[logs] Wrapped batch processor doesn't trigger correct log pool

[CodeBlanch]

I worked through an issue with a user who wrapped the BatchLogRecordExportProcessor in a custom processor:

    configure.AddProcessor(new FilteringProcessor<LogRecord>(new BatchLogRecordExportProcessor(exporter), ShouldUpload));

    internal sealed class FilteringProcessor<T> : BaseProcessor<T>
    {
        private readonly BaseProcessor<T> inner;
        private readonly Func<T, bool> filter;

        public FilteringProcessor(BaseProcessor<T> inner, Func<T, bool> filter)
        {
            this.inner = inner;
            this.filter = filter;
        }

        public override void OnEnd(T activity)
        {
            // Call the underlying processor
            // only if the Filter returns true.
            if (this.filter(activity))
            {
                this.inner.OnEnd(activity);
            }
        }
    }

In that case the SDK fails to switch into "shared pool" mode:

opentelemetry-dotnet/src/OpenTelemetry/Logs/LoggerProviderSdk.cs

Line 172 in eab0a7c

public bool ContainsBatchProcessor(BaseProcessor<LogRecord> processor)

Workaround

    configure.AddProcessor(new FilteringBatchLogRecordProcessor(ShouldUpload, exporter));

    internal sealed class FilteringBatchLogRecordProcessor : BatchLogRecordExportProcessor
    {
        private readonly Func<LogRecord, bool> filter;

        public FilteringBatchLogRecordProcessor(Func<LogRecord, bool> filter, BaseExporter<LogRecord> exporter)
            : base(exporter)
        {
            this.filter = filter;
        }

        public override void OnEnd(LogRecord logRecord)
        {
            // Call the underlying processor
            // only if the Filter returns true.
            if (this.filter(logRecord))
            {
                base.OnEnd(logRecord);
            }
        }
    }