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Building Server Services with Visual FoxPro. Session V17. Rainer Becker. dFPUG, Germany. Who Am I?. German FoxPro User Group http://www.dfpug.de/forum German VFP DevCon FoxX Professional (4x200 pages) Wizards & Builders GmbH http://www.wizards-builders.com MVP, MCSD, speaker/writer

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Building server services with visual foxpro

Building Server Services with Visual FoxPro

Session V17

Rainer Becker

dFPUG, Germany

FoxTeach 2001


Who am i
Who Am I?

  • German FoxPro User Group

    http://www.dfpug.de/forum

    • German VFP DevCon

    • FoxX Professional (4x200 pages)

  • Wizards & Builders GmbH

    http://www.wizards-builders.com

  • MVP, MCSD, speaker/writer

    • But I am not bilingual !

FoxTeach 2001


Defining the problem

Defining the problem

What is the problem we solve with a remote server service ?

FoxTeach 2001


Services on a server
Services on a Server

Multiply performance by direct table access instead of network traffic for (examples):

  • Database reorg/reindex

  • Structure modification/update

  • Data synchronization

  • Data import (host)/export

  • Complex queries/reports

  • Long-running process (e.g. re-booking)

FoxTeach 2001


How to call a server app
How to call a Server App

  • CREATEOBJECT

    • only local registration with /REGSERVER or REGSRV32.EXE

  • CREATEOBJECTX

    • remote registration with CLIREG32.EXE

    • But still no asynchronous connection...

      But: Server Application must run independent from Client App!

FoxTeach 2001


Automatic start on a server
Automatic Start on a Server

  • AUTOEXEC.BAT

    • Only for DOS Command

  • AUTOSTART folder

    • Only for active user

  • SCHEDULER

    • Configuration problem

  • SERVICE

    • Currently the most suitable solution

FoxTeach 2001


Installing a service

Installing a “Service“

How to define a VFP server service on Windows NT ?

FoxTeach 2001


Installation of a service
Installation of a “Service“

  • Configuration / System Management / Services

    • Only allows changing of existing services (e.g. execution type, used account)

    • “Allow Interactive Relation to Desktop“

  • Wizard “SRVINSTW.EXE“ allows interactive installation of a service

  • Interface for a service cannot be supplied with VFP -> SRVANY.EXE

FoxTeach 2001


Using the install wizard
Using the Install Wizard

  • P1: [x] Install a service

  • P2: [x] Local Machine

  • P3: Service Name „Remote Server“

  • P4: Executable File „SRVANY.EXE“

  • P5: [x] Service is its own process

  • P6: [x] System account

    • [x] Allow Service to interact with Desktop

  • P7: [x] Automatic

  • P8: Finish

FoxTeach 2001


Configure srvany exe
Configure SRVANY.EXE

  • Call REGEDIT.EXE

  • Navigate to “HKEY_LOCAL_MACHINE \SYSTEM\CurrentControlSet\Services\”

  • Navigate to your “Remote Service“

  • Right mouse: Option “New“, Sub-option “Key“, Value “Parameters“

  • “New”, “Char”, “Application“, Value “ “<Drive>:<path>\<vgremote>.exe“

  • “New”, “Char”, “AppDirectory“, Value “<Drive>:\<path>“

  • Optional “AppParameters“, Value “NONE“

FoxTeach 2001


How to start a service
How to start a Service

  • Various Options to start/stop:

    • Interactive with system configuration

    • NET START/STOP “service name“

    • SC START via SC commandline utility of Windows NT

  • Problem: Applet does not see VFP-status but only SRVANY-status (even “ “QUIT“ still allows to start/stop/restart the service) – confusing for admins!

FoxTeach 2001


Unattended installation
Unattended Installation

  • INSTSRV.EXE parameters

    • Service name

    • Exe location

    • (-a account name)

    • (-p account password)

    • REMOVE

FoxTeach 2001


Implementing remote server

Implementing Remote Server

How to implement a remote server application ?

FoxTeach 2001


Parameter passing
Parameter Passing

  • No access via object reference

  • Parameter table instead

    • User, Password (encrypted)

    • Module, Object, Method, Parameter

      Or

    • Script-Memo (Single/Multi-Line)

    • ErrorRetry

FoxTeach 2001


Setup methods
Setup Methods

  • Settings

  • SetVars / Properties

  • Set OnShutDown / Shutdown

  • Set OnError+ErrorHandler / ErrorMethod

  • OpenTable

  • Endless Loop / Timer (snp)

FoxTeach 2001


Problems with endless loops
Problems with Endless Loops

  • Normally you get an endless loop by accident with no work at all, but

    • A typical endless loop produces 100% workload in the Task Manager

    • Additionally, it creates a GUI error with SYS(2335,0) (unattended servermode)

  • Solution: Use READ EVENTS with a timer which fires CLEAR EVENTS

    • (still you get problems with sys(2335,0)...)

