arch-3: context management in the openedge® reference architecture john sadd engineering fellow and...

ARCH-3: Context Management in the OpenEdge® Reference Architecture

John Sadd

Engineering Fellow and OpenEdge Evangelist

© 2006 Progress Software Corporation2ARCH-3 Context Management in the OERA

Agenda

Client to Database – a brief history AppServer™ modes and issues Thinking about procedures and context Maintaining context on the client Maintaining context on the server Conclusions


The good (very) old days: host-based

FIND FIRST Customer

FIND NEXT Customer

/* Process Customer 1 */


Everything on one box


The good (not so) old days: client/server

FIND FIRST Customer

FIND NEXT Customer



Clien

t ne

two

rkin

g

Client PC Server


Client/server limitations: Performance

FIND FIRST Customer

FIND NEXT Customer



Clien

t ne

two

rkin

g

Client PC

All code executes on the client

Server


Client/server limitations: OpenEdge client platform only

FIND FIRST Customer

FIND NEXT Customer



Clien

t ne

two

rkin

g

Server


What to do, what to do…

Host-basedClient/Server

AppServer


OpenEdgeAppServer

PO ProDataSet™

The Bigger Picture – Today and Tomorrow

Purchase Order Business Logic

HeaderData

DetailData

OtherData

PurchaseOrderProxy

.NET™ User Interface

Jonas Grumby

110 Desert Isle Path

Minnow, HI

OK

Cancel

C#

OpenEdge.NET Interface

Flexibility for client platforms and integration needs

ABL or

WebSpeed™

Interface

WebClient™ / HTML

User InterfaceJonas Grumby

110 Desert Isle Path

Minnow, HI

OK

Cancel

OpenEdgeABL Interface

ABL

OpenEdgeWeb Services Interface


Agenda

Client to Database – a brief history AppServer modes and issues Thinking about procedures and context Maintaining context on the client Maintaining context on the server Conclusions


Improving network performance with the AppServer

RUN CustProc.p ON hAppServ

(“FIRST”, OUTPUT ttCust)C

ustP

roc.p

Client AppServer

Business logic code

executes on the server


Using a bound AppServer session in “state-aware” mode

RUN FindCust IN hCust

(“FIRST”, OUTPUT ttCust)

RUN FindCust IN hCust

(“NEXT”, OUTPUT ttCust)



RUN CustProc.p ON hAppServer

PERSISTENT set hCust.C

ustP

roc.p

Client AppServer


Scalability and bound AppServers

client

client

client

client

client

client

AppServer session

AppServer session

AppServer session

AppServer session

AppServer session

AppServer session


Using the AppServer in “stateless” mode

AppServer session

AppServer session

AppServer session

AppServer session

AppServer session

AppServer session

Ap

pS

erver bro

ker

All clien

t requ

ests


Using the AppServer in “stateless” mode– FIND FIRST

AppServer session 1

AppServer session

AppServer session

AppServer session

AppServer session

AppServer session

Ap

pS

erver bro

ker

RUN CustProc.p ON hAS

(“FIRST”, OUTPUT ttCust)


Using the AppServer in “stateless” mode – FIND NEXT

AppServer session

AppServer session 2NEXT What??

AppServer session

AppServer session

AppServer session

AppServer session

Ap

pS

erver bro

ker

RUN CustProc.p ON hAS

(“NEXT”, OUTPUT ttCust)


Advantages to using stateless mode

Allows sharing of server resources by many clients Promotes scalability Allows for load balancing and other optimizations Allows AppServer access from other platforms


Challenges using stateless mode

Can’t run procedures PERSISTENT without binding the AppServer session• Server procedure won’t keep track of you

• Can’t run internal procedures

Can’t get a procedure handle for non-persistent procedures

Can’t maintain client-specific context within an AppServer session


Unmanaged “state-free” mode

Not even a persistent CONNECTION-ID for the AppServer broker

Recommended for use with Web services or other connectionless environment• Service-Oriented Application on the bus

Issues are essentially the same as with stateless


Agenda



Context Management Basics

Target environment is client to stateless or statefree AppServer

Each interaction is independent Maintain context between related interactions


Dealing with context in a stateless world: binding for the duration of a task

Run a procedure PERSISTENT on a stateless AppServer session• This binds the session for the life of the

procedure

• Supports multiple calls that are part of a single ‘task’

• The session is unbound when the procedure instance is deleted


Managing context for a task

Agreement

Validate

Customer if ? then

Context

Enter

Order if ? then

Confirm

Inventory if ? then

Calculate

Price if ? then

Agreement

Order

Entry

Task

Agreement

Customer Entity

Order Entity

Inventory Entity

Pricing Entity


Managing a task by binding a stateless AppServer

Agreement

Validate Customer

if ?

