logback.xml.erb

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

  <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file><%= @log_file %></file>
    <encoder>
      <pattern>%-4relative [%thread] %-5level %logger{35} - %msg %n</pattern>
    </encoder>

    <rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
      <fileNamePattern><%= @log_archive_pattern %></fileNamePattern>
      <minIndex>1</minIndex>
      <maxIndex>10</maxIndex>
    </rollingPolicy>

    <triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
      <maxFileSize>10MB</maxFileSize>
    </triggeringPolicy>
  </appender>
  <% @log_levels.each do |key, level| -%>
  <logger name="<%= key %>" level="<%= level %>"/>
  <% end %>
  <root level="<%= @log_level %>">
    <appender-ref ref="FILE" />
  </root>
</configuration>