Class CoprocessorClassLoader
- All Implemented Interfaces:
Closeable
,AutoCloseable
This ClassLoader always tries to load classes from the specified coprocessor jar first actually using URLClassLoader logic before delegating to the parent ClassLoader, thus avoiding dependency conflicts between HBase's classpath and classes in the coprocessor jar.
Certain classes are exempt from being loaded by this ClassLoader because it would prevent them from being cast to the equivalent classes in the region server. For example, the Coprocessor interface needs to be loaded by the region server's ClassLoader to prevent a ClassCastException when casting the coprocessor implementation.
A HDFS path can be used to specify the coprocessor jar. In this case, the jar will be copied to local at first under some folder under ${hbase.local.dir}/jars/tmp/. The local copy will be removed automatically when the HBase server instance is stopped.
This ClassLoader also handles resource loading. In most cases this ClassLoader will attempt to load resources from the coprocessor jar first before delegating to the parent. However, like in class loading, some resources need to be handled differently. For all of the Hadoop default configurations (e.g. hbase-default.xml) we will check the parent ClassLoader first to prevent issues such as failing the HBase default configuration version check.
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Field Summary
Modifier and TypeFieldDescriptionprivate static final String[]
If the class being loaded starts with any of these strings, we will skip trying to load it from the coprocessor jar and instead delegate directly to the parent ClassLoader.private static final ConcurrentMap<org.apache.hadoop.fs.Path,
CoprocessorClassLoader> External class loaders cache keyed by external jar path.private static final Pattern
A locker used to synchronize class loader initialization per coprocessor jar fileprivate static final org.slf4j.Logger
A set used to synchronized parent path clean up.private static final Pattern[]
If the resource being loaded matches any of these patterns, we will first attempt to load the resource with the parent ClassLoader.private static final String
Fields inherited from class org.apache.hadoop.hbase.util.ClassLoaderBase
DEFAULT_LOCAL_DIR, LOCAL_DIR_KEY, parent
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Constructor Summary
ModifierConstructorDescriptionprivate
CoprocessorClassLoader
(ClassLoader parent) Creates a JarClassLoader that loads classes from the given paths. -
Method Summary
Modifier and TypeMethodDescriptionstatic void
static Collection<? extends ClassLoader>
static CoprocessorClassLoader
getClassLoader
(org.apache.hadoop.fs.Path path, ClassLoader parent, String pathPrefix, org.apache.hadoop.conf.Configuration conf) Get a CoprocessorClassLoader for a coprocessor jar path from cache.static CoprocessorClassLoader
getIfCached
(org.apache.hadoop.fs.Path path) getResource
(String name) private void
init
(org.apache.hadoop.fs.Path pathPattern, String pathPrefix, org.apache.hadoop.conf.Configuration conf) protected boolean
isClassExempt
(String name, String[] includedClassPrefixes) Determines whether the given class should be exempt from being loaded by this ClassLoader.Class<?>
Class<?>
protected boolean
Determines whether we should attempt to load the given resource using the parent first before attempting to load the resource using this ClassLoader.Methods inherited from class java.net.URLClassLoader
addURL, close, definePackage, findClass, findResource, findResources, getPermissions, getResourceAsStream, getURLs, newInstance, newInstance
Methods inherited from class java.security.SecureClassLoader
defineClass, defineClass
Methods inherited from class java.lang.ClassLoader
clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findClass, findLibrary, findLoadedClass, findResource, findSystemClass, getClassLoadingLock, getDefinedPackage, getDefinedPackages, getName, getPackage, getPackages, getParent, getPlatformClassLoader, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, getUnnamedModule, isRegisteredAsParallelCapable, loadClass, registerAsParallelCapable, resolveClass, resources, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners
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Field Details
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LOG
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TMP_JARS_DIR
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classLoadersCache
private static final ConcurrentMap<org.apache.hadoop.fs.Path,CoprocessorClassLoader> classLoadersCacheExternal class loaders cache keyed by external jar path. ClassLoader instance is stored as a weak-reference to allow GC'ing when it is not used (@see HBASE-7205) -
CLASS_PREFIX_EXEMPTIONS
If the class being loaded starts with any of these strings, we will skip trying to load it from the coprocessor jar and instead delegate directly to the parent ClassLoader. -
RESOURCE_LOAD_PARENT_FIRST_PATTERNS
If the resource being loaded matches any of these patterns, we will first attempt to load the resource with the parent ClassLoader. Only if the resource is not found by the parent do we attempt to load it from the coprocessor jar. -
libJarPattern
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locker
A locker used to synchronize class loader initialization per coprocessor jar file -
parentDirLockSet
A set used to synchronized parent path clean up. Generally, there should be only one parent path, but using a set so that we can support more.
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Constructor Details
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CoprocessorClassLoader
Creates a JarClassLoader that loads classes from the given paths.
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Method Details
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init
private void init(org.apache.hadoop.fs.Path pathPattern, String pathPrefix, org.apache.hadoop.conf.Configuration conf) throws IOException - Throws:
IOException
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getIfCached
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getAllCached
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clearCache
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getClassLoader
public static CoprocessorClassLoader getClassLoader(org.apache.hadoop.fs.Path path, ClassLoader parent, String pathPrefix, org.apache.hadoop.conf.Configuration conf) throws IOException Get a CoprocessorClassLoader for a coprocessor jar path from cache. If not in cache, create one.- Parameters:
path
- the path to the coprocessor jar file to load classes fromparent
- the parent class loader for exempted classespathPrefix
- a prefix used in temp path name to store the jar file locallyconf
- the configuration used to create the class loader, if needed- Returns:
- a CoprocessorClassLoader for the coprocessor jar path
- Throws:
IOException
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loadClass
- Overrides:
loadClass
in classClassLoader
- Throws:
ClassNotFoundException
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loadClass
public Class<?> loadClass(String name, String[] includedClassPrefixes) throws ClassNotFoundException - Throws:
ClassNotFoundException
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getResource
- Overrides:
getResource
in classClassLoader
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isClassExempt
Determines whether the given class should be exempt from being loaded by this ClassLoader.- Parameters:
name
- the name of the class to test.- Returns:
- true if the class should *not* be loaded by this ClassLoader; false otherwise.
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loadResourceUsingParentFirst
Determines whether we should attempt to load the given resource using the parent first before attempting to load the resource using this ClassLoader.- Parameters:
name
- the name of the resource to test.- Returns:
- true if we should attempt to load the resource using the parent first; false if we should attempt to load the resource using this ClassLoader first.
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