amaliujia commented on code in PR #11412:
URL: https://github.com/apache/ozone/pull/11412#discussion_r4202884643
##########
hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/transport/server/ratis/ContainerStateMachine.java:
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@@ -889,6 +897,102 @@ public CompletableFuture<Message> query(Message request) {
}
}
+ /** Serves a Ratis read-only data stream. Only ReadBlock is supported, see
{@link #streamReadBlock}. */
+ @Override
+ public long transferTo(Message request, WritableByteChannel stream) throws
IOException {
+ try {
+ metrics.incNumQueryStateMachineOps();
+ final ContainerCommandRequestProto requestProto =
message2ContainerCommandRequestProto(request);
+ if (requestProto.getCmdType() != Type.ReadBlock) {
+ throw new IOException("Unsupported command for a read-only data
stream: " + requestProto.getCmdType());
+ }
+ return streamReadBlock(dispatcher, requestProto, stream);
+ } catch (IOException e) {
+ metrics.incNumQueryStateMachineFails();
+ throw e;
+ }
+ }
+
+ /**
+ * Reads a block and writes each ReadBlock response to the stream as one
reply:
+ * {@code [int: metadata length][metadata: the response without its
data][data]}.
+ * Then closes the stream, which sends the terminal reply.
+ * If the read fails, this method throws without closing the stream. Ratis
sends the failure as the terminal reply.
+ *
+ * @return the number of bytes written to the stream
+ */
+ static long streamReadBlock(ContainerDispatcher dispatcher,
ContainerCommandRequestProto request,
Review Comment:
Curious why we make this as static? Is it for easy testing?
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