Test: Support multiple threads writing to subprocess_results.log

[heifner]

The read only tests use multiple threads to push transactions. These end up trying to write to the subprocess_results.log at the same time. Protect the write with a lock.

[greg7mdp]

Wouldn't the following work and avoid re-opening the file every time checkOutputFileWrite is called?

        with Utils._check_output_lock:
            if not hasattr(Utils, "checkOutputFile"):
                Utils.checkOutputFilename=f"{Utils.DataPath}/subprocess_results.log"
                if Utils.Debug: Utils.Print("opening %s in dir: %s" % (Utils.checkOutputFilename, os.getcwd()))
                Utils.checkOutputFile=open(Utils.checkOutputFilename,"w")

        with Utils._check_output_lock:
            Utils.checkOutputFile.write(Utils.FileDivider + "\n")
            Utils.checkOutputFile.write("start={%s}\n" % (time))
            Utils.checkOutputFile.write("cmd={%s}\n" % (" ".join(cmd)))
            Utils.checkOutputFile.write("cout={%s}\n" % (output))
            Utils.checkOutputFile.write("cerr={%s}\n" % (error))
            Utils.checkOutputFile.write("stop={%s}\n" % (stop))

[heifner]

Wouldn't the following work and avoid re-opening the file every time checkOutputFileWrite is called?

I kind of like opening to append each time. The close makes sure it is flushed. Not like performance matters here.

[greg7mdp]

Sound fine. Still I think we should take the lock for the open as well to avoid contention when writing into Utils.checkOutputFilename.