From b656e05aaf71208a7c146839b6432fe2aaaea5a6 Mon Sep 17 00:00:00 2001
From: Chris Lu <chris.lu@gmail.com>
Date: Sun, 29 Mar 2020 00:55:40 -0700
Subject: [PATCH] HDFS: support chunk cache

---
 .../java/seaweedfs/client/ChunkCache.java     | 27 ++++++++++
 .../java/seaweedfs/client/SeaweedRead.java    | 49 ++++++-------------
 .../java/seaweedfs/client/SeaweedWrite.java   |  3 +-
 3 files changed, 43 insertions(+), 36 deletions(-)
 create mode 100644 other/java/client/src/main/java/seaweedfs/client/ChunkCache.java

diff --git a/other/java/client/src/main/java/seaweedfs/client/ChunkCache.java b/other/java/client/src/main/java/seaweedfs/client/ChunkCache.java
new file mode 100644
index 000000000..e249d4524
--- /dev/null
+++ b/other/java/client/src/main/java/seaweedfs/client/ChunkCache.java
@@ -0,0 +1,27 @@
+package seaweedfs.client;
+
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
+
+import java.util.concurrent.TimeUnit;
+
+public class ChunkCache {
+
+    private final Cache<String, byte[]> cache;
+
+    public ChunkCache(int maxEntries) {
+        this.cache = CacheBuilder.newBuilder()
+                .maximumSize(maxEntries)
+                .expireAfterAccess(1, TimeUnit.HOURS)
+                .build();
+    }
+
+    public byte[] getChunk(String fileId) {
+        return this.cache.getIfPresent(fileId);
+    }
+
+    public void setChunk(String fileId, byte[] data) {
+        this.cache.put(fileId, data);
+    }
+
+}
diff --git a/other/java/client/src/main/java/seaweedfs/client/SeaweedRead.java b/other/java/client/src/main/java/seaweedfs/client/SeaweedRead.java
index 8e850f87e..ad92ba006 100644
--- a/other/java/client/src/main/java/seaweedfs/client/SeaweedRead.java
+++ b/other/java/client/src/main/java/seaweedfs/client/SeaweedRead.java
@@ -10,14 +10,14 @@ import org.apache.http.util.EntityUtils;
 
 import java.io.Closeable;
 import java.io.IOException;
-import java.io.OutputStream;
-import java.nio.ByteBuffer;
 import java.util.*;
 
 public class SeaweedRead {
 
     // private static final Logger LOG = LoggerFactory.getLogger(SeaweedRead.class);
 
+    static ChunkCache chunkCache = new ChunkCache(1000);
+
     // returns bytesRead
     public static long read(FilerGrpcClient filerGrpcClient, List<VisibleInterval> visibleIntervals,
                             final long position, final byte[] buffer, final int bufferOffset,
@@ -57,42 +57,23 @@ public class SeaweedRead {
     }
 
     private static int readChunkView(long position, byte[] buffer, int startOffset, ChunkView chunkView, FilerProto.Locations locations) throws IOException {
-        if (chunkView.cipherKey != null) {
-            return readEncryptedChunkView(position, buffer, startOffset, chunkView, locations);
+
+        byte[] chunkData = chunkCache.getChunk(chunkView.fileId);
+
+        if (chunkData == null) {
+            chunkData = doFetchFullChunkData(chunkView, locations);
         }
 
-        // TODO: read the chunk and returns the chunk view data here
+        int len = (int) (chunkView.logicOffset - position + chunkView.size);
+        System.arraycopy(chunkData, (int) chunkView.offset, buffer, startOffset, len);
 
-        HttpClient client = new DefaultHttpClient();
-        HttpGet request = new HttpGet(
-                String.format("http://%s/%s", locations.getLocations(0).getUrl(), chunkView.fileId));
+        chunkCache.setChunk(chunkView.fileId, chunkData);
 
-        if (!chunkView.isFullChunk) {
-            request.setHeader(HttpHeaders.ACCEPT_ENCODING, "");
-            request.setHeader(HttpHeaders.RANGE,
-                    String.format("bytes=%d-%d", chunkView.offset, chunkView.offset + chunkView.size - 1));
-        }
-
-        try {
-            HttpResponse response = client.execute(request);
-            HttpEntity entity = response.getEntity();
-
-            int len = (int) (chunkView.logicOffset - position + chunkView.size);
-            OutputStream outputStream = new ByteBufferOutputStream(ByteBuffer.wrap(buffer, startOffset, len));
-            entity.writeTo(outputStream);
-            // LOG.debug("* read chunkView:{} startOffset:{} length:{}", chunkView, startOffset, len);
-
-            return len;
-
-        } finally {
-            if (client instanceof Closeable) {
-                Closeable t = (Closeable) client;
-                t.close();
-            }
-        }
+        return len;
     }
 
-    private static int readEncryptedChunkView(long position, byte[] buffer, int startOffset, ChunkView chunkView, FilerProto.Locations locations) throws IOException {
+    private static byte[] doFetchFullChunkData(ChunkView chunkView, FilerProto.Locations locations) throws IOException {
+
         HttpClient client = new DefaultHttpClient();
         HttpGet request = new HttpGet(
                 String.format("http://%s/%s", locations.getLocations(0).getUrl(), chunkView.fileId));
@@ -124,9 +105,7 @@ public class SeaweedRead {
             throw new IOException("fail to decrypt", e);
         }
 
-        int len = (int) (chunkView.logicOffset - position + chunkView.size);
-        System.arraycopy(data, (int) chunkView.offset, buffer, startOffset, len);
-        return len;
+        return data;
 
     }
 
diff --git a/other/java/client/src/main/java/seaweedfs/client/SeaweedWrite.java b/other/java/client/src/main/java/seaweedfs/client/SeaweedWrite.java
index 5bf24ef68..178234d5a 100644
--- a/other/java/client/src/main/java/seaweedfs/client/SeaweedWrite.java
+++ b/other/java/client/src/main/java/seaweedfs/client/SeaweedWrite.java
@@ -45,7 +45,8 @@ public class SeaweedWrite {
 
         String etag = multipartUpload(targetUrl, auth, bytes, bytesOffset, bytesLength, cipherKey);
 
-        // TODO: cache fileId ~ bytes here
+        // cache fileId ~ bytes
+        SeaweedRead.chunkCache.setChunk(fileId, bytes);
 
         entry.addChunks(FilerProto.FileChunk.newBuilder()
                 .setFileId(fileId)