diff options
Diffstat (limited to 'netsvcs/lib/README')
| -rw-r--r-- | netsvcs/lib/README | 270 |
1 files changed, 0 insertions, 270 deletions
diff --git a/netsvcs/lib/README b/netsvcs/lib/README deleted file mode 100644 index a85ce77b82f..00000000000 --- a/netsvcs/lib/README +++ /dev/null @@ -1,270 +0,0 @@ -This directory provides a number of network services that utilize the -ACE wrapper features. - - . Logging_Strategy -- Controls the output of all services that are - invoked along with the Logging_Strategy service. Please see below for - details on how to control the output. - - . [Thr_]Server_Logging_Handler.* -- Implements server portion - of the ACE distributed logging service. Both multi-threaded - and single-threaded implementations are provided. - - . Client_Logging_Handler.* -- Implements the client portion - of the ACE distributed logging service. - - . Name_Handler.* -- Implements a distributed name service that - allows applications to bind, find, and unbind names in - a distributed system. - - . Token_Handler.* -- Implements a distributed token service - that allows distributed applications to acquire and release - locks in a distributed system. - - . Time_Handler.* -- Implements a distributed time service that - allows distributed applications to synchronize their - time. - -The remainder of this README file explains how these services work. - -==================== Logging_Strategy Service ==================== -The Logging_Strategy Service can be used to control the output of all the -network services. It can be invoked with certain flags that determine -where the output of all the services should go. - -The Logging_Strategy Service sets the flags in ACE_Log_Msg which in turn -controls all the streams through macros such as ACE_DEBUG, ACE_ERROR, -and ACE_ERROR_RETURN. - -If default behavior is required, the Logging_Strategy Service need not be -invoked or it can be invoked with no paramaters. Here are the command -line arguments that can be given to the Logging_Strategy Service: -<CODE> - - -f <flag1>|<flag2>|<flag3> (etc...) -</CODE> - where a flag can be any of the following: - - STDERR -- Write messages to stderr. - LOGGER -- Write messages to the local client logger deamon. - OSTREAM -- Write messages to the ostream that gets created by - specifying a filename (see below) - VERBOSE -- Display messages in a verbose manner - SILENT -- Do not print messages at all - -Note: If more than one flag is specified, the flags need to be 'OR'ed -as above syntax shows. Make sure there is no space in between the flag -and '|'. - - -s filename - - If the OSTREAM flag is set, this can be used to specify the -filename where the output should be directed. Note that if the OSTREAM -flag is set and no filename is specified, ACE_DEFAULT_LOGFILE will be -used to write the output to. - -Examples: - -To direct output only to STDERR, specify command line arguments as: - "-f STDERR" - -To direct output to both STDERR and a file called "mylog", specify -command line arguments as: - "-f STDERR|OSTREAM -s mylog" - -==================== Name Service ==================== - -This file describes the principles of the Name_Server server test -application. - -1. Startup configuration - --------------------- - -To communicate with the server process, a client needs to know the -INET_Addr, where the server offers its service. Class Name_Options -holds all the configuration information of the Name Service. This -consists of : - - - nameserver_port : Port number where the server process expects requests - - nameserver_host : hostname where the server process resides - - namespace_dir : directory that holds the NameBinding databases - - process_name : name of the client process (argv[0]), NameBindings of - a ProcessLocal namespace are stored in file - "namespace_dir/process_name". NameBindings of NodeGlobal - namespace are stored in "namespace_dir/localnames". - NameBindings of Net_Local namespace are stored in file - "namespace_dir/globalnames" on the server host. - These configuration parameters are passed to the process as commandline - arguments to main: - -p nameserver port - -h nameserver host - -l namespace directory - - The main program _must_ initialize an instance of Name_Options with name - name_options (since the shared libraries depend on this). Main should - look like : - - #include "ace/Name_Options.h" - - Name_Options name_options; - - int main(int argc, char **argv) - { - name_options.process_name(argv[0]); - name_options.parse_args (argc, argv); - ...... - } - -See the examples in the tests subdirectory of -...Name_Server/Client-Server/client and -...Name_Server/Client-Server/server - - -2. Class Naming_Context - ------------------- - -This is the main workhorse of the Name Service. It is used by client -processes as well as by the server process. It manages all accesses to -the appropriate NameBinding database (that is the file where -NameBindings are stored) and it also manages the communication between -a client process and the server (by using class Name_Proxy, which is a -private member of Naming_Context). (Note: no IPC is necessary, if a -client process runs on the same host as the server). - -The strategy for all public methods