FoxTeach 2001


Job execution methods
Job Execution Methods

  • Scan Job-Table

  • JobLock

  • JobProcess

    • Macro execution

    • Script-compiling

    • COM-Server creation/call (snp)

  • Repositioning

  • JobUnlock

FoxTeach 2001


Call com servers
Call COM Servers

  • CREATEOBJECT

    • Call an .EXE instead of .DLL to survive execution failure

  • LOGIN

    • encryption for security

  • Method-Call

    • COMRETURNERROR if exclusive access is needed but not available

  • Return Value

FoxTeach 2001


Configuration with constants
Configuration with Constants

  • Name, Title, Caption

  • Table, Path

  • Retry on Error

  • Timer: Break between jobs

  • Master-User / -Password

  • Exclusive Access ComReturnError

  • For Discussion of constants see session V18 Dynamic Constants

FoxTeach 2001


Logfile activity
Logfile / Activity

  • Low-Level Text File for Job-Log

    • Datetime start/end, result/failure

  • NT Eventlog not implemented yet

    • WinAPI-problems occured

  • Monitor activity from Client (snp)

  • Restart via Starter Application

    • CreateObjectX for Starter not Server

FoxTeach 2001


Connect the client

Connect the Client

How to connect the client to the remote server application ?

FoxTeach 2001


Client implementation
Client Implementation

  • Implementation as a service class

    • Reusability needed

  • Data access to job-table needed

    • Place in a different class for later change of table format or parameter passing type

  • Read/Write Job-Table

    • Read status information (see below)

    • Timer for status information

  • „Call once“ or „Call many“ jobs

FoxTeach 2001


Client methods
Client Methods

  • IsServerActive

  • ServerStart

  • JobCreate

  • JobStatusGet

  • JobTimerCreate (Thermometer)

FoxTeach 2001


Thermometer update
Thermometer Update

  • Status information is wanted for long-running remote jobs, but

    • Server application cannot update Job-Table as it is locked by the remote server service

  • Solution: 1:1-related table for status information OR pass THIS for a callback mechanism

    • Use a wrapper object reference

FoxTeach 2001


The exclusive client problem
The “exclusive client“ Problem

  • Some useful server jobs need exclusive database access(e.g. reorg, reindex, pack, backup)

  • Client application can insert a job into job-table, but that‘s it

    • Server application will terminate again and again as long as user is logged into app

  • Depends on your implementation of semaphores and locking

FoxTeach 2001


Special tricks
Special Tricks

How can we extend the potential power of remote server services ?

FoxTeach 2001


Multiple server services
Multiple Server Services

  • Even on a single processor server, more than one instance might be useful to shorten processing time

    • See example in VFPSP3.CHM

    • Just place a RUN-Task in job-table...

  • Memory consumption problems might be reduced by Multi-Threaded VFP-Runtime (see SP3)

FoxTeach 2001


Mq msts
MQ / MSTS

  • Parameter table can be replaced by Message Queue Server

    • No current experience

  • Instantiation time might be reduced by use of MS Transaction Server

    • No current experience

FoxTeach 2001


Service as webservice
Service as “WebService“

  • Remote Server Service built as COM Server convertable to Web service

    • with Toolkit in Visual Studio 6.0 or VFP 7.0

  • Build a table-interface-Webservice

    • Send Job-Table entry as XML-record

    • Implement Client functions for COM-server

  • See Session V19 “Creating and Using SOAP Web Services with Visual FoxPro“ by Rick Strahl

FoxTeach 2001


Additional material

Additional Material

Where to go from here ? Where to find additional information ?

FoxTeach 2001


Visit other sessions
Visit other Sessions

  • V14 “Building World-Class Visual FoxPro COM Servers“

    • Kevin McNeish

  • V19 “Creating and Using SOAP Web Services with Visual FoxPro“

    • Rick Strahl

FoxTeach 2001


Tools docs on companion cd
Tools/Docs on Companion CD

  • SRVINSTW.EXE (install wizard)

  • INSTSRV.EXE (install tool)

  • SRVANY.EXE (service interface)

  • SRVANY.WRI (documentation)

  • W2RKTOOL.CHM (NT Resource Kit)

FoxTeach 2001


Foxteach web update page

FoxTeach Web Update Page

www.dbcentral.com

This session will NOT have web updates.

FoxTeach 2001


Thank you

Thank you!

Please remember to fill out your evaluation.

FoxTeach 2001


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