How to add HTTP Headers Logback Logstash - http-headers

Question

I read through the following documentation but cannot figure out what other configuration I need: https://github.com/logstash/logstash-logback-encoder#header-fields
My config file:
<include resource="org/springframework/boot/logging/logback/defaults.xml" />
<include resource="org/springframework/boot/logging/logback/console-appender.xml" />
<property name="LOG_FILE" value="${LOG_FILE:-${LOG_PATH:-${LOG_TEMP:-${java.io.tmpdir:-/tmp}}}/spring.log}"/>
<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
<encoder class="net.logstash.logback.encoder.LogstashEncoder">
<customFields>{"app_name":"${APP_NAME:-N/A}","app_version":"${APP_VERSION:-N/A}","hostname":"${HOST:-N/A}","environment":"${environment:-${ENVIRONMENT:-N/A}}"}</customFields>
<includeContext>false</includeContext>
<timeZone>UTC</timeZone>
</encoder>
<encoder class="net.logstash.logback.encoder.LogstashAccessEncoder">
<fieldNames>
<requestHeaders>request_headers</requestHeaders>
</fieldNames>
</encoder>
<file>${LOG_FILE}</file>
<rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
<fileNamePattern>${LOG_FILE_ROTATION:-${LOG_FILE}%d{yyyy-MM-dd}.%i}</fileNamePattern>
<maxHistory>${LOG_FILE_ROTATION_MAX_HISTORY:-1}</maxHistory>
<totalSizeCap>${LOG_FILE_ROTATION_TOTAL_SIZE_CAP:-3GB}</totalSizeCap>
<maxFileSize>${LOG_FILE_ROTATION_MAX_FILE_SIZE:-1GB}</maxFileSize>
</rollingPolicy>
</appender>
<root level="${LOG_LEVEL:-INFO}">
<appender-ref ref="CONSOLE" />
<appender-ref ref="FILE" />
</root>
</configuration>
Error:
java.lang.IllegalStateException: Logback configuration error detected:
ERROR in ch.qos.logback.core.joran.spi.Interpreter#19:29 - no applicable action for [requestHeaders], current ElementPath is [[configuration][appender][encoder][fieldNames][requestHeaders]]

Answer 1

The xml configuration file you provided appears to be for logback-classic (since it includes <root level=...).
Automatic logging of request headers by logstash-logback-encoder is only available for IAccessEvents logged via logback-access.
In other words, automatic logging of request headers is not available for ILoggingEvents logged via a Logger from logback-classic. However, you can manually include them when using logback-classic as described below.
Logging of request headers with logback-access
To log request headers for IAccessEvents logged via logback-access, follow the instructions for setting up logback-access for tomcat or jetty, and add the following to your logback-access.xml. (Note this is not the logback.xml file used by logback-classic)
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<configuration>
<appender name="console" class="ch.qos.logback.core.ConsoleAppender">
<encoder class="net.logstash.logback.encoder.LogstashAccessEncoder">
<fieldNames>
<requestHeaders>request_headers</requestHeaders>
</fieldNames>
</encoder>
</appender>
<appender-ref ref="console"/>
</configuration>
This configuration was tested using logstash-logback-encoder 5.3. Note that the xml element names are different in logstash-logback-encoder versions prior to 5.0, so ensure you are using 5.0+ with that configuration.
Logging of request headers with logback-classic
logstash-logback-encoder does not provide first-class support for logging request headers via logback-classic. However, you include them in a log event logged via a Logger by using event-specific custom fields.
For example, in a class that has access to the http request (such as a servlet filter), you could do something like this:
Map<String, String> httpHeadersMap = ...; // get http request headers as a map
LOGGER.info("request", StructuredArguments.entries(httpHeadersMap));
and configure a LogbackEncoder in your logback.xml like this:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<configuration>
<appender name="console" class="ch.qos.logback.core.ConsoleAppender">
<encoder class="net.logstash.logback.encoder.LogstashEncoder"/>
</appender>
<root level="info">
<appender-ref ref="console" />
</root>
</configuration>