LotusScript Survival Tips for Large Systems

Bill Buchanhadsl.com

• Introduction

• What do we need?

• Logging

• Performance

• Code Reuse

• Weirdness

Agenda

• I am:

• Bill Buchan, CEO, hadsl

• LotusScript expert since 1997, Large systems experience

Introduction

Direction?

• Lets consider the following slide...

Whats New In LotusScript?

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Whats new in LotusScript?

• The Class libraries have generally grown with each release

• Leveraging feature-specific stuff such as ID Vault in 8.5.0

What does this mean?

• LotusScript is still an invaluable tool in your armoury for creating Business Logic

• Its easy, its multi-platform

• Its NOT the future in terms of Client or Web

• Check out all the xPages sessions here

• No excuses

What do we need?

• Large environments need:

• Stability

• Scalability

• If you cant measure it, you cant manage it

• You want to do more, with less time and less people

What do we need?

• Stable performance

• We cant keep adding new servers every time we add a new application/database instance

• We cant let a single application wreak havoc on our systems

What do we need?

• Code Reuse. Of course.

• We have less resources doing more work

• We need to test more effectively

Logging

• Why do logging?

• As a rule of thumb, if its scheduled, critical, or running in someplace you cant immediately check, you need logging

• You need to know:

• When and where did it start, stop

• Was it successful

Logging

• If something happens, and you find out from the users

• You have failed

Logging

• Lots of solutions available

• For instance, use ‘msgbox’ to log to the console.

• Admins hate this

• It’ll never be acted upon

Logging Solutions

• Check out OpenLog at OpenNTF

• Add two lines of code, and you have a comprehensive log

• Free and Easy

• No excuses

SuperLogging

• Consider Performance

• Opening a notes database - even from Script - opens the default view

• Log database views can get large

• It can be slow

SuperLogging

• Why not

• Create a new document and populate as normal

• Stamp it with start and stop times - handy for measuring load

• Add Server, Database, Agent and User

• But then use notesdocument.send()

SuperLogging

• Sending log documents by email means:

• The process is not waiting for you to save the log document (and update the views) - huge performance increase

• The log database need not be local

• The user processes do NOT need access to the log database

SuperLogging

• Once you start emailing in Log Documents, you can do more:

• Spot when agents DONT trigger a log document - and do something about it

• Spot when NEW agents start creating logs

SuperLogging

• Remember, ALL code has to log accurately

• LotusScript, Java, xPages

• Javascript?

Performance

• We application developers can create fantastic applications

• And we can create horrible ones

• Ones that really kill servers.

• Lets talk about...

Performance:Views

• Your application needs views. Of course it does. But does it need them all?

• ‘Click-sort’ columns are evil

• Use more ‘Categorised’ views

Performance:Views

• How can I tell the size of a view?

• Admin client, select database, Tools, Manage Views

Performance:Views

Performance:Views

Performance:Views

• Create as few views as possible

• Don’t use Click-sort on columns unless absolutely necessary. Each click-sort column creates another copy of the view

Performance:Agents

• Scheduled Agents have to be well-behaved

• Agent Manager doesn't really do a great job in killing runaway agents

• It certainly doesn't throttle agents which consume lots of CPU

• And it only runs one or two agents at a time

Performance:Agents

• So how to we minimise our Agent Footprint?

• Write them to fit the potential size of your application

• If there are lots of documents to process, let the agent run multiple times

Performance:Agents

• Use Agent Profiling to find out how long your agents take against a representative quantity of documents

• ‘It worked in testing’ is not an excuse.

• Its an admission your testing wasn’t rigorous enough

Performance:Agents

• To enable Agent Profiling, check the ‘Profile This agent’ in Agent Properties.

• Once its ran, you can view which calls its made, and how much time it took

Performance:Agents

Performance:Agents

• You can see

• When the agent ran

• Where it ran

• Where it spent time

• Invaluable for performance tuning

Performance:Agents

• Now. Lets take it one step further

• How about collecting ALL agent profiles from ALL databases and storing them in a database?

• NOT recommended for production environments

Performance:Agents

• Recipe:

• Take ‘TriggerHappy’ from OpenNTF

• Have it listen to ALL document saves on the server

• If the form is called "$BEProfileR7"

• Forward the document to another database

Performance:Agents

• For more information on this, visit:

• http://www.billbuchan.com/imported-20091119232548/2010/2/2/universal-agent-profiling-in-domino.html

• URL is in IBM Standard Download Notation.

