Support init mode and document with it. (#1900)

apm-dist/bin/oapServiceInit.bat

+@REM
+@REM  Licensed to the Apache Software Foundation (ASF) under one or more
+@REM  contributor license agreements.  See the NOTICE file distributed with
+@REM  this work for additional information regarding copyright ownership.
+@REM  The ASF licenses this file to You under the Apache License, Version 2.0
+@REM  (the "License"); you may not use this file except in compliance with
+@REM  the License.  You may obtain a copy of the License at
+@REM
+@REM      http://www.apache.org/licenses/LICENSE-2.0
+@REM
+@REM  Unless required by applicable law or agreed to in writing, software
+@REM  distributed under the License is distributed on an "AS IS" BASIS,
+@REM  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@REM  See the License for the specific language governing permissions and
+@REM  limitations under the License.
+
+@echo off
+
+setlocal
+set OAP_PROCESS_TITLE=Skywalking-Collector
+set OAP_HOME=%~dp0%..
+set OAP_OPTS="-Xms256M -Xmx512M -Doap.logDir=%OAP_HOME%\logs"
+
+set CLASSPATH=%OAP_HOME%\config;.;
+set CLASSPATH=%OAP_HOME%\oap-libs\*;%CLASSPATH%
+
+if defined JAVA_HOME (
+ set _EXECJAVA="%JAVA_HOME%\bin\java"
+)
+
+if not defined JAVA_HOME (
+ echo "JAVA_HOME not set."
+ set _EXECJAVA=java
+)
+
+start "%OAP_PROCESS_TITLE%" %_EXECJAVA% "%OAP_OPTS%" -cp "%CLASSPATH%" -Dmode=init org.apache.skywalking.oap.server.starter.OAPServerStartUp
+endlocal

apm-dist/bin/oapServiceInit.sh

+# 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.
+
+#!/usr/bin/env sh
+
+PRG="$0"
+PRGDIR=`dirname "$PRG"`
+[ -z "$OAP_HOME" ] && OAP_HOME=`cd "$PRGDIR/.." >/dev/null; pwd`
+
+OAP_LOG_DIR="${OAP_HOME}/logs"
+JAVA_OPTS=" -Xms256M -Xmx512M"
+
+if [ ! -d "${OAP_HOME}/logs" ]; then
+    mkdir -p "${OAP_LOG_DIR}"
+fi
+
+_RUNJAVA=${JAVA_HOME}/bin/java
+[ -z "$JAVA_HOME" ] && _RUNJAVA=java
+
+CLASSPATH="$OAP_HOME/config:$CLASSPATH"
+for i in "$OAP_HOME"/oap-libs/*.jar
+do
+    CLASSPATH="$i:$CLASSPATH"
+done
+
+OAP_OPTIONS=" -Doap.logDir=${OAP_LOG_DIR}"
+
+eval exec "\"$_RUNJAVA\" ${JAVA_OPTS} ${OAP_OPTIONS} -classpath $CLASSPATH -Dmode=init org.apache.skywalking.oap.server.starter.OAPServerStartUp \
+        2>${OAP_LOG_DIR}/oap.log 1> /dev/null &"
+
+if [ $? -eq 0 ]; then
+    sleep 1
+	echo "SkyWalking OAP started successfully!"
+else
+	echo "SkyWalking OAP started failure!"
+	exit 1
+fi

docs/en/setup/backend/backend-init-mode.md

+# Init mode
+SkyWalking backend supports multiple storage implementors. Most of them could initialize the storage, 
+such as Elastic Search, Database automatically when the backend startup in first place.
+
+But there are some unexpected happens based on the storage, such as
+`When create Elastic Search indexes concurrently, because of several backend instances startup at the same time.`,
+there is a change, the APIs of Elastic Search would be blocked without any exception.
+And this has more chances happen in container management platform, like k8s.
+
+That is where you need **Init mode** startup.
+
+## Solution
+Only one single instance should run in **Init mode** before other instances start up.
+And this instance will exit graciously after all initialization steps are done.
+
+Use `oapServiceInit.sh`/`oapServiceInit.bat` to start up backend. You should see the following logs
+> 2018-11-09 23:04:39,465 - org.apache.skywalking.oap.server.starter.OAPServerStartUp -2214 [main] INFO  [] - OAP starts up in init mode successfully, exit now...
+
+## Kubernetes
+Initialization in this mode would be included in our Kubernetes scripts and Helm.
\ No newline at end of file

docs/en/setup/backend/backend-setup.md

@@ -54,6 +54,8 @@ We recommend you to read the feature documents in our following order.
 
 1. [Overriding settings](backend-setting-override.md) in application.yml is supported
 1. [IP and port setting](backend-ip-port.md). Introduce how IP and port set and be used.
+1. [Backend init mode startup](backend-init-mode.md). How to init the environment and exit graciously.
+Read this before you try to initial a new cluster.
 1. [Cluster management](backend-cluster.md). Guide you to set backend server in cluster mode.
 1. [Deploy in kubernetes](backend-k8s.md). Guide you to build and use SkyWalking image, and deploy in k8s.
 1. [Choose storage](backend-storage.md). As we know, in default quick start, backend is running with H2

oap-server/server-starter/src/main/java/org/apache/skywalking/oap/server/starter/OAPServerStartUp.java

@@ -36,6 +36,12 @@ public class OAPServerStartUp {
         try {
             ApplicationConfiguration applicationConfiguration = configLoader.load();
             manager.init(applicationConfiguration);
+
+            String mode = System.getProperty("mode");
+            if ("init".equals(mode)) {
+                logger.info("OAP starts up in init mode successfully, exit now...");
+                System.exit(0);
+            }
         } catch (ConfigFileNotFoundException | ModuleNotFoundException | ProviderNotFoundException | ServiceNotProvidedException | ModuleConfigException | ModuleStartException e) {
             logger.error(e.getMessage(), e);
             System.exit(1);