Troubleshooting
So let's talk about troubleshooting a little bit more. I can tell you, I did need to do some troubleshooting to get that million ratings job running successfully on my Spark cluster. We'll start by talking about logs. Where are the logs? We saw some stuff scroll by from the driver script, and in practice, if you're running on EMR, that's pretty much all you'll have to go on. Now, as I showed you, if you're in standalone mode and you have access directly, on the network to your master node, all the log information is displayed in this beautiful graphical form in the web UI. However, when you're running on top of YARN, those logs end up getting distributed and you need to collect them after the fact using this command: yarn ...
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