Performance:Agents

• A common scenario

• We build an agent to examine a lot of documents, and update a few of them, every night.

• The database grows

• Your admin kills you.

Performance:Agents

• Remember:

• Agent Manager is like a crumbly old relative - Everyone loves him

• But he’s quite shaky on his feet

• And smells

• Don’t abuse him

Performance:Agents

• Changing the maximum agent run-time on the server document is CHEATING

Performance:Agents

• Re-architect the agent

• It starts up, figures out how long it has to run, and works out its termination time.

• Maximum time minus 2 mins

• Keep working till expiry time

• Have the agent run a few times - say every 10 mins for 3 hours overnight

Performance:Agents

• So:

• Own & Understand your agent performance

• Don’t abuse agent manager

• Don’t let it kill your system

Code Re-use

• Don't reinvent the wheel every time

• That leaves far too little time for the pub

• Oh - and it means re-testing from scratch every time

• Be Lazy

Code Re-use

• So

• If your an old-fashioned script guy, create a standard script library that encapsulates:

• Standard Logging

• Configuration lookup

Code Re-Use

• If your a little bored with this (and who isn't?)

• Create a LotusScript class which encapsulates all boring logic

• Extend this class in your own code for the business logic

• Simplify the target code

Code Re-use

• For example:

class baseClassPublic Sub logMsg(msg as String)

‘ do stuffend sub

public sub raiseError()‘ do stuff

end subend class

Code Re-use class myLogicClass as baseclass

Private Function myStuff(waffle as String)on error goto errorhandler

call logMsg(“hello world”)

‘ Do stuffexitFunction:

exit function errorhandler:

call me.raiseError()resume exitFunction

end functionend class

Code Re-use

• Remove the responsibility for

• Logging

• Error handling

• Other boring stuff

• From your business logic

Weirdness

• Sometimes, we have to walk on the wild side

• Just sometimes, we like to stroke our misshapen little ego

• Or we actually have a business reason

• Whatever

Weirdness: Lists• Use lists - they’re not hard.

Dim Pres list as StringPres(“George”) = “Bush”Pres(“Bill”) = “Clinton”

Print “Georges’s last name is: “ + Pres(“George”)if not isElement(Pres(“Chad”)) then _print “Chad wasn’t found”

forall thisPres in Pres Print listtag(thisPres) + “ “ + thisPresend forall

Weirdness:C-API

• LotusScript never does everything. Sometimes you have to call out to C-API

• What is C-API?

• Over 700 functions that you can get to using C code

• Downside: Creating & Supporting code on every platform you support. Eugh.

Weirdness: C-API

• So how can the lazy programmer call C-API functions from LotusScript?

Declare Function W32_NSFGetServerLatency Lib LIB_W32 Alias {NSFGetServerLatency} (_Byval ServerName As Lmbcs String, _Byval Timeout As Long, _retClientToServerMS As Long, _retServerToClientMS As Long, _ServerVersion As Integer) As Integer

Weirdness: C-API• Now lets exploit this declaration

Public Function getServerLatency _ (strServer As String) As LongDim nnServer As New NotesName(strServer) Dim ToServer As Long, fromServer As Long Dim ver As Integer Dim timeout As Longtimeout = 1000' 1000ms == 1 second

Call W32_NSFGetServerLatency(nnServer.Canonical,_ timeout, _toServer, fromServer, ver)

' Return both directional latencies added togethergetServerLatency = fromServer + ToServerEnd Function

Weirdness: C-API

• Now do this for every function, and every platform you wish to support.

• Euch

Weirdness: Execute

• You all know how to do ‘Evaluate’ right?

Dim V as variantV = evaluate( “ @Name( [CN]; @UserName ) “ )print V(0)

‘ Result is ‘Bill Buchan’

Weirdness: Execute

• Boring. Lets write some code to write some code

Dim S as StringS = “ msgbox | Hello World | “V = execute ( S )

Weirdness: Execute

• What is this doing?

• We can populate a string with valid Lotusscript Code

• And then execute it.

• Why on earth would this be useful?

• We could, for instance, generate our platform specific C-API calls

Weirdness: C-API

• Check out the ls2capi.com web site

• And check out my ls2capi database on

• http://hadsl.com/hadsl.nsf/Documents/LS2CAPI+-+Calling+Notes+C-API+from+LotusScript!OpenDocument

• Step through it in the debugger.. ;-)

Conclusion

• Use these techniques to deal with large systems

• Minimise, Simplify and Productionalise your code

• Learn xPages