Timeout to read from Alluxio

Question

I encountered this error while performing a Presto query on Alluxio. What does this timeout mean, and how can I fix it?

com.facebook.presto.spi.PrestoException: Error opening Hive split alluxio://xxxxx:19998/s3/data/m-00020 (offset=134217728, length=67108864) using org.apache.hadoop.mapred.TextInputFormat: Timeout to read 39963328512 from [id: 0x23615709, L:/xxxxx:34740 - R:xxxxx/xxxxx:29999]

Answer 1

You will receive this error when the Alluxio worker takes too long (configurable through alluxio.user.network.netty.timeout) to provide data to the client.

One simple workaround is to increase timeout.

However, this is generally a symptom of the worker being overloaded in some way. Common things to check in your setup:

1. Alluxio worker load, possibly a problem if your compute is co-located and there is no resource management
2. Alluxio worker to under file system load/bandwidth, this is often a bottleneck for remote storages like object stores.

If these are bottlenecks, you can try reducing the concurrency or increasing the number of nodes in your cluster.