com.facebook.buck.util.cache.impl

Class StackedFileHashCache

java.lang.Object

com.facebook.buck.util.cache.impl.StackedFileHashCache

All Implemented Interfaces:

FileHashCache, FileHashLoader

public class StackedFileHashCache
extends Object
implements FileHashCache

Wraps a collection of ProjectFilesystem-specific ProjectFileHashCaches as a single cache, implementing a Chain of Responsibility to find and forward operations to the correct inner cache. As this "multi"-cache is meant to handle paths across different ProjectFilesystems, as opposed to paths within the same ProjectFilesystem, it is a distinct type from ProjectFileHashCache.

This "stacking" approach provides a few appealing properties:

1. It makes it easier to module path roots with differing hash cached lifetime requirements. Hashes of paths from roots watched by watchman can be cached indefinitely, until a watchman event triggers invalidation. Hashes of paths under roots not watched by watchman, however, can only be cached for the duration of a single build (as we have no way to know when these paths are modified). By using separate ProjectFileHashCaches per path root, we can construct a new StackedFileHashCache on each build composed of either persistent or ephemeral per-root inner caches that properly manager the lifetime of cached hashes from their root.
2. Modeling the hash cache around path root and sub-paths also works well with a current limitation with our watchman events in which they only store relative paths, with no reference to the path root they originated from. If we stored hashes internally indexed by absolute path, then we wouldn't know where to anchor the search to resolve the path that a watchman event refers to (e.g. a watch event for `foo.h` could refer to `/a/b/foo.h` or `/a/b/c/foo.h`, depending on where the project root is). By indexing hashes by pairs of project root and sub-path, it's easier to identity paths to invalidate (e.g. `foo.h` would invalidate (`/a/b/`,`foo.h`) and not (`/a/b/`,`c/foo.h`)).
3. Since the current implementation of inner caches and callers generally use path root and sub-path pairs, it allows avoiding any overhead converting to/from absolute paths.

Nested Class Summary

Nested classes/interfaces inherited from interface com.facebook.buck.util.cache.FileHashCache

FileHashCache.FileHashCacheVerificationResult

Constructor Summary

Constructors

Constructor and Description
StackedFileHashCache(com.google.common.collect.ImmutableList<? extends ProjectFileHashCache> caches)

Method Summary

Modifier and Type	Method and Description
static StackedFileHashCache	createDefaultHashCaches(ProjectFilesystem filesystem, FileHashCacheMode fileHashCacheMode)
java.util.stream.Stream<Map.Entry<Path,com.google.common.hash.HashCode>>	debugDump()
com.google.common.hash.HashCode	get(Path path)
com.google.common.hash.HashCode	get(ProjectFilesystem filesystem, Path path) Return the HashCode for the given relative Path under the given ProjectFilesystem.
com.google.common.collect.ImmutableList<? extends ProjectFileHashCache>	getCaches()
com.google.common.hash.HashCode	getForArchiveMember(Path relativeArchivePath, Path memberPath)
com.google.common.hash.HashCode	getForArchiveMember(ProjectFilesystem filesystem, Path relativeArchivePath, Path memberPath) Return the HashCode for the given relative ArchiveMemberPath under the given ProjectFilesystem.
long	getSize(Path path)
long	getSize(ProjectFilesystem filesystem, Path path) Return the size of the given relative Path under the given ProjectFilesystem.
void	invalidate(Path path)
void	invalidateAll()
StackedFileHashCache	newDecoratedFileHashCache(java.util.function.Function<ProjectFileHashCache,ProjectFileHashCache> decorateDelegate)
void	set(Path path, com.google.common.hash.HashCode hashCode)
void	set(ProjectFilesystem filesystem, Path path, com.google.common.hash.HashCode hashCode) Set the HashCode for the given relative Path under the given ProjectFilesystem.
FileHashCache.FileHashCacheVerificationResult	verify()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

StackedFileHashCache

public StackedFileHashCache(com.google.common.collect.ImmutableList<? extends ProjectFileHashCache> caches)

Method Detail

createDefaultHashCaches

public static StackedFileHashCache createDefaultHashCaches(ProjectFilesystem filesystem,
                                                           FileHashCacheMode fileHashCacheMode)

invalidate

public void invalidate(Path path)

Specified by:

invalidate in interface FileHashCache

invalidateAll

public void invalidateAll()

Specified by:

invalidateAll in interface FileHashCache

get

public com.google.common.hash.HashCode get(Path path)
                                    throws IOException

Specified by:

get in interface FileHashLoader

Throws:

IOException

getSize

public long getSize(Path path)
             throws IOException

Specified by:

getSize in interface FileHashLoader

Throws:

IOException

getForArchiveMember

public com.google.common.hash.HashCode getForArchiveMember(Path relativeArchivePath,
                                                           Path memberPath)
                                                    throws IOException

Specified by:

getForArchiveMember in interface FileHashLoader

Throws:

IOException

set

public void set(Path path,
                com.google.common.hash.HashCode hashCode)
         throws IOException

Specified by:

set in interface FileHashCache

Throws:

IOException

verify

public FileHashCache.FileHashCacheVerificationResult verify()
                                                     throws IOException

Specified by:

verify in interface FileHashCache

Throws:

IOException

debugDump

public java.util.stream.Stream<Map.Entry<Path,com.google.common.hash.HashCode>> debugDump()

Specified by:

debugDump in interface FileHashCache

get

public com.google.common.hash.HashCode get(ProjectFilesystem filesystem,
                                           Path path)
                                    throws IOException

Description copied from interface: FileHashLoader

Return the HashCode for the given relative Path under the given ProjectFilesystem.

Specified by:

get in interface FileHashLoader

Throws:

IOException

getForArchiveMember

public com.google.common.hash.HashCode getForArchiveMember(ProjectFilesystem filesystem,
                                                           Path relativeArchivePath,
                                                           Path memberPath)
                                                    throws IOException

Description copied from interface: FileHashLoader

Return the HashCode for the given relative ArchiveMemberPath under the given ProjectFilesystem.

Specified by:

getForArchiveMember in interface FileHashLoader

Throws:

IOException

getSize

public long getSize(ProjectFilesystem filesystem,
                    Path path)
             throws IOException

Description copied from interface: FileHashLoader

Return the size of the given relative Path under the given ProjectFilesystem.

Specified by:

getSize in interface FileHashLoader

Throws:

IOException

set

public void set(ProjectFilesystem filesystem,
                Path path,
                com.google.common.hash.HashCode hashCode)
         throws IOException

Description copied from interface: FileHashCache

Set the HashCode for the given relative Path under the given ProjectFilesystem.

Specified by:

set in interface FileHashCache

Throws:

IOException

newDecoratedFileHashCache

public StackedFileHashCache newDecoratedFileHashCache(java.util.function.Function<ProjectFileHashCache,ProjectFileHashCache> decorateDelegate)

getCaches

public com.google.common.collect.ImmutableList<? extends ProjectFileHashCache> getCaches()