本文首发自https://www.cnblogs.com/slankka/ 转载请注明出处。
本文的主要内容是介绍如何动态加载Flink作业的UDF。
Classloader
加载UDF一定是classLoader做的，而作业启动的过程中，App ClassLoader的具体实现类为：
static class AppClassLoader extends URLClassLoader
而URLClassLoader 看名字是支持URL的。
实际情况
已知在Flink的启动参数-C中加入Flink的UDF可以成功执行作业提交过程。
static final Option CLASSPATH_OPTION =
new Option(
"C",
"classpath",
true,
"Adds a URL to each user code "
+ "classloader on all nodes in the cluster. The paths must specify a protocol (e.g. file://) and be "
+ "accessible on all nodes (e.g. by means of a NFS share). You can use this option multiple "
+ "times for specifying more than one URL. The protocol must be supported by the "
+ "{@link java.net.URLClassLoader}.");
但是Flink(1.13以前)会报错：
Caused by: org.apache.flink.table.api.ValidationException: SQL validation failed. Can't resolve udf class com.slankka.flink.udf.PlusTwoFunc
at org.apache.flink.table.planner.calcite.FlinkPlannerImpl.org$apache$flink$table$planner$calcite$FlinkPlannerImpl$$validate(FlinkPlannerImpl.scala:152)
at org.apache.flink.table.planner.calcite.FlinkPlannerImpl.validate(FlinkPlannerImpl.scala:111)
at org.apache.flink.table.planner.operations.SqlToOperationConverter.convert(SqlToOperationConverter.java:189)
at org.apache.flink.table.planner.operations.SqlToOperationConverter.convertSqlInsert(SqlToOperationConverter.java:564)
at org.apache.flink.table.planner.operations.SqlToOperationConverter.convert(SqlToOperationConverter.java:248)
at org.apache.flink.table.planner.delegation.ParserImpl.parse(ParserImpl.java:77)
at org.apache.flink.table.api.internal.TableEnvironmentImpl.sqlUpdate(TableEnvironmentImpl.java:733)
at com.slankka.rtc.flinkplatform.sql.SqlJob.lambda$start$0(SqlJob.java:123)
at java.lang.Iterable.forEach(Iterable.java:75)
at com.slankka.rtc.flinkplatform.sql.SqlJob.start(SqlJob.java:116)
at com.slankka.rtc.flinkplatform.sql.SqlJobDriver.main(SqlJobDriver.java:14)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:349)
... 11 more
Caused by: java.lang.RuntimeException: Can't resolve udf class com.slankka.flink.udf.PlusTwoFunc
at org.apache.flink.table.catalog.CatalogFunctionImpl.isGeneric(CatalogFunctionImpl.java:77)
at org.apache.flink.table.catalog.hive.factories.HiveFunctionDefinitionFactory.createFunctionDefinition(HiveFunctionDefinitionFactory.java:63)
at org.apache.flink.table.catalog.FunctionCatalog.resolvePreciseFunctionReference(FunctionCatalog.java:570)
at org.apache.flink.table.catalog.FunctionCatalog.lambda$resolveAmbiguousFunctionReference$2(FunctionCatalog.java:614)
at java.util.Optional.orElseGet(Optional.java:267)
at org.apache.flink.table.catalog.FunctionCatalog.resolveAmbiguousFunctionReference(FunctionCatalog.java:614)
at org.apache.flink.table.catalog.FunctionCatalog.lookupFunction(FunctionCatalog.java:361)
at org.apache.flink.table.planner.catalog.FunctionCatalogOperatorTable.lookupOperatorOverloads(FunctionCatalogOperatorTable.java:97)
at org.apache.calcite.sql.util.ChainedSqlOperatorTable.lookupOperatorOverloads(ChainedSqlOperatorTable.java:67)
at org.apache.calcite.sql.validate.SqlValidatorImpl.performUnconditionalRewrites(SqlValidatorImpl.java:1260)
at org.apache.calcite.sql.validate.SqlValidatorImpl.performUnconditionalRewrites(SqlValidatorImpl.java:1275)
at org.apache.calcite.sql.validate.SqlValidatorImpl.performUnconditionalRewrites(SqlValidatorImpl.java:1245)
