Tag: developer tips

Alluxio Developer Tip: Why am I seeing the error “User yarn is not configured for any impersonation. impersonationUser: foo?”

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Impersonation is simply the ability for one user to act on behalf of another user. For example, say user ‘yarn’ has the credentials to connect to a service, but user ‘foo’ does not. Therefore, user ‘foo’ would never be able to access the service. However, user ‘yarn’ can access the service and impersonate (act on behalf of) user ‘foo’, allowing access to user ‘foo’. Therefore, impersonation enables one user to access a service on behalf of another user.
The impersonation feature defines how users can act on behalf of other users. Therefore, it is important to know who the users are.

Top 10 Tips for Making the Spark + Alluxio Stack Blazing Fast

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The Apache Spark + Alluxio stack is getting quite popular particularly for the unification of data access across S3 and HDFS. In addition, compute and storage are increasingly being separated causing larger latencies for queries. Alluxio is leveraged as compute-side virtual storage to improve performance. But to get the best performance, like any technology stack, you need to follow the best practices. This article provides the top 10 tips for performance tuning for real-world workloads when running Spark on Alluxio with data locality giving the most bang for the buck.

Developer Tip: Why Did My Job Fail with Error Message “Class alluxio.hadoop.FileSystem not found”?

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From time to time, a question pops up on the user mailing list referencing job failures with the error message “java.lang.ClassNotFoundException: Class alluxio.hadoop.FileSystem not found”. This post explains the reason for the failure and the solution to the issue when it occurs.
This error indicates the Alluxio client is not available at runtime. This causes an exception when the job tries to access the Alluxio filesystem but fails to find the implementation of Alluxio client to connect to the service.