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|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<!-- $Id$ -->
<title>Options for TAO Components</title>
</head>
<body bgcolor="#ffffff" link="#000fff" vlink="#ff0f0f" text="#000000">
<hr>
<p></p>
<h2 align="center">Options for TAO Components</h2>
<h3>Table of Contents</h3>
<ul>
<li><a href="#MOT">Introduction</a> </li>
<li><a href="#choose">Choosing the Right Approach</a> </li>
<li><a href="#EXP">TAO's ORB Configuration Options</a>
<ul>
<li><a href="#EV">Environment Variables</a> </li>
<li><a href="#CLO">Command-line Options</a>
<ol>
<li><a href="#CSCB">Controlling Service Configurator Behavior </a>
</li>
<li><a href="#CDI">Controlling Debugging Information </a> </li>
<li><a href="#ORP">Optimizing Request Processing </a> </li>
<li><a href="#CMPS">Connection Management and Protocol
Selection </a> </li>
<li><a href="#MO">Miscellaneous Options </a></li>
</ol>
</li>
<li><a href="#SVC">Service Configuration File </a>
<ol>
<li><a href="#TRF">Simple and Advanced Resource Factories </a>
<ol>
<li><a href="#TDRF">TAO_Default_Resource_Factory </a> </li>
<li><a href="#TARF">TAO_Advanced_Resource_Factory </a></li>
</ol>
</li>
<li><a href="#TSSF">Server_Strategy_Factory </a> </li>
<li><a href="#TCSF">Client_Strategy_Factory </a></li>
</ol>
</li>
</ul>
</li>
</ul>
<hr>
<h3><b><a name="MOT">Introduction</a></b></h3>
TAO is a highly flexible ORB that contains a wide range of ORB
configuration options. One or more of these options can be combined
to meet various application requirements, such as low-latency,
predictable real-time behavior, or small memory footprint. TAO's ORB
configuration options are managed by an object-oriented framework
within the ORB Core that contains the following types of entities:
<ul>
<li><b>Settings</b>, which are options that can be assigned values
differing from their default settings. Examples include setting the
size of a Portable Object Adapter (POA)'s active object map or
configuring the ORB to print debugging information as it processes
requests. A few of these are run-time options, while a majority of
them are compile-time options.
<p></p>
</li>
<li><b>Resources</b>, which are objects used internally by TAO, such
as a <em>reactor</em> framework that demultiplexes new connection and
data requests from a client or <em>synchronization mechanisms</em>
used to regulate access to certain parts of the ORB.
<p></p>
</li>
<li><b>Strategies</b>, which are objects that use the <b>Resource</b>
entities to perform various ORB tasks, such as connection management,
concurrency, and demultiplexing.
<p></p>
</li>
<li><b>Factories</b>, which TAO uses to create and consolidate its
many resources and strategies into a manageable number of factories
that can be (re)configured into the ORB conveniently and consistently
by ORB and application developers.
<p></p>
</li>
</ul>
The set of TAO ORB configuration options that are represented by the
settings, resources, strategies, and factories can be specified via
<b>environment variables</b>, <b>service configuration files</b>, and
<b>command-line arguments</b>, as outlined below:
<ul>
<li> <b>Environment variables</b> are limited to specifying the
interoperable object reference (IOR) and port number of TAO's Naming
Service, Trading Service and Implementation Repository. They are
limited in flexibility and don't provide the most important
configuration hooks necessary to configure TAO for real-time and
high-performance applications.
<p></p>
</li>
<li> <b>Command-line options</b> are passed to the ORB
initialization
factory method, <code>CORBA::ORB_init()</code>, by an application
using the standard <i>argc, argv</i> tuple passed to the application's
<code>main()</code>. Most of the options that can be exercised
through
environment variables can also be manipulated through command-line
options. Command-line options override the environment variable
settings if both are enabled.
<p></p>
</li>
<li> The <b>Service Configurator</b> is a framework that can be used
to statically and dynamically configure components into middleware and
applications. The information comprising the names of these
components and their corresponding options are specified in a service
configurator file, whose default file name is
<code>svc.conf</code>. The service configurator is opened and
processed by the ORB in <code>CORBA::ORB_init()</code>. The service
configurator processing is done after all the command-line options
have been<!-- Bala, should this be "processed" or just "parsed"?
There could be a different -->
parsed.
<p><!-- It should be just "parsed". The options from the command lines
<!-- are just parsed in ORB_init () and stored for later use -->
<!-- For the service configurator it is tricky. To be on the safer
<!-- side I would say "processed". --></p>
</li>
</ul>
<p></p>
<hr width="25%" align="left">
<p></p>
<h3><a name="choose">Choosing the Right Approach</a></h3>
TAO's command-line options are useful when there's a fixed set of
configuration options, each of which has a predefined list of
alternative values. Conversely, TAO's service configurator file is
useful for configuring a broader range of resources, strategies, and
factories. Generally speaking, the service configurator file allows
the user to <br>
<ul>
<li>configure the existing components (<em>i.e.</em>, resources,
strategies and factories) based on the predefined list of alternatives
that TAO provides or
<p> </p>
</li>
<li>extend the existing factories by providing user-defined
components and dynamically load them through the service configurator
mechanism. </li>
</ul>
Additionally, the service configurator mechanism allows an
application to control the behavior of the ORB using extensible
configuration information. In general, the command-line configuration
options are provided in TAO
in order to leverage preexisting configuration settings that are
compiled within the TAO ORB. Users are not allowed to change these
settings. In contrast, those options that require more flexible
manipulation of resources, strategies, and factories must be
configured via <a href="#SVC">service configuration files</a>. As a
result, the command-line options and the service configurator options
cannot be used interchangeably.
<p></p>
<hr>
<h3><b><a name="EXP">TAO's ORB Configuration Options</a></b></h3>
This section provides a detailed overview of how to configure TAO's
options using environment variables, command-line options, and service
configuration files.
<p></p>
<hr width="25%" align="left">
<h3><a name="EV">Environment Variables</a></h3>
As mentioned earlier, environment variables have a limited use in TAO
ORB configuration. The currently supported environment variables are
listed below. They are used to specify the IOR and port numbers for
three of TAO's ORB services.
<blockquote>
<p>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Environment Variable</th>
<th>Description</th>
</tr>
<tr>
<td><code>NameServicePort</code> <em>which</em></td>
<td>Specifies which port the Naming Service is listening on for
multicast requests. </td>
</tr>
<tr>
<td><code>TradingServicePort</code> <em>which</em></td>
<td>Specifies which port the Trading Service is listening on
for multicast requests. </td>
</tr>
<tr>
<td><code>ImplRepoServicePort</code> <em>which</em></td>
<td>Specifies which port the Implementation Repository is
listening on for multicast requests. </td>
</tr>
</tbody>
</table>
</p>
</blockquote>
In addition to being able to define the port where these known services
are listening for multicast requests, as above, it is possible to set
an environment variable that specifies the IOR of any named service.
