This post is for those using ServiceBus who would like to see the contents of a BrokeredMessage from a live debug session or dump file.
Open the dump file in windbg and load SOS. Then execute the following command:
!dumpheap -type BrokeredMessage -stat
What you’re looking for is this:
MT Count TotalSize Class Name
000007fe98f5c6a0 150 45600 Microsoft.ServiceBus.Messaging.BrokeredMessage
That gives you the MT for BrokeredMessage. If you’ve enabled .prefer_dml 1 then you can
click on the MT and get a list of all the objects in memory. If you’re in CDB the command
is !DumpHeap -mt 000007fe98f5c6a0. If you’re in WinDBG but don’t have DML on, you
should turn it on. Your life will get much easier.
Address MT Size
00000003807279f0 000007fe98f5c6a0 304
0000000380730470 000007fe98f5c6a0 304
0000000380738ef0 000007fe98f5c6a0 304
0000000380741970 000007fe98f5c6a0 304
Now click on one of the addresses or run !do 0000000380741970 (or whatever equivalent address on your system):
Name: Microsoft.ServiceBus.Messaging.BrokeredMessage
MethodTable: 000007fe98f5c6a0
EEClass: 000007fe98f6d2f8
Size: 304(0x130) bytes
File: C:\Program Files\Workflow Manager\1.0\Workflow\Artifacts\Microsoft.ServiceBus.dll
Fields:
MT Field Offset Type VT Attr Value Name
000007fef745dea0 4001922 d8 System.Int32 1 instance 512 headerStreamInitialSize
000007fef745dea0 400192a dc System.Int32 1 instance 3 version
000007fef745f650 400192b 8 System.IO.Stream 0 instance 0000000380727818 bodyStream
000007fef745b0f0 400192c 10 System.String 0 instance 0000000000000000 correlationId
000007fef745b0f0 400192d 18 System.String 0 instance 000000038071f1b0 sessionId
What we’re interested in is the bodyStream. Find a BrokeredMessage where the bodyStream is not null and click on it’s value:
Name: Microsoft.ServiceBus.Messaging.BufferedInputStream
MethodTable: 000007fe9907d010
EEClass: 000007fe9906ed00
Size: 64(0x40) bytes
File: C:\Program Files\Workflow Manager\1.0\Workflow\Artifacts\Microsoft.ServiceBus.dll
Fields:
MT Field Offset Type VT Attr Value Name
000007fef745b6d0 4000198 8 System.Object 0 instance 0000000000000000 __identity
000007fef74ad740 4001fec 10 ...eam+ReadWriteTask 0 instance 0000000000000000 _activeReadWriteTask
000007fef7465fc0 4001fed 18 ...ing.SemaphoreSlim 0 instance 0000000000000000 _asyncActiveSemaphore
000007fe9907d2e0 4001794 20 ...rManagerByteArray 0 instance 0000000380727858 data
000007fef7458340 4001795 28 ...m.IO.MemoryStream 0 instance 0000000380727880 innerStream
000007fef745c9c8 4001796 30 System.Boolean 1 instance 0 disposed
Note that I remove the static fields since they’re not useful for this post.
The field that I’m after is the innerStream. This field is the actual MemoryStream that contains the message. This looks like:
Name: System.IO.MemoryStream
MethodTable: 000007fef7458340
EEClass: 000007fef6e70548
Size: 80(0x50) bytes
File: C:\Windows\Microsoft.Net\assembly\GAC_64\mscorlib\v4.0_4.0.0.0__b77a5c561934e089\mscorlib.dll
Fields:
MT Field Offset Type VT Attr Value Name
000007fef745b6d0 4000198 8 System.Object 0 instance 0000000000000000 __identity
000007fef74ad740 4001fec 10 ...eam+ReadWriteTask 0 instance 0000000000000000 _activeReadWriteTask
000007fef7465fc0 4001fed 18 ...ing.SemaphoreSlim 0 instance 0000000000000000 _asyncActiveSemaphore
000007fef745f268 40020dd 20 System.Byte[] 0 instance 0000000380723800 _buffer
000007fef745dea0 40020de 30 System.Int32 1 instance 0 _origin
000007fef745dea0 40020df 34 System.Int32 1 instance 0 _position
000007fef745dea0 40020e0 38 System.Int32 1 instance 9359 _length
000007fef745dea0 40020e1 3c System.Int32 1 instance 9359 _capacity
000007fef745c9c8 40020e2 40 System.Boolean 1 instance 0 _expandable
000007fef745c9c8 40020e3 41 System.Boolean 1 instance 1 _writable
000007fef745c9c8 40020e4 42 System.Boolean 1 instance 0 _exposable
000007fef745c9c8 40020e5 43 System.Boolean 1 instance 1 _isOpen
000007fef74865e8 40020e6 28 ...Int32, mscorlib]] 0 instance 0000000000000000 _lastReadTask
We want two bits of data from the MemoryStream: buffer and length. The buffer has the byte[] containing the message. The best way to see the data is to write it out to a file. In order to do this use the following command:
.writemem memorystream.xml 0x0000000380723800+10 L?0n9359
Note that I add 16 bytes to get to the content of the byte[] (that’s the +10). The length is written in decimal in the output above so I use 0n to specify decimal.
The XML file will have the contents of the BrokeredMessage object.
I don’t have a good way to dump all the BrokeredMessages. Instead what I did was get the MT for MemoryStream and run the following commands:
.foreach (myobj {!dumpheap -mt 000007fef7458340 -short}) { .printf "%p\n", poi(${myobj}+20) }
.foreach (myobj {!dumpheap -mt 000007fef7458340 -short}) { .printf "%i\n", poi(${myobj}+38) }
Note that +20 is the offset for the buffer and +38 is the offset for the length. These statements will dump out the memory addresses and lengths line by line. I then take the two as input to a linq query that dumps out the .writemem commands and paste that back into windbg. Once I figure out how to do a poi inside a poi, I can come up with one command to dump all BrokeredMessage contents to files.