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diff --git a/TAO/orbsvcs/tests/AVStreams/server_discovery/README b/TAO/orbsvcs/tests/AVStreams/server_discovery/README deleted file mode 100644 index ef0a7af2cea..00000000000 --- a/TAO/orbsvcs/tests/AVStreams/server_discovery/README +++ /dev/null @@ -1,189 +0,0 @@ -Greetings, person designated to complete the AVDemo!, - -This document details my design for the AVDemo, just how far I got in -implementing those designs, and what remains to be done. First, let me -explain that I had originally intended to use the JavaIDL ORB for this -demo, but their implementation of demarshalling Anys tossed -CORBA::Unknown and NullPointer exceptions like a sailor tossing -cookies in a typhoon. So then, I figured I could use the VisiBroker -for Java ORB, while continuing to use the nifty jdk1.2 GUI extensions ---- the "swing" components --- which I had already begun to -incorporate into the demo. However, in this latest version of the JDK, -the system classes are located automatically, and their path is not -required in the CLASSPATH environment variable. Since the Java CORBA -package names are standardized, I couldn't arrange the package search -order so that the VisiBroker packages were searched before the JavaIDL -ones. Conflicts occurred. - -At this point, frustrated and dejected, I renounced Java ORBS -entirely, and decided to implement the client interaction using C++ -TAO while keeping the GUI using Java1.2, and have the GUI invoke -native methods when it needed to fetch information from the Trading -Service. If you're unfamiliar with the Java Native Interface (JNI), -now's the time to get familiar, since this demo relies heavily on it, -but I'll give you a brief synopsis. In the Java code you declare -methods as native by prefixing the declaration with the 'native' -keyword. Once you've compiled the Java source into byte code, you run -the 'javah' program to generate C/C++ function declarations. The names -of this functions are the product of name mangling the Java methods, -so the Java Runtime can call "dlsym" to retrieve a pointer to the -function's implementation when the native method is invoked in Java -code. At some point prior to invoking the native method, your Java -code must explicitly load the shared library in which your native -method implementations reside by calling System.loadLibrary (). Of -course, when I attempted to load the shared library contating my -TAO Trading Service client code, Java threw an -UnsatisfiedLinkException, not because it couldn't locate the library -as the misleading error message reported, but for some mysterious -reason which Carlos suspects has something to do with the native TAO -threads clashing with the Java VM's user-level threads. (In retropsect -I could have enabled native threads which seem to be supported in -Java1.2 for Solaris, but what I came up with is a more elgant design -anyway). After trying various hacks, I settled on the following -design. Brace yourself.... - -DEMO VISION - -My goals for this first demo were modest. And became increasingly more -modest as I began meeting failure at every door. My full intentions -are described in my thesis (doc/papers/ugthesis_seth), but since I can -already sense your guffawing at the notion of reading my thesis, I'll -summarize for you -- right now. Essentially, I wanted the initial query -to the Trading Service to be as productive as possible, eliminating -the possibility that attempting to connect to a server in the returned -offers will fail. Thus, that initial query will should include things -like: can accept another connection, supports the media formats -understood by the client, can transmit at a rate suitable to the -client's limiting bandwidth. Moreover, the client might want to limit -the pool of possible servers based on content --- must have movies of -a certain category --- or server performance --- must have a load less -than 2.4. This kind of configuration information can be obtained -through dialogue boxes in the GUI, and then formatted as a constraint -string in the OMG Standard Constraint language. The results --- -performance properties and movie offerings for each server --- would -be displayed in the GUI, and the user would nominate a server who -offers the best performance for the content desired by the user. - -DEMO REALITY --- the Server Side - -orbsvcs/tests/AVStreams/mpeg/source/server contains the code for the -augmented server --- augmented from the original server because it -uses the TAO_Property_Exporter to form a service offer that it exports -to a Trading Service instance. Properties exported by the -augmented_server include: maxmimum number of connections allowed, -current number of connections, list of movies offered and their -attributes, performance statistics (CPU usage, disk usage, load, -etc...). The TAO_Property_Exporter presents a kind of uniform -interface for exporting static and dynamic properties --- every -property mentioned above is dynamic except perhaps the maximum number -of connections allowed. There are actually three types of properties -exportable by Property_Exporter: static, where the value of the -property is stored twice: once in the offer and once in the MMDevice's -CosProperty::PropertySet; semi-dynamic, where the value of the -property is stored in the property set, and a dynamic property in the -service offer retrieves the value from the property set (this is -useful for MMDevice dynamic properties); and dynamic, where the value -of the property isn't stored anywhere, but lazily-evaluated by a -dynamic property in the offer (this is useful for non-MMDevice -properties). - -Classes that export properties via the TAO_Property_Exporter inherit -from the TAO_Exportable interface. The define_properties and -export_properties methods allow an exporting class to encapsulate the -exporting of its own properties. The augmented server has three -TAO_Exportable classes representing three categories of properties: 1) -The AV_Audio_MMDevice exports those properties that are also -properties of the MMDevice --- properties that are used in the -lower-level AVStream stream establishment negotiation. The properties -are static and semi-dynamic. Hence when its define_properties method -is invoked, the AV_Audio_MMDevice adds to the Service Type Description -PropStructSeq, the names, types, and modes of each of the properties -its exporting. When its define_properties method is invoked, the -AV_Audio_MMDevice uses the TAO_Property_Exporter reference it's passed -to export its properties. 