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<html>
<!-- $Id: users_guide.html,v 1.23 2003/04/16 23:21:03 graziano Exp $ -->
<head>
<title>Network Weather Service User's Guide</title>
</head>
<body>
<h1>Running the NWS</h1>
<p>
Four programs located in your installation bin subdirectory start NWS daemon
processes, called "hosts", that provide
<a href="#nws_nameserver">directory services</a>,
<a href="#nws_memory">persistent storage</a>,
<a href="#nws_sensor">resource monitoring</a>, and
<a href="#nws_forecaster">forecasting</a>. Each of these hosts
listens for service requests on a particular port. You specify an NWS host by
giving the machine it's running on and the port it's listening to in the form
<i>machine</i>[:<i>port</i>] (the DNS name or IP address followed optionally by
a colon and port number). For example, the NWS host specified as
vermillion.ufo.edu:8090 is a process located on the machine
vermillion.ufo.edu that listens on port 8090.
<p>
The other programs located in the bin subdirectory are utility programs
designed to
<ul>
<li><a href="#add_forecast">derive forecasts from a series of measurements</a>
<li><a href="#ctrl_host">determine NWS host status</a>
<li><a href="#halt_activity">stop monitoring resource availability</a>
<li><a href="#host">convert between DNS names and IP addresses</a>
<li><a href="#html-hosts">produce HTML tables of inter-host bandwidth and
latency measurements</a>
<li><a href="#nws-hostadmin">ease administration of NWS hosts</a>
<li><a href="#nws_extract">extract measurements and forecasts from the NWS</a>
<li><a href="#nws_insert">store new measurements in the NWS</a>
<li><a href="#nws_ping">test the connection to an NWS sensor</a>
<li><a href="#nws_search">query the configuration of the NWS system</a>
<li><a href="#start_activity">start monitoring resource availability</a>
<li><a href="#whattime">convert NWS time stamps to a date and time</a>
</ul>
Each of these programs contacts one or more NWS hosts through their listening
ports in order to fulfill your requests.
<p><hr>
<h1>The NWS Environment</h1>
<p>
Most of the NWS programs require you to enter host names, port numbers, and
other initialization information. You can specify default values for much of
this information, either by setting environment variables before running the
programs or by storing the defaults in the nws initialization file ~/.nwsrc.
The NWS programs recognize each of the names listed below. During execution
the programs look first for an environment variable with this name; if none has
been set, they then search the initialization file for a line consisting of
that name followed by an equals sign and a value. Lines in the initialization
file that begin with "#" are ignored, so you can include comments in your file.
Any values you specify via the command line override the environment values.
<p>
<table>
<tr>
<td><b>EXTRACT_FIELDS</b>
<td>The fields printed by nws_extract. If this variable is not set, the
program prints, in order, time, measurement, MAE forecast, MAE error,
MSE forecast, MSE error, source, destination, and resource for each
forecast.
<tr>
<td><b>FORECASTER_PORT</b>
<td>The port forecasters should listen to for incoming messages.
Forecasters use port 8070 if this variable is not set.
<tr>
<td><b>JOURNAL_SIZE</b>
<td>Then number of records memories store in their journals, which record
all measurements stored by memories. Memories store 2000 records if
this variable is not set. Memory journals are intended for future NWS
development, so you should have no need to set this variable.
<tr>
<td><b>MEMORY_DIR</b>
<td>The directory where memories should store measurements. Memories use
the current working directory if this variable is not set.
<tr>
<td><b>MEMORY_PORT</b>
<td>The port memories should listen to for incoming messages. Memories use
port 8050 if this variable is not set.
<tr>
<td><b>MEMORY_SIZE</b>
<td>The number of measurements memories should retain for each resource.
Memories store 2000 measurements if this variable is not set.
<tr>
<td><b>NAME_SERVER</b>
<td>The host specification of the name server other hosts should contact
for directory information. The default name server is "noname", so you
must always specify a name server through environment variables, the
initialization file, or the command line.
<tr>
<td><b>NAME_SERVER_PORT</b>
<td>The port name servers should listen to for incoming messages. Name
servers use port 8090 if this variable is not set.
<tr>
<td><b>NAME_SERVER_LDAP</b>
<td>If this variable exists, regardless of its value, then NWS processes
will use LDAP instead of the NWS wire protocol to communicate with name
servers.
<tr>
<td><b>SENSOR_MEMORY</b>
<td>The host specification of the memory that sensors should contact in
order to store their resource measurements. Sensors contact the memory
running on the same machine, listening to the default memory port, if
this variable is not set.
<tr>
<td><b>SENSOR_PORT</b>
<td>The port sensors should listen to for incoming messages. Sensors use
port 8060 if this variable is not set.
</table>
<p>
A typical ~/.nwsrc file might look like this:
<pre>
NAME_SERVER = vermillion.ufo.edu
NAME_SERVER_PORT = 8888
MEMORY_DIR = /tmp/nwsinfo
</pre>
<p>
This would indicate that hosts should contact vermillion.ufo.edu at
port 8888 for registration information. The third line indicates that
memories should place measurements into files in the directory
/tmp/nwsinfo.
<p><a name="nws_nameserver"><hr></a>
<h1>Starting a Name Server</h1>
<p>
You'll probably want to start by setting up an NWS name server. This is an NWS
host that provides all other hosts with information about the location and
abilities of other NWS hosts. You can use the
<a href="#nws_search">nws_search</a> program to view registrations stored with
a name server. Run the program as a background process.
<p>
<b>nws_nameserver</b> [<b>-c</b> <i>seconds</i>]
[<b>-e</b> <i>file</i>]
[<b>-f</b> <i>file</i>]
[<b>-l</b> <i>file</i>]
[<b>-p</b> <i>port</i>] <b>&</b>
<p>
<table>
<tr>
<td><b>-c</b>
<td>Specifies how frequently the name server should delete expired
registrations from the registration file. The default is 3600 (once an
hour).
<tr>
<td><b>-e</b>
<td>Specifies a file where the name server should record error messages.
By default, error messages are sent to standard error.
<tr>
<td><b>-f</b>
<td>Specifies a file where the name server should store registrations. The
default is the file <b>registrations</b> in the current working
directory.
<tr>
<td><b>-l</b>
<td>Specifies a file where the name server should record log messages. By
default, log messages are sent to standard output.
<tr>
<td><b>-p</b>
<td>Specifies the port that the name server should listen to for messages.
This overrides any default value from the environment or ~/.nwsrc.