Context

Enter

Order

if

?

Confirm

Inventory

if ? Calculate

Price

if ?Agreement

Task

Agreement

Client

RUN PERSISTENT

DELETE PROCEDURE

AppServer

This method is strongly discouraged!• Uncontrolled binding to client

• Not suitable for SOA direction


Accessing shared procedure instances

Pre-start commonly used PERSISTENT procedures as part of AppServer start-up

Use a ‘gateway’ (Service Interface) procedure to route client requests

Or: • Have the Service Interface start procedures

the first time they are needed Session manager on the server


Using a Service Interface procedure and session manager

Client Server

UI Procedure

DATASET dsOrder

Business Entity

DATASET dsOrder

Data-Access Object

DATASET dsOrder

RUN fetchOrder

IN hdsOrder

(. . . ,

OUTPUT

DATASET

dsOrder

BY-REFERENCE)

RUN FetchWhere

IN hEntity

(. . .,

OUTPUT

DATASET

phFetchDataSet

BY-REFERENCE)

fetchWhere:

FILL

ATTACH

Cli

ent

Pro

xy

Ser

vice

In

terf

ace

Session Manager


Using a Session Manager

DEFINE TEMP-TABLE ttEntity FIELD EntityName AS CHARACTER

FIELD EntityHandle AS HANDLE FIELD DAOHandle AS HANDLE INDEX EntityName EntityName.

FUNCTION getEntityHandle RETURNS HANDLE (INPUT pcEntityName AS CHARACTER): DEFINE VARIABLE hEntity AS HANDLE. FIND FIRST ttEntity WHERE ttEntity.EntityName

= pcEntityName NO-ERROR. IF NOT AVAILABLE (ttEntity) THEN hEntity = startEntity(pcEntityName). ELSE hEntity = ttEntity.EntityHandle. RETURN hEntity.END FUNCTION. /* getEntityHandle */


Using a Session Manager - 2

FUNCTION startEntity RETURNS HANDLE (INPUT pcEntityName AS CHARACTER): DEFINE VARIABLE hEntity AS HANDLE. DEFINE VARIABLE hAccess AS HANDLE. RUN VALUE("be" + pcEntityName + ".p") PERSISTENT SET hEntity NO-ERROR. IF VALID-HANDLE(hEntity) THEN DO:

CREATE ttEntity. ASSIGN ttEntity.EntityName = pcEntityName ttEntity.EntityHandle = hEntity. END. RETURN hEntity.END FUNCTION. /* startEntity */


Alternatives for maintaining context

Pass context information back and forth between client and server• The context is held on the client

Store context between client requests in a shared data store • All AppServer sessions can read and write it

• The context is held on the server


Using the AppServer in “stateless” mode

AppServer session

AppServer session

AppServer session

AppServer session

AppServer session

AppServer session

Ap

pS

erver bro

ker

All clien

t requ

ests


Agenda



Passing Context between Client and Server

Context/Parameter temp-table passes context back and forth

Name & Value fields allow flexibility Or just use a delimited list in a CHAR param Context is maintained on the client Useful for moderate amounts of data

• Also for context used on the client

• And for context modified on the client


context/parameter

temp-table

Context Between Client and Server -- Batching

Client Server

UI Procedure

DATASET dsOrder

Business Entity

DATASET dsOrder

RUN fetchOrder

IN hdsOrder

(. . . ,

OUTPUT

DATASET

dsOrder

BY-REFERENCE)

RUN FetchWhere

IN hEntity

(. . .,

OUTPUT

DATASET

phFetchDataSet

BY-REFERENCE)

Clie

nt

Pro

xy P

roce

du

re

Ser

ver

Gat

eway

Pro

ced

ure

WhereString = “…”

NextRowid = 63524


Using a context temp-table

FIND ttContext WHERE ttContext.ContextName = "WhereString" NO-ERROR.IF NOT AVAILABLE(ttContext) THENDO: CREATE ttContext. ttContext.ContextName = "WhereString".END.ttContext.ContextValue = "OrderNum = " + STRING(iOrderNum).

