ServerXmlHttpRequest hanging sometimes when doing

Question

I have a job that periodically does some work involving ServerXmlHttpRquest to perform an HTTP POST. The job runs every 60 seconds.

And normally it runs without issue. But there's about a 1 in 50,000 chance (every two or three months) that it will hang:

IXMLHttpRequest http = new ServerXmlHttpRequest();

http.open("POST", deleteUrl, false, "", "");
http.send(stuffToDelete); <---hang

When it hangs, not even the Task Scheduler (with the option enabled to kill the job if it takes longer than 3 minutes to run) can end the task. I have to connect to the remote customer's network, get on the server, and use Task Manager to kill the process.

And then its good for another month or three.

Eventually i started using Task Manager to create a process dump,

so i could analyze where the hang is. After five crash dumps (over the last 11 months or so) i get a consistent picture:

ntdll.dll!_NtWaitForMultipleObjects@20()  
KERNELBASE.dll!_WaitForMultipleObjectsEx@20()
user32.dll!MsgWaitForMultipleObjectsEx()
user32.dll!_MsgWaitForMultipleObjects@20()
urlmon.dll!CTransaction::CompleteOperation(int fNested) Line 2496
urlmon.dll!CTransaction::StartEx(IUri * pIUri, IInternetProtocolSink * pOInetProtSink, IInternetBindInfo * pOInetBindInfo, unsigned long grfOptions, unsigned long dwReserved) Line 4453    C++
urlmon.dll!CTransaction::Start(const wchar_t * pwzURL, IInternetProtocolSink * pOInetProtSink, IInternetBindInfo * pOInetBindInfo, unsigned long grfOptions, unsigned long dwReserved) Line 4515    C++
msxml3.dll!URLMONRequest::send()
msxml3.dll!XMLHttp::send()
Contoso.exe!FrobImporter.TFrobImporter.DeleteFrobs Line 971
Contoso.exe!FrobImporter.TFrobImporter.ImportCore Line 1583
Contoso.exe!FrobImporter.TFrobImporter.RunImport Line 1070
Contoso.exe!CommandLineProcessor.TCommandLineProcessor.HandleFrobImport Line 433
Contoso.exe!CommandLineProcessor.TCommandLineProcessor.CoreExecute Line 71
Contoso.exe!CommandLineProcessor.TCommandLineProcessor.Execute Line 84
Contoso.exe!Contoso.Contoso Line 167
kernel32.dll!@BaseThreadInitThunk@12()
ntdll.dll!__RtlUserThreadStart()
ntdll.dll!__RtlUserThreadStart@8()

So i do a ServerXmlHttpRequest.send, and it never returns. It will sit there for days (causing the system to miss financial transactions, until come Sunday night i get a call that it's broken).

It is of no help unless someone knows how to debug code, but the registers in the stalled thread at the time of the dump are:

EAX 00000030
EBX 00000000
ECX 00000000
EDX 00000000
ESI 002CAC08
EDI 00000001
EIP 732A08A7
ESP 0018F684
EBP 0018F6C8
EFL 00000000 

• Windows Server 2012 R2
• Microsoft IIS/8.5

Default timeouts of ServerXmlHttpRequest

You can use serverXmlHttpRequest.setTimeouts(...) to configure the four classes of timeouts:

• resolveTimeout: The value is applied to mapping host names (such as "www.microsoft.com") to IP addresses; the default value is infinite, meaning no timeout.
• connectTimeout: A long integer. The value is applied to establishing a communication socket with the target server, with a default timeout value of 60 seconds.
• sendTimeout: The value applies to sending an individual packet of request data (if any) on the communication socket to the target server. A large request sent to a server will normally be broken up into multiple packets; the send timeout applies to sending each packet individually. The default value is 30 seconds.
• receiveTimeout: The value applies to receiving a packet of response data from the target server. Large responses will be broken up into multiple packets; the receive timeout applies to fetching each packet of data off the socket. The default value is 30 seconds.

The KB305053 (a server that decides to keep the connection open will cause serverXmlHttpRequest to wait for the connection to close) seems like it plausibly could be the issue. But the 30 second default timeout would have taken care of that.

Possible workaround - Add myself to a Job

The Windows Task Scheduler is unable to terminate the task; even though the option is enabled to do do.

I will look into using the Windows Job API to add my self process to a job, and use SetInformationJobObject to set a time limit on my process:

• CreateJobObject
• AssignProcessToJobObject
• SetInformationJobObject

to limit my process to three minutes of execution time:

PerProcessUserTimeLimit
If LimitFlags specifies JOB_OBJECT_LIMIT_PROCESS_TIME, this member is the per-process user-mode execution time limit, in 100-nanosecond ticks. Otherwise, this member is ignored.

The system periodically checks to determine whether each process associated with the job has accumulated more user-mode time than the set limit. If it has, the process is terminated.

If the job is nested, the effective limit is the most restrictive limit in the job chain.

Although since Task Scheduler uses Job objects to also limit a task's time, i'm not hopeful that the Job Object can limit a job either.

Edit: Job objects cannot limit a process by process time - only user time. And with a process idle waiting for an object, it will not accumulate any user time - certainly not three minutes worth.

Bonus Reading

• How can a ServerXMLHTTP GET request hang? (GET, not POST)
• KB305053: ServerXMLHTTP Stops Responding When You Send a POST Request (which says the timeout should expire; where mine does not)
• MS Forums: oHttp.Send - Hangs (HEAD, not POST)
• MS Forums: ASP to test SOAP WebService using MSXML2.ServerXMLHTTP Send hangs
• CC to MS Support Forums

Answer 1

Consider switching to a newer, supported API.

• msxml6.dll using MSXML2.ServerXMLHTTP.6.0
• winhttpcom.dll using WinHttp.WinHttpRequest.5.1.

The msxml3.dll library is no longer supported and is only kept around for compatibility reasons. Plus, there were a number of security and stability improvements included with msxml4.dll (and newer) that you are missing out on.