[ZEPPELIN-6459] Align Docker image logging configuration and documentation with Log4j2

docs/quickstart/docker.md

@@ -142,7 +142,8 @@ Zeppelin service runs on local server, it auto configure itself to use `DockerIn
  - ${ZEPPELIN_HOME}/interpreter/${interpreterGroupName}
  - ${ZEPPELIN_HOME}/conf/zeppelin-site.xml
  - ${ZEPPELIN_HOME}/conf/log4j.properties
- - ${ZEPPELIN\_HOME}/conf/log4j\_yarn_cluster.properties
+ - ${ZEPPELIN_HOME}/conf/log4j2.properties
+ - ${ZEPPELIN_HOME}/conf/log4j_yarn_cluster.properties
  - HADOOP\_CONF_DIR
  - SPARK\_CONF_DIR
  - /etc/krb5.conf

docs/setup/deployment/docker.md

@@ -40,6 +40,12 @@ docker run -p 8080:8080 -e ZEPPELIN_IN_DOCKER=true --rm --name zeppelin apache/z
 Notice, please specify environment variable `ZEPPELIN_IN_DOCKER` when starting zeppelin in docker, 
 otherwise you can not see the interpreter log.
 
+Note: `ZEPPELIN_IN_DOCKER` applies to the all-in-one image built from
+`scripts/docker/zeppelin/bin` (the `Dockerfile` referenced under "Building dockerfile
+locally" below). The split `zeppelin-server`/`zeppelin-interpreter` images described in
+"Build docker image for Zeppelin server & interpreters" already log to stdout by
+default and don't need or support this flag.
+
 * Zeppelin will run at `http://localhost:8080`.
 
 If you want to specify `logs` and `notebook` dir, 

scripts/docker/zeppelin/bin/Dockerfile

@@ -78,6 +78,11 @@ RUN echo "$LOG_TAG Download Zeppelin binary" && \
     chmod 775 ${ZEPPELIN_HOME} && \
     chmod -R 775 /opt/conda
 
+# These 4 files are all required by bin/common.sh, not obsolete duplicates:
+# log4j.properties / log4j_docker.properties configure reload4j, which backs the
+# server and most interpreters; log4j2.properties / log4j2_docker.properties
+# configure the real Log4j2 core that Flink bundles transitively. The "_docker"
+# variants are only picked up when the ZEPPELIN_IN_DOCKER env var is set.
 COPY log4j.properties ${ZEPPELIN_HOME}/conf/
 COPY log4j_docker.properties ${ZEPPELIN_HOME}/conf/
 COPY log4j2.properties ${ZEPPELIN_HOME}/conf/

zeppelin-plugins/launcher/docker/src/main/java/org/apache/zeppelin/interpreter/launcher/DockerInterpreterProcess.java

@@ -547,6 +547,7 @@ private void copyRunFileToContainer(String containerId)
     copyFiles.put(
         zeplConfPath + "/zeppelin-site.xml", containerZeplConfPath + "/zeppelin-site.xml");
     copyFiles.put(zeplConfPath + "/log4j.properties", containerZeplConfPath + "/log4j.properties");
+    copyFiles.put(zeplConfPath + "/log4j2.properties", containerZeplConfPath + "/log4j2.properties");
     copyFiles.put(zeplConfPath + "/log4j_yarn_cluster.properties",
         containerZeplConfPath + "/log4j_yarn_cluster.properties");