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To make use of this APIs, we have introduced a shim layer as part of TEZ-2924. The basic shim interface defines the various APIs whose implementations are version-specific and the version-specific shim implementation provides the runtime implementation to match the version of Hadoop. The Hadoop shims are discovered via ServiceLoaders (no configuration knobs required). The Tez framework will cycle through all providers that it finds on its classpath, query each one to see if it supports the current version of Hadoop and pick the first Shim that does.
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