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Admission and Aid @ Princeton. Tim Hogan [email protected] Background. First EJB project in ’98 – ’99 Learning experience 3 Users Proved that a Servlet/EJB/RDBMS application can be built and works Did not address performance or availability issues Non-mission critical application

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Admission and aid @ princeton l.jpg
Admission and Aid @ Princeton

Tim Hogan

[email protected]

Admission and Aid @ Princeton

Background l.jpg

  • First EJB project in ’98 – ’99

    • Learning experience

    • 3 Users

    • Proved that a Servlet/EJB/RDBMS application can be built and works

    • Did not address performance or availability issues

    • Non-mission critical application

  • Several Servlet (then JSP) applications followed.

    • Reached a bigger audience

    • Increased number of skilled developers

    • Increased understanding of performance and availability issues

    • App Servers improved / Specs evolved

    • Still not mission critical

Admission and Aid @ Princeton

Background cont l.jpg
Background (cont.)

  • Time Collection project

    • On-line time cards for 3500 hourly employees

    • Full calculation of wages including overtime and job differentials

    • Mission critical – 22x7

    • Internal to Princeton

  • NOW – Admission and Financial Aid

    • Allow all applicants to apply on-line

      • Admission – part 1 only

      • Financial Aid

    • Current students can apply for aid on-line

    • Back office processes too

    • Mission critical

    • Internal and External to Princeton

    • 24x7

Admission and Aid @ Princeton

Business scope l.jpg
Business Scope

  • For all applicants:

    • Provide a registration and log in mechanism

    • Allow applicants to save their applications and come back later to submit

    • Provide customized forms depending on applicant’s status

      • U.S., Canadian, International

      • 2-parent household, divorced, independent students

    • Provide on-demand validation

  • For current students – Financial Aid only:

    • Same as above but no registration needed

    • Can apply for current or upcoming academic year

Admission and Aid @ Princeton

Business scope cont l.jpg
Business Scope (cont)

  • Back office processes – Admissions

    • Print out applications

    • Search facilities

  • Back office processes – Financial Aid

    • Support “Need Analysis” – figuring out how much aid you can get. 3 separate methods:

      • Princeton method

      • Federal method

      • Non-custodial method

    • Each method is a series of formulas and sub-formulas that can be “tweaked” along the way. Also, formulas differ by academic year

    • Support “Packaging” – figuring out what combination of scholarships, grants, jobs to give to a student

Admission and Aid @ Princeton

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Business Scope (cont.)

  • Financial Aid processes (cont.)

    • Scholarship allocation – after packaging is complete, auto-allocate scholarships in the most efficient way.

      • Allocate non-Princeton scholarships first

      • Some scholarships are very specific (e.g., Boy Scouts from Kentucky)

Admission and Aid @ Princeton

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Technical Architecture

  • N-tier

    • Client - Ns 4.7+ or IE 4.0+

      • IE 5.5+ only for back office

    • Apache 1.3.26 w/Open SSL on Solaris 2.8

    • WebLogic 6.1 sp1 on Solaris 2.8

    • Oracle 8.1 on Solaris 2.8

  • LDAP for authentication of students and staff

  • Yale CAS authentication for applicants

  • SSL between browser and web server only

  • Automated batch feeds (via maestro)

  • 24x7

Admission and Aid @ Princeton

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v 1.3.26

Open SSL

WebLogic 6.1




Oracle 8.x

Technical Architecture


Web Server

App Server

DB Server




Authentication Server

Admission and Aid @ Princeton

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Some Stats

  • 22 Entity Beans – all CMP

  • 4 Stateless Session Beans

  • 132 Business/Support classes

  • 10 Servlets

  • 108 JSPs

  • 40 distinct windows

Admission and Aid @ Princeton

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Yale’s CAS

  • CAS – Common Authentication Service

  • Allows “single sign-on” between Admission and Fin Aid applications.

    • Cookies must be enabled

    • Provide your own authentication class

    • At entry point of each app you want to involve, add CAS jsp tags to automatically handle single sign-on process.

  • Customized and installed in 2 weeks

    • Mostly learning curve issues

  • CAS architecture

Admission and Aid @ Princeton

Using cas l.jpg



Log In and



Fin Aid

Using CAS

2. Apply

3. validate

4. Exit

1. Log In

8. Log Out

5. Apply

6. validate

7. Exit

Admission and Aid @ Princeton

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Using CAS – Rules of thumb

  • Each app is a standalone WL instance

  • Each application is responsible for its own session management once a user has entered

  • Each app has only 1 entry point that coordinates with CAS

  • “Exit” invalidates the session for that app and redirects back to CAS

Admission and Aid @ Princeton

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Application Design – Rules of Thumb

  • Standard "MVC" design

  • JSPs for painting screens

    • Java script for field validation only

    • Liberal use of java “beans” to minimize java code in JSPs

    • Put all your java code “at the top”

  • Servlets to manage screen flow and coordination between JSPs and session beans

    • Did not use one “controller” servlet that delegates to other servlets

    • Common behavior via subclassing

    • Avoid doGet(), use doPost() instead

  • Stateless session beans as "transaction controllers“

  • Domain objects contain business logic and map directly to an entity EJB

Admission and Aid @ Princeton

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Application Design (cont.)