For example <code>NameServiceIOR=<which>,TradingServiceIOR=<which>,
ImplRepoServiceIOR=<which>, MyServiceIOR=<which></code>. This
will have a similar effect to defining an -ORBInitRef value on the
command line (see below). Any value set as a command line -ORBInitRef
option will override any value set as an environment variable for the
same service name.<br>
<br>
In general, setting environment variables is not particularly portable
or convenient, which is why users can also set these options via
command-line options. The example shown below demonstrates a
deployment scenario where the client and Naming Service run on the
same host:
<p><code>
% NameService.exe -ORBEndpoint iiop://localhost:12345
</code></p>
<p><code>
% client.exe -ORBInitRef NameService=iiop://localhost:12345
</code></p>
<p>An explanation of these command-line options appears below. </p>
<p></p>
<hr width="25%" align="left">
<h3><a name="CLO">Command-line Options</a></h3>
TAO's run-time behavior can also be controlled by passing options via
the CORBA initialization method <code>CORBA::ORB_init()</code>. ORB
initialization options are commonly passed into the program from the
command-line, using the <code>argc</code> and <code>argv</code>
parameters available to the <code>main()</code> function.
<p>Command-line options can be classified into the following groups
according to their purposes:</p>
<ol>
<li><a href="#CSCB">Controlling Service Configurator Behavior</a> </li>
<li><a href="#CDI">Controlling Debugging Information</a> </li>
<li><a href="#ORP">Optimizing Request Processing</a> </li>
<li><a href="#CMPS">Connection Management and Protocol Selection</a> </li>
<li><a href="#MO">Miscellaneous Options</a>
</li>
</ol>
We describe each of these five groups of options below.
<p></p>
<h4><a name="CSCB">1. Controlling Service Configurator Behavior</a></h4>
The options described below influence the behavior of the ORB's <a
href="#SVC">service configurator, which is opened and processed <em>after</em>
the command-line options
have been parsed. </a>
<p></p>
<blockquote><a href="#SVC"> </a>
<p><a href="#SVC"> </a>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Option</th>
<th>Description</th>
</tr>
<tr>
<td><code>-ORBSvcConf</code> <em>config filename</em></td>
<td>Specifies the name of the file used to read service
configuration directives via the Service Configurator framework. By
default, a service configurator-based application will look for a file
named <code>"svc.conf"</code> in the current directory. </td>
</tr>
<tr>
<td><code>-ORBSvcConfDirective</code> <em>directivestring</em></td>
<td>Specifies a service configuration directive, which is
passed to the Service Configurator. You can pass multiple of these
options on the same command-line. </td>
</tr>
</tbody>
</table>
</p>
</blockquote>
<h4><a name="CDI">2. Controlling Debugging Information</a></h4>
During application development and testing, it is often necessary to
control the amount and type of debugging information output by the
ORB. The following options enable TAO to provide debugging
information at several levels of granularity.
<p></p>
<blockquote>
<p>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Option</th>
<th>Description</th>
</tr>
<tr>
<td><code>-ORBDebug</code></td>
<td>Instructs the ORB to print debugging messages from the
service configurator framework. This option does not have a value but
is used as a toggle to enable or disable debugging messages.</td>
</tr>
<tr>
<td><code>-ORBDebugLevel </code><em>level</em></td>
<td>Control the level of debugging in the ORB. Higher numbers
generate more output (try 10). The default value of this option is 0.</td>
</tr>
<tr>
<td><code>-ORBVerboseLogging <em>level (0|1|2)</em</code></td>
<td>Controls the amount of status data printed on each line of
the debug log. Higher numbers generate more output.
The default value of this option is 0. </td>
</tr>
<tr>
<td><code>-ORBLogFile</code> <em>Logfilename</em></td>
<td>Causes all <code>ACE_DEBUG</code> and <code>ACE_ERROR</code>
output to be redirected to the designated <code>Logfilename</code>. </td>
</tr>
<tr>
<td><code>-ORBObjRefStyle</code> <em>IOR/URL</em></td>
<td>Specifies the user-visible style of object references. The <code>IOR</code>
style (default) is the conventional CORBA object reference, whereas the
<code>URL</code> style looks more like a URL.
</td>
</tr>
</tbody>
</table>
</p>
</blockquote>
<h4><a name="ORP">3. Optimizing Request Processing</a></h4>
It is often possible to <a href="performance.html">increase TAO's
throughput and reduce latency</a> by optimizing certain stages of
request processing in the ORB. The following command-line options
control various optimizations during request processing.
<p></p>
<blockquote>
<p>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Option</th>
<th>Description</th>
</tr>
<tr>
<td><code>-ORBCDRTradeoff</code> <em>maxsize</em></td>
<td><a name="-ORBCDRTradeoff"></a>Control the strategy to
tradeoff between copy vs. no copy marshaling of octet sequences. If an
octet sequence is smaller than <code>maxsize</code> (which defaults to
<code>ACE_DEFAULT_CDR_MEMORY_TRADEOFF</code>) -- and the
current message block contains enough space for it -- the octet
sequence is copied instead of appended to the CDR stream. </td>
</tr>
<tr>
<td><code>-ORBCollocation</code> <em>global/per-orb/no</em></td>
<td><a name="-ORBCollocation"></a>Specifies the use of
collocation object optimization. If <code>global</code> is specified
(default), objects in the same process will be treated as collocated.