</table>
<p>
This command, executed on orange.ufo.edu, starts an NWS name server that uses
the default port and stores registrations and message output in the directory
$HOME/NWSdir:
<pre>
nws_nameserver -e $HOME/NWSdir/nameserver.err \
-f $HOME/NWSdir/registrations \
-l $HOME/NWSdir/nameserver.log &
</pre>
<a name="registrations">
<p>
</a>
<h2>NWS Registrations</h2>
<p>
NWS registrations follow the LDAP model. Each registered object consists of a
set of attributes, each of which has a name and a value. Every object has a
<b>name</b> attribute, which (usually uniquely) identifies the object, and an
<b>objectclass</b> attribute, which specifies what sort of item the object
represents. Other attributes are specific to particular <b>objectclass</b>
values.
<p>
NWS host registrations have an <b>objectclass</b> value of <b>nwsHost</b>.
The other attributes associated with NWS host registrations are:
<table>
<tr>
<td><b>hostType</b>
<td>One of <b>forecaster</b>, <b>memory</b>, or <b>sensor</b>. No
registration record is presently entered for the name server itself.
<tr>
<td><b>ipAddress</b>
<td>The IP address used to contact the host. This attribute may have
multiple values if the host can be contacted through multiple addresses.
<tr>
<td><b>owner</b>
<td>The login of the person who started the host.
<tr>
<td><b>port</b>
<td>The port on which the host receives messages.
<tr>
<td><b>started</b>
<td>The date and time when the host was started.
<tr>
<td><b>version</b>
<td>The version of the NWS sources used to create the host.
</table>
<p>
NWS sensors register objects with an <b>objectclass</b> value of
<b>nwsSkill</b>. These objects represent services that the sensor can
perform, and different sensors may register different skills. These skills are
used with the <a href="#start_activity">start_activity</a> program to configure
NWS resource monitoring. In addition to <b>name</b> and <b>objectclass</b>
attributes, each registered skill has a <b>host</b> attribute, which is the
registration name of the sensor that registered the skill, and a
<b>skillName</b> attribute that identifies the type of service that the skill
represents. In addition, each skill has a set of option attributes which
indicate ways in which the skill can be configured. The values of these
configuration options indicate the number and type of configuration values that
you can specify for these options when requesting the service. For example, a
value of <b>0_to_10_int</b> for the <b>cpuMonitor</b> skill's <b>nice</b>
option indicates that you can specify up to 10 integer values for the
<b>nice</b> option when requesting that an NWS sensor begin monitoring CPU
availability. The currently supported skills and their associated options are:
<table>
<tr>
<td><b>cpuMonitor</b>
<td>This skill monitors the fraction of CPU available to both newly-started
and existing processes. It has the option attribute
<b>nice:0_to_10_int</b>, which indicates that you can monitor the CPU
available for processes running at up to 10 different nice values. If
you do not specify any nice values, the NWS monitors CPU availability
only for nice 0 processes.
<tr>
<td><b>diskMonitor</b>
<td>This skill monitors the amount of space available on a disk. It has
the option attribute <b>path:1_to_10_string</b>, which indicates that
you must specify between 1 and 10 file paths. The sensor monitors the
amount of space available on the disks that hold the directories or
files specified by these paths.
<tr>
<td><b>memoryMonitor</b>
<td>This skill monitors the amount of free memory available on the machine.
It has no option attributes and is available only on Linux systems.
<tr>
<td><b>tcpConnectMonitor</b>
<td>This skill monitors the time required to establish a TCP connection
between each pair of a set of machines. It has the option attribute
<b>target:1_to_100_sensor</b>, which indicates that you must specify
between 1 and 100 NWS sensors to contact. (This only applies when you
use this skill under the <b>periodic</b> control (see below). When run
under the <b>clique</b> control, the <b>tcpConnectMonitor</b> target
sensors are taken from the clique membership.)
<tr>
<td><b>tcpMessageMonitor</b>
<td>This skill monitors the TCP bandwidth and latency between each pair of
a set of machines. It has the attributes <b>size:0_to_1_int</b>,
<b>message:0_to_1_int</b>, and <b>buffer:0_to_1_int</b>. These allow
you to specify, in kilobytes, the total data size, individual
<i>send</i>() message size, and socket buffer size used for bandwidth
tests. If you do not specify these values, the NWS sends 64kB of data
in four 16kB messages, using a socket buffer size of 32kB. Like the
<b>tcpConnectMonitor</b> skill, <b>tcpMessageMonitor</b> also has the
option attribute <b>target:1_to_100_sensor</b> which must be specified
when using the skill under the <b>periodic</b> control.
</table>
<p>
Skills operate under the control of sensor <b>control</b> objects, which
determine the frequency and timing of experiments. These objects have an
<b>objectclass</b> value of <b>nwsControl</b>. In addition to <b>name</b>
and <b>objectclass</b> attributes, each registered control has a <b>host</b>
attribute, which is the registration name of the sensor that registered the
control, and a <b>controlName</b> attribute that identifies the type of
control. Different controls support different skills, and each control has a
set of configuration options that you can use to guide its operation. The
currently supported controls and their associated skills and options are:
<table>
<tr>
<td><b>clique</b>
<td>This control coordinates experiments between a set of NWS sensors,
called the <i>members</i> of the clique. These members take turns
conducting experiments, and only one member will conduct experiments
at any time. This is useful for avoiding contention when conducting
network experiments between machines. The clique control can be used
with either the <b>tcpConnectMonitor</b> or <b>tcpMessageMonitor</b>
skill. It has the option attributes <b>member:2_to_100_sensor</b>,
indicating that you must specify between 2 and 100 NWS sensors as
participating members of the clique, and <b>period:0_to_1_int</b>,
which indicates that you may specify the number of seconds between
connection attempts between any pair of hosts. If you do not specify a
period, the NWS will compute one.
<tr>
<td><b>periodic</b>
<td>This control can be used with any of the skills listed above to conduct
experiments at fixed intervals. It has the option attribute
<b>period:0_to_1_int</b> that allows you to specify how often
experiments should be conducted.
</table>
<p>
When an NWS sensor receives a service request, it registers an
<b>nwsActivity</b> object. The attributes of an activity object are the union
of those of the control and skill objects used to start the activity, but the
option attributes in the activity object indicate the values used for
configuration. For example, a <b>cpuMonitor</b> activity might have a
<b>nice:0,19</b> attribute, indicating that the sensor is monitoring CPU
availability for both nice 0 and nice 19 processes. Each activity also has
a <b>resource</b> attribute that lists the resources it is measuring. The
resources that the NWS presently measures are:
<table>
<tr>
<td><b>availableCpu</b>
<td>The fraction of CPU available to a newly-started process. This
resource is measured by the <b>cpuMonitor</b> skill.
<tr>
<td><b>bandwidthTcp</b>
<td>The speed with which data can be sent to a target sensor, in megabits
per second. This resource is measured by the <b>tcpMessageMonitor</b>
skill.
<tr>
<td><b>connectTimeTcp</b>
<td>The amount of time, in milliseconds, required to establish a TCP
connection to a target sensor. This resource is measured by the
<b>tcpConnectMonitor</b> skill.
