Package com.google.cloud.hadoop.gcsio

Class GoogleCloudStorageReadChannel

    • Field Detail

      • currentPosition

        protected long currentPosition

      • contentChannelPosition

        protected long contentChannelPosition

      • metadataInitialized

        protected boolean metadataInitialized

    • Constructor Detail

      • GoogleCloudStorageReadChannel

        public GoogleCloudStorageReadChannel​(com.google.api.services.storage.Storage gcs,
                                     StorageResourceId resourceId,
                                     ApiErrorExtractor errorExtractor,
                                     ClientRequestHelper<com.google.api.services.storage.model.StorageObject> requestHelper,
                                     @Nonnull
                                     GoogleCloudStorageReadOptions readOptions)
                              throws IOException
        Constructs an instance of GoogleCloudStorageReadChannel.
        Parameters:
        gcs - storage object instance
        resourceId - contains information about a specific resource
        requestHelper - a ClientRequestHelper used to set any extra headers
        readOptions - fine-grained options specifying things like retry settings, buffering, etc. Could not be null.
        Throws:
        IOException - on IO error

    • Method Detail

      • setMaxRetries

        public void setMaxRetries​(int maxRetries)
        Sets the number of times to automatically retry by re-opening the underlying contentChannel whenever an exception occurs while reading from it. The count of attempted retries is reset whenever at least one byte is successfully read, so this number of retries refers to retries made without achieving any forward progress.

      • read

        public int read​(ByteBuffer buffer)
         throws IOException
        Reads from this channel and stores read data in the given buffer.

        On unexpected failure, will attempt to close the channel and clean up state.

        Specified by:
        read in interface ReadableByteChannel
        Specified by:
        read in interface SeekableByteChannel
        Parameters:
        buffer - buffer to read data into
        Returns:
        number of bytes read or -1 on end-of-stream
        Throws:
        IOException - on IO error

      • isOpen

        public boolean isOpen()
        Tells whether this channel is open.
        Specified by:
        isOpen in interface Channel
        Returns:
        a value indicating whether this channel is open

      • closeContentChannel

        protected void closeContentChannel()
        Closes the underlying ReadableByteChannel.

        Catches and ignores all exceptions as there is not a lot the user can do to fix errors here and a new connection will be needed. Especially SSLExceptions since the there's a high probability that SSL connections would be broken in a way that causes Channel.close() itself to throw an exception, even though underlying sockets have already been cleaned up; close() on an SSLSocketImpl requires a shutdown handshake in order to shut down cleanly, and if the connection has been broken already, then this is not possible, and the SSLSocketImpl was already responsible for performing local cleanup at the time the exception was raised.

      • position

        @CanIgnoreReturnValue
public SeekableByteChannel position​(long newPosition)
                             throws IOException
        Sets this channel's position.

        This method will throw an exception if newPosition is greater than object size, which contradicts SeekableByteChannel contract. TODO(user): decide if this needs to be fixed.

        Specified by:
        position in interface SeekableByteChannel
        Parameters:
        newPosition - the new position, counting the number of bytes from the beginning.
        Returns:
        this channel instance
        Throws:
        FileNotFoundException - if the underlying object does not exist.
        IOException - on IO error

      • size

        public long size()
          throws IOException
        Returns size of the object to which this channel is connected.

        Note: this method will return -1 until metadata will be lazily initialized during first read(java.nio.ByteBuffer) method call.

        Specified by:
        size in interface SeekableByteChannel
        Returns:
        size of the object to which this channel is connected after metadata was initialized (during first read) or -1 otherwise.
        Throws:
        IOException - on IO error

      • setSize

        protected void setSize​(long size)
        Sets size of this channel to the given value.

      • validatePosition

        protected void validatePosition​(long position)
                         throws IOException
        Validates that the given position is valid for this channel.
        Throws:
        IOException

      • initMetadata

        protected void initMetadata​(com.google.api.client.http.HttpHeaders headers)
                     throws IOException
        Initializes metadata (size, encoding, etc) from HTTP headers. Used for lazy initialization when fail fast is disabled.
        Throws:
        IOException

      • initMetadata

        protected void initMetadata​(@Nullable
                            String encoding,
                            long sizeFromMetadata,
                            long generation)
                     throws IOException
        Initializes metadata (size, encoding, etc) from passed parameters.
        Throws:
        IOException

      • createDataRequest

        protected com.google.api.services.storage.Storage.Objects.Get createDataRequest()
                                                                         throws IOException
        Throws:
        IOException

      • createMetadataRequest

        protected com.google.api.services.storage.Storage.Objects.Get createMetadataRequest()
                                                                             throws IOException
        Throws:
        IOException