If <code>per-orb</code> is specified, only objects in the same ORB are
treated as collocated. When <em>no</em> is specified, no objects are
treated as collocated. </td>
</tr>
<tr>
<td><code>-ORBCollocationStrategy</code> <em>thru_poa/direct</em>
</td>
<td>Specifies what type of collocated object to use. If the <code>thru_poa</code>
(default) strategy is used, TAO uses the collocation object
implementation that respects POA's current state and policies. When
using the <code>direct</code> strategy, method invocations on
collocated objects become direct calls to servant without checking
POA's status, which can increase performance. If you use the <code>direct</code>
strategy, your interfaces must be compiled with the <code><a
href="compiler.html#collocation-stubs">-Gd</a></code> IDL <a
href="compiler.html">compiler option</a>. </td>
</tr>
<tr>
<td><code>-ORBNodelay</code> <em>boolean (0|1)</em></td>
<td><a name="-ORBNodelay"></a>Enable or disable the <code>TCP_NODELAY</code>
option (Nagle's algorithm). By default, <code>TCP_NODELAY</code> is
enabled.</td>
</tr>
<tr>
<td><code>-ORBRcvSock</code> <em>receive buffer size</em></td>
<td><a name="-ORBRcvSock"></a>Specify the size of the socket
receive buffer as a positive, non-zero integer. If not specified, the <code>ACE_DEFAULT_MAX_SOCKET_BUFSIZ</code>
default is used.</td>
</tr>
<tr>
<td><code>-ORBSndSock</code> <em>send buffer size</em></td>
<td><a name="-ORBSndSock"></a>Specify the size of the socket
send buffer as a positive, non-zero integer. If not specified, the <code>ACE_DEFAULT_MAX_SOCKET_BUFSIZ</code>
default is used.</td>
</tr>
<tr>
<td><code>-ORBStdProfileComponents</code> <em>boolean (0|1)</em></td>
<td><a name="-ORBStdProfileComponents"></a>If <em>0</em> then
the ORB does not generate the OMG standardized profile components, such
as the ORB type and code sets. Notice that the presence of this
components is optional in GIOP 1.1 The default value is controlled by a
compile-time flag (check orbconf.h).</td>
</tr>
<tr>
<td><code>-ORBSingleReadOptimization</code> <em>boolean (0|1)</em></td>
<td><a name="-ORBSingleReadOptimization"></a>This option
controls whether TAO's ``single read optimization'' is used when
receiving requests. If this option is disabled (<code>0</code>), the
ORB will do two reads to read a request: one reads the request header
and the other reads the request payload. If this option is enabled (<code>1</code>),
the ORB will do a read of size <code>TAO_MAXBUFSIZE</code>, hoping to
read the entire request. If more than one request is read they will be
queued up for processing later.
<p> This option defaults to <code>1</code> because it can
provide better performance. However, in the case of RT-CORBA, this
option should be set to <code>0</code>. Consider the following
scenario: (1) two requests are read from one socket, (2) the additional
request is queued, and (3) the ORB uses its Reactor's notification
mechanism to wake up the follower threads. If at the same time,
however, new requests arrive on others sockets of higher priority the
lower priority queued message will be processed before the newly
arrived higher priority request since Reactor notifications are given
preferences over normal I/O, thereby causing priority inversion.</p>
</td>
</tr>
<tr>
<td><code>-ORBDisableRTCollocation</code> <em>boolean
(0|1)</em></td> <td><a name="-ORBDisableRTCollocation"></a>This
option controls whether the application wants to use or discard
RT collocation decisions made by the RT ORB. A value of true
disables RT collocation decisions and falls back on the default
collocation decisions implemented in the default ORB. This is
very useful for applications using the RT ORB and doesn't want
to use the RT collocation decisions but fallback on the default
decisions for better performance. The default value is
<code>0</code>. </td>
</tr>
</tbody>
</table>
</p>
</blockquote>
<h4><a name="CMPS">4. Connection Management and Protocol Selection</a></h4>
TAO can send and receive requests and replies using various <a
href="pluggable_protocols">transport protocols</a>. Each protocol has
its own concept of an <a href="ORBEndpoint.html">endpoint</a>.
The following options manage connections and control protocol
selection within a TAO application.
<p></p>
<blockquote>
<p>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Option</th>
<th>Description</th>
</tr>
<tr>
<td><code>-ORBDefaultInitRef</code> <em>IOR prefix</em></td>
<td><a name="-ORBDefaultInitRef"></a>This argument allows
resolution of initial references not explicitly specified with
-ORBInitRef. It requires a URL prefix that, after appending a slash '/'
('|' for the UIOP pluggable protocol) and a simple object key, forms a
new URL to identify an initial object reference. The URL prefix format
currently supported is based on the standard <code>corbaloc</code>
mechanism in the CORBA <a href="INS.html">Interoperable Naming
Service. </a></td>
</tr>
<tr>
<td><code>-ORBDottedDecimalAddresses</code> <em>boolean (0|1)</em></td>
<td><a name="-ORBDottedDecimalAddresses"></a>Use the dotted
decimal notation for addresses. This option can be used to workaround
broken DNS implementations and may also reduce the time spent resolving
IP addresses. By default, this option is disabled (<code>0</code>)
since domain names are the standard address notation for IORs.</td>
</tr>
<tr>
<td><code>-ORBEndpoint</code> <em>endpoint</em></td>
<td><a name="-ORBEndpoint"></a>This option is similar to the <code>-ORBListenEndPoints</code>
option described below. <font color="red">This option will be
deprecated in later versions on TAO since the CORBA specification now
defines the <code>-ORBListenEndpoints</code> option instead. </font> </td>
</tr>
<tr>
<td><code>-ORBListenEndpoints</code> <em>endpoint</em></td>
<td><a name="-ORBListenEndpoints"></a> This option was
introduced with the CORBA <a
href="http://cgi.omg.org/docs/orbos/01-01-04.pdf"> ORT </a> (Object
Reference Template) specification. It instructs a server ORB to listen
for requests on the interface specified by <code>endpoint</code>. TAO <a
href="ORBEndpoint.html"> endpoints</a> are specified using a URL style
format. An endpoint has the form:
<blockquote><code>protocol://V.v@addr1,...,W.w@addrN </code></blockquote>
where <code>V.v</code> and <code>W.w</code> are optional protocol
versions for each address. An example of an IIOP endpoint is:
<blockquote><code>iiop://<i><em>hostname</em></i>:<i><em>port</em></i>
</code></blockquote>
Sets of endpoints may be specified using multiple <code>-ORBEndpoint</code>
options or by delimiting endpoints with a semi-colon (;). For example,
<blockquote><code>-ORBEndpoint iiop://localhost:9999
-ORBEndpoint uiop:///tmp/mylocalsock -ORBEndpoint shmiop://10002 </code></blockquote>
is equivalent to:
<blockquote><code>-ORBEndpoint
'iiop://localhost:9999;uiop:///tmp/mylocalsock;shmiop://10002' </code></blockquote>
Notice the single quotes (') in the latter option specification. Single
quotes are needed to prevent the shell from interpreting text after the
semi-colon as another command to run.
<p>If an endpoint is specified without an <code>addr</code>
such as the following: </p>
<blockquote><code>-ORBEndpoint uiop:// -ORBEndpoint shmiop:// </code></blockquote>
then a default endpoint will be created for the specified protocol.
