Hi, Thanks for reporting the error and sharing the results of your detailed analysis!
I don't have enough insight into the Kafka consumer, but noticed that you said you've been running your application for over a year and only noticed the faulty behavior recently. Flink 1.4.0 was released in mid December last year. Did you observe the bug before you migrated to 1.4.0? I'll add Gordon to the thread who is the expert about Flink's Kafka consumer. Best, Fabian 2018-02-27 0:02 GMT+01:00 Philip Doctor <philip.doc...@physiq.com>: > Hello, > > I’m using Flink 1.4.0 with FlinkKafkaConsumer010 and have been for almost > a year. Recently, I started getting messages of the wrong length in Flink > causing my deserializer to fail. Let me share what I’ve learned: > > > > 1. All of my messages are 520 bytes exactly when my producer places > them in kafka > 2. About 1% of these messages have this deserialization issue in flink > 3. When it happens, I read 10104 bytes in flink > 4. When I write the bytes my producer creates to a file on disk > (rather than kafka) my code reads 520 bytes and consumes them without issue > off of disk > 5. When I use kafka tool (http://www.kafkatool.com/index.html) to > dump the contents of my topic to disk, and read each message one at a time > off of disk, my code reads 520 bytes per message and consumes them without > issue > 6. When I write a simple Kafka consumer (not using flink) I read one > message at a time it’s 520 bytes and my code runs without issue > > > > #5 and #6 are what lead me to believe that this issue is squarely a > problem with Flink. > > > > However, it gets more complicated, I took the messages I wrote out with > both my simple consumer and the kafka tool, and I load them into a local > kafka server, then attach a local flink cluster and I cannot reproduce the > error, yet I can reproduce it 100% of the time in something closer to my > production environment. > > > > I realize this latter sounds suspicious, but I have not found anything in > the Kafka docs indicating that I might have a configuration issue here, yet > my simple local setup that would allow me to iterate on this and debug has > failed me. > > > > I’m really quite at a loss here, I believe there’s a Flink Kafka consumer > bug, it happens exceedingly rarely as I went a year without seeing it. I > can reproduce it in an expensive environment but not in a “cheap” > environment. > > > > Thank you for your time, I can provide my sample data set in case that > helps. I dumped it on my google drive https://drive.google.com/file/d/ > 1h8jpAFdkSolMrT8n47JJdS6x21nd_b7n/view?usp=sharing that’s the full data > set, about 1% of it ends up failing, it’s really hard to figure out which > message since I can’t read any of the message that I receive and I get data > out of order. > > > > >
