Cloud Data Access
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Classpath Related Errors

The Hadoop S3 filesystem clients need the Hadoop-specific filesystem clients and third party S3 client libraries to be compatible with the Hadoop code, and any dependent libraries to be compatible with Hadoop and the specific JVM.

The classpath must be set up for the process talking to S3. If this is code running in the Hadoop cluster, then the JARs must be on that classpath. This includes distcp.

ClassNotFoundException Errors

ClassNotFoundException: org.apache.hadoop.fs.s3a.S3AFileSystem
ClassNotFoundException: org.apache.hadoop.fs.s3native.NativeS3FileSystem
ClassNotFoundException: org.apache.hadoop.fs.s3.S3FileSystem

These are the Hadoop classes, found in the hadoop-aws JAR. An exception reporting that one of these classes is missing means that this JAR is not on the classpath.

Similarly, this error


or similar errors related to another com.amazonaws class mean that one or more of the aws-*-sdk JARs are missing.

To solve the issue, add the missing JARs to the classpath.

Missing Method in com.amazonaws Class

This can be triggered by incompatibilities between the AWS SDK on the classpath and the version with which Hadoop was compiled.

The AWS SDK JARs change their signature between releases often, so the only way to safely update the AWS SDK version is to recompile Hadoop against the later version.

There is nothing the Hadoop team can do here; if you get this problem, then you are on your own. The Hadoop developer team did look at using reflection to bind to the SDK, but there were too many changes between versions for this to work reliably. All it did was postpone version compatibility problems until the specific codepaths were executed at runtime. This was actually a backward step in terms of fast detection of compatibility problems.

Missing Method in a Jackson Class

This is usually caused by version mismatches between Jackson JARs on the classpath. All Jackson JARs on the classpath must be of the same version.