1. Scheduled agents should be monitored to ensure they are running successfully on servers. A central log database can be used to store status documents from agents and alert if reports are overdue. 2. Logging is important for scheduled agents but the NotesLog model can result in large log files. It is better to develop a "ticker-tape" style log facility that stores each log entry in a small document. 3. When designing scheduled agents, consider how to handle processing large amounts of data within the limited runtime. The agent may need to run multiple times and checkpoint processing to avoid timeouts.

1. © 2007 Wellesley Information Services. All rights reserved.
Best Practices to
Write, Deploy, and
Monitor Scheduled
Agents
Bill Buchan
HADSL

2. 2
What We’ll Cover …
• Overview
• Agent Manager introduction
• Agent Manager: Scalability
• Scheduled agents: Tips and traps
• Scheduled agents: Monitoring
• Wrap-up

3. 3
Introduction
• Who is the target audience?
 Lotus Notes developers who use server-based agents
• What is this talk about?
 It’s difficult to imagine a complex Notes application without
some form of scheduled agent
 However, these are often deployed quickly without much
thought as to how they can be managed and operated on a
reliable basis
 This session attempts to remedy this

4. 4
Who Am I?
• Bill Buchan
• Dual Principal Certified Lotus Professional (PCLP) in
Domino v3, v4, v5, v6, v7
• 10+ years senior development consultancy for
Enterprise customers
 Learn from my pain!
• 5+ years code auditing
• CEO of HADSL
 Developing best-practice tools

5. 5
Overview
• This session:
 Is mostly slide-based
 Contains a few code examples
 Is a deep dive in terms of theory
 Summarizes 10+ years of enterprise code auditing

6. 6
What We’ll Cover …
• Overview
• Agent Manager introduction
• Agent Manager: Scalability
• Scheduled agents: Tips and traps
• Scheduled agents: Monitoring
• Wrap-up

7. 7
Agent Manager: Introduction
• It’s been in Domino since version 3
• It handles both scheduled and triggered agents
• It handles @Formula, Java, and LotusScript agents
• It’s a very efficient place to run code
 Because it’s running on the server, it benefits from all the
server database, view, and document caches

8. 8
Agent Manager: Introduction (cont.)
• It changes behavior for daytime and nighttime operation
 Defined in the server document
 These are the defaults
 Should these be changed?
 I don’t recommend it …

9. 9
Agent Manager: Security
• Three types of agent
security:
 Do not allow restricted
operations (default)
 Allow restricted operations
 Allow restricted operations with full administration rights

10. 10
Agent Manager: Security (cont.)
• What does this mean?
 Restrictions based on the code you write in your agent
• Restricted operations include:
 File I/O: File operations, kill, chdir, etc.
 Network operations (in Java)
 Using a disk-based NotesLog
 Environment variables
 Encryption and signing(!)
 Embedded objects
 Calling C API-based routines

11. 11
Agent Manager: Security (cont.)
• Agent security was introduced on ND6
 Beware
• On a v5 upgrade to v6 or v7 upgrade, ALL agents by
default are set to level 1
 You have to find the agents that run restricted code, and
“upgrade” them
 Either examine every agent or use automated tooling, such as
Teamstudio Analyzer
 www.teamstudio.com

12. 12
Agent Manager: Agent Types
• Scheduled agents
 Schedule a repeat time period
 Select either “All Servers” or a
particular target server
• Triggered agents
 From a client
 Before and after mail delivery
 After document creation
 After document is pasted
• Remember:
 Agents can call other agents
 Useful for mixing languages …

13. 13
What We’ll Cover …
• Overview
• Agent Manager introduction
• Agent Manager: Scalability
• Scheduled agents: Tips and traps
• Scheduled agents: Monitoring
• Wrap-up

14. 14
Scheduled Agents in LotusScript
• Scheduled agents are:
 Pieces of code that you create which can run on the server or
workstation at pre-defined intervals
 You can choose to run it on a particular server, or ALL servers
that this database exists on
 They are single-threaded
 They have a time limit
 If they exceed this time limit, they will be killed
 In this event, the “Terminate” code is executed
 You may have two instances of the same agent executing at
the same time …
 Bear this in mind during design

15. 15
Scheduled Agents: Time Limit
• If the agent will take a long time, it should:
 Record its start time
 Find out how long the task should run on this server
 Stop processing before this time period occurs
 Record its state so that it can restart
 This might be as little as marking each document as
“processed”
 Log its progress, and allow you to see any issues
• Or:
 Re-architect the solution to avoid this
• This sounds difficult …

16. 16
Demo
Demo
Brief Overview of
AgentClass

17. 17
Scheduled Agents: Setting Frequency
• The agent schedule gives you a number of choices
 The shortest time period is five minutes
 Remember, during the day there is, by default, only one agent
manager thread
 If you have hundreds of “five-minute” agents scheduled for
five minute intervals, the Agent Manager thread will be
overloaded …
• If you need more frequent time periods, re-architect the
solution by using triggers
 Is this triggered by a mail-in document, document paste, etc.?
 Alternatively, use TriggerHappy
 Open source project, www.openntf.org
 Can trigger LotusScript agents on Extension Manager
events