<tr>
<td><b>currentCpu</b>
<td>The fraction of CPU available to a process that is already running.
This resource is measured by the <b>cpuMonitor</b> skill.
<tr>
<td><b>freeDisk</b>
<td>The amount of space, in megabytes, unused on a disk. This resource is
measured by the <b>diskMonitor</b> skill.
<tr>
<td><b>freeMemory</b>
<td>The amount of space, in Megabytes, unused in memory. This resource is
measured by the <b>memoryMonitor</b> skill.
<tr>
<td><b>latencyTcp</b>
<td>The amount of time, in milliseconds, required to transmit a TCP message
to a target sensor. This resource is measured by the
<b>tcpMessageMonitor</b> skill.
</table>
<p>
An activity generates one or more series of measurements, each of which is
registered as an <b>nwsSeries</b> object. The
<a href="#nws_extract">nws_extract</a> program uses these registrations to
retrieve measurements for display and forecasting.
Along with <b>name</b> and <b>objectclass</b> attributes, <b>nws_series</b>
registrations include the following attributes:
<table>
<tr>
<td><b>host</b>
<td>This is the registration name of the NWS sensor that is generating the
series measurements.
<tr>
<td><b>memory</b>
<td>This is the registration name of the NWS memory that is storing the
series measurements.
<tr>
<td><b>resource</b>
<td>This indicates what resource the series measures.
<tr>
<td><b>target</b>
<td>For series that measure resource availability of an inter-machine
resource (e.g. bandwidth), this attribute is the specification of the
NWS sensor that is the target of the measurements. Single-machine
series (e.g. CPU availability) do not have this attribute.
<tr>
<td><b>unitLabel</b>
<td>This is a string that indicates what units the measurement values in
the series represent. For example, the <b>unitLabel</b> attribute
value for bandwidth series is <b>Megabits/second</b>, while the value
for CPU series is <b>CPU Fraction</b>.
</table>
<p><a name="nws_memory"><hr></a>
<h1>Starting a Memory Host</h1>
<p>
After setting up your name server, you'll need to start an NWS memory. This is
an NWS host that stores and retrieves measurements for other hosts. Run the
program as a background process.
<p>
<b>nws_memory</b> [<b>-C</b> <i>cache entries</i>]
[<b>-d</b> <i>directory</i>]
[<b>-e</b> <i>file</i>]
[<b>-l</b> <i>file</i>]
[<b>-N</b> <i>host</i>]
[<b>-L</b>]
[<b>-p</b> <i>port</i>]
[<b>-s</b> <i>size</i>] <b>&</b>
<p>
<table>
<tr>
<td><b>-C</b>
<td>Specifies the number of cache entries to use internally.
<b>nws_memory</b> maintains an internal write-thru LRU cache of time-series
data to speed fetch times. Each entry is <b>fileSize * 50</b> bytes in size,
where <b>fileSize</b> is the size set by the <b>-s</b> described below.
The default is 256 entries and a <b>fileSize</b> of 2000 records implying
a default memory footprint of approximately 25 megabytes. Increasing
this value will aid fetch performance at the expense of in-core memory
footprint.
<tr>
<td><b>-d</b>
<td>Specifies the directory where the memory should store its measurements.
This overrides any default value from the environment or ~/.nwsrc. The
amount of required storage space depends on how many resources you
monitor, but 10-15 MB is typical.
<tr>
<td><b>-e</b>
<td>Specifies a file where the memory should record error messages. By
default, error messages are sent to standard error.
<tr>
<td><b>-l</b>
<td>Specifies a file where the memory should record log messages. By
default, log messages are sent to standard output.
<tr>
<td><b>-N</b>
<td>Specifies the NWS name server that this memory should contact. This
overrides any default value from the environment or ~/.nwsrc.
<tr>
<td><b>-L</b>
<td>Specifies that this memory should communicate with its name server
using the LDAP protocol instead of the NWS wire protocol.
<tr>
<td><b>-p</b>
<td>Specifies the port that the memory should listen to for messages. This
overrides any default value from the environment or ~/.nwsrc.
<tr>
<td><b>-s</b>
<td>Specifies how many measurements should be retained for each resource.
This overrides any default value from the environment or ~/.nwsrc and
has a default value of 2000 records.
</table>
<p>
This command, executed on orange.ufo.edu, starts an NWS memory that uses port
8055, registers itself with the name server previously started on orange, and
stores measurements and message output in the directory $HOME/NWSdir:
<pre>
nws_memory -d $HOME/NWSdir \
-e $HOME/NWSdir/memory.err \
-l $HOME/NWSdir/memory.log \
-N orange.ufo.edu \
-p 8055 &
</pre>
<p>
This command, executed on red.ufo.edu, starts an NWS memory that uses the
default port, stores measurements in the subdirectory RedNWS, and registers
itself with the name server previously started on orange:
<pre>
nws_memory -d RedNWS/ \
-N orange.ufo.edu &
</pre>
<p><a name="nws_sensor"><hr></a>
<h1>Starting a Sensor Host</h1>
<p>
After starting a memory host, you can set up an NWS sensor host on one or more
machines to monitor resource availability. After starting a sensor host, you
can use the <a href="#start_activity">start_activity</a> program to specify
which resources it should monitor. Run the program in the background.
<p>
<b>nws_sensor</b> [<b>-c</b> <b>yes</b>/<b>no</b>]
[<b>-a</b> <i>name</i>]
[<b>-e</b> <i>file</i>]
[<b>-l</b> <i>file</i>]
[<b>-M</b> <i>host</i>]
[<b>-N</b> <i>host</i>]
[<b>-L</b>]
[<b>-p</b> <i>port</i>] <b>&</b>
<p>
<table>
<tr>
<td><b>-a</b> <td>Specifies a name for the host other than the default. This is useful for hosts that are multi-homed.
<tr>
<td><b>-c</b>
<td>Specifies whether or not the sensor should immediately begin monitoring
CPU availability for nice 0 processes (the <b>cpuMonitor</b> skill).
The default is <b>yes</b>.
<tr>
<td><b>-e</b>
<td>Specifies a file where the sensor should record error messages. By
default, error messages are sent to standard error.
<tr>
<td><b>-l</b>
<td>Specifies a file where the sensor should record log messages. By
default, log messages are sent to standard output.
<tr>
<td><b>-M</b>
<td>Specifies the NWS memory that the sensor should use to store its
measurements. This overrides any default value from the environment
or ~/.nwsrc.
<tr>
<td><b>-N</b>
<td>Specifies the NWS name server that this sensor should contact. This
overrides any default value from the environment or ~/.nwsrc.
<tr>
<td><b>-L</b>
<td>Specifies that this sensor should communicate with its name server
using the LDAP protocol instead of the NWS wire protocol.
<tr>
<td><b>-p</b>
<td>Specifies the port that the sensor should listen to for messages. This
overrides any default value from the environment or ~/.nwsrc.
