Admission and Aid @

Princeton

Admission and Aid @ Princeton

Tim Hoganthogan@princeton.edu

Admission and Aid @

Princeton

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

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.)

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

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)

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

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

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

Technical Architecture

encrypted

Web Server App Server DB Server

Authentication Server

Client

TrustedSub-Net

Apachev 1.3.26Open SSL

WebLogic 6.1

NS LDAP

DatabaseOracle 8.x

Browser

Admission and Aid @

Princeton

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

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

Log In andRegistration(CAS)

Admission

Fin Aid

Browser1. Log In

2. Apply

3. validate

4. Exit

5. Apply

6. validate7. Exit

8. Log Out

Admission and Aid @

Princeton

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

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

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

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

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

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

Technical Issues

Performance Should we cluster? Development environment Why use EJB

Admission and Aid @

Princeton

Performance

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

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

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

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

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

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

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

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

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

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

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

The End

Thank You

Tim Hoganthogan@princeton.edu

Admission and Aid @

Princeton

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 ADJ_AGI = M_AGI + F_AGI – F_MEDEXP 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

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

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

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

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

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

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

Non-Standard Ports

Log In andRegistration(CAS)

Admission

Fin Aid

Apacheapps.princeton.edu

7000

8000

9000

3 URLs:https://apps.princeton.edu:7000/https://apps.princeton.edu:8000/https://apps.princeton.edu:9000/

Admission and Aid @

Princeton

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

Non-Standard Ports (cont.)

Log In andRegistration(CAS)

Admission

Fin Aid

Apacheapps.princeton.edu

admit.princeton.edu

3 URLs:https://admit.princeton.edu/https://cas.princeton.edu/https://finaid.princeton.edu/

cas.princeton.edu

finaid.princeton.edu