  • Entity beans – CMP only

    • Local interfaces used, not remote interfaces

  • 1 Entity Bean = 1 Table

    • Not “course grained” – but do map to business entities.

  • Entity Bean Guidelines

    • Entity Beans are only directly accessed by other Entity Beans or Session Beans. That is, Servlets/JSPs do NOT access Entity Beans.

    • Entity relationships managed via CMP, NOT managed by Session Beans (as in earlier projects) – big performance improvement.

Admission and Aid @ Princeton

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Application Design (Cont.)

  • An entity bean has an associated "domain object" (a regular java class)

    • Can be stored in the HTTP session

    • Can be used by Servlet/JSP/EJBs/etc

  • Entity beans only used where we have objects (tables) that are directly updated during a transaction

Admission and Aid @ Princeton

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Application Design (Cont)

  • Static/lookup tables

    • We use one (large) singleton class to access all static tables

    • Lazy initialization

    • Static data queried once and stored internally

  • Implications:

    • Assume data does not change frequently

    • Must restart server to refresh

  • Future enhancement

    • Administrative function to clear out static tables from memory. This will force a reload

Admission and Aid @ Princeton

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Application Design (cont.)

  • 600+ unique data items, each is uniquely named and is consistent across:

    • txtStuFirstName (HTML)

    • stuFirstName, getStuFirstName(), setStuFirstName() (java/EJB)

    • STU_FIRST_NAME (database)

  • Heavy use of reflection to move data items between HTML -> Java domain objects -> EJB -> Database

    • Very easy to add data items later

    • Very little coding (reflection takes care of it)

  • Standardized 100+ abbreviations

Admission and Aid @ Princeton

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Technical Issues

  • Performance

  • Should we cluster?

  • Development environment

  • Why use EJB

Admission and Aid @ Princeton

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  • On-line applications had to be as fast as possible

    • Each movement between pages posted all data from that page and it had to be cached

    • “Saving” the application had to be fast

    • Saving data to 9 different tables

  • Original implementation used BMP where bean relationships were managed by Session Bean

    • 3 - 5 seconds to save

  • Moved to CMP (which handled all relationships too)

    • 0.5 seconds to save

Admission and Aid @ Princeton

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Performance (cont.)

  • Volume Testing – Financial Aid

  • We knew our peak times and volumes based on previous years paper applications

    • Early Decision (Nov 1) – 2000 applications

    • Regular Decision (Feb 1) – 5000 applications

  • Assume 50% are submitted during the last 3 days.

  • Performance Goal – support 9000 applications over the course of 3 days

    • 3K/day – during 8 hour period (8pm – 4am)…378 apps/hr

Admission and Aid @ Princeton

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Performance (cont.)

  • Load Runner – Mercury Interactive

  • Simulated 100 simultaneous users submitting 5 applications in 30 minutes

    • 2 sec avg response time

  • Maxed out the testing machine first

  • 1000 apps/hr seems good enough for us

Admission and Aid @ Princeton

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Performance (cont.)

  • 200 meg ram allocated to app server

  • JRE 1.3.1 Hotspot – Server mode

  • Hardware Sizing

    • Estimate transaction volume at peak and non-peak times.

    • Advice from BEA Consultant

      • Memory is most important

      • Many smaller servers is better than one large one

      • Recommended clustering

    • Choose server type (small/medium/large)

    • Chose ES250 - Dual 300Mhz, 2 Gig ram

      • Allows for more CPUs

      • Max out memory

  • Put all static content on Apache so app server is not burdened with it

    • *.gif, *.css, *.js

  • Cache all static data in a singleton

Admission and Aid @ Princeton

Clustering l.jpg

  • Like our other applications, we did not use clustering

    • Expensive licensing (20K / cpu)

    • Generally, overkill for our application

    • 24x7 = keep it up most of the time

  • However, we now have 7 WebLogic applications all running on the same app server

    • Each runs its own WL instance

  • If this machine crashes, we’re in big trouble

  • We are considering clustering in the context of general availability of ALL WL applications

    • Gives us a redundant app server

  • Recently, a DB server that supports 20+ apps died

Admission and Aid @ Princeton

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Development Environment

  • Developers can choose any IDE they want

  • 2 used WebGain and WL on W2K desktop

  • 1 used VisualAge on W2K and ran WL on Solaris

    • Used SMB to map Unix directory to Windows drive

  • PVCS for source control

  • Note: our code is compiled in VA on W2K, and runs on Solaris 2.8 – no problem

Admission and Aid @ Princeton

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Development Environment

  • We have 4 environments

    • DEV, QA, PROD are all exactly the same

      • Solaris 2.8 with same patch level

      • Same exact directory structure

      • Same exact WL version and patches

      • Same exact Apache

    • Developers can opt to have their own “local” environment

      • On their W2K desktop or unique Unix directory (pre-dev)

    • This makes migration very easy

  • We DON’T deploy as WAR file

    • Not practical when you only need to change 1 JSP

Admission and Aid @ Princeton

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Why use EJB?