at org.apache.calcite.sql.validate.SqlValidatorImpl.validateScopedExpression(SqlValidatorImpl.java:1009)
at org.apache.calcite.sql.validate.SqlValidatorImpl.validate(SqlValidatorImpl.java:724)
at org.apache.flink.table.planner.calcite.FlinkPlannerImpl.org$apache$flink$table$planner$calcite$FlinkPlannerImpl$$validate(FlinkPlannerImpl.scala:147)
... 26 more
Caused by: java.lang.ClassNotFoundException: com.slankka.flink.udf.PlusTwoFunc
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at org.apache.flink.table.catalog.CatalogFunctionImpl.isGeneric(CatalogFunctionImpl.java:72)
... 40 more
这个调用链非常清楚，提交作业的程序是：
private final URLClassLoader userCodeClassLoader;
org.apache.flink.client.program.PackagedProgram#callMainMethod
这里已经进入作业的main函数了。使用的类加载器是：UserCodeClassLoader
this.extractedTempLibraries =
this.jarFile == null
? Collections.emptyList()
: extractContainedLibraries(this.jarFile);
this.userCodeClassLoader =
ClientUtils.buildUserCodeClassLoader(
getJobJarAndDependencies(),
classpaths,
getClass().getClassLoader(),
configuration);
再看UserCodeClassLoader的构建过程：
实际上已经加载了-C参数指定的JAR了
public static URLClassLoader buildUserCodeClassLoader(
List<URL> jars, List<URL> classpaths, ClassLoader parent, Configuration configuration) {
URL[] urls = new URL[jars.size() + classpaths.size()];
for (int i = 0; i < jars.size(); i++) {
urls[i] = jars.get(i);
}
for (int i = 0; i < classpaths.size(); i++) {
urls[i + jars.size()] = classpaths.get(i);
}
final String[] alwaysParentFirstLoaderPatterns =
CoreOptions.getParentFirstLoaderPatterns(configuration);
final String classLoaderResolveOrder =
configuration.getString(CoreOptions.CLASSLOADER_RESOLVE_ORDER);
FlinkUserCodeClassLoaders.ResolveOrder resolveOrder =
FlinkUserCodeClassLoaders.ResolveOrder.fromString(classLoaderResolveOrder);
final boolean checkClassloaderLeak =
configuration.getBoolean(CoreOptions.CHECK_LEAKED_CLASSLOADER);
return FlinkUserCodeClassLoaders.create(
resolveOrder,
urls,
parent,
alwaysParentFirstLoaderPatterns,
NOOP_EXCEPTION_HANDLER,
checkClassloaderLeak);
}
但不知为何，仍旧出现上述错误。
临时解决方案
可以自行编译CatalogFunctionImpl.java 适用于Flink-1.13以下所有版本
@Override
public boolean isGeneric() {
if (functionLanguage == FunctionLanguage.PYTHON) {
return true;
}
try {
ClassLoader cl = Thread.currentThread().getContextClassLoader();
Class c = Class.forName(className, true, cl);
if (UserDefinedFunction.class.isAssignableFrom(c)) {
return true;
}
} catch (ClassNotFoundException e) {
throw new RuntimeException(String.format("Can't resolve udf class %s", className), e);
}
return false;
}
在Flink作业的main函数的开头自行加载UDF Flink-1.13 以前有此问题。
//动态加载Jar
public static void loadJar(List<URL> jarUrl) {
//从URLClassLoader类加载器中获取类的addURL方法
Method method = null;
try {
method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
} catch (NoSuchMethodException | SecurityException ignore) {
}
// 获取方法的访问权限
assert method != null;
boolean accessible = method.isAccessible();
try {
//修改访问权限为可写
if (!accessible) {
method.setAccessible(true);
}
// 获取系统类加载器
URLClassLoader classLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();
//jar路径加入到系统url路径里
for (URL jar : jarUrl) {
method.invoke(classLoader, jar);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
method.setAccessible(accessible);
}
}
新解决方案
[Flink-20606] Flink-1.13 已经修复此问题。