Sahil Takiar created HDFS-14478:
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Summary: Add libhdfs APIs for readFully and openFile
Key: HDFS-14478
URL: https://issues.apache.org/jira/browse/HDFS-14478
Project: Hadoop HDFS
Issue Type: Improvement
Components: hdfs-client, libhdfs, native
Reporter: Sahil Takiar
Assignee: Sahil Takiar
HADOOP-15229 added a "FileSystem builder-based openFile() API" that allows
specifying configuration values for opening files (similar to HADOOP-14365).
The {{PositionedReadable#readFully}} APIs have always existed.
Both of these APIs should be exposed by libhdfs.
Adding support for {{readFully}} should be straight-forward (a new libhdfs API
called {{hdfsPreadFully}} whose implementation is similar to {{hdfsPread}}).
Support for {{openFile}} will be a little tricker as it is asynchronous and
{{FutureDataInputStreamBuilder#build}} returns a {{CompletableFuture}}.
At a high level, the API for {{openFile}} could look something like this:
{code:java}
LIBHDFS_EXTERNAL
struct hdfsOpenFileBuilder *hdfsOpenFileBuilderAlloc(hdfsFS fs,
const char *path, int flags);
LIBHDFS_EXTERNAL
void hdfsOpenFileBuilderFree(struct hdfsOpenFileBuilder *bld);
LIBHDFS_EXTERNAL
struct hdfsOpenFileBuilder *hdfsOpenFileBuilderMust(hdfsFS fs,
const char *key, const char *value);
LIBHDFS_EXTERNAL
struct hdfsOpenFileBuilder *hdfsOpenFileBuilderOpt(hdfsFS fs,
const char *key, const char *value);
LIBHDFS_EXTERNAL
hdfsFileFuture *hdfsOpenFileBuilderBuild(struct hdfsOpenFileBuilder *bld);
LIBHDFS_EXTERNAL
void hdfsOpenFileFutureFree(struct hdfsFileFuture *future);
LIBHDFS_EXTERNAL
hdfsFile hdfsOpenFileFutureGet(struct hdfsFileFuture *future);
LIBHDFS_EXTERNAL
hdfsFile hdfsOpenFileFutureGet(struct hdfsFileFuture *future, int64_t
timeout, const char* timeUnit);
LIBHDFS_EXTERNAL
void hdfsOpenFileFutureCancel(struct hdfsFileFuture *future,
bool mayInterruptIfRunning);
{code}
Instead of exposing all the functionality of {{CompleteableFuture}} libhdfs
would just expose the functionality of {{Future}}.
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