DirectStreamObserver does not respect channel isReady

Output channel stalled for 1023s, outbound thread CHAIN MapPartition (MapPartition at [1]PerformInference) -> FlatMap (FlatMap at ExtractOutput[0]) -> Map (Key Extractor) -> GroupCombine (GroupCombine at GroupCombine: PerformInferenceAndCombineResults_dep_049/GroupPredictionsByImage) -> Map (Key Extractor) (1/1). See: https://issues.apache.org/jira/browse/BEAM-4280 for the history for this issue.
Feb 18, 2022 11:51:05 AM org.apache.beam.vendor.grpc.v1p36p0.io.grpc.netty.NettyServerTransport notifyTerminated
INFO: Transport failed
org.apache.beam.vendor.grpc.v1p36p0.io.netty.util.internal.OutOfDirectMemoryError: failed to allocate 2097152 byte(s) of direct memory (used: 1205862679, max: 1207959552)
at org.apache.beam.vendor.grpc.v1p36p0.io.netty.util.internal.PlatformDependent.incrementMemoryCounter(PlatformDependent.java:754)
at org.apache.beam.vendor.grpc.v1p36p0.io.netty.util.internal.PlatformDependent.allocateDirectNoCleaner(PlatformDependent.java:709)
at org.apache.beam.vendor.grpc.v1p36p0.io.netty.buffer.PoolArena$DirectArena.allocateDirect(PoolArena.java:645)
at org.apache.beam.vendor.grpc.v1p36p0.io.netty.buffer.PoolArena$DirectArena.newChunk(PoolArena.java:621)
at org.apache.beam.vendor.grpc.v1p36p0.io.netty.buffer.PoolArena.allocateNormal(PoolArena.java:204)
at org.apache.beam.vendor.grpc.v1p36p0.io.netty.buffer.PoolArena.tcacheAllocateNormal(PoolArena.java:188)