| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.htrace; |
| |
| import java.lang.reflect.Constructor; |
| import org.apache.commons.logging.Log; |
| import org.apache.commons.logging.LogFactory; |
| import org.apache.htrace.impl.AlwaysSampler; |
| import org.apache.htrace.impl.NeverSampler; |
| |
| /** |
| * A {@link Sampler} builder. It reads a {@link Sampler} class name from the provided |
| * configuration using the {@link #SAMPLER_CONF_KEY} key. Unqualified class names |
| * are interpreted as members of the {@code org.apache.htrace.impl} package. The {@link #build()} |
| * method constructs an instance of that class, initialized with the same configuration. |
| */ |
| public class SamplerBuilder { |
| |
| // TODO: should follow the same API as SpanReceiverBuilder |
| |
| public final static String SAMPLER_CONF_KEY = "sampler"; |
| private final static String DEFAULT_PACKAGE = "org.apache.htrace.impl"; |
| private final static ClassLoader classLoader = |
| SamplerBuilder.class.getClassLoader(); |
| private final HTraceConfiguration conf; |
| private static final Log LOG = LogFactory.getLog(SamplerBuilder.class); |
| |
| public SamplerBuilder(HTraceConfiguration conf) { |
| this.conf = conf; |
| } |
| |
| public Sampler build() { |
| Sampler sampler = newSampler(); |
| if (LOG.isTraceEnabled()) { |
| LOG.trace("Created new sampler of type " + |
| sampler.getClass().getName(), new Exception()); |
| } |
| return sampler; |
| } |
| |
| private Sampler newSampler() { |
| String str = conf.get(SAMPLER_CONF_KEY); |
| if (str == null || str.isEmpty()) { |
| return NeverSampler.INSTANCE; |
| } |
| if (!str.contains(".")) { |
| str = DEFAULT_PACKAGE + "." + str; |
| } |
| Class cls = null; |
| try { |
| cls = classLoader.loadClass(str); |
| } catch (ClassNotFoundException e) { |
| LOG.error("SamplerBuilder cannot find sampler class " + str + |
| ": falling back on NeverSampler."); |
| return NeverSampler.INSTANCE; |
| } |
| Constructor<Sampler> ctor = null; |
| try { |
| ctor = cls.getConstructor(HTraceConfiguration.class); |
| } catch (NoSuchMethodException e) { |
| LOG.error("SamplerBuilder cannot find a constructor for class " + str + |
| "which takes an HTraceConfiguration. Falling back on " + |
| "NeverSampler."); |
| return NeverSampler.INSTANCE; |
| } |
| try { |
| return ctor.newInstance(conf); |
| } catch (ReflectiveOperationException e) { |
| LOG.error("SamplerBuilder reflection error when constructing " + str + |
| ". Falling back on NeverSampler.", e); |
| return NeverSampler.INSTANCE; |
| } catch (Throwable e) { |
| LOG.error("SamplerBuilder constructor error when constructing " + str + |
| ". Falling back on NeverSampler.", e); |
| return NeverSampler.INSTANCE; |
| } |
| } |
| } |