</table>
<p>
This command, executed on orange.ufo.edu, starts an NWS sensor that uses the
memory started above on red.ufo.edu to store its measurements:
<pre>
nws_sensor -M red.ufo.edu -N orange.ufo.edu &
</pre>
<p>
This command, executed on red.ufo.edu, also uses the memory running on red:
<pre>
nws_sensor -N orange.ufo.edu &
</pre>
<p><a name="nws_forecaster"><hr></a>
<h1>Starting a Forecaster Host</h1>
<p>
NWS forecaster hosts analyze resource availability measurements collected by
NWS sensors to forecast how much of the resources will be available in the near
future. Since the <a href="#nws_extract">nws_extract</a> program computes its
forecasts directly, you only need to start a forecaster process if you want to
write programs that use remote forecasting services. Run the forecaster
program in the background.
<p>
<b>nws_forecast</b> [<b>-D</b>] [<b>-e</b> <i>file</i>]
[<b>-l</b> <i>file</i>]
[<b>-N</b> <i>host</i>]
[<b>-L</b>]
[<b>-p</b> <i>port</i>] <b>&</b>
<table>
<tr>
<td><b>-D</b>
<td>Enables debugging output.
<tr>
<tr>
<td><b>-e</b>
<td>Specifies a file where the forecaster should record error messages. By
default, error messages are sent to standard error.
<tr>
<td><b>-l</b>
<td>Specifies a file where the forecaster should record log messages. By
default, log messages are sent to standard output.
<tr>
<td><b>-N</b>
<td>Specifies the NWS name server that this forecaster should contact.
This overrides any default value from the environment or ~/.nwsrc.
<tr>
<td><b>-L</b>
<td>Specifies that this forecaster should communicate with its name server
using the LDAP protocol instead of the NWS wire protocol.
<tr>
<td><b>-p</b>
<td>Specifies the port that the forecaster should listen to for messages.
This overrides any default value from the environment or ~/.nwsrc.
</table>
<p>
This command, executed on green.ufo.edu, starts an NWS forecaster:
<pre>
nws_forecast -e GreenNWS/fore.err \
-l GreenNWS/fore.log \
-N orange.ufo.edu &
</pre>
<p><a name="add_forecast"><hr></a>
<h1>Generating Forecasts</h1>
<p>
The add_forecasts program is a filter that derives forecasts from a series of
measurements. It takes from standard input a series of lines that contain
time-stamp/measurement pairs and prints these lines to standard output along
with forecast and forecast error values. Any text that follows the time-stamp
and measurement is taken to be a series name, and forecasts can be added to
multiple series.
<p>
For example, given the input
<p>
<pre>
953834769 1.007150 blue.ufo.edu numbers
953834779 1.012400
953834789 1.020350
953834799 1.025690
953834809 1.031060
953834819 1.033760
953834829 0.996740
953834839 0.966310
953834849 0.941820
953834859 0.929860
953834857 0.689050 green.ufo.edu numbers
953834867 0.734150
953834877 0.797280
953834888 0.793330
953834898 0.812850
953834908 0.829850
953834918 0.851220
953834928 0.889380
953834938 0.909760
953834948 0.771710
</pre>
<p>
add_forecast produces the output
<p>
<pre>
953834769 1.007150 1.007150 0.000000 blue.ufo.edu numbers
953834779 1.012400 1.012400 0.005250
953834789 1.020350 1.020350 0.006600
953834799 1.025690 1.025690 0.006180
953834809 1.031060 1.031060 0.005978
953834819 1.033760 1.033760 0.005322
953834829 0.996740 1.010508 0.006850
953834839 0.966310 0.966310 0.010219
953834849 0.941820 0.941820 0.012003
953834859 0.929860 0.929860 0.011998
953834857 0.689050 0.689050 0.000000 green.ufo.edu numbers
953834867 0.734150 0.734150 0.045100
953834877 0.797280 0.797280 0.054115
953834888 0.793330 0.793330 0.037393
953834898 0.812850 0.812850 0.032925
953834908 0.829850 0.829850 0.029740
953834918 0.851220 0.851220 0.028345
953834928 0.889380 0.889380 0.029747
953834938 0.909760 0.909760 0.028576
953834948 0.771710 0.774437 0.025738
</pre>
<p>
The third column of output lists the forecast derived from previous
measurements for the series; the fourth column the observed error in the
forecasts to that point.
<p><a name="ctrl_host"><hr></a>
<h1>Controlling Running Hosts</h1>
<p>
You can use the ctrl_host program to send one of a selection of commands to a
running NWS host. These commands control and test the operation of the
target hosts.
<p>
<b>ctrl_host</b> [<b>-t</b> <i>seconds</i>]
[<b>-z</b>]
<i>command</i>
<i>host</i> [<i>host</i> ...]
<p>
<table>
<tr>
<td><b>-t</b>
<td>Specifies a time out value for attempts to contact the target hosts.
The default is 10 seconds, which may be insufficient for contacting
hosts over a very slow network.
<tr>
<td><b>-z</b>
<td>Suppresses the production of error messages. This can be useful for
scripts that automate host testing.
</table>
<p>
<i>command</i> must be one of the following. Abbreviations are allowed.
<p>
<table>
<tr>
<td><b>error</b>
<td>Directs the host to suppress or resume error message output.
<tr>
<td><b>halt</b>
<td>Directs the host to exit.
<tr>
<td><b>log</b>
<td>Directs the host to suppress or resume log message output.
<tr>
<td><b>register</b>
<td>Directs the host to register with a new name server using the NWS
wire protocol and start using that in place of its old name server.
The first host given on the command line is used as the name server
with which the rest of the hosts listed should register.
<tr>
<td><b>ldap_register</b>
<td>Directs the host to register with a new name server using the LDAP
protocol and start using that in place of its old name server.
The first host given on the command line is used as the name server
with which the rest of the hosts listed should register.
<tr>
<td><b>test</b>
<td>Directs the host to check its registration with the NWS name server and
report the results.
</table>
<p><a name="halt_activity"><hr></a>
<h1>Stopping NWS Activities</h1>
<p>
The halt_activity program allows you to tell the NWS to stop monitoring a
resource or set of resources.
<p>
<b>halt_activity</b> [<b>-N</b> <i>host</i>]
[<b>-L</b>]
[<b>-S</b> <i>host</i>]
<i>name</i>
<p>
<table>
<tr>
<td><b>-N</b>
<td>Specifies the NWS name server that contains directory information for
the activity. This overrides any default value from the environment or
~/.nwsrc.
<tr>
<td><b>-L</b>
<td>Specifies that communication with the name server should be done using
the LDAP protocol instead of the NWS wire protocol.
<tr>
<td><b>-S</b>
<td>Specifies a sensor to contact to stop the activity. The program
normally determines this information by contacting the name server.
