call user-specified scripts/commands to notify the health status
• Support writing logs into syslog or file

Krake runs as a daemon and can be configured by a xml styled configuration file. Krake can run in most Unix like environment, incl. Linux and xBSD.

Installation

Requires:

• libevent2
• libmnl

Read the INSTALL file in the source code tree.

General Usage

The krake daemon supports the following options:

    --config/-c             Assign the configruation file
    --reload/-r             Reload the configruation file
    --show/-s               Show health status, -s all for all monitor, -s monitor_name for one monitor
    --quit/-q               Shutdown krake
    --version/-v            Show Krake version
    --help/-h               Show this help

Configuration

Default configuration file: $prefix/etc/krake.conf, the $prefix refers to the parameter passed to configure script while compile the source code.

Example:

    <?xml version="1.0"?>
    <krk_config>
            <monitor>                               <!--Keyword for krake configuration, monitor can more than one-->
                    <name>monitor1</name>               <!--name of a monitor-->
                    <status>enable</status>             <!--Only can be enable or disable; 
                                                        when enable, also starts the monitor's timer;
                                                        when disable, also stops the monitor's timer-->
                    <checker>http</checker>             <!--specify a checker using by a monitor-->
                    <checker_param>send-file:"~/request" 
                            expected-file:"~/response"</checker_param>    <!--checker's parameters, see below-->
                    <interval>5</interval>              <!--interval of monitor's timer in seconds-->
                    <timeout>3</timeout>                <!--time out value of checked host in seconds-->
                    <failure_threshold>3</failure_threshold>            <!--how many times of failures happen, marking host as down-->
                    <success_threshold>3</success_threshold>            <!--how many times of successes happen, marking host as up-->
                    <node>
                            <host>10.1.1.2</host>               <!--ip address of a checked host, either ipv4 address is valid-->
                            <port>8080</port>                   <!--port number of a checked host, range is 1 ~ 65535-->
                    </node>
                    <node>
                            <host>10.1.1.3</host>               <!--ip address of a checked host, either ipv4 address is valid-->
                            <port>8080</port>                   <!--port number of a checked host, range is 1 ~ 65535-->
                    </node>
                    <script>~/notifier.sh</script>              <!--failure notification, if user specify this option,
                                                          when a failure of a checked host is deteceted, krake will call this script-->
            </monitor>
            <log>                               <!--set logging attributes-->
                    <logtype>syslog</logtype>       <!--set the type of logs that krake sends, value can be file, syslog-->
                    <loglevel>notice</loglevel>          <!--set the level of logs, under which the logs will not be sent out-->
            </log>
    </krk_config>

If don't want to use this file, you can assign another xml file by krake command line

After you make some modifications to the configuration file, you can use "krake -r" to force the daemon reload the configuration file without stopping the current detection.

Configuration of the Checkers

At current stage, only http checker has the checker parameters.

http checker:
    
    <checker-param>send-file:"/path/to/a/file" expected-file:"/path/to/a/file"</checker-param>

This let you to specify what to send and what to expected to receive when you use the http checker.
You can write the http packet into a send file and tell Krake what to send.

If these parameters are missing, then Krake will send a minimum http request packet as:
    GET / HTTP/1.0
    Host: test
    Connection: Close

and expect only the 200 status of the http response.
http checker now only supports HTTP 1.0 protocol.