Thursday, November 24, 2005

Building a Better Link Monitor using WMI – Exchange 2003

Someone asked me a question last week about using the Queue class’s in Exchange 2003 and this got me thinking about link monitors. Link monitors are a little bit old terminology these days although I really used to like the old site and link monitors in Exchange 5.5 especially the visual representation. Now there are monitors on Exchange 2003 and while useful they are really lacking in being able to tell you if there actually is a problem and what that problem might be.

So I decided to see if I could build a better link monitor that would one tell me when there is a problem and also let me know in the warning email what that problem might be. Eg if there are lot of messages queuing up send me a dump of what the message queues looks like and tell me what messages are in the queue. Then with any luck I can tell from the email if there really is a problem that I might need to look at or if its just a temporarily large volume of email being sent. Eg the first thing you do when you get a warning about a problem with mail queues is to go and check what’s in them so I was trying to cut this step out.

So the solution I put together was a script that would listen for modification events on the Exchange_SMTPQueue Wmi class with a filter so it would only take action when the number of message in any of the queues went over a configured threshold. When the threshold is reached it would query all queues on the box and build a html table of the results and it would also then enumerate the messages in the queues that were over threshold and create a html table of the result of this enumeration. The html tables would then form the body of an alert email which would be sent. To stop the script sending email every update period which is about every 15 seconds or so the script tracks the last time an alert was sent so it will only send 1 alert per hour if the queues are still over threshold.

The script itself uses 3 WMI queries the first query listens for the Queue modification events. The second query enumerates the queues the third query enumerates the messages within a queue that are over threshold. A mail is then sent over SMTP using CDOEX/CDOSYS. The script itself can be run locally or remotely as long as there is CDOEX or CDOSYS installed on avaible on the machine to send the message.

To use the script you need to configure four things within the script the first is the computer name the second is the email address its sending from the email address its sending to and the server its sending through so the following 4 lines needs to be customised.

cComputerName = "."
objEmail.From = ""
objEmail.To = ""
objEmail.Configuration.Fields.Item("") = "Servername"
I’ve put a download copy of the script here the script itself looks like

cComputerName = "."
MessageThreshold = 5
LastAlertSent = dateadd("h",-1,now())
Set objWMIService = GetObject("winmgmts:" _
& "{impersonationLevel=impersonate}!\\" & _
cComputerName & "\root\MicrosoftExchangeV2")
Set colMonitoredEvents = objWMIService.ExecNotificationQuery _
("SELECT * FROM __InstanceOperationEvent WITHIN 10 WHERE " _
& "Targetinstance ISA 'Exchange_SMTPQueue' and TargetInstance.MessageCount >= "
& MessageThreshold)
Set objLatestEvent = colMonitoredEvents.NextEvent
Wscript.echo now() & " " & objLatestEvent.TargetInstance.LinkName & " " &
objLatestEvent.TargetInstance.MessageCount & " " &
if LastAlertSent < dateadd("h",-1,now()) then
call EnumSMTPQueues()
LastAlertSent = now()
end if

sub EnumSMTPQueues()
Const cWMINameSpace = "root/MicrosoftExchangeV2"
Const cWMIInstance = "Exchange_SMTPQueue"
HtmlMsgbody = "<table border=""1"" width=""100%"" cellpadding=""0"" bordercolor=""#000000""><tr><td
bordercolor=""#FFFFFF"" align=""center"" bgcolor=""#000080"">" _
& "<b><font color=""#FFFFFF"">Queue Name</font></b></td><td bordercolor=""#FFFFFF""
align=""center"" bgcolor=""#000080""<b><font color=""#FFFFFF"">Message
Count</font></b></td>" _
& "<td bordercolor=""#FFFFFF"" align=""center"" bgcolor=""#000080""><b><font
color=""#FFFFFF"">Queue Size</font></b></td></tr>"
strWinMgmts = "winmgmts:{impersonationLevel=impersonate}!//"& _
Set objWMIExchange = GetObject(strWinMgmts)
If Err.Number <> 0 Then
WScript.Echo "ERROR: Unable to connect to the WMI namespace."
Set listExchange_PublicFolders = objWMIExchange.InstancesOf(cWMIInstance)
For Each objExchange_SMTPQueue in listExchange_PublicFolders
HtmlMsgbody = HtmlMsgbody & "<tr><td>" & objExchange_SMTPQueue.LinkName &
"</td><td>" & objExchange_SMTPQueue.MessageCount _
& "</td><td>" & objExchange_SMTPQueue.size & "</td></tr>"
WScript.echo objExchange_SMTPQueue.LinkName & " " &
objExchange_SMTPQueue.MessageCount & " " & objExchange_SMTPQueue.size
if objExchange_SMTPQueue.MessageCount >= MessageThreshold then
wql ="Select * From Exchange_QueuedSMTPMessage Where LinkId='" &
wql = wql & "' And LinkName='" & objExchange_SMTPQueue.Linkname & "' And
ProtocolName='SMTP' And "
wql = wql & "QueueId='" & objExchange_SMTPQueue.QueueID & "' And QueueName='" &
objExchange_SMTPQueue.Queuename &"' And"
wql = wql & " VirtualMachine='" & objExchange_SMTPQueue.VirtualMachine & "'"
wql = wql & " And VirtualServerName='" & objExchange_SMTPQueue.VirtualServerName
& "'"
quehtml = quehtml & getmess(wql)
end if
End If
HtmlMsgbody = HtmlMsgbody & "</table><BR><B>Message Queues</B><BR>" & quehtml
Set objEmail = CreateObject("CDO.Message")
objEmail.From = ""
objEmail.To = ""
objEmail.Subject = "Queue Threshold Exceeded"
objEmail.HTMLbody = HtmlMsgbody
= 2
= "Servername"
= 25
wscript.echo "message sent"
End sub

