Using logback 1.2.3 in Spring Boot 2.3.2. What I’m seeing is that upon startup, the file is created with size 0 and doesn’t flush. The default buffer size is 8k, no? Shouldn’t it flush every 8k? If I close my app, then the logfile is written (about 17k). Logback-spring.xml is below. This is on Windows 10 x64.

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE configuration>

<configuration>

<include resource="org/springframework/boot/logging/logback/base.xml" />

<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">

<file>${LOG_PATH}/${LOG_FILE}.log</file>

<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">

<fileNamePattern>${LOG_PATH}/${LOG_FILE}.%d{yyyy-MM-dd}.log</fileNamePattern>

<maxHistory>7</maxHistory>

</rollingPolicy>

<encoder>

<pattern>${FILE_LOG_PATTERN}</pattern>

</encoder>

</appender>

<root level="INFO">

<appender-ref ref="CONSOLE" />

<appender-ref ref="FILE" />

</root>

</configuration>