Hi,
I've created an action under Utility - Environment which runs a process, waits for it to finish, and reads its standard output. This custom action works fine most of the time, except that 20-30% of the time the stdout comes out empty. I know that the process itself always outputs to stdout, it just seems that sometimes BP is unable to read it properly.
My custom action is a combination of 2 existing actions in Utility - Environment: "Start Process Read StdErr and StdOut" and "Run Process Until Ended". I had to create my own custom action because (1) "Start Process Read StdErr and StdOut" doesn't have a 'Working Folder' or a 'Timeout' parameter and (2) it is not clear to me if this action actually waits for the process to end (I may be wrong about this last point). On the other hand, obviously Run Process Until Ended explicitly appears to wait for the process to end, but it does not read stdout or stderr. Therefore, I was able to combine both actions into one, which (usually) does both things I need, that is, is waits for the process to end or a timeout AND also reads the stdout. This is the code for the action I created:
timedOut = False
Dim startTime as Date = Date.Now
Dim processName As String = appn
Dim proc As New Process() With {
.StartInfo = New ProcessStartInfo() With {
.FileName = processName,
.Arguments = args,
.WorkingDirectory = dir,
.UseShellExecute = False,
.CreateNoWindow = False,
.RedirectStandardError = True,
.RedirectStandardOutput = True
}
}
Using proc
proc.Start()
Dim standardOutput = proc.StandardOutput.ReadToEndAsync()
Dim standardError = proc.StandardError.ReadToEndAsync()
timedOut = Not proc.WaitForExit(CInt(timeout.TotalMilliseconds))
If standardOutput.isCompleted Then Standard_Output = standardOutput.Result
If standardError.isCompleted Then Standard_Error = standardError.Result
End Using
As mentioned, this action typically works except for when stdout comes out empty, as evidenced by the logs. The timeout is set to a pretty long time and my action is not raising its built-in timeout exception, so that's probably not it. I'm tempted to think that BP is simply unreliably reading this action's output, but I don't know how to improve my code (the line If standardOutput.isCompleted Then Standard_Output = standardOutput.Resultis pretty clear).
Some forum posts talk about adding delays or retries, or checking your data items, but that doesn't seem to apply here. Others recommend having BP just read the log.txt that my process creates (which would add some complexity) or provide alternative code, but I don't really think it should be necessary. I mean, the above code is pretty straight-forward no?
Any ideas? Thanks
PS. For context, the process I'm running is a Python script, but I don't believe the specific type of process should matter too much for this question.
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Jaime Salazar
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