Add customized log file with 7 day retention (#455)

Dockerfile

@@ -60,6 +60,7 @@ COPY mcstatus /usr/local/bin
 
 VOLUME ["/data","/mods","/config"]
 COPY server.properties /tmp/server.properties
+COPY log4j2.xml /tmp/log4j2.xml
 WORKDIR /data
 
 ENTRYPOINT [ "/start" ]

log4j2.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="WARN" packages="com.mojang.util">
+    <Appenders>
+        <Console name="SysOut" target="SYSTEM_OUT">
+            <PatternLayout pattern="[%d{HH:mm:ss}] [%t/%level]: %msg%n" />
+        </Console>
+        <Queue name="ServerGuiConsole">
+            <PatternLayout pattern="[%d{HH:mm:ss} %level]: %msg%n" />
+        </Queue>
+        <RollingRandomAccessFile name="File" fileName="logs/latest.log" filePattern="logs/%d{yyyy-MM-dd}-%i.log.gz">
+            <PatternLayout pattern="[%d{HH:mm:ss}] [%t/%level]: %msg%n" />
+            <Policies>
+                <TimeBasedTriggeringPolicy />
+                <OnStartupTriggeringPolicy />
+            </Policies>
+            <DefaultRolloverStrategy>
+                <Delete basePath="logs">
+                    <IfFileName glob="*.log.gz" />
+                    <IfLastModified age="7d" />
+                </Delete>
+            </DefaultRolloverStrategy>
+        </RollingRandomAccessFile>
+    </Appenders>
+    <Loggers>
+        <Root level="info">
+            <filters>
+                <MarkerFilter marker="NETWORK_PACKETS" onMatch="DENY" onMismatch="NEUTRAL" />
+            </filters>
+            <AppenderRef ref="SysOut"/>
+            <AppenderRef ref="File"/>
+            <AppenderRef ref="ServerGuiConsole"/>
+        </Root>
+    </Loggers>
+</Configuration>

start-minecraftFinalSetup

@@ -27,6 +27,16 @@ if [ -n "$ICON" -a ! -e server-icon.png ]; then
   fi
 fi
 
+# Set up log configuration
+LOGFILE="/data/log4j2.xml"
+if [ ! -e "$LOGFILE" ]; then
+  log "Creating log4j2.xml in ${LOGFILE}"
+  cp /tmp/log4j2.xml "$LOGFILE"
+else
+  log "log4j2.xml already created, skipping"
+fi
+JVM_OPTS="-Dlog4j.configurationFile=/data/log4j2.xml ${JVM_OPTS}"
+
 # Make sure files exist and are valid JSON (for pre-1.12 to 1.12 upgrades)
 log "Checking for JSON files."
 JSON_FILES=$(find . -maxdepth 1 -name '*.json')