<p></p>
</td>
</tr>
<tr>
<td><code>-ORBImplRepoServicePort</code> <em>portspec</em></td>
<td>Specifies which port the Implementation Repository is
listening on for multicast requests. By default, the <code>TAO_DEFAULT_IMPLREPO_SERVER_REQUEST_PORT</code>
(10018) is used.</td>
</tr>
<tr>
<td><code>-ORBInitRef</code> <em>ObjectId=IOR</em></td>
<td><a name="-ORBInitRef"></a>Allows specification of an
arbitrary object reference for an initial service. The IOR could be in
any one of the following formats: OMG <code>IOR</code>, <code>URL</code>,
<code>corbaloc</code> (including <code>uioploc</code>) or <code>file</code>.
<code>corbaloc</code> is a multiple end-point IOR understood by
<code>ORB::string_to_object()</code> and used as a
boot-strapping mechanism by the <code>ORB::resolve_initial_references()</code>.
The mappings specified through this argument override the ORB
install-time defaults. The <code>file://pathname</code> interprets the
contents of the <code>pathname</code> file as an object reference in
any of the above formats. </td>
</tr>
<tr>
<td><code>-ORBMulticastDiscoveryEndpoint</code> <em>endpoint</em></td>
<td>Specifies the <code>endpoint</code> that should be used
for locating the Naming Service through multicast. <em>endpoint</em>
is of the form <code>ip-number:port-number</code> (<em>e.g.</em>, <code>"tango.cs.wustl.edu:1234"</code>
or <code>"128.252.166.57:1234"</code>). If there is no <code>':'</code>
in the end_point it is assumed to be a port number, with the IP address
being <code>INADDR_ANY</code>. </td>
</tr>
<tr>
<td><code>-ORBNameServicePort</code> <em>portspec</em></td>
<td>Specifies which port the Naming Service is listening on for
multicast requests. By default, the <code>TAO_DEFAULT_NAME_SERVICE_REQUEST_PORT</code>
(10013) value is used.</td>
</tr>
<tr>
<td> <a
href="http://cvs.doc.wustl.edu/viewcvs.cgi/*checkout*/TAO/docs/ORBEndpoint.html?rev=HEAD"><code>-ORBTradingServicePort</code>
<em>portspec</em></a></td>
<td> <a
http://cvs.doc.wustl.edu/viewcvs.cgi/tao/docs/orbendpoint.html?rev="HEAD"">Specifies
to which port the Trading Service is listening on for multicast
requests. By default, the <code>TAO_DEFAULT_TRADING_SERVICE_REQUEST_PORT</code>
(10016) value is used.</a></td>
</tr>
<tr>
<td> <code>-ORBUseIMR</code> <em>boolean (0|1)</em></td>
<td>This argument specifies that for POAs with the <code>PERSISTENT</code>
policy, that the TAO <a href="implrepo/">Implementation Repository</a>
should be used for notification of startup and shutdown and object
references should be changed to use the Implementation Repository also.
</td>
</tr>
</tbody>
</table>
</p>
</blockquote>
<h4><a name="MO">5. Miscellaneous Options</a></h4>
Options in this category don't control the behavior of the ORB in
terms of resouces or strategies. Instead, they are helper options
provided for specific application requirements.
<blockquote>
<p>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Option</th>
<th>Description</th>
</tr>
<tr>
<td><code>-ORBId</code> <em>orb_name</em></td>
<td><a name="-ORBId"></a>This option allows the name of an ORB
to be set to <code>orb_name</code>. The ORBId will be passed to the
ORB_init() method to differentiate coexisting ORBs (when there are more
than one ORBs).</td>
</tr>
<tr>
<td><code>-ORBServerId</code> <em>server_id</em></td>
<td><a name="-ORBId"></a>This option allows setting a name/id
to a server to uniquely identify a server to TAO's <a href="implrepo">Implementation
Repository</a>. </td>
</tr>
<tr>
<td><code>-ORBDaemon</code></td>
<td>Specifies that the ORB should <em>daemonize</em> itself, <em>i.e.</em>,
run as a background process. This option is only meaningful on OS
platforms that support daemonization.</td>
</tr>
</tbody>
</table>
</p>
</blockquote>
<p></p>
<hr width="25%" align="left">
<h3><a name="SVC">The Service Configurator File</a></h3>
Internally, TAO uses the <a
href="http://www.cs.wustl.edu/%7Eschmidt/PDF/Svc-Conf.pdf">ACE Service
Configurator framework</a> to allow applications to configure the ORB
at run-time. Applications provide a file named <code>svc.conf</code>
with options that configure appropriate strategies in to the ORB. The
options enable developers to control the behavior of the factories,
strategies, and resources that the ORB uses. By default, TAO provides
the following set of factories:
<p></p>
<ol>
<li><a href="#TRF">Default Resource and Advanced Resource Factories.</a>
This factory controls the creation of configurable resources used by
TAO's ORB core. The resource factory is responsible for constructing
and providing access to various resources used by the ORB irrespective
of whether they perform client or server roles. ORB resources include
reactors, protocol factories, message flushing strategies, connection
purging strategies and different IOR parsers.
<p> </p>
</li>
<li> <a href="#TSSF">Server Strategy Factory.</a> This factory
creates various strategies of special utility to the ORB that is useful
for controlling the behavior of servers. This factory is responsible
for creating strategies useful for server objects like the concurrency
strategy and the request demultiplexing strategies used by the POA.
<p> </p>
</li>
<li> <a href="#TCSF">Client Strategy Factory.</a> This factory
creates various strategies of special utility to the ORB, useful for
controlling the behavior of clients. This factory is responsible for
creating strategies useful for clients such as request multiplexing
strategies, wait strategies, connect strategies etc.
<p></p>
</li>
</ol>
Options specified via a <code>svc.conf</code> file can represent
either the components provided by TAO (including the
<code>Resource_Factory</code>, and the
<code>Server_Strategy_Factory</code> and
<code>Client_Strategy_Factory</code>) or customized components
developed by the users. The service configurator file
(<code>svc.conf</code>) provided by the user identifies the components
to be loaded with the required strategies for each component.