function getmess(wql)
quehtml = "<table border=""1"" width=""100%""><tr><td bgcolor=""#008000""
align=""center""><b><font color=""#FFFFFF"">Date Sent</font></b></td>" _
& "<td bgcolor=""#008000"" align=""center""><b><font color=""#FFFFFF"">Sent
& " <td bgcolor=""#008000"" align=""center""><b><font color=""#FFFFFF"">Recipients</font></b></td>"_
& " <td bgcolor=""#008000"" align=""center""><b><font color=""#FFFFFF"">Subject</font></b></td>"_
& " <td bgcolor=""#008000"" align=""center""><b><font color=""#FFFFFF"">Size</font></b></td></tr>"
Const cWMINameSpace = "root/MicrosoftExchangeV2"
strWinMgmts = "winmgmts:{impersonationLevel=impersonate}!//" & cComputerName &
"/" & cWMINameSpace
Set objWMIExchange = GetObject(strWinMgmts)
Set listExchange_MessageQueueEntries = objWMIExchange.ExecQuery(wql)
For each objExchange_MessageQueueEntries in listExchange_MessageQueueEntries
recieved =
4), Mid(objExchange_MessageQueueEntries.Received, 5, 2),
Mid(objExchange_MessageQueueEntries.Received, 7, 2)) & " " &
timeserial(Mid(objExchange_MessageQueueEntries.Received, 9,
2),Mid(objExchange_MessageQueueEntries.Received, 11,
2),Mid(objExchange_MessageQueueEntries.Received,13, 2))))
Wscript.echo recieved & " " & objExchange_MessageQueueEntries.Sender & " " &
objExchange_MessageQueueEntries.Subject _
& " " & objExchange_MessageQueueEntries.size & " " &
quehtml = quehtml & "<tr><td>" & recieved &"</td><td>" &
objExchange_MessageQueueEntries.Sender & "</td><td>" &
Recipients:","") & "</td><td>" _
& objExchange_MessageQueueEntries.Subject & "</td><td>" &
objExchange_MessageQueueEntries.size & "</td></tr>"
quehtml = quehtml & "</table>"
getmess = quehtml
end function


professional web design specialist said...

tricky and neat....i will however try this one.

Anonymous said...

Hello Glen,
Will this script work with Exchange 2000?


Glen said...

No not in it current state there are less WMI classes availible on a Exchange 2000 server. You would need to rewrite from scratch using the different classes and some things might not be possible

Anonymous said...

Thanks again for your reply.


Robert D said...

Nice spript Glen
I wonder is i possible to generate an eventin the eventlog if the MessageThreshold is over the limit ex. 5

Glen said...

To log an event is pretty easy just create a shell object. Eg this will log a critical event

set evtlog = createobject("Wscript.Shell")
evtlog.LogEvent EVENT_ERROR, "Mail Queue threshold Exceeded 5"

Adam said...

Hello Glen,
Your script is only monitor SMTP queue, do you know a way to monitor a MAPI queue that is used in Lotus Connector?

Glen said...

I don't have any servers that use these type of connectors so i cant speak from any experience. The MTS-In/Out queues are folders in a special mailbox that is created in the Exchange store. Im not sure if you can enumerate messages via WMI from this mailbox you should be able to work it out by maybe poking around with the WMI CIM studio which is a part of the WMI SDK. You might also need to look at doing a packet capture with something like etheral of what Exchange System Manager is doing when you enumerate the messages in thoses queue's you should then be able to extract the query from the capture and reuse it in your code. The only other way i could think you could monitor this is you use one of the Exchange mailbox access API's Mapi,webdav,exoldb to view the messages that are in those folders.

brij said...

can you provide a managed version of same in C#...


RAAJ said...

i am getting error with line 71 character 1 "For each objExchange_MessageQueueEntries in listExchange_MessageQueueEntries"

Please help