  • Technically, we don’t need EJB in our apps because

    • Transactions don’t span multiple sources

    • Our services don’t need to be remotable (location independent, distributed)

  • However, we use EJB because:

    • It’s very very fast

    • Auto commit and rollback (very convenient)

    • Built-in relationship management with the 2.0 spec

    • We don’t have to write SQL (very lazy)

  • One EJB “bug”

    • Transactions spanning multiple tables are not always updated in the correct order (we had to disable constraints to get around this)

Admission and Aid @ Princeton

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Monitoring Availability

  • Tivoli – every 5 minutes

    • Checks for a static page on Apache – is Apache OK?

    • Logs in – is CAS OK?

    • Goes to the “Welcome” page – is the App Server OK?

    • Logs out

  • If one of these fails, we get a page

Admission and Aid @ Princeton

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Usage Stats

  • 98% of our users are IE 5.0 or higher

    • Most are IE 5.5 or 6.0

    • This includes most AOL users

  • 1% AOL browser

  • 1% Netscape (usually on MAC)

  • Average session time is 40 minutes

  • Usually 2 or 3 visits

    • Check it all out (5 minutes)

    • Fill it our for real (40 minutes)

  • Of the 3000 Fin Aid applications:

    • About 15 had cookies disabled

    • No one had java script disabled

Admission and Aid @ Princeton

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Usage Stats (cont.)

  • Peak times – 8:00pm – Midnight

    • Moves across time zones

    • A lag over the Pacific, then starts up again in China

  • # Fin Aid applications

    • 2132 - USA

    • 622 – Canada

    • 220 – India

    • 180 – China

  • Over 35 countries represented

  • 2/3 are students, 1/3 parents

Admission and Aid @ Princeton

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The End

Thank You

Tim Hogan

[email protected]

Admission and Aid @ Princeton

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Design Challenge #1

  • Calculations and formulas change from year to year

  • System must handle multiple versions of formulas simultaneously

  • Formulas are defined in Reverse Polish Notation

  • Formulas are based on labels

    • M_AGI = 67800


    • Therefore, every data item is a String in the database because it can be an actual number or a formula

  • Formulas are then associated with a particular “need method” and academic year

  • We can make all calculations table based which can be modified by user

Admission and Aid @ Princeton

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Design Challenge #2

  • On-screen validation must be flexible

  • Used a table-based approach – a validation engine

  • Validation Table defines

    • Screen name

    • Java object involved

    • Field name

    • Validation criteria

      • Field format / required / relationship to other fields / method name [for special validation]

  • Heavy use of reflection

  • Validation logic is a simple table change

Admission and Aid @ Princeton

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Issue - Performance (Specs)

  • Goals

    • Support 100 simultaneous users with 3 sec response time

    • Run payroll calculations in allotted time window (2 hours)

    • Size hardware as best as possible and allow room to grow

Admission and Aid @ Princeton

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Issue - Performance (Approaches)

  • Use App Server (EJB) for web transactions only.

  • Run mass updates in "batch" mode while App Server is down.

  • Only App Server can update database while it is up.

  • Cache everything:

    • Entity beans

    • Lookup tables / Rule tables (Singletons)

    • DB Connections

  • Static content on Web Server, not App Server

  • Split large batch jobs into smaller ones running in parallel.

  • Minimize/eliminate external DB calls. Duplicate data instead.

Admission and Aid @ Princeton

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Issue - Performance (Tuning)

  • Used tool WebLoad by RadView Software

  • Each “user transaction” added 30 time entries then removed them all (many servlet / EJB hits and db IO)

  • Did not simulate “think time”

  • Started with 50 users and increased by 25 until 3-sec response time was reached at 150 users.

Admission and Aid @ Princeton

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Issue - Monitor Availability

  • WebLogic provides a “ping” utility

    • Via maestro (scheduling software), ping the server every 5 minutes.

    • If ping fails 3 times, assume the server is locked up or dead.

      • Recycle server

      • Send out beeper and e-mail

  • During high volume periods, ping fails even though server is ok.

    • We automatically recycled the server during a very heavy period!

  • Now, we also check if Unix process is alive

    • kill –0 pid

Admission and Aid @ Princeton

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Non-Standard Ports

  • To support multiple WL apps on one machine, each runs off a different Unix port

  • We define an Apache virtual host that maps to that WL instance

    • We must define a separate VH for each WL instance because the WebLogic/Apache proxy bridge requires it

Admission and Aid @ Princeton

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Log In and



Fin Aid

Non-Standard Ports

3 URLs:

Admission and Aid @ Princeton

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Non-Standard Ports

  • However, some ISPs do not allow HTTP or HTTPS access via non-standards port (any port not 80 or 443)

  • We’ve moving to a named-based virtual host approach (vs the port-based virtual host approach)

  • This means we have many more certificates to manage too

Admission and Aid @ Princeton

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Log In and



Fin Aid

Non-Standard Ports (cont.)

3 URLs:

Admission and Aid @ Princeton