<p>A <code>svc.conf</code> file is <em><b>not</b></em> required to
run
TAO applications since TAO provides a set of default values for
strategies useful for the most common use cases, <em>i.e.</em>, the
default values are set for all options. When a TAO application calls
<code>CORBA::ORB_init()</code> it will try to find the
<code>svc.conf</code> file. If found, TAO will parse and process the
directives in the file; if not found, the default value for the
default components will be used.</p>
<hr width="25%" align="left">
<h4><a name="TRF">1. Default and Advanced Resource Factories</a></h4>
Many of TAO's ORB Core resources are fixed, including the allocators
for
the incoming and outgoing data paths, and data structures for the
various
maps and lists maintained by the ORB. There is some flexibility,
however, in the choice of a reactor, the selection of transport
protocols, choice of data flushing strategy, various forms of
connection resource management strategies and possibility of using
different IOR parsers. The resource factories supported by TAO
include the <code>Resource_Factory</code> and
<code>Advanced_Resource_Factory</code>. TAO provides defaults of these
factories, as well as the specialized resource factories described
below:
<blockquote>
<p>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Resource Factory</th>
<th>Description</th>
</tr>
<tr>
<td><code><a href="#TDRF">Resource Factory</a></code></td>
<td>Unless configured otherwise, this is the default resource
factory used by the ORB.The resource factory is responsible for
creating and providing access to various resources used by the server
and client ORBs. The resources managed by this factory include creation
of acceptor and connector registries, choice of data flushing strategy,
limits for connection resource management, types of CDR buffers used
for marshalling and demarshalling data, and different IOR parsers. </td>
</tr>
<tr>
<td><code><a href="#TARF">Advanced Resource Factory</a></code></td>
<td>This factory provides more advanced configuration options
in the addition to all the features of the default resource factory.<br>
<br>
The advanced resource factory gives more control than the default
resource factory over the type of resources used and how those
resources are accessed. In addition to the options provided by the
default resource factory, the advanced resource factory provides
options that allow selecting different reactors, choosing different
transport mechanisms and selecting the right connection purging
strategy to maintain limits on resources used. The advanced resource
factory was created to allow more advanced options while keeping the
footprint of the default resource factory small.<br>
<br>
The advanced resource factory inherits from the default resource
factory and accepts all of its options in addition to its own. </td>
</tr>
<tr>
<td><code>Qt Resource Factory</code></td>
<td>This is a specialized resource factory providing the means
for integrating with the Qt GUI toolkit from Trolltech. </td>
</tr>
<tr>
<td><code>Xt Resource Factory</code></td>
<td>This is a specialized resource factory providing the means
for integrating with the X Window System's Xt Intrinsics toolkit. </td>
</tr>
</tbody>
</table>
</p>
</blockquote>
<p></p>
<h4><a name="TDRF">1.1. Resource_Factory</a></h4>
Typically, the above options are exercised via the service
configurator (svc.conf) file. The following line in the
<code>svc.conf</code> file (all in one line)
<p> <code>static
Resource_Factory "[list of options]"</code></p>
<p>will load the default
resource factory with the options listed within the double quotes. The
following table shows the list of possible options that can be
specified within the double quotes in the above directive. There is an <a
href="http://cvs.doc.wustl.edu/viewcvs.cgi/TAO/tests/LongUpcalls/svc.conf?rev=HEAD">
online</a> example of how this is used in TAO.</p>
<p></p>
<blockquote>
<p>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Option</th>
<th>Description</th>
</tr>
<tr>
<td><code>-ORBReactorMaskSignals</code> <em>0/1</em></td>
<td>ACE select reactors mask signals during upcalls to the
event handlers. This is only useful if the application is going to trap
those signals and handle them in any special way. Disabling the mask
can improve performance by reducing the number of kernel level locks. </td>
</tr>
<tr>
<td><code>-ORBProtocolFactory</code> <em>factory</em></td>
<td><a name="-ORBProtocolFactory"></a>Specify which pluggable
protocol factory to load. By default, only the factory for the IIOP
protocol (<code>IIOP_Factory</code> is loaded.
<p>For example, if some protocol called <em><code>Foo</code></em>
whose factory was called <em><code>Foo_Factory</code></em> was
available, then it could be loaded into TAO by specifying <code>-ORBProtocolFactory
Foo_Factory</code> in the service configurator file. The <em><code>Foo</code></em>
pluggable protocol would then be available for use. </p>
</td>
</tr>
<tr>
<td><code>-ORBIORParser</code> <em>parser</em></td>
<td><a name="-ORBIORParser"></a>Name an IOR Parser to load. IOR
Parsers are used to interpret strings passed to <code>ORB::string_to_object()</code>.
By default the ORB can handle multiple string formats, including <code>IOR:</code>,
<code>corbaloc:</code>, <code>corbaname:</code>, and <code>file:</code>.
The application developer can <a
href="http://cvs.doc.wustl.edu/viewcvs.cgi/*checkout*/TAO/docs/ior_parsing.html?rev=HEAD">add
new IOR formats </a>using this option. </td>
</tr>
<tr>
<td><code>-ORBConnectionPurgingStrategy</code> <em>type</em></td>
<td><a name="-ORBConnectionPurgingStrategy"></a>Opened
connections are added to the transport cache so they can be reused.