of Naming_Context is common : - -1. Transform the format of the arguments to ACE_SString (which is - internally used) if necessary. - -2. check if work can be done locally : -> call the appropriate local_* method - otherwise call the appropriate global_* method. - -Removing Name_Bindings from the database (either with unbind or -rebind) uses the ACE_Malloc class configured with the -ACE_MMAP_Memory_Pool. This allows memory to be reclaimed when -name/value tuples are unbound. - -3. Class Name_Server - ---------------- - -The Name_Server registers in its run method its Name_Acceptor -(instantiated with the INET_Addr) at the Reactor, to receive incoming -requests. - -4. Class Name_Acceptor - ------------------ - -The Name_Acceptor allocates in its handle_input routine a new instance -of class Name_Handler on the heap, and accepts connections into this -Name_Handler. - -5. Class Name_Handler - ----------------- - -The Name_Handler represents the server side of communication between -client and server. It interprets incoming requests to the Net_Local -namespace and dele- gates the requests to its own Naming_Context -(which is the Net_Local namespace on the current host). For -communication it uses the helper classes Name_Request (which up to now -needs not only contain the request from the client, but also the -appropriate reply from the server) and Name_Reply. Note that I want -to change the usage of these classes to make the structure of the -software clearer. - -6. Dependencies - ------------ - -As the Name service must be able to handle wide character strings, it -uses ACE_WString String classes. - - -==================== Time Service ==================== - -The following is a description of the Time Server clerk and server -services: - -1. Startup configuration - --------------------- - -Configuring a server requires specifying the port number of the -server. This can be specified as a command line argument as follows: - - -p <port number> - -A clerk communicates with one or more server processes. To communicate -with the server process, a client needs to know the INET_Addr, where -the server offers its service. The configuration parameters namely the -server port and server host are passed as command line arguments when -starting up the clerk service as follows: - - -h <server host1>:<server port1> -h <server host2>:<server port2> ... - -Note that multiple servers can be specified in this manner for the -clerk to connect to when it starts up. The server name and the port -number need to be concatenated and separated by a ":". In addition, -the timeout value can also be specified as a command line argument as -follows: - - -t timeout - -The timeout value specifies the time interval at which the clerk -should query the servers for time updates. - -By default a Clerk does a non-blocking connect to a server. This can -be overridden and a Clerk can be made to do a blocking connect by -using the -b flag. - -Here is what a config file would look like for starting up a server at -port 20202: - -dynamic Time_Service Service_Object * ../lib/libnet_svcs.so:_make_ACE_TS_Server_Acceptor() "-p 20202" - -Here is what a config file would look like for starting up a clerk -that needs to connect to two servers, one at tango and one at lambada: - -dynamic Time_Server_test Service_Object *../lib/libnet_svcs.so:_make_ACE_TS_Clerk_Connector () "-h tango:20202 -h lambada:20202 -t 4" - -[Note: these files would vary if the services are run on NT] - - -2. Class TS_Server_Handler - ----------------------- - -TS_Server_Handler represents the server side of communication between -clerk and server. It interprets incoming requests for time updates, -gets the system time, creates a reply in response to the request and -then sends the reply to the clerk from which it received the request. -For communication it uses the helper class Time_Request. - -3. Class TS_Server_Acceptor - ------------------------ - -TS_Server_Acceptor allocates in its handle_input routine a new instance -of class TS_Server_Handler on the heap, and accepts connections into this -TS_Server_Handler. - -4. Class TS_Clerk_Handler - ---------------------- - -TS_Clerk_Handler represents the clerk side of communication between -clerk and server. It generates requests for time updates every timeout -period and then sends these requests to all the servers it is -connected to asynchronously. It receives the replies to these requests -from the servers through its handle_input method and then adjusts the -time using the roundtrip estimate. It caches this time which is later -retrieved by TS_Clerk_Processor. - -5. Class TS_Clerk_Processor - ------------------------ - -TS_Clerk_Processor creates a new instance of TS_Clerk_Handler for -every server connection it needs to create. It periodically calls -send_request() of every TS_Clerk_Handler to send a request for time -update to all the servers. In the process, it retrieves the latest -time cached by each TS_Clerk_Handler and then uses it to compute its -notion of the local system time. - -6. Algorithms - ---------- - -Currently, updating the system time involves taking the average of all -the times received from the servers.
\ No newline at end of file |