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<h1>6 Quality Of Service and Admin Properties</h1>
<h3><a name="id65103">6.1
Quality Of Service and Admin Properties</a></h3>
<p>This chapter explains the allowed properties for
<span class="bold_code"><a href="CosNotification_QoSAdmin.html">CosNotification_QoSAdmin</a></span> and
<span class="bold_code"><a href="CosNotification_AdminPropertiesAdmin.html">CosNotification_AdminPropertiesAdmin</a></span>.
</p>
<h4>Quality Of Service</h4>
<p>The cosNotification application supports the following QoS settings:</p>
<table border="1" cellpadding="2" cellspacing="0">
<tr>
<td align="left" valign="middle"><strong>QoS</strong></td>
<td align="left" valign="middle"><strong>Range</strong></td>
<td align="left" valign="middle"><strong>Default</strong></td>
</tr>
<tr>
<td align="left" valign="middle">EventReliability</td>
<td align="left" valign="middle">BestEffort/Persistent</td>
<td align="left" valign="middle">BestEffort</td>
</tr>
<tr>
<td align="left" valign="middle">ConnectionReliability</td>
<td align="left" valign="middle">BestEffort/Persistent</td>
<td align="left" valign="middle">BestEffort</td>
</tr>
<tr>
<td align="left" valign="middle">Priority</td>
<td align="left" valign="middle">+/-32767</td>
<td align="left" valign="middle">0</td>
</tr>
<tr>
<td align="left" valign="middle">OrderPolicy</td>
<td align="left" valign="middle">Any-, Fifo-, Priority- and Deadline-Order</td>
<td align="left" valign="middle">PriorityOrder</td>
</tr>
<tr>
<td align="left" valign="middle">DiscardPolicy</td>
<td align="left" valign="middle">RejectNewEvents, Any-, Fifo-, Lifo-, Priority- and Deadline-Order</td>
<td align="left" valign="middle">RejectNewEvents</td>
</tr>
<tr>
<td align="left" valign="middle">MaximumBatchSize</td>
<td align="left" valign="middle">long() > 0</td>
<td align="left" valign="middle">1</td>
</tr>
<tr>
<td align="left" valign="middle">PacingInterval</td>
<td align="left" valign="middle">TimeBase::TimeT (see cosTime)</td>
<td align="left" valign="middle">0</td>
</tr>
<tr>
<td align="left" valign="middle">StartTimeSupported</td>
<td align="left" valign="middle">boolean</td>
<td align="left" valign="middle">false</td>
</tr>
<tr>
<td align="left" valign="middle">StopTimeSupported</td>
<td align="left" valign="middle">boolean</td>
<td align="left" valign="middle">false</td>
</tr>
<tr>
<td align="left" valign="middle">MaxEventsPerConsumer</td>
<td align="left" valign="middle">long() > 0</td>
<td align="left" valign="middle">100</td>
</tr>
<tr>
<td align="left" valign="middle">Timeout</td>
<td align="left" valign="middle">TimeBase::TimeT (see cosTime)</td>
<td align="left" valign="middle">No timeout</td>
</tr>
</table>
<em>Table
6.1:
Table 1: Supported QoS Settings</em>
<br>
<br>
<br>
<br>
<p><strong>Comments on the table 'Supported QoS Settings':</strong></p>
<dl>
<dt><strong><strong>EventReliability</strong></strong></dt>
<dd>To allow full Persistent EventReliability, every event must
be stored in a stable storage which would create a relatively
huge overhead. Hence, only lightweight version of the Persistent
QoS is supported. The configuration parameters <span class="code">max_events</span>,
<span class="code">interval_events</span> and <span class="code">timeout_events</span> determine
the behavior of this setting.</dd>
<dt><strong><strong>ConnectionReliability</strong></strong></dt>
<dd>If this QoS is set to BestEffort and a client object returns anything
other than <span class="code">ok</span> to its associated Proxy, the Proxy will discard
all events and terminate. Using Persistent and anything other than <span class="code">ok</span>
is returned, events will be dropped but the proxy will retry later when
next delivery is due. A child may not have Persistent while its parent
has BestEffort QoS set, e.g., Proxy vs. Admin. If <span class="code">OBJECT_NOT_EXIST</span>,
<span class="code">NO_PERMISSION</span> or <span class="code">CosEventComm_Disconnected</span> is thrown,
the associated object will terminate even if this parameter is
set to Persistent.</dd>
<dt><strong><strong>Priority</strong></strong></dt>
<dd>This QoS will treat all events as if they have the Priority equal to
current value, unless the event itself contains a Priority setting,
this event will be treated accordingly. Note: for this property to
have any effect, the DiscardPolicy and/or OrderPolicy must be set
to PriorityOrder.</dd>
<dt><strong><strong>OrderPolicy</strong></strong></dt>
<dd>If set to PriorityOrder, events with the highest Priority will be
delivered first. Deadline order will forward events with shortest
expiry time first. If two events have the same priority, they will be
delivered in FIFO-order.</dd>
<dt><strong><strong>DiscardPolicy</strong></strong></dt>
<dd>If set to PriorityOrder and MaxEventsPerConsumer limit is
reached, events
with the lowest Priority will be discarded first. Deadline order will
discard events with shortest expiry time first.</dd>
<dt><strong><strong>MaximumBatchSize</strong></strong></dt>
<dd>Only valid if the object is supposed to handle a sequence of structured
events and determines the largest amount of events that may be passed
each time.</dd>
<dt><strong><strong>PacingInterval</strong></strong></dt>
<dd>Determines how long an object will wait before forwarding a structured
event sequence of length equal to, or less than MaximumBatchSize.
