java.lang.UnsupportedOperationException if trying to export logs from empty file

[phansier]

Describe the bug
LogRecordFromDiskExporter.exportStoredBatch() called periodically (once per 10 seconds) can read empty file and try to export it content.
But it throws java.lang.UnsupportedOperationException from inside of AttributesMapper with empty message.

Steps to reproduce
Same as SignalFromDiskExporter.kt#L69 in opentelemetry-android

What did you expect to see?
Probably it could ignore empty file and to not throw the exception.
Or add additional info into exception's message.

What did you see instead?
Stacktrace:

java.lang.UnsupportedOperationException
   	at io.opentelemetry.contrib.disk.buffering.internal.serialization.mapping.common.AttributesMapper.addValue(AttributesMapper.java:88)
   	at io.opentelemetry.contrib.disk.buffering.internal.serialization.mapping.common.AttributesMapper.protoToAttributes(AttributesMapper.java:35)
   	at io.opentelemetry.contrib.disk.buffering.internal.serialization.mapping.logs.LogRecordDataMapper.addExtrasToSdkItemBuilder(LogRecordDataMapper.java:94)
   	at io.opentelemetry.contrib.disk.buffering.internal.serialization.mapping.logs.LogRecordDataMapper.mapToSdk(LogRecordDataMapper.java:84)
   	at io.opentelemetry.contrib.disk.buffering.internal.serialization.mapping.logs.ProtoLogsDataMapper.protoToSignalItem(ProtoLogsDataMapper.java:38)
   	at io.opentelemetry.contrib.disk.buffering.internal.serialization.mapping.logs.ProtoLogsDataMapper.protoToSignalItem(ProtoLogsDataMapper.java:20)
   	at io.opentelemetry.contrib.disk.buffering.internal.serialization.mapping.common.BaseProtoSignalsDataMapper.fromProto(BaseProtoSignalsDataMapper.java:59)
   	at io.opentelemetry.contrib.disk.buffering.internal.serialization.deserializers.LogRecordDataDeserializer.deserialize(LogRecordDataDeserializer.java:28)
   	at io.opentelemetry.contrib.disk.buffering.internal.exporter.FromDiskExporterImpl.lambda$exportStoredBatch$0$io-opentelemetry-contrib-disk-buffering-internal-exporter-FromDiskExporterImpl(FromDiskExporterImpl.java:70)
   	at io.opentelemetry.contrib.disk.buffering.internal.exporter.FromDiskExporterImpl$$ExternalSyntheticLambda0.apply(D8$$SyntheticClass:0)
   	at io.opentelemetry.contrib.disk.buffering.internal.storage.files.ReadableFile.readAndProcess(ReadableFile.java:90)
   	at io.opentelemetry.contrib.disk.buffering.internal.storage.Storage.readAndProcess(Storage.java:120)
   	at io.opentelemetry.contrib.disk.buffering.internal.storage.Storage.readAndProcess(Storage.java:98)
   	at io.opentelemetry.contrib.disk.buffering.internal.exporter.FromDiskExporterImpl.exportStoredBatch(FromDiskExporterImpl.java:61)
   	at io.opentelemetry.contrib.disk.buffering.LogRecordFromDiskExporter.exportStoredBatch(LogRecordFromDiskExporter.java:37)

What version and what artifacts are you using?
Gradle, using opentelemetry-instrumentation-bom = "2.21.0"

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[LikeTheSalad]

Hi @phansier

Based on the issue description, this sounds like a duplicate of #2257 that was addressed on this PR a while ago. So it might be that you're using an old version of disk buffering from before the fix was introduced.

I noticed that you mentioned that the version you're using comes from this bom: opentelemetry-instrumentation-bom = "2.21.0", but I don't think said bom contains the disk buffering artifact afaik, so I can't tell from it what version of disk-buffering you are using. If you're getting it as a transitive dependency from OTel Android, then I'd suggest you bump OTel Android to its latest version; otherwise, I'd suggest you to declare disk-buffering as a dependency and use its latest version.

If you use disk-buffering directly and not via OTel Android, please bear in mind that the latest version contains API breaking changes that were introduced to stabilize the API (so there shouldn't be any more breaking changes in the future), in which case you should take a look at disk-buffering's README to learn how to use the new API.

[phansier]

Thank you. We are using 1.49.0-alpha of io.opentelemetry.contrib:opentelemetry-disk-buffering
Probably this is the reason.