However, if a process continues to run and these connections are not
reused, the cache will continue to grow. Therefore, before each new
connection, the cache is checked and purged if it has reached the limit
specified by the -ORBConnectionCacheMax option or the system default if
that option was not used. The possible values for type are lru, lfu,
fifo and null. The default is LRU (Least Recently Used). The others LFU
(Least Frequently Used), FIFO (First In First Out), and null (No
connections are purged) are contained within the TAO Strategies
library. </td>
</tr>
<tr>
<td><code>-ORBConnectionCacheMax</code> <em>limit</em></td>
<td><a name="-ORBConnectionCacheMax"></a>The transport cache
will grow to a maximum of the specified limit. The default is system
dependent, but can be overridden at compile-time by defining the
preprocessor macro TAO_CONNECTION_CACHE_MAXIMUM. </td>
</tr>
<tr>
<td><code>-ORBMuxedConnectionMax</code> <em>number</em></td>
<td><a name="-ORBMuxedConnectionMax"></a>The transport cache
allows only specified number of connections-per-QoS property to be
added to connection cache. Threads not getting the connections will
wait for the connections to be released. This option is more useful for
transports using a muxed connection strategy and want control over the
number of connections that are created by the active threads. </td>
</tr>
<tr>
<td><code>-ORBConnectionCachePurgePercentage</code> <em>percent</em></td>
<td><a name="-ORBConnectionCachePurgePercentage"></a>If the
transport cache is purged, the specified percentage (20 by default) of
the total number of connections cached will be closed. </td>
</tr>
<tr>
<td><code>-ORBConnectionCacheLock</code> <em>locktype</em></td>
<td><a name="-ORBConnectionCacheLock"></a>Specify the type of
lock to be used by the Connection Cache. Possible values for lock type
are <code>thread</code>, which specifies that an inter-thread mutex is
used to guarantee exclusive access, and <code>null</code>, which
specifies that no locking be performed. The default is thread. </td>
</tr>
<tr>
<td><code>-ORBCorbaObjectLock</code> <em>locktype</em></td>
<td><a name="-ORBCorbaObjectLock"></a> Specify the type of lock
to be used by CORBA::Object. The lock is needed within the CORBA object
to synchronize the state when the same object is shared by multiple
threads. Possible values for lock type are <code>thread</code>, which
specifies that an inter-thread mutex is used to guarantee exclusive
access, and <code>null</code>, which specifies that no locking be
performed. The default is thread. The <code>null</code> lock option is
useful when there is only one thread in the system. This option can be
used to minimize the amount of memory consumed by the locks in
applications where locks are not needed. The memory growth problem gets
particularly exacerbated for applications dealing with hundreds and
thousands of objects. </td>
</tr>
<tr>
<td><code>-ORBObjectKeyTableLock</code> <em>locktype</em></td>
<td><a name="-ORBObjectKeyTableLock"></a> Specify the type of
lock to be used by the ObjectKey table. ObjectKey table keeps track of
the ObjectKeys that are generated and made available through IORs. The
table manages the life time of the object keys within the ORB through a
reference counting mechanism. Possible values for lock type are <code>thread</code>,
which specifies that an inter-thread mutex is used to guarantee
exclusive access, and <code>null</code>, which specifies that no
locking be performed. The default is thread. </td>
</tr>
<tr>
<td><code>-ORBFlushingStrategy</code> <em>type</em></td>
<td><a name="-ORBFlushingStrategy"></a>By default TAO provides
three strategies to flush queued messages. The <code>leader_follower</code>
strategy uses the Reactor and non-blocking I/O to send the outgoing
messages, this strategy participates in the Leader/Followers protocol
to synchronize access to the Reactor. The <code>reactive</code>
strategy uses the Reactor but does not take part in the
Leader/Followers protocol, thus it is better used only in single
threaded applications. Finally, the <code>blocking</code> strategy
flushes the queue as soon as it becomes "full", and blocks the thread
until all the data is sent.
</td>
</tr>
</tbody>
</table>
</p>
</blockquote>
<h4><a name="TARF">1.2. Advanced_Resource_Factory</a></h4>
This factory is located in the <code>TAO_Strategies</code> library. It
accepts the options below as well as those described above in the
<code>Resource_Factory</code>. This factory can be loaded dynamically
using a service configurator directive of the form (all on one line):
<p><code>dynamic Advanced_Resource_Factory Service_Object
*</code><br>
<code>TAO_Strategies:_make_TAO_Advanced_Resource_Factory
() "-ORBReactorType select_st" </code></p>
<p>It can also be loaded statically by doing the following:</p>
<p></p>
<ul>
<li>Add <code>#include "tao/Strategies/advanced_resource.h"</code>
to the file containing <code>main()</code>. </li>
<li>Link the TAO_Strategies library into the executable. </li>
<li>Specify a service configurator directive of the form: <code>static
Advanced_Resource_Factory "-ORBReactorType select_st"</code> </li>
</ul>
You can
omit the <code>#include</code> if you always use dynamic libraries.
<p>Loading the <code>Advanced_Resource_Factory</code> disables the
<code>Resource_Factory</code>. Any directives for the
<code>Resource_Factory</code> will have no effect (and generate
warnings telling you so). The following table lists the options that
can be provided in double quotes. An example is available <a
href="http://cvs.doc.wustl.edu/viewcvs.cgi/TAO/performance-tests/Latency/Single_Threaded/svc.conf?rev=HEAD">online
</a> that shows how to specify this option in the svc.conf file.</p>
<p></p>
<blockquote>
<p>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Option</th>
<th>Description</th>
</tr>
<tr>
<td><code>-ORBReactorType</code> <em>which</em></td>
<td><a name="-ORBReactorType"></a>Specify what kind of reactor
the ORB uses. The default reactor is the ACE_TP_Reactor.
<table border="1" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th><em>which</em></th>
<th>Reactor</th>
</tr>
<tr>
<td><code>select_mt</code></td>
<td>Use the multi-thread select-based reactor.</td>
</tr>
<tr>
<td><code>select_st</code></td>
<td>Use the single-thread select-based reactor.</td>
</tr>
<tr>
<td><code>fl</code></td>
<td>Use the FLReactor (FLTK-based).</td>
</tr>
<tr>
<td><code>wfmo</code></td>
<td>Use the WFMO reactor (Win32 only).</td>
</tr>
<tr>
<td><code>msg_wfmo</code></td>
<td>Use the MsgWFMO reactor (Win32 only).</td>
</tr>
<tr>
<td><code>tp</code></td>
<td>Use the <code>ACE_TP_Reactor</code>, a select based
thread-pool reactor which is the
MT_NO_UPCALL means use a client connection handler that
participates in the leader-follower model like MT, but, like
RW, does not allow handling of nested upcalls within the
waiting thread.
default.</td>
</tr>
</tbody>
</table>
</td>
</tr>
<tr>
<td><code>-ORBReactorThreadQueue</code> <em>which</em></td>
<td><a name="-ORBReactorThreadQueue"></a>Applies only to the
ACE_TP_Reactor, i.e., when <code>-ORBReactorType</code> = <code>tp</code>,
and specifies the order, last-in-first-out (<em>which</em> = <code>LIFO</code>),
the default, or first-in-first-out (<em>which</em> = <code>FIFO</code>),
in which waiting threads are selected to run by the
ACE_Select_Reactor_Token. </td>
</tr>
<tr>
<td><code>-ORBInputCDRAllocator</code> <em>which</em></td>
<td><a name="-ORBInputCDRAllocator"></a>Specify whether the ORB
uses locked (<em>which</em> = <code>thread</code>) or lock-free (<em>which</em>
= <code>null</code>) allocators for the incoming CDR buffers. Though <code>null</code>
should give the optimal performance; we made the default <code>thread</code>.