If set to 0, which is the default behavior, no timeout is used and
the events are forwarded when the MaximumBatchSize is reached.</dd>
<dt><strong><strong>StartTimeSupported</strong></strong></dt>
<dd>If set to true events which contains the QoS Property <span class="code">StartTime</span>
(TimeBase::UtcT - absolute time) will not be delivered until the
StartTime value have been exceeded. See also the <span class="code">cosTime</span> application.</dd>
<dt><strong><strong>StopTimeSupported</strong></strong></dt>
<dd>If set to true, events which contain the QoS Properties <span class="code">StopTime</span>
(TimeBase::UtcT - absolute time) or <span class="code">Timeout</span> (TimeBase::TimeT -
relative time) will be discarded if the object has not been able to
deliver the event in time. See also the <span class="code">cosTime</span> application.</dd>
<dt><strong><strong>MaxEventsPerConsumer</strong></strong></dt>
<dd>The maximum number of events the associated object may store before discarding
events in the way described by the DiscardPolicy.</dd>
<dt><strong><strong>Timeout</strong></strong></dt>
<dd>If this QoS property is not included in the event, and the Property
<span class="code">StopTimeSupported</span> equals true, this setting will be applied
if events cannot be delivered within its time limit.</dd>
</dl>
<div class="warning">
<div class="label">Warning</div>
<div class="content"><p>
<p>Several of the above QoS Properties can be changed during run-time but we strongly advice
not to since, if a relatively large amount of events are waiting for delivery, some of the
QoS settings would require a total reorder of the events. The QoS property <span class="code">ConnectioReliability</span>
may <strong>never</strong> be updated during run-time since it may cause deadlock. Run-time, in this case,
means activating the Channel by sending the first event.</p>
</p></div>
</div>
<h4>Setting Quality Of Service</h4>
<p>Assume we have a Consumer Admin object which we want to change
the current Quality of Service. Typical usage:</p>
<div class="example"><pre>
QoSPersistent =
[#'CosNotification_Property'
{name='CosNotification':'ConnectionReliability'(),
value=any:create(orber_tc:short(),
'CosNotification':'Persistent'())}],
'CosNotification_QoSAdmin':set_qos(Ch, QoSPersistent),
</pre></div>
<p>If it is not possible to set the requested QoS the <span class="code">UnsupportedQoS</span>
exception is raised, which includes a sequence of <span class="code">PropertyError</span>'s
describing which QoS, possible range and why is not allowed. The error
codes are:</p>
<ul>
<li>UNSUPPORTED_PROPERTY - QoS not supported for this type of target object.</li>
<li>UNAVAILABLE_PROPERTY - due to current QoS settings the given property
is not allowed.</li>
<li>UNSUPPORTED_VALUE - property value out of range; valid range is returned.</li>
<li>UNAVAILABLE_VALUE - due to current QoS settings the given value is
not allowed; valid range is returned.</li>
<li>BAD_PROPERTY - unrecognized property.</li>
<li>BAD_TYPE - type of supplied property is incorrect.</li>
<li>BAD_VALUE - illegal value.</li>
</ul>
<p>The CosNotification_QoSAdmin interface also supports an operation
called <span class="code">validate_qos/2</span>. The purpose of this operations is to check
if a QoS setting is supported by the target object and if so, the operation
returns additional properties which could be optionally added as well.</p>
<h4>Admin Properties</h4>
<p>The cosNotification application supports the following Admin Properties:</p>
<table border="1" cellpadding="2" cellspacing="0">
<tr>
<td align="left" valign="middle"><strong>Property</strong></td>
<td align="left" valign="middle"><strong>Range</strong></td>
<td align="left" valign="middle"><strong>Default</strong></td>
</tr>
<tr>
<td align="left" valign="middle">MaxQueueLength</td>
<td align="left" valign="middle">0</td>
<td align="left" valign="middle">0</td>
</tr>
<tr>
<td align="left" valign="middle">MaxConsumers</td>
<td align="left" valign="middle">long() >= 0</td>
<td align="left" valign="middle">0</td>
</tr>
<tr>
<td align="left" valign="middle">MaxSuppliers</td>
<td align="left" valign="middle">long() >= 0</td>
<td align="left" valign="middle">0</td>
</tr>
</table>
<em>Table
6.2:
Table 2: Supported Admin Properties</em>
<p>According to the OMG specification the default values for Admin Properties
is supposed to be <span class="code">0</span>, which means that no limit applies to these
properties.</p>
<div class="note">
<div class="label">Note</div>
<div class="content"><p>
<p>Admin Properties can only be set on a Channel Object level, i.e.,
they will not have an impact on any Admin or Proxy Objects. Currently,
setting the Admin Property <span class="code">MaxQueueLength</span> have no effect since
we cannot discard events accordingly to the Quality of Service Property
<span class="code">DiscardPolicy</span>.</p>
</p></div>
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