Feature limit caching to prescribed number of bytes per file (#6009)

* feature: we can check if a fileId is already in the cache

We using this to protect cache from adding the same needle to
the cache over and over.

* fuse mount: Do not start dowloader if needle is already in the cache

* added maxFilePartSizeInCache property to ChunkCache

If file very large only first maxFilePartSizeInCache bytes
are going to be put to the cache (subject to the needle size
constrains).

* feature: for large files put in cache no more than prescribed number of bytes

Before this patch only the first needle of a large file was intended for
caching. This patch uses maximum prescribed amount of bytes to be put in
cache. This allows to bypass default 2MB maximum for a file part stored
in the cache.

* added dummy mock methods to satisfy interfaces of ChunkCache

1 files changed, 1 insertions, 1 deletions

diff --git a/weed/filer/reader_at.go b/weed/filer/reader_at.go
index d475e6e11..b70942edc 100644
--- a/weed/filer/reader_at.go
+++ b/weed/filer/reader_at.go
@@ -199,7 +199,7 @@ func (c *ChunkReadAt) readChunkSliceAt(buffer []byte, chunkView *ChunkView, next
 		return fetchChunkRange(buffer, c.readerCache.lookupFileIdFn, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped, int64(offset))
 	}
 
-	n, err = c.readerCache.ReadChunkAt(buffer, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped, int64(offset), int(chunkView.ChunkSize), chunkView.ViewOffset == 0)
+	n, err = c.readerCache.ReadChunkAt(buffer, chunkView.FileId, chunkView.CipherKey, chunkView.IsGzipped, int64(offset), int(chunkView.ChunkSize), (uint64(chunkView.ViewOffset)+chunkView.ChunkSize) <= c.readerCache.chunkCache.GetMaxFilePartSizeInCache())
 	if c.lastChunkFid != chunkView.FileId {
 		if chunkView.OffsetInChunk == 0 { // start of a new chunk
 			if c.lastChunkFid != "" {