TAO optimizations for octet sequences will not work in all cases when
the allocator does not have locks (for example if the octet sequences
are part of a return value). Using locked allocators also allows the
users to take advantage of the TAO octet sequence extensions to
preserve the buffer after the upcall. </td>
</tr>
<tr>
<td><code>-ORBAMHResponseHandlerAllocator</code> <em>which</em></td>
<td><a name="-ORBAMHResponseHandlerAllocator"></a>Specify whether the ORB
uses locked (<em>which</em> = <code>thread</code>) or lock-free (<em>which</em>
= <code>null</code>) allocators for the AMH response handlers.</td>
</tr>
<tr>
<td><code>-ORBAMIResponseHandlerAllocator</code> <em>which</em></td>
<td><a name="-ORBAMIResponseHandlerAllocator"></a>Specify whether the ORB
uses locked (<em>which</em> = <code>thread</code>) or lock-free (<em>which</em>
= <code>null</code>) allocators for the AMI response handlers.</td>
</tr>
<tr>
<td><code>-ORBReactorRegistry</code> <em>registry_type</em></td>
<td><a name="-ORBReactorRegistry"></a>This option is no longer
supported. The Advanced Resource Factory will emit an error if you
attempt its use. </td>
</tr>
</tbody>
</table>
</p>
</blockquote>
<h4><a name="TSSF">2. Server_Strategy_Factory</a></h4>
Certain elements of the ORB relate only to a TAO server. In this
context, the server is any application that passively accepts
connection from other processes and receives requests from those other
connections. The server strategy factory is responsible for supporting
features of TAO that are specific to servers. In particular, these
include the following strategies:
<ul>
<li> The <em>concurrency strategies</em> control the thread creation
flags and other concurrency related behaviors.
<p></p>
</li>
<li> The <em>demuliplexing strategies</em> are used
to locate servants inside the POA that are responsible for handling
requests.
<p></p>
</li>
</ul>
TAO provides a default server strategy factory called
<code>Server_Strategy_Factory</code>
<p>Typically, the following options are set via the service
configurator
(svc.conf) file. The following line in the svc.conf file (all in one
line)</p>
<p><code>static Server_Strategy_Factory "[list of
options]"</code></p>
<p>would load all the options listed within "". An
example is available <a
href="http://cvs.doc.wustl.edu/viewcvs.cgi/TAO/performance-tests/Latency/Single_Threaded/svc.conf?rev=HEAD">online</a>
that shows how to specify this option in the <code>svc.conf</code>
file. </p>
<p></p>
<blockquote>
<p>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Option</th>
<th>Description</th>
</tr>
<tr>
<td><a name="orb_concurrency"><code>-ORBConcurrency</code></a> <em>which</em></td>
<td>Specify which concurrency strategy to use. Range of values
is <code>reactive</code> for a purely Reactor-driven concurrency
strategy or <code>thread-per-connection</code> for creating a new
thread to service each connection. The default is reactive. </td>
</tr>
<tr>
<td><a name="server_timeout"><code>-ORBThreadPerConnectionTimeout</code></a>
<em>milliseconds</em></td>
<td>In many platforms it is impossible to interrupt the server
threads created by the <code>thread-per-connection</code> model. This
is because these threads are blocked in <code>read()</code> operations
(and not in <code>select()</code>). As a workaround, the server
threads periodically poll the ORB to find out if they should shutdown.
This option controls the period of the polling, expressed in
milliseconds. Applications that do not shutdown, or that can otherwise
ensure that no server threads will be running at shutdown (for example
if all the clients terminate before the server) can disable the
polling using the magic value <code>INFINITE</code>.
<p>If the option is not provided then the ORB uses the
compile-time flag <code>TAO_DEFAULT_THREAD_PER_CONNECTION_TIMEOUT</code>,
this flag also expresses the time in milliseconds (as a string
constant) and the magic value <code>"INFINITE"</code> can be used to
disable polling entirely. This yields a slight performance improvement
(around 1%). </p>
</td>
</tr>
<tr>
<td><code>-ORBActiveObjectMapSize</code> <em>active object map
size</em></td>
<td>Specify the size of the active object map. If not
specified, the default value is 64.</td>
</tr>
<tr>
<td><code>-ORBUseridPolicyDemuxStrategy</code> <em>user id
policy based demultiplexing strategy</em></td>
<td>Specify the demultiplexing lookup strategy to be used with
the user id policy. The <em>demultiplexing strategy</em> can be one of
<code>dynamic</code> or <code>linear</code>. This option
defaults to using the <code>dynamic</code> strategy. </td>
</tr>
<tr>
<td><code>-ORBSystemidPolicyDemuxStrategy</code> <em>system id
policy based demultiplexing strategy</em></td>
<td>Specify the demultiplexing lookup strategy to be used with
the system id policy. The <em>demultiplexing strategy</em> can be one
of <code>dynamic</code>, <code>linear</code>, or <code>active</code>.
This option defaults to use the <code>dynamic</code> strategy when <code>-ORBAllowReactivationOfSystemids</code>
is true, and to <code>active</code> strategy when <code>-ORBAllowReactivationOfSystemids</code>
is false. </td>
</tr>
<tr>
<td><code>-ORBUniqueidPolicyReverseDemuxStrategy</code> <em>unique
id policy based reverse demultiplexing strategy</em></td>
<td>Specify the reverse demultiplexing lookup strategy to be
used with the unique id policy. The <em>reverse demultiplexing strategy</em>
can be one of <code>dynamic</code> or <code>linear</code>. This
option defaults to using the <code>dynamic</code> strategy. </td>
</tr>
<tr>
<td><code>-ORBAllowReactivationOfSystemids</code> <em>allows
reactivation of system ids</em></td>
<td>Specify whether system ids can be reactivated, i.e., once
an id that was generated by the system has been deactivated, will the
user reactivate a new servant using the old id. If the user is not
going to use this feature, the IORs can be shortened, an extra
comparison in the critical upcall path removed, and some memory on the
server side can be saved. The <code>ORBAllowReactivationOfSystemids</code>
can be <code>0</code> or <code>1</code>. This option defaults to <code>1</code>.
</td>
</tr>
<tr>
<td><code>-ORBActiveHintInIds</code> <em>adds an active hint
in
ids</em></td>
<td>Specify whether an active hint should be added to ids. With
active hints, ids can be found quickly. However, they lead to larger
IORs. Note that this option is disregarded <code>if
-ORBAllowReactivationOfSystemids</code> is set to <code>0</code>. The <em>-ORBActiveHintInIds</em>
can be <code>0</code> or <code>1</code>. This option defaults to <code>1</code>.
</td>
</tr>
<tr>
<td><code>-ORBPoaMapSize</code> <em>poa map size</em></td>
<td>Specify the size of the POA map. If not specified, the
default value is 24.</td>
</tr>
<tr>
<td><code>-ORBPersistentidPolicyDemuxStrategy</code> <em>persistent
id policy based demultiplexing strategy</em></td>
<td>Specify the demultiplexing lookup strategy to be used with
the persistent id policy. The <em>demultiplexing strategy</em> can be
one of <code>dynamic</code> or <code>linear</code>. This option
defaults to using the <code>dynamic</code> strategy. </td>
</tr>
<tr>
<td><code>-ORBTransientidPolicyDemuxStrategy</code> <em>transient
id policy based demultiplexing strategy</em></td>
<td>Specify the demultiplexing lookup strategy to be used with
the transient id policy. The <em>demultiplexing strategy</em> can be
one of <code>dynamic</code>, <code>linear</code>, or <code>active</code>.