Specifying the sensor yourself can sometimes be useful if your
connection to the name server is slow, or if you want to use a specific
clique member to halt a clique.
</table>
The <b>halt_activity</b> program contacts the name server to retrieve
information about the specified activity, then contacts the sensor in charge of
the activity to terminate it. See the
<a href="#start_activity">start_activity</a> program for information on
how to resume monitoring resources after a halt.
<p><a name="host"><hr></a>
<h1>Accessing DNS Information</h1>
<p>
The host program prints IP addresses and DNS names for each address or name you
give on the command line. This is similar to the standard tool of the same
name that is available on many Unix systems.
<p>
<b>host</b> <i>name</i> [...]
<p>
A pair of examples:
<pre>
host www.whitehouse.gov yahoo.com
www.whitehouse.gov 198.137.240.92 198.137.240.91
yahoo.com 204.71.200.243 204.71.200.245
host 198.137.240.91
www1.whitehouse.gov 198.137.240.91
</pre>
<p><a name="html-hosts"><hr></a>
<h1>Producing Tables of NWS Measurements</h1>
<p>
The html-hosts script uses the <a href="#nws_extract">nws_extract</a> program
to produce an HTML table of inter-machine bandwidth and latency measurements
and forecasts.
<p>
<b>html-hosts</b> <i>host</i> <i>host</i> [...]
<p>
For example, assuming that the NWS activities were conducting tcpMessageMonitor
activities between the machines blue.ufo.edu, green.ufo.edu, orange.ufo.edu
and red.ufo.edu, the following command would produce a 4-by-4 table that could
be incorporated into a web page:
<p>
<pre>
html-hosts blue.ufo.edu green.ufo.edu orange.ufo.edu red.ufo.edu
</pre>
<p><a name="nws-hostadmin"><hr></a>
<h1>Administering NWS Hosts</h1>
<p>
The nws-hostadmin script can assist you in the task of tracking NWS hosts. It
is especially useful for keeping track of NWS hosts running on remote machines.
<p>
<b>nws-hostadmin</b> <i>command</i>
[ [<b>-b</b> <i>path</i>]
[<b>-B</b> <i>path</i>]
[<b>-f</b> <i>path</i>]
[<b>-m</b> <i>path</i>]
[<b>-M</b> <i>path</i>]
[<b>-l</b> <i>login</i>]
[<b>-L</b> <i>login</i>]
[<b>-s</b> <i>switches</i>]
[<b>-S</b> <i>switches</i>]
<i>hosts</i> ... ]
<p>
<table>
<tr>
<td><b>-b<br>-B</b>
<td>Use the specified path to find the NWS binaries for the next host set
(<b>-b</b>) or for all subsequent host sets (<b>-B</b>). By default,
the script expects to find the NWS binaries in the directory
$HOME/nws/bin.
<tr>
<td><b>-f</b>
<td>Use the specified path to find the NWS hosts data base (see below). By
default, the script uses $HOME/.nwshosts.
<tr>
<td><b>-l<br>-L</b>
<td>Use the specified login as the remote user id for the next host set
(<b>-l</b>) or for all subsequent host sets (<b>-L</b>). By default,
the script uses $USER.
<tr>
<td><b>-m<br>-M</b>
<td>Use the specified path as the remote shell program for the next host
set (<b>-m</b>) or for all subsequent host sets (<b>-M</b>). By
default, the script uses ssh.
<tr>
<td><b>-s<br>-S</b>
<td>Pass the specified switches when starting the next host set (<b>-s</b>)
or when starting all remaining host sets (<b>-S</b>). By default, the
script passes -e and -l switches that direct the host to place its
error and log output into the directory $HOME/nws/<i>machine</i>.
Memories are also passed a -d switch that directs them to store data
files in the same directory.
</table>
<p>
<i>command</i> must be one of the following. Abbreviations are allowed.
<table>
<tr>
<td><b>add</b>
<td>Adds the host to the NWS hosts data base (see below), without affecting
the host itself.
<tr>
<td><b>cycle</b>
<td>Equivalent to <b>halt</b> followed by <b>start</b>.
<tr>
<td><b>forget</b>
<td>Removes the host from the NWS hosts data base (see below), without
affecting the host itself.
<tr>
<td><b>halt</b>
<td>Sends a message indicating that the host should exit.
<tr>
<td><b>kill</b>
<td>A stronger form of <b>halt</b>. It sends a SIGKILL signal to the
host process(es).
<tr>
<td><b>purge</b>
<td>Equivalent to <b>halt</b> followed by <b>forget</b>.
<tr>
<td><b>revive</b>
<td>Equivalent to <b>test</b>, followed by <b>start</b> if the host is dead.
<tr>
<td><b>start</b>
<td>Begins execution of the host.
<tr>
<td><b>test</b>
<td>Displays the status of the host.
</table>
<p>
<i>hosts</i> has the format
<i>machine</i>[:<i>type</i>[:<i>port</i>][,<i>type</i>[:<i>port</i>]...]].
The <i>type</i> is one of <b>forecaster</b>, <b>memory</b>, <b>nameserver</b>,
or <b>sensor</b>, indicating the NWS host of interest. Abbreviations can be
used. You only need to specify a <i>port</i> if more than one host of a
particular type is running on the same machine, or if you're starting a host
and wish to use a port other than the default. If only the machine is
specified, the script applies the command to all hosts running on the machine.
<p>
If <i>hosts</i> is omitted altogether, the script applies the command to all
hosts listed in the NWS hosts data base. The script stores in this data base a
list of NWS hosts that have been specified as part of either an <b>add</b> or a
<b>start</b> command. Each record lists the machine name, host type, port, NWS
binary path, and switches for a particular NWS host. When the script is asked
to manage NWS hosts, it queries this data base to determine what hosts are
running and how they can be contacted. The script uses the ctrl_host program
to contact NWS hosts, so this program must be available in some directory
listed in your PATH environment variable.
<p>
As one example, this command would use rsh to start a memory, sensor, and
forecaster on orange.ufo.edu and ssh (the default) to start the same three
hosts on yellow.ufo.edu:
<pre>
nws-hostadmin start -m rsh orange.ufo.edu -b /usr/local/nws yellow.ufo.edu
</pre>
<p>
("-M rsh" would indicate that rsh should be used for both orange and yellow.)
