HDFS-14111. hdfsOpenFile on HDFS causes unnecessary IO from file offset 0. Contributed by Sahil Takiar.
Signed-off-by: Wei-Chiu Chuang <weichiu@apache.org>
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@ -740,6 +740,7 @@ public boolean hasCapability(String capability) {
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case StreamCapabilities.READAHEAD:
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case StreamCapabilities.DROPBEHIND:
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case StreamCapabilities.UNBUFFER:
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case StreamCapabilities.READBYTEBUFFER:
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return true;
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default:
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return false;
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@ -59,6 +59,12 @@ public interface StreamCapabilities {
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*/
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String UNBUFFER = "in:unbuffer";
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/**
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* Stream read(ByteBuffer) capability implemented by
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* {@link ByteBufferReadable#read(java.nio.ByteBuffer)}.
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*/
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String READBYTEBUFFER = "in:readbytebuffer";
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/**
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* Capabilities that a stream can support and be queried for.
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*/
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@ -1779,6 +1779,7 @@ public boolean hasCapability(String capability) {
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case StreamCapabilities.READAHEAD:
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case StreamCapabilities.DROPBEHIND:
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case StreamCapabilities.UNBUFFER:
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case StreamCapabilities.READBYTEBUFFER:
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return true;
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default:
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return false;
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@ -1013,7 +1013,7 @@ static hdfsFile hdfsOpenFileImpl(hdfsFS fs, const char *path, int flags,
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return f{is|os};
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*/
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int accmode = flags & O_ACCMODE;
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jstring jStrBufferSize = NULL, jStrReplication = NULL;
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jstring jStrBufferSize = NULL, jStrReplication = NULL, jCapabilityString = NULL;
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jobject jConfiguration = NULL, jPath = NULL, jFile = NULL;
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jobject jFS = (jobject)fs;
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jthrowable jthr;
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@ -1171,16 +1171,22 @@ static hdfsFile hdfsOpenFileImpl(hdfsFS fs, const char *path, int flags,
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file->flags = 0;
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if ((flags & O_WRONLY) == 0) {
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// Try a test read to see if we can do direct reads
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char buf;
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if (readDirect(fs, file, &buf, 0) == 0) {
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// Success - 0-byte read should return 0
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// Check the StreamCapabilities of jFile to see if we can do direct reads
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jthr = newJavaStr(env, "in:readbytebuffer", &jCapabilityString);
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if (jthr) {
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ret = printExceptionAndFree(env, jthr, PRINT_EXC_ALL,
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"hdfsOpenFile(%s): newJavaStr", path);
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goto done;
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}
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jthr = invokeMethod(env, &jVal, INSTANCE, jFile, HADOOP_ISTRM,
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"hasCapability", "(Ljava/lang/String;)Z", jCapabilityString);
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if (jthr) {
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ret = printExceptionAndFree(env, jthr, PRINT_EXC_ALL,
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"hdfsOpenFile(%s): FSDataInputStream#hasCapability", path);
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goto done;
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}
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if (jVal.z) {
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file->flags |= HDFS_FILE_SUPPORTS_DIRECT_READ;
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} else if (errno != ENOTSUP) {
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// Unexpected error. Clear it, don't set the direct flag.
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fprintf(stderr,
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"hdfsOpenFile(%s): WARN: Unexpected error %d when testing "
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"for direct read compatibility\n", path, errno);
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}
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}
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ret = 0;
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@ -1191,6 +1197,7 @@ done:
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destroyLocalReference(env, jConfiguration);
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destroyLocalReference(env, jPath);
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destroyLocalReference(env, jFile);
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destroyLocalReference(env, jCapabilityString);
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if (ret) {
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if (file) {
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if (file->file) {
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@ -503,7 +503,10 @@ TEST_F(HdfsExtTest, TestReadStats) {
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hdfsFileFreeReadStatistics(stats);
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EXPECT_EQ(0, hdfsCloseFile(fs, file));
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EXPECT_EQ(0, errno);
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// Since libhdfs is not guaranteed to set errno to 0 on successful
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// operations, we disable this check for now, see HDFS-14325 for a
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// long term solution to this problem
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// EXPECT_EQ(0, errno);
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}
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//Testing working directory
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