On Mon, 2016-08-08 at 12:45 +0200, Michael Dürig wrote:
> The segment node store inlines blobs up to a size of 16512 bytes.
> This
> is probably the reason you are not able to get them from the blob
> store.
Good point. So it's expected that this happens and to test blob
handling I would need to use 'large' blobs?
Robert
>
> Michael
>
> On 8.8.16 12:38 , Robert Munteanu wrote:
> >
> > Hi,
> >
> > I'm trying to understand the behaviour of NodeStore.createBlob and
> > NodeStore.getBlob. For context, I'm experimenting with creating a
> > MultiplexingNodeStore [1] , and this multiplexing would neet to
> > include
> > the blob handling as well.
> >
> > But before that, I'm trying to understand something basic :-)
> >
> > I have created a SegmentNodeStore with a FileBlobStore
> >
> > BlobStore blobStore = new FileBlobStore(blobStorePath);
> > FileStore store =
> > FileStore.builder(storePath).withBlobStore(blobStore).build();
> > SegmentNodeStore instance =
> > SegmentNodeStore.builder(store).build();
> >
> > After that I have tried to retrieve a blob from the same store
> >
> > Blob createdBlob = globalStore.createBlob(SMALL_BLOB);
> > Blob retrievedBlob =
> > globalStore.getBlob(createdBlob.getReference());
> >
> > where
> >
> > private static final InputStream SMALL_BLOB = new
> > ByteArrayInputStream("hello, world".getBytes());
> >
> > To my surprise, retrievedBlob is null, since it has a null id.
> >
> > I've traced the calls to understand what is going on, and in
> > SegmentBlob.getBlobId() the blobId is null, since the 'head'
> > variable
> > is the following code has the value 0.
> >
> > byte head = segment.readByte(offset);
> > if ((head & 0xf0) == 0xe0) {
> > // 1110 xxxx: external value, small blob ID
> > return readShortBlobId(segment, offset, head);
> > } else if ((head & 0xf8) == 0xf0) {
> > // 1111 0xxx: external value, long blob ID
> > return readLongBlobId(segment, offset);
> > } else {
> > return null;
> > }
> >
> > Now, this works as expected for a DocumentNodeStore backed by H2,
> > so
> > something is not entirely right.
> >
> > So my question is - why does this happen?
> >
> > 1) Is this sequence of calls (createBlob/getBlob) not supposed to
> > be
> > symmetric?
> > 2) Am I configuring the SegmentNodeStore incorrectly?
> > 3) Is it a bug to file against the SegmentNodeStore?
> >
> > If you're curious, the full test code is at [2], although I haven't
> > committed the variant which checks the SegmentNodeStore for blob
> > handling consistency.
> >
> > Thanks,
> >
> > Robert
> >
> > [1]: https://github.com/apache/jackrabbit-oak/compare/trunk...rombe
> > rt:f
> > eatures/nodestore-multiplex?expand=1
> > [2]: https://github.com/rombert/jackrabbit-oak/blob/99cd3d8b81213fa
> > 03a2
> > ebee2ad754081dbd5977f/oak-
> > it/src/test/java/org/apache/jackrabbit/oak/plugins/memory/multiplex
> > /Mul
> > tiplexingMemoryNodeStoreTest.java
> >