The nws binaries on orange.ufo.edu are located in $HOME/nws/bin, while those
on yellow.ufo.edu are found in /usr/local/nws. Assuming that the NWS hosts
data base did not previously exist, it would now contain six records, one for
each started host:
<pre>
orange.ufo.edu memory:8050 nws/bin
orange.ufo.edu sensor:8060 nws/bin
orange.ufo.edu forecaster:8070 nws/bin
yellow.ufo.edu memory:8050 /usr/local/nws
yellow.ufo.edu sensor:8060 /usr/local/nws
yellow.ufo.edu forecaster:8070 /usr/local/nws
</pre>
<p>
The subsequent command
<pre>
nws-hostadmin test
</pre>
<p>
would display the current status of each of these six hosts. If only the
sensor and memory running on orange were of interest, then the command
<pre>
nws-hostadmin test orange.ufo.edu:sen,mem
</pre>
<p>
would display the desired information. The sequence of commands
<pre>
nws-hostadmin halt yellow.ufo.edu:forecaster
nws-hostadmin revive yellow.ufo.edu
</pre>
<p>
would have the effect of restarting the yellow forecaster. The first command
terminates the running forecaster, while the second tests the status of all
three yellow hosts, restarting the forecaster when it determines that the host
is no longer running. A simpler way to do this would be the single command
<pre>
nws-hostadmin cycle yellow.ufo.edu:forecaster
</pre>
<p>
As it operates, the script displays a status for each NWS host of interest:
<p>
<table>
<tr>
<td><b>confused</b>
<td>The host is running but responds strangely to test messages.
<tr>
<td><b>cycled</b>
<td>The host has been halted and started again.
<tr>
<td><b>dead</b>
<td>The host is not running.
<tr>
<td><b>forgotten</b>
<td>The host has been removed from the NWS hosts data base.
<tr>
<td><b>halted</b>
<td>The host has been halted.
<tr>
<td><b>healthy</b>
<td>The host is responding properly to test messages.
<tr>
<td><b>killed</b>
<td>The host has been killed.
<tr>
<td><b>purged</b>
<td>The host has been halted and forgotten.
<tr>
<td><b>revived</b>
<td>The host was dead and has been started again.
<tr>
<td><b>sick</b>
<td>The host is running, but it may have lost contact with the name server.
<tr>
<td><b>started</b>
<td>The host has been started.
<tr>
<td><b>uncycled</b>
<td>An attempt to restart a host after halting it has failed.
<tr>
<td><b>unhaltable</b>
<td>An attempt to halt the host has failed.
<tr>
<td><b>unkillable</b>
<td>An attempt to send a kill signal to the host has failed.
<tr>
<td><b>unresponsive</b>
<td>The host is running, but it is not responding to test messages. A
slow network connection may be the only problem.
<tr>
<td><b>unrevivable</b>
<td>An attempt to restart a dead host has failed.
<tr>
<td><b>unstarted</b>
<td>An attempt to start the host has failed.
</table>
<p><a name="nws_extract"><hr></a>
<h1>Accessing NWS Measurements</h1>
<p>
The nws_extract program provides easy access to NWS measurements and forecasts.
<p>
<b>nws_extract</b> [<b>-a</b>]
[<b>-f</b> <i>fieldList</i>]
[<b>-h</b> <i>n</i>]
[<b>-M</b> <i>host</i>]
[<b>-n</b> <i>n</i>]
[<b>-N</b> <i>host</i>]
[<b>-L</b>]
[<b>-t</b> <i>n</i>]
[<b>-w</b>]
<i>resource</i>
[<i>filter</i>]
<i>host</i> [<i>host</i> ...]
<p>
<table>
<tr>
<td><b>-a</b>
<td>Treat all listed machines as experiment sources. By default, the
program treats the first machine as the experiment source and the
others as experiment destinations. Use this switch to get information
about all pairs of machines.
<tr>
<td><b>-f</b>
<td>Specifies which information you would like displayed. <i>fieldList</i>
is a comma-delimited list of forecast field names that you would like
to see. The recognized names are <b>destination</b>, the destination
host specification, <b>mae_error</b>, the computed error in the Mean
Absolute Error forecast, <b>mae_forecast</b>, the Mean Absolute Error
forecast itself, <b>mae_method</b>, the forecasting method used to
compute the Mean Absolute Error forecast, <b>measurement</b>, the
measured resource availability, <b>mse_error</b>, the computed error in
the Mean Square Error forecast, <b>mse_forecast</b>, the Mean Square
Error forecast itself, <b>mse_method</b>, the forecasting method used
to compute the Mean Square Error forecast, <b>resource</b>, the
name of the resource measured, <b>source</b>, the source host
specification, and <b>time</b>, the time the measurement was taken.
These field names may all be abbreviated, so you can, for example, use
"me" instead of "measurement" and "t" instead of "time." This
overrides any default value from the environment or ~/.nwsrc.
<tr>
<td><b>-h</b>
<td>Include a column header in the display after every <i>n</i>
measurements. A value of 0 suppresses the column header. The default
value is 20.
<tr>
<td><b>-M</b>
<td>Specifies the memory to contact to retrieve measurements. nws_extract
normally determines this information by contacting the name server.
Specifying this switch may improve response if all the resource
measurements you are retrieving are stored by a single memory.
<tr>
<td><b>-n</b>
<td>Specifies the number of forecasts or measurements to display initially
for each series. The program prints 20 by default.
<tr>
<td><b>-N</b>
<td>Specifies the NWS name server that contains directory information for
the NWS hosts of interest. This overrides any default value from the
environment or ~/.nwsrc. You only need to specify a name server if the
memories that are storing the resource measurements of interest are
registered with a name server other than the default and you have not
specified a -M switch.
<tr>
<td><b>-L</b>
<td>Specifies that communication with the name server should be done using
the LDAP protocol instead of the NWS wire protocol.
<tr>
<td><b>-t</b>
<td>Specifies how far in the past to display measurements. By default, the
program displays an hour's worth of information.
<tr>
<td><b>-w</b>
<td>Specifies that the program, after displaying the initial measurements
and forecasts, should continue to display additional information as new
measurements are taken. The program will continue to update its
display until you abort it with ^C.
</table>
<p>
<i>resource</i> specifies the resource of interest. See the discussion of
<a href="#registrations">registrations</a> above for the list of resources
measured by the NWS. You can use abbreviations of any of these standard
resource names. Alternately, you can specify a resource name that specifies
measurements stored in the NWS using the <a href="#nws_insert">nws_insert</a>
program.
<p>
<i>filter</i> has the same format as the filter used with the
<a href="#nws_search">nws_search</a> program. It can be used to differentiate
between multiple measurement series being collected for the same resource. If
you do not specify a filter, nws_extract displays all measurement series being
collected for the resources you list.
<p>
Using the colors clique example described above, you could get a running report
of red -> orange bandwidth measurements and forecasts by the command:
<pre>
nws_extract -w band red.ufo.edu orange.ufo.edu
</pre>
<p>
Dropping the "-w" from this command would give you a single list of
measurements and forecasts for the past hour instead of a running report, while
adding "-a" would give you both red -> orange and orange -> red values.
Similarly,
<pre>
nws_extract -f time,measurement -t 900 avail purple.ufo.edu
</pre>
<p>
would give you a snapshot report of available CPU fraction over the past 15
minutes.
