[GitHub] [tez] abstractdog commented on a diff in pull request #98: TEZ-4039: Tez should inject dag id, query id into MDC

[GitBox <gi...@apache.org>]

abstractdog commented on code in PR #98:
URL: https://github.com/apache/tez/pull/98#discussion_r1003232833


##########
tez-common/src/main/java/org/apache/tez/util/LoggingUtils.java:
##########
@@ -0,0 +1,147 @@
+/**
+* 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.tez.util;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.util.Arrays;
+import java.util.Hashtable;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.log4j.helpers.ThreadLocalMap;
+import org.apache.tez.dag.api.TezConfiguration;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public final class LoggingUtils {
+  private static final Logger LOG = LoggerFactory.getLogger(LoggingUtils.class);
+
+  private LoggingUtils() {}
+
+  @SuppressWarnings("unchecked")
+  public static void initLoggingContext(ThreadLocalMap threadLocalMap, Configuration conf,
+      String dagId, String taskAttemptId) {
+    Hashtable<String, String> data = (Hashtable<String, String>) threadLocalMap.get();
+    if (data == null) {
+      data = new NonClonableHashtable<String, String>();
+      threadLocalMap.set(data);
+    }
+    data.put("dagId", dagId == null ? "" : dagId);
+    data.put("taskAttemptId", taskAttemptId == null ? "" : taskAttemptId);
+
+    String[] mdcKeys = conf.getStrings(TezConfiguration.TEZ_MDC_CUSTOM_KEYS,
+        TezConfiguration.TEZ_MDC_CUSTOM_KEYS_DEFAULT);
+
+    if (mdcKeys.length == 0) {
+      return;
+    }
+
+    String[] mdcKeysValuesFrom = conf.getStrings(TezConfiguration.TEZ_MDC_CUSTOM_KEYS_CONF_PROPS,
+        TezConfiguration.TEZ_MDC_CUSTOM_KEYS_CONF_PROPS_DEFAULT);
+    LOG.info("MDC_LOGGING: setting up MDC keys: keys: {} / conf: {}", Arrays.asList(mdcKeys),
+        Arrays.asList(mdcKeysValuesFrom));
+
+    int i = 0;
+    for (String mdcKey : mdcKeys) {
+      // don't want to fail on incorrect mdc key settings, but warn in app logs
+      if (mdcKey.isEmpty() || mdcKeysValuesFrom.length < i + 1) {
+        LOG.warn("cannot set mdc key: {}", mdcKey);
+        break;

Review Comment:
   if we hit this it means that mdcKey is most probably empty, so we had:
   ```
   tez.mdc.custom.keys=
   ```
   as it's very unlikely that the user set something like this:
   ```
   tez.mdc.custom.keys=,something_which_matters
   ```
   if we split string by commas and find empty string, it makes no sense to loop further, or at least I cannot figure out a valid use-case



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