From ba3c730e35bcdb662396955c3cc6f7de628034c8 Mon Sep 17 00:00:00 2001 From: Andrew Or Date: Wed, 20 Aug 2014 17:07:39 -0700 Subject: [SPARK-3140] Clarify confusing PySpark exception message We read the py4j port from the stdout of the `bin/spark-submit` subprocess. If there is interference in stdout (e.g. a random echo in `spark-submit`), we throw an exception with a warning message. We do not, however, distinguish between this case from the case where no stdout is produced at all. I wasted a non-trivial amount of time being baffled by this exception in search of places where I print random whitespace (in vain, of course). A clearer exception message that distinguishes between these cases will prevent similar headaches that I have gone through. Author: Andrew Or Closes #2067 from andrewor14/python-exception and squashes the following commits: 742f823 [Andrew Or] Further clarify warning messages e96a7a0 [Andrew Or] Distinguish between unexpected output and no output at all --- python/pyspark/java_gateway.py | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/python/pyspark/java_gateway.py b/python/pyspark/java_gateway.py index c7f7c1fe59..6f4f62f23b 100644 --- a/python/pyspark/java_gateway.py +++ b/python/pyspark/java_gateway.py @@ -54,12 +54,19 @@ def launch_gateway(): gateway_port = proc.stdout.readline() gateway_port = int(gateway_port) except ValueError: + # Grab the remaining lines of stdout (stdout, _) = proc.communicate() exit_code = proc.poll() error_msg = "Launching GatewayServer failed" - error_msg += " with exit code %d! " % exit_code if exit_code else "! " - error_msg += "(Warning: unexpected output detected.)\n\n" - error_msg += gateway_port + stdout + error_msg += " with exit code %d!\n" % exit_code if exit_code else "!\n" + error_msg += "Warning: Expected GatewayServer to output a port, but found " + if gateway_port == "" and stdout == "": + error_msg += "no output.\n" + else: + error_msg += "the following:\n\n" + error_msg += "--------------------------------------------------------------\n" + error_msg += gateway_port + stdout + error_msg += "--------------------------------------------------------------\n" raise Exception(error_msg) # Create a thread to echo output from the GatewayServer, which is required -- cgit v1.2.3