[Kernel] Handle KernelEngineException when reading the _last_checkpoint file
#3086
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vkorukanti
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UncheckedIOException when reading the _last_checkpoint fileKernelEngineException when reading the _last_checkpoint file
scottsand-db
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May 16, 2024
| * Throws when the {@link Engine} encountered an error while executing an operation. | ||
| */ | ||
| public class KernelEngineException extends RuntimeException { | ||
| private static final String msgT = "Encountered an error from the underlying engine " + |
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what does the capital T mean in msgT?
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It was a shortened messageTemplate. Renaming it to msgTemplate
kernel/kernel-api/src/main/java/io/delta/kernel/internal/checkpoints/Checkpointer.java
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kernel/kernel-api/src/main/java/io/delta/kernel/internal/checkpoints/Checkpointer.java
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| * any) wrapped in this exception as cause. E.g. | ||
| * {@link IOException} thrown while trying to read from a Delta | ||
| * log file. It will be wrapped in this exception as cause. | ||
| * @throws KernelException When encountered an operation or state that is invalid or |
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for KernelEngineException you state i'ts for exceptions that occur in the Engine.
Am I correct in assuming that KernelException is for exceptions that occur in the Kernel, not in the engine? Can you add that very short clarification here?
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That is correct. Clarified.
kernel/kernel-defaults/src/test/scala/io/delta/kernel/defaults/LogReplayMetricsSuite.scala
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vkorukanti
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May 16, 2024
…checkpoint` file (#3086) There is an issue with the `CloseableIterator` interface that Kernel is using. Currently, it extends Java's `iterator`, which doesn't throw any exceptions. We use `CloseableIterator` when returning data read from a file or any incremental data access. Any `IOException` in `hasNext` or `next` is wrapped in a `UncheckedIOException` or `RuntimeException`. Users of the `CloseableIterator` need to catch for `UncheckedIOException` or `RuntimeException` explicitly and look at the cause if they are interested in the `IOException`. This is not consistent and causes problems for the code that want to handle exceptions like `FileNotFoundException` (subclass of `IOException`) and take further actions. * Change the `CloseableIterator.{next, hasNext}` contract to expect `KernelEngineException` for any exceptions that occur while executing in the `Engine`. * Update the `DefaultParquetHandler` and `DefaultJsonHandler` to throw `KernelEngineException` instead of `UncheckedIOException` or `RuntimeException`. * In the checkpoint metadata loading method, catch `KernelEngineException` and see if the cause is `FileNotFoundException.` If yes, don't retry loading.
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There is an issue with the
CloseableIteratorinterface that Kernel is using. Currently, it extends Java'siterator, which doesn't throw any exceptions. We useCloseableIteratorwhen returning data read from a file or any incremental data access. Any IOException inhasNextornextis wrapped in aUncheckedIOExceptionorRuntimeException. Users of theCloseableIteratorneed to catch forUncheckedIOExceptionorRuntimeExceptionexplicitly and look at the cause if they are interested in theIOException. This is not consistent and causes problems for the code that want to handle exceptions likeFileNotFoundException(subclass ofIOException) and take further actions.CloseableIterator.{next, hasNext}contract to expectKernelEngineExceptionfor any exceptions that occur while executing in theEngine.DefaultParquetHandlerandDefaultJsonHandlerto throwKernelEngineExceptioninstead ofUncheckedIOExceptionorRuntimeException.KernelEngineExceptionand see if the cause isFileNotFoundException.If yes, don't retry loading.