18. 18
Triggered Agents
• Triggered agents are:
 Pieces of code that can run on servers or workstations, and
operate on certain triggers
 Before or after a document has been mailed to a database
 When a document is pasted into a database
 When a document has been updated
• Agent manager has mechanisms to ensure that it does
NOT trigger too often
 Usually needs at least two minutes between each agent run
 Mail-in agents may not trigger enough:
 So if you have to rely on a mail-in database, create another
mechanism to pick up all “unprocessed” documents, such
as a status view

19. 19
What About Agent.RunOnServer?
• In LotusScript, when you use “notesagent.RunOnServer”
or “tell amgr run … ”
 Agent manager appears to spawn a new agent thread
 The agent does not get terminated if it exceeds the agent
run-time on the server document
 The agent appears to run in its own memory space
 There is no connection to the agent
 You cannot tell it to quit
• This means:
 Try not to use this technique in production
 If you do, be especially careful about:
 Making sure it terminates
 Logging all activity

20. 20
What We’ll Cover …
• Overview
• Agent Manager introduction
• Agent Manager: Scalability
• Scheduled agents: Tips and traps
• Scheduled agents: Monitoring
• Wrap-up

21. 21
Tip: Memory Space
• Scheduled agents share the server memory pool
• Be careful of how much memory you consume
 Offences, such as keeping large number of NotesDocument
objects open at any time, should be avoided
• If you have to “read” a large number of documents, do
some operation, then update a small number of them
 Read the comparison information and the NoteID into memory
(Custom Classes and Lists are good for this)
 Do the operation
 When updating the document, use the NoteID to quickly
reopen and save the document

22. 22
Trap: Profile Documents
• Profile documents are documents that do not appear in
views, and are easily accessible from LotusScript and
@Formula language
 Very useful for configuration settings, etc.
• However, Agent Manager tends to cache these
 If the profile document contains rapidly changing information,
there is a danger that your agent will not receive the most
up-to-date information
• So:
 Don’t store rapidly changing information in a profile document

23. 23
Tip: Execution Time
• As mentioned earlier, you have a limited amount of time
to achieve your goal with a scheduled agent
• If you are in danger of exceeding this, re-architect
 For instance, if this agent:
 Runs once per day
 Collects all “outstanding” documents
 Processes them
 Then have this agent:
 Run multiple times
 Store its last completion point and run from that point

24. 24
Trap: Garbage Collection
• Custom Classes and Lists allow you to store
information in the memory in a structured manner
 This leads to simpler code and faster execution
• However:
 If you attempt to “clean up” heavily interlinked objects in your
code, you may confuse the garbage collector
 It may crash Agent Manager, the server, or a client process
• So:
 LotusScript’s garbage collector is pretty good
 Just let it happen naturally

25. 25
Tip: “Trusted Servers”
• Before Domino 6, scheduled agents could access
databases on the current server only
• Now, if the “Trusted Servers” field is populated, you
may access databases on other servers
• This means that you are no longer required to have
replicas of databases on every server in order to collect
information from that server
 No more “replication storms”
 However, the link to the other server has to be reliable

26. 26
Trap: Run on All Servers
• You can set an agent to run on all servers that the
database exists on
 Very useful for distributing workload
• Be careful to make wide-ranging changes on one
instance of the database
 A worst practice story:
 100K document database, 15 instances
 Agent set to update all documents — every HOUR on
each server
 Replication pushes out design elements first
 Result:
 4.8 million new documents
 Database grew from 3GB  15GB!

27. 27
Tip: Cache Open Views
• Every time you open a view, it may be refreshed
 A very time-consuming operation
• Use a “list” to keep all open views in a central location
Dim allViews list as NotesView
Set allViews(“nabNames”) = dbNAB.getView(“($People)”)
Set allViews(“Lookup”) = dbThis.GetView(“vLookup”)
…
Set doc = allViews(“Lookup”).getFirstDocument
…

28. 28
Trap: Timing and Replication Lag
• On a distributed application:
 Users and agents update documents
 Replication is used to move documents around
• Remember, when looking at document round-trip time,
budget at least:
 Two replication cycles
 One Agent Manager cycle
• You might lessen the agent cycle time to reduce
replication conflicts

29. 29
Tip: Profile Those Agents!
• Domino can “profile” your agent
 Agent Properties, “Profile this agent”
 Once it has run, right click and select
“View Profile Results”

30. 30
Tip: Profile Those Agents! (cont.)
• The agent profiles are saved in profile documents
 Form = “$BEProfileR7”
 Subject = AgentName + “Profile”
 Results in body text
 You can programmatically find and analyze these
• Check out Teamstudio’s Profiler tool
 Can give you run-time analysis of your own functions
 Also, free tools include:
 Class Browser
 Call Tree Analysis, etc.
 http://blogs.teamstudio.com

31. 31
Trap: Remote Debugging
• Remote debugging should allow you to debug your
agent while running on the server
 I haven’t heard of ANYONE getting this to work successfully
• My advice:
 Test scheduled agents by constructing test harnesses you can
run manually
• This means:
 The agents should have as little code in them as possible
 All your code should be in script libraries!

