szetszwo commented on a change in pull request #298:
URL: https://github.com/apache/incubator-ratis/pull/298#discussion_r533447995
##########
File path:
ratis-examples/src/main/java/org/apache/ratis/examples/filestore/FileStoreStateMachine.java
##########
@@ -153,6 +163,55 @@ public TransactionContext
startTransaction(RaftClientRequest request) throws IOE
return reply.thenApply(ExamplesProtos.ReadReplyProto::getData);
}
+ class LocalStream implements DataStream {
+ private final DataChannel dataChannel;
+
+ LocalStream(DataChannel dataChannel) {
+ this.dataChannel = dataChannel;
+ }
+
+ @Override
+ public DataChannel getDataChannel() {
+ return dataChannel;
+ }
+
+ @Override
+ public CompletableFuture<?> cleanUp() {
+ return CompletableFuture.supplyAsync(() -> {
+ try {
+ dataChannel.close();
+ return true;
+ } catch (IOException e) {
+ return FileStoreCommon.completeExceptionally("Failed to close data
channel", e);
+ }
+ });
+ }
+ }
+
+ @Override
+ public CompletableFuture<DataStream> stream(RaftClientRequest request) {
+ final ByteString reqByteString = request.getMessage().getContent();
+ final StreamWriteRequestHeaderProto proto;
+ try {
+ proto = StreamWriteRequestHeaderProto.parseFrom(reqByteString);
+ } catch (InvalidProtocolBufferException e) {
+ return FileStoreCommon.completeExceptionally(
+ "Failed to parse stream header", e);
+ }
+ return files.createDataChannel(proto.getPath().toStringUtf8())
+ .thenApply(LocalStream::new);
+ }
+
+ @Override
+ public CompletableFuture<?> link(DataStream stream, LogEntryProto entry) {
+ LOG.info("link {}", stream);
+ if (stream == null) {
+ return JavaUtils.completeExceptionally(new IllegalStateException("Null
stream: entry=" + entry));
+ }
+ dataStreamToLogEntryMap.put(stream, entry);
Review comment:
link(..) is to tell the state machine which stream to use in
applyTransaction(..). In FileStore, the request header has the path so that we
may use it to look up the file. The path is the key to get the corresponding
data. link(..) in FileStore may not be very useful since we have the path in
the header.
Suppose we don't have the path in the header. Then link(..) becomes very
important since it can map LogEntry to data. Otherwise, we don't know which
file should be used in applyTransaction(..).
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