2) TAO_Video_Repository in addition to being -a TAO_Exportable is also a TAO_Dynamic_Property. In define_properties -is exports itself as a dynamic property with the TAO_Property_Exporter -its passed, and when called back, parses a manifest of available -movies, obtains information about them by parsing the headers of each -of the media files, and returns this information of a sequence of -structs, each struct containing the attributes of an individual -movie. The IDL code for this structure --- TAO_VR::Movie --- can be -found in VideoRepository.idl. 3) TAO_Machine_Properties is also a -dynamic property --- serveral actually. For each of the ten or so -performance properties, it exports a dynamic property with itself as -the evaluation interface reference. When its evalDP method is called, -it obtains the value for the statistic whose name is in the prop_name -parameter. The statistics are gathered by SunRPC from the rstatd -daemon and cached. The cache expires every so often and is then -refreshed by another rpc call, obviating the need for an rpc call for -every call to evalDP. - -DEMO REALITY --- the Client Side - -The Server Selection portion of the demo is actually a Java VM -embedded in a TAO Trading Service client. The main program bootstraps -the vm, initializes the ORB and bootstraps to the Trading Service, -performs the initial query of the Trading Service, and invokes the -'main' method on the Java Server_Discovery class. Embedding the VM in -this way is possible because of the JNI Invocation interface. On the -C++ side of things, the Trader_Client class queries the Trading -Service and caches the results in a two-tier hashtable: the first tier -maps the server name to who the offer belongs to a second-tier -hashtable, which maps each property name in the offer to its -value. The Server_Discovery.cpp file implements each of the native -methods used in the java portion of the demo, and each method -implementation follows the same pattern: convert the java string -paraemters into C++ strings, obtain the Trader_Client singleton -instance, delegate to that instance, and convert the return results to -Java objects. - -The Server_Discovery class creates a JFrame with a JDesktopPane as its -ContentPane. The first window onto the Desktop is a -Server_Discovery_Selection pane which it split (JSplitPane) into two -halves: the upper portion containing a hierarcical menu (JTree) of -available movies, organized by category, title, and server; and the -bottom portion containing a table (JTable) of attributes for a selected -movie. The Server_Discovery class uses the native methods in -Server_Discovery_Util, get_server_names and get_movie_info, to supply -Server_Discovery_Selection with the information necessary to create -its displays. When a user clicks on a leaf node of the hierarchical -menuthe bottom half displays the table for that -server's movie offering. The table displays the contents of -TAO_VR::Movie structure for the selected movies. Also in the tables -are clickable labels to display the performance information for the -server, and to call up a web page describing the movie. - -For viewing the performance a Server_Discovery_Perf JInternalFrame is -created in a callback to the Server_Discovery (a Mediator object). The -Server_Discovery_Perf is supplied with the names of each of the -performance properties, instantiates a Strip_Chart for each one, and -spawns a thread to periodically update each chart by calling -Server_Discovery_Util.evaluate_performance_property for the chart's -property_name. For viewing a web page describing the movie, the -Server_Discovery_Browser, when given the description field of the -TAO_VR::Movie structure, will load a JEditorPane to fetch the page and -display the parsed html! Pretty damn slick. The "browser" will also -respond to clicks on hyperlinks and fetch the selected pages! No joke! - -Finally, if the user clicks on the button at the bottom of the -selection frame, Server_Discovery_Selection calls the native method -load_movie, which uses a UNIX socket to connect to the controller -process of the AV client, and passes it the name of the movie and the -IOR of the MMDevice interface. The AV client then transmutes the IOR -to an MMDevice object reference, and establishes the AV -stream. Hoorah! - -WHAT'S WRONG WITH THE DEMO? - -Well, the first native method invocation --- get_server_names --- -works as verified by ACE_DEBUG messages, but hangs on returning from -it. Once this problem is solved, all that remains is to ensure the GUI -looks and works as I've envisioned, and to code the interaction between -the Server Discovery and A/V client. - -That, my friend, is the demo in an anxiously written nutshell. Enjoy! -Don't forget to set the JAVA_ROOT enivronment variable to the location -of the lastest JDK version (when I was here, that was -/project/doc/pkg/jdk1.2beta4)! - --- Seth Widoff, sbw1@cs.wustl.edu
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