/* …and the same for NextRowid */

Useful for any flexible set of parameters or context values in a single interface


Agenda



Context Maintained on the Server

Hold context in a shared server-side data store• Typically a database table

Useful for context not to pass back and forth• Session context such as language, authorization

that does not change

• Also useful for large amounts of context data

Storing context on the server can be the best universal approach


Built-in support for UUIDs and GUIDs in 10.1A

Requires a Context ID passed from the client GENERATE-UUID

• Universal Unique IDentifier• Returns a 16-byte RAW (binary) value• Guaranteed unique across all space and time

GUID (<uuid-value> )• Global Unique IDentifier• Converts a UUID into a 36-character GUID

– XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX

SUBSTRING(BASE64-ENCODE(GENERATE-UUID),1,22)• Yields a more compact 22-character string


Context ID parameter

Context Stored on the Server

Client Server

UI Procedure

DATASET dsOrder

Business Entity

DATASET dsOrder

RUN fetchOrder

IN hdsOrder

(. . . ,

OUTPUT

DATASET

dsOrder

BY-REFERENCE)

RUN FetchWhere

IN hEntity

(. . .,

OUTPUT

DATASET

phFetchDataSet

BY-REFERENCE)

Clie

nt

Pro

xy P

roce

du

re

Ser

ver

Gat

eway

Pro

ced

ure

ContextID = 95847

Context

95847 English Auth …


ProDataSet and Temp-Table Context

Store retrieved data in a context table• For WebSpeed or other clients with no

ProDataSet support

• RAW fields and BLOBs for generic storage

• Or store as XML in CHARACTER format

Store successive updates before commit• Allows partial validation on the server

• Final update ProDataSet rebuilt from context


ProDataSet or Temp-Table Data as Context

Client Server

Web browser Business Entity

DATASET dsOrderBrowser code

RUN FetchWhere

IN hEntity

(. . .,

OUTPUT

DATASET

phFetchDataSet

BY-REFERENCE)

Ser

ver

Gat

eway

Pro

ced

ure

ContextID = 95847

Context

95847 Order 1 Line 1



“OrderNum = 1”

95847 Ord 1 L 1 Q 20

95847 Ord 1 L 1 Q 20

Application


Defining a context management table

SessionID – identify a client session ContextID – identify a specific task or transaction

within a session ContextName – Table name or other tag (like

‘WhereString’) ContextValue – Primary key value for a table, or

string value for another tag isBeforeRow – flag for ProDataSet rows RowSequence – for ordering table rows TimeStamp – when the row was created or last

updated (also a DeleteTime for cleanup) RawData – temp-table row data


Creating a context row

phBuffer:RAW-TRANSFER(TRUE, /* from buffer to RAW */

BUFFER ContextStore:BUFFER-FIELD("RawData")).

ASSIGN ContextStore.TimeStamp = NOW ContextStore.DeleteTime = DATETIME-TZ( DATE(NOW) + 1, MTIME (NOW), TIMEZONE(NOW)).

CREATE ContextStore.ASSIGN ContextStore.ContextID = pcContextID ContextStore.ContextName = phBuffer:Name ContextStore.ContextValue = cKeyValues ContextStore.RowSequence = piSequence ContextStore.isBeforeRow = FALSE.


ContextStore rows

wxyz eOrder 27 1 FALSEabcd raw buffer

wxyz eOline 27 1 1 FALSEabcd raw buffer

wxyz eOline 27 2 2 FALSEabcd raw buffer

Sessio

nID

Co

ntextID

Co

ntextN

ame

Co

ntextV

alue

Ro

wS

equ

ence

isBefo

reRo

w

Raw

Data


RAW-TRANSFER limitations

Low-level – does not recognize fields or other buffer specifics

Temp-table definitions must match exactly Use for short-term storage


Agenda



Design for the OpenEdge AppServer

AppServer lets you locate business logic where it belongs to improve performance

AppServer is the basis for all Open Client access, .NET support, Web services, etc.

Stateless or statefree mode gives you the greatest flexibility and scalability

Avoid binding the AppServer to a client session


Design context management into your application as a “feature”

Store small amounts of context on client Store larger amounts of data on server Design general solutions into your application

architecture Consider needs of platforms like WebSpeed

and Web services for SOA


Design for the future

Prepare your application for future requirements• WebSpeed for a browser-based UI

• .NET, PDA, or other new UI platforms

• Access as Web Services

• Service Oriented Architecture


PSDN white papers on Implementing the OpenEdge Reference Architecture

-- The Service Interface Layer

-- Context Management


Questions?


Thank you foryour time

arch-3: context management in the openedge® reference architecture john sadd engineering fellow and...

Documents

progress software corporation

process customer

bound appserver session

client platforms

brief history appserver

client networkingserver

contextmaintaining context

clientmaintaining context