This option defaults to using the <code>active</code> strategy. </td>
</tr>
<tr>
<td><code>-ORBActiveHintInPOANames</code> <em>adds an active
hint in poa names</em></td>
<td>Specify whether an active hint should be added to POA
names. With active hints, POA names can be found quickly. However, they
lead to larger IORs. The <code>-ORBActiveHintInPOANames</code> can be <code>0</code>
or <code>1</code>. This option defaults to <code>1</code>. </td>
</tr>
<tr>
<td><code>-ORBThreadFlags</code> <em>thread flags</em></td>
<td>Specify the flags used for thread creation. Flags can be
any logical-OR combination of <code>THR_DETACHED</code>, <code>THR_BOUND</code>,
<code>THR_NEW_LWP</code>, <code>THE_SUSPENDED</code>. The
default is <code>THR_BOUND | THR_DETACHED</code> . </td>
</tr>
<tr>
<td><code>-ORBPOALock</code> <em>lock type</em></td>
<td><a name="-ORBPOALock"></a>Specify the type of lock to be
used for POA accesses. Possible values for <em>lock type</em> are <code>thread</code>,
which specifies that an inter-thread mutex is used to guarantee
exclusive access, and <code>null</code>, which specifies that no
locking be performed. The default is <code>thread</code>.</td>
</tr>
</tbody>
</table>
</p>
</blockquote>
<h4><a name="TCSF">3. Client_Strategy_Factory</a></h4>
Similar to the
server strategy factory, the client strategy factory supports those
elements of TAO that are specific to the behavior of clients, which
are any CORBA applications that actively establish connections, submit
requests, and perhap receive responses. The client strategy factory
provides control over several resources used by clients. TAO provides
a default client strategy factory called
<code>Client_Strategy_Factory</code>.
<p>Typically, the following options are set via the service
configurator
(<code>svc.conf</code>) file. The following line in the
<code>svc.conf</code> file (all in one line)</p>
<p><code>static
Client_Strategy_Factory "[list of options]"</code></p>
<p> would load all
the options listed within "". An example is available <a
href="http://cvs.doc.wustl.edu/viewcvs.cgi/TAO/performance-tests/Latency/Single_Threaded/svc.conf?rev=HEAD">online</a>
that shows how to specify this option in the <code>svc.conf</code>
file.</p>
<p></p>
<blockquote>
<p>
<table border="2" cellpadding="0" cellspacing="2">
<tbody>
<tr>
<th>Option</th>
<th>Description</th>
</tr>
<tr>
<td><code><a name="#-ORBProfileLock">-ORBProfileLock</a></code>
<em>which</em></td>
<td>Specify the kind of synchronization primitive for the
Profiles. Default is <em>thread</em>, which means that a regular
thread mutex is used. The second option is <em>null</em>, which means
a null lock is used. This makes sense in case of optimizations and is
allowed when no forwarding is used or only a single threaded client. </td>
</tr>
<tr>
<td><code>-ORBClientConnectionHandler</code> <em>MT | ST | RW
/ MT_NOUPCALL</em><br>
<code>-ORBWaitStrategy</code> <em>MT / ST / RW / MT_NOUPCALL
</em>
</td>
<td><a name="-ORBClientConnectionHandler"></a><em>ST</em> means
use the single-threaded client connection handler, i.e., the leader
follower model will not be used. However, <em>ST</em> does support
nested upcalls and handling of new requests while waiting for the reply
from a server.
<p><em>MT</em> means use the multi-threaded client connection
handler which uses the leader follower model. This model allows the use
of multiple threads with a single Reactor. </p>
<p><em>RW</em> selects a strategy that simply blocks in <code>recv()</code>
when waiting for a response from the server instead of waiting in the
Reactor. The <em>RW</em> strategy only works when the application does
not have to worry about new request showing up when waiting for a
response. Further, this strategy cannot be used with Asynchronous
Method Invocation (AMI) calls. Therefore, this strategy is appropriate
only for "pure" synchronous clients. Note that applications with nested
upcalls are not "pure" synchronous clients. Also note that this
strategy will only effect two way calls, since there is no waiting for
one way calls. This strategy can also be used in an application that is
both a client and a server if the server side is handled by a separate
thread and the client threads are "pure" clients. </p>
<p>
MT_NOUPCALL means use a client connection handler that
participates in the leader-follower model like MT, but, like
RW, does not allow handling of nested upcalls within the
waiting thread. Note that with this strategy it is possible
to "run out of threads" in a thread pool, and that TAO doesn't
grow thread pools. Unlike RW, this does not require <a
href="-ORBTransportMuxStrategy">-ORBTransportMuxStrategy <em>EXCLUSIVE</em></a>.
<!--
I'm not sure what the effect of AMI on this option is.
-->
</p>
<p>Default for this option is <em>MT</em>. </p>
</td>
</tr>
<tr>
<td><code>-ORBTransportMuxStrategy</code> <em>EXCLUSIVE | MUXED</em></td>
<td><a name="-ORBTransportMuxStrategy"></a><em>EXCLUSIVE</em>
means that the Transport does not multiplex requests on a connection.
At a time, there can be only one request pending on a connection.
<p><em>MUXED</em> means that Transport multiplexes more than
one request at the same time on a connection. This option is often used
in conjunction with AMI, because multiple requests can be sent "in
bulk." </p>
<p>Default for this option is <em>MUXED</em>. </p>
</td>
</tr>
<tr>
<td><code>-ORBConnectStrategy</code> <em>type</em></td>
<td><a name="-ORBConnectStrategy"></a>TAO provides three
strategies to connect to remote servers. The default <em>leader_follower</em>
strategy uses the Reactor and non-blocking connects to connect and this
strategy participates in the Leader/Followers protocol to synchronize
access to the Reactor. The <em>reactive</em> strategy uses the Reactor
for non-blocking connects but does not take part in the
Leader/Followers protocol, thus it is better used only in single
threaded applications. Finally, the <em>blocked</em> strategy as the
name implies, blocks the thread until connection is complete. Some of
the protocols in TAO (such as SHMIOP and SSLIOP) can only use the <em>blocked</em>
strategy.
</td>
</tr>
</tbody>
</table>
</p>
</blockquote>
<hr>
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