32. 32
Tip: Allowing Users to Manage Scheduled Agents
• One common issue is allowing non-designers in
production environments control over agents
 Specifically, how often they run, on which servers, etc.
• Rescheduling an agent usually means:
 Updating the template and refreshing the database design
 However, in larger environments, this may be impractical
• One approach is to:
 Schedule the agent to run frequently on all servers
 Check a configuration document within the same database to
see if this agent should run at this time on this server
 Remember: Profile documents may cache and not show
new information for a significant period of time

33. 33
What We’ll Cover …
• Overview
• Agent Manager introduction
• Agent Manager: Scalability
• Scheduled agents: Tips and traps
• Scheduled agents: Monitoring
• Wrap-up

34. 34
Logging — Introduction
• Scheduled Agents should have:
 Logging. This logging should provide:
 Run-time information
 When did the agent start, where, and why?
 How many operations did it process?
 Error information
 For instance, if a run-time error was triggered, where
and how was it triggered? If there was a data error,
where did this occur? Did the agent then process
beyond this data error?

35. 35
Logging — Style
• However:
 The NotesLog model creates a new document for every
log line
 This means that you either have minimal logging, or a
huge log file
• I recommend:
 You develop your own “ticker-tape” style log facility
 Similar to Notes log.nsf
 Color code different levels of error for easy debugging
 Count errors on the log view

36. 36
• This logging achieves:
 Size
 Each log document is small
 Ease of use
 Errors are highlighted and easy to find
• Optional enhancements
 Have a configuration document that shows only logging
documents up to a particular log level
Logging — Style (cont.)

37. 37
Logging — Performance
• Huge log databases are slow to open and consume lots
of space if replicated to all servers
• Why not mail log documents to a central log database?
 Fast
 Your agent doesn’t have to open the log
 Easy
 It’s very easy to set up a mail-in database and send the log
document via mail
 Secure
 You don’t have to grant author access for all users

38. 38
Monitoring — Introduction
• Scheduled agents are rarely monitored
 Bad practice
 Failures are often found first by the users
• Business-critical agents should:
 Create a status document at the end of each run
 Possibly mail that status document to a central location
 Another agent should monitor those responses, and alert
operations if a status document is overdue

39. 39
Monitoring — Requirements
• All scheduled agents should then:
 Be aware of which servers they start on
 Be aware of the amount of time they can run for
 Be aware of their final status
 Report success/failure criteria
 Be able to report other statistical information
• A central log database should then:
 Be aware of which databases, which servers, and which
scheduled agents are expected to report
 Raise alerts if these reports are overdue

40. 40
Demo
Demo
Brief Overview of
AgentClass with
Monitoring

41. 41
What We’ll Cover …
• Overview
• Agent Manager introduction
• Agent Manager: Scalability
• Scheduled agents: Tips and traps
• Scheduled agents: Monitoring
• Wrap-up

42. 42
Resources
• My object-orientated programming presentation
 www.billbuchan.com/web.nsf/htdocs/BBUN6MQECQ.htm
• Steve McConnell, Code Complete, Second Edition,
(Microsoft Press, 2004).
 www.amazon.com/gp/product/0735619670
• OpenNTF projects — OpenLog and Stubby
 www.OpenNTF.org
• The Notes FAQ!
 www.keysolutions.com/NotesFAQ

43. 43
Resources (cont.)
• SearchDomino.com — LotusScript Learning Guide
 http://searchdomino.techtarget.com/originalContent/
0,289142,sid4_gci1001826,00.html
• Brian Benz and Rocky Oliver, Lotus Notes and Domino 6
Programming Bible (Wiley, 2003).
 www.amazon.com/gp/product/0764526111
• THE VIEW
 Mark Roden, “Simple Methods for Creating HTML-Formatted
E-mail in Domino Web Applications and Scheduled
Agents” (May/June 2003).
 www.eView.com

44. 44
7 Key Points to Take Home
• Agent Manager is a harsh taskmaster
• Scheduled Agents should be time-sensitive
 Run quickly and behave well
 Profile your agents to understand where they spend their time
• Object-orientated techniques can:
 Help manage complexity
 Add standard code
• “If you can’t measure it, you can’t manage it”

45. 45
7 Key Points to Take Home (cont.)
• Monitoring scheduled agents:
 Is not hard
 Aids environmental stability
 But be sensitive to how much logging information your
application generates
• Ensure that your agent security level is set correctly
• Avoid “notesAgent.RunOnServer” in production code
 It may create unmanageable Agent Manager “zombie”
processes …

46. 46
Your Turn!
How to Contact Me:
Bill Buchan
Bill@hadsl.com