<p>
Supposing that the NWS was collecting green.ufo.edu available cpu measurements
for both nice 0 and nice 19 processes, then the commands
<pre>
nws_extract avail -f time,measurement "(nice=0)" green.ufo.edu
nws_extract avail -f time,measurement "(nice=19)" green.ufo.edu
nws_extract avail -f time,measurement green.ufo.edu
</pre>
would display, respectively, only the nice 0 measurements, only the nice 19
measurements, and both sets of measurements.
<p><a name="nws_search"><hr></a>
<h1>Accessing NWS Registrations</h1>
<p>
The nws_search displays objects registered with the NWS name server.
<p>
<b>nws_search</b> [<b>-a</b>]
[<b>-f</b> <b>yes</b>/<b>no</b>]
[<b>-N</b> <i>host</i>]
[<b>-L</b>]
[<b>-v</b>]
<i>filter</i>
[<i>attribute</i> ...]
<p>
<table>
<tr>
<td><b>-a</b>
<td>Indicates that only attribute names should be displayed, not values.
<tr>
<td><b>-f</b>
<td>Indicates whether to format the program output, listing one attribute
per line and padding the names. The default is <b>yes</b>.
<tr>
<td><b>-N</b>
<td>Specifies the NWS name server of interest. This overrides any default
value from the environment or ~/.nwsrc.
<tr>
<td><b>-L</b>
<td>Specifies that communication with the name server should be done using
the LDAP protocol instead of the NWS wire protocol.
<tr>
<td><b>-v</b>
<td>Indicates that only values should be displayed, not attribute names.
</table>
<p>
The search filter has a format patterned after LDAP filters and determines
which objects should be retrieved. Each term in a search filter specifies, in
parentheses, an attribute name and a value or value range which the
retrieved objects must have. See the discussion of
<a href="#registrations">NWS registrations</a> above for the set of attributes
supported by the NWS. nws_search supports the relational operators =, <=,
and >=, and wild cards (*) may be included in the value for the = operator.
(nws_search recognizes the LDAP "sounds like" operator, ~=, but treats it
identically to =.) Logical and, or, and not operations (&, |, !) may be
used as prefix operators to combine filter terms into more complex filters. In
addition, the shorthand filters <b>activities</b>, <b>cliques</b>,
<b>forecasters</b>, <b>hosts</b>, <b>memories</b>, <b>sensors</b>,
<b>series</b> and <b>skills</b> (or an abbreviation of these) can be used
instead of the longer objectclass specifications. Some examples:
<pre>
<i>Retrieve all activity registrations:</i>
nws_search "(objectclass=nwsActivity)" <i>or</i>
nws_search <b>activities</b>
<i>Retrieve all clique registrations:</i>
nws_search "(&(objectclass=nwsActivity)(control=clique))" <i>or</i>
nws_search <b>cliques</b>
<i>Retrieve all forecaster host, memory host, or sensor host registrations:</i>
nws_search "(hostType=forecaster)" <i>or</i>
nws_search <b>forecasters</b>
nws_search "(hostType=memory)" <i>or</i>
nws_search <b>memories</b>
nws_search "(hostType=sensor)" <i>or</i>
nws_search <b>sensors</b>
<i>Retrieve all control registrations:</i>
nws_search "(objectclass=nwsControl)" <i>or</i>
nws_search <b>controls</b>
<i>Retrieve all host registrations:</i>
nws_search "(hostType=*)"
nws_search <b>hosts</b>
<i>Retrieve all series registrations:</i>
nws_search "(objectclass=nwsSeries)" <i>or</i>
nws_search <b>series</b>
<i>Retrieve all skill registrations:</i>
nws_search "(objectclass=nwsSkill)" <i>or</i>
nws_search <b>skills</b>
<i>Retrieve all hosts running on 111.222.333.444:</i>
nws_search "(ip=111.222.333.444)"
<i>Retrieve all cliques of which green.ufo.edu is not a member:</i>
nws_search "(&(objectclass=nwsActivity)(control=clique)(!(member=*green.ufo.edu:*)))"
</pre>
<p><a name="nws_insert"><hr></a>
<h1>Storing Measurements in the NWS</h1>
<p>
The nws_insert program provides a way to store measurements from other programs
in an NWS memory. After storing measurements in the NWS, you can use the
<a href="#nws_extract">nws_extract</a> program to generate forecasts based on
these measurements.
<p>
<b>nws_insert</b> [<b>-f</b> <i>file</i>]
[<b>-M</b> <i>host</i>]
<i>resource</i>
<i>machine</i> [<i>machine</i>]
<p>
<table>
<tr>
<td><b>-f</b>
<td>Specifies a file name from which the measurements should be read. The
program reads from standard input by default.
<tr>
<td><b>-M</b>
<td>Specifies a memory in which to store the measurements. By default, the
program attempts to select the best available memory.
</table>
<p>
nws_insert recognizes the standard NWS resource names (see the discussion of
<a href="#registrations">NWS registrations</a> above), so you can, for
example, store your own bandwidth measurements. However, a more likely use of
this program is to store measurements for a resource that the NWS does not
currently track, such as disk access time. Any resource name of up to 30
characters can be used for this purpose. The NWS remembers the name you use,
and you can later use the same name with <a href="#nws_extract">nws_extract</a>
in order to retrieve measurements or generate forecasts. The two machines can
be given as either DNS names or IP addresses. The first specifies the
measurement source; the second specifies the measurement destination for
inter-machine resources.
<p>
Each line of input to nws_insert consists of a pair of numbers. The first
indicates the time that the measurement was taken and is represented by a
number of seconds since midnight, 1/1/1970 GMT (the value returned by the Unix
<i>time</i>() system call). The second is a floating point number that
represents the value of the measurement. Blank lines and lines beginning with
'#' are ignored; these can be used to format and comment your data files. For
example, an input file named "speedo.dat" for nws_insert might contain these
lines:
<pre>
# These are latency measurements taken periodically by the speedo utility.
# They measure latency between orange.ufo.edu and green.ufo.edu.
911826158 1.045000
911828415 0.445000
911829922 1.030000
911831030 1.182000
911831947 1.042000
911832926 1.003000
911834240 1.040000
911835179 0.999000
911836339 1.047000
911837431 1.098000
911838593 1.057000
911839682 1.056000
911841052 1.043000
911842529 1.022000
911844053 1.026000
911844935 1.057000
911846314 0.917000
911847821 1.045000
911849317 1.023000
911850663 1.031000
</pre>
<p>
You could store these measurements in the NWS using the command
<pre>
nws_insert -f speedo.dat speedo_latency orange green
</pre>
<p>
Afterward, you could generate a forecast for these measurements:
<pre>
nws_extract -h 0 speedo_latency orange green
911826158 1.045000 1.045000 0.225317 Median orange green speedo_latency
911828415 0.445000 1.045000 0.225854 Median
911829922 1.030000 1.045000 0.224959 Median
911831030 1.182000 1.045000 0.224144 Median
911831947 1.042000 1.042000 0.223261 Median
911832926 1.003000 1.042000 0.222392 Median
911834240 1.040000 1.042000 0.221523 Median
911835179 0.999000 1.042000 0.220668 Median
911836339 1.047000 1.045000 0.219813 Median
911837431 1.098000 1.050353 0.218975 Trimmed_Median
911838593 1.057000 1.059176 0.218133 Trimmed_Median
911839682 1.056000 1.057771 0.217297 Adjusted_Mean
911841052 1.043000 1.041021 0.216469 Adjusted_Mean
911842529 1.022000 1.040234 0.215647 Adjusted_Mean
911844053 1.026000 1.039937 0.214831 Adjusted_Mean
911844935 1.057000 1.043271 0.214021 Adjusted_Mean
911846314 0.917000 1.039064 0.213277 Adjusted_Mean
911847821 1.045000 1.042239 0.212478 Adjusted_Mean
911849317 1.023000 1.041830 0.211687 Adjusted_Mean
911850663 1.031000 1.039059 0.210900 Trimmed_Median
</pre>
<p><a name="nws_ping"><hr></a>
<h1>Testing connections to NWS sensors</h1>
<p>
The nws_ping program contacts NWS sensors on remote machines and reports the
observed latency and bandwidth.
<p>
<b>nws_ping</b> [<b>-repeat</b> <i>seconds</i>]
[<b>-size</b> <i>experiment,buffer,message</i>]
[<b>-timeout</b> <i>seconds</i>]
<i>host</i> [ ... ]
<p>
<table>
<tr>
<td><b>-repeat</b>
<td>Indicates the program should continuously re-establish connections and
conduct experiments with the sensors every <i>seconds</i> seconds. If
this switch is not present, the program exits after one test.
<tr>
<td><b>-size</b>
<td>Allows configuration of the data sizes used in communicating to the
sensors. The <i>experiment</i> value specifies the total number of
kilobytes to transmit, the <i>message</i> value the number of kilobytes
per message, and the <i>buffer</i> value the TCP buffer size. If this
switch is not present, the program sends 64 kilobytes in four
16-kilobyte messages, using a buffer size of 32 kilobytes.
<tr>
<td><b>-timeout</b>
<td>Indicates the number of seconds that should be allowed to lapse before
a connection is considered to have failed. The default is 10.
</table>
<p>
This command measures the bandwidth and latency to blue.ufo.edu and
green.ufo.edu:
<pre>
nws_ping blue.ufo.edu green.ufo.edu
(64k,32k,16k) to blue.ufo.edu:8060: bandwidthTcp: 0.963341 Megabits/second latencyTcp: 98.685000 Milliseconds
(64k,32k,16k) to green.ufo.edu:8060: bandwidthTcp: 0.387839 Megabits/second latencyTcp: 156.394000 Milliseconds
</pre>
<p><a name="start_activity"><hr></a>
<h1>Starting NWS Activities</h1>
<p>
You can use the start_activity program to control which resources NWS sensors
monitor.
<p>
<b>start_activity</b> [<b>-F</b>] [<b>-a</b>] [<b>-f</b> <i>file</i>]
<i>host</i>
[<i>optionAttribute</i> ...]
<p>
<table>
<tr>
<td><b>-F</b>
<td>Force the sensor to start this activity even a record of it
still exists in the nws_nameserver.
</tr>
<td><b>-a</b>
<td>Restart all activities of this host (in this case, other arguments
are not read).
</tr>
<tr>
<td><b>-f</b>
<td>Specifies a file from which option attribute values should be read.
Blank lines in this file are ignored, as is any text following a "#".
Additional option attribute values may be listed on the command line.
</tr>
</table>
<p>
<i>host</i> specifies the sensor to contact. Each <i>optionAttribute</i> is a
<i>name</i>:<i>value</i> pair that specifies one configuration parameter.
The <b>name</b>, <b>controlName</b>, and <b>skillName</b> option attributes are
valid for all activities. <b>name</b> specifies the name with which the
activity is registered with the NWS name server. If you do not specify a
<b>name</b> attribute, the program will generate one for you. <b>skillName</b>
and <b>controlName</b> determine which resources the activity monitors and how
frequently measurements are made. Which other option attribute names are
recognized depends on the skill and control. If you do not specify a
<b>controlName</b> or a <b>skillName</b> attribute, start_activity will try to
determine the values from the other options you list. See the discussion on
<a href="#registrations">NWS registrations</a> above for a list of supported
skills and controls and their associated option attributes.
<p>
For example, here are the contents of a options attributes file that configures
a tcpMessageMonitor activity between four machines:
<pre>
name:colors
controlName:clique
skillName:tcpMessageMonitor
member:orange.ufo.edu
member:yellow.ufo.edu
member:red.ufo.edu
member:green.ufo.edu
size:32
period:120
</pre>
<p>
The ordering of the lines and the number of option attributes specified on each
line are unimportant. A file with these contents would specify the same
option attributes as the one above:
<pre>
member:yellow.ufo.edu size:32 skillName:tcpMessageMonitor period:120
member:orange.ufo.edu name:colors member:red.ufo.edu controlName:clique
</pre>
<p>
Assuming that this file was named "myclique", a command to start this activity
running would be:
<pre>
start_activity -f myclique red.ufo.edu
</pre>
<p>
Specifying any of the other participating sensors -- orange, yellow, or
green -- instead of red as the host to contact would work equally well. If you
later wanted to replace green with purple, you would edit the option attributes
file to read:
<pre>
name:colors
controlName:clique
skillName:tcpMessageMonitor
member: orange.ufo.edu
member: yellow.ufo.edu
member: red.ufo.edu
# member: green.ufo.edu
member: purple.ufo.edu
period: 120
</pre>
<p>
(you could delete the line containing green rather than commenting it), use the
<a href="#halt_activity">halt_activity</a> program to stop colors, then
invoke start_activity again:
<pre>
start_activity -f myclique yellow.ufo.edu
</pre>
<p>
This command would direct the sensor on orange.ufo.edu to begin measuring
CPU availability for both nice 0 and nice 19 processes:
<pre>
start_activity start orange.ufo.edu nice:0 nice:19
</pre>
<p><a name="whattime"><hr></a>
<h1>Convert Time-Stamps to Dates and Times</h1>
<p>
NWS measurements are stored using a time-stamp, expressed as a number of
seconds since 1/1/1970 GMT (the value returned by the Unix <i>time</i>() system
call). The whattime program takes a list of these numbers and displays them
in readable form.
<p>
<b>whattime</b> <i>time-stamp</i> [...]
<p>
For example:
<pre>
whattime 953834769 911837431
953834769 == Thu Mar 23 10:06:09 2000
911837431 == Mon Nov 23 08:10:31 1998
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