Writing an access log

Configuring logging framework
- logback
- log4j2
Customizing a log format
- Retrieving values from RequestLog
- Customizing timestamp format
Customizing an access log writer
Customizing an access logger

Configuring logging framework

To write an access log, you need to configure a logging framework first. The following configurations are simple examples of logback.xml and log4j2.xml respectively.

logback

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
      <pattern>%-4relative [%thread] %-5level %logger{35} - %msg%n</pattern>
    </encoder>
  </appender>

  <appender name="ACCESS" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>access.log</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
      <!-- daily rollover -->
      <fileNamePattern>access.%d{yyyy-MM-dd}-%i.log</fileNamePattern>
      <!-- each file should be at most 1GB, keep 30 days worth of history, but at most 30GB -->
      <maxFileSize>1GB</maxFileSize>
      <maxHistory>30</maxHistory>
      <totalSizeCap>30GB</totalSizeCap>
    </rollingPolicy>
    <encoder>
      <pattern>%msg%n</pattern>
    </encoder>
  </appender>

  <logger name="com.linecorp.armeria.logging.access" level="INFO" additivity="false">
    <appender-ref ref="ACCESS"/>
  </logger>

  <root level="DEBUG">
    <appender-ref ref="CONSOLE"/>
  </root>
</configuration>

log4j2

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Appenders>
    <Console name="CONSOLE" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
    <RollingFile name="ACCESS" fileName="access.log"
                 filePattern="access.%d{MM-dd-yyyy}-%i.log.gz">
      <PatternLayout>
        <Pattern>%m%n</Pattern>
      </PatternLayout>

      <Policies>
        <!-- daily rollover -->
        <TimeBasedTriggeringPolicy/>
        <!-- each file should be at most 1GB -->
        <SizeBasedTriggeringPolicy size="1GB"/>
      </Policies>
      <!-- keep 30 archives -->
      <DefaultRolloverStrategy max="30"/>
    </RollingFile>
  </Appenders>

  <Loggers>
    <Logger name="com.linecorp.armeria.logging.access" level="INFO" additivity="false">
      <AppenderRef ref="ACCESS"/>
    </Logger>
    <Root level="DEBUG">
      <AppenderRef ref="CONSOLE"/>
    </Root>
  </Loggers>
</Configuration>

Customizing a log format

Access logging is disabled by default. If you want to enable it, you need to specify an AccessLogWriter. You may use one of the pre-defined log formats.

import com.linecorp.armeria.server.ServerBuilder;
import com.linecorp.armeria.server.logging.AccessLogWriter;

ServerBuilder sb = Server.builder();
// Use NCSA common log format.
sb.accessLogWriter(AccessLogWriter.common(), true);
// Use NCSA combined log format.
sb.accessLogWriter(AccessLogWriter.combined(), true);
// Use your own log format.
sb.accessLogFormat("...log format...");
...

You can have different AccessLogWriters for VirtualHosts and Services.

ServerBuilder sb = Server.builder();
AccessLogWriter fallbackLogWriter = ...
sb.accessLogWriter(fallbackLogWriter);

sb.virtualHost("foo.com")
  .accessLogWriter(AccessLogWriter.combined(), true)
  .service((ctx, req) -> HttpResponse.of(OK)); // This service will log using the combined format.
  ...

sb.route()
  .get("/commonAccessLog")
  .accessLogWriter(AccessLogWriter.common(), true)
  .build((ctx, req) -> HttpResponse.of(OK)); // This service will log using the common format.

// This service will log using the fallbackLogWriter.
sb.service("/fallbackLogWriter", (ctx, req) -> HttpResponse.of(OK));

Pre-defined log formats are as follows.

Tokens for the log format are listed in the following table.

Tokens	Condition support	Description
`%A`	No	the local IP address
`%a`	No	the IP address of the client who initiated a request. Use `%{c}a` format string to get the remote IP address where the channel is connected to, which may yield a different value when there is an intermediary proxy server. This value relies on the `clientAddress()` and `remoteAddress()` methods of `ServiceRequestContext`, please refer to Getting an IP address of a client who initiated a request about how to configure the `ServerBuilder` to get the client address you interest.
`%h`	No	the remote hostname or IP address if DNS hostname lookup is not available
`%I`	No	the request ID. Use `%{short}I` format string to get the short form.
`%l`	No	the remote logname of the user (not supported yet, always write `-`)
`%u`	No	the name of the authenticated remote user (not supported yet, always write `-`)
`%t`	No	the date, time and time zone that the request was received, by default in `strftime` format %d/%b/%Y:%H:%M:%S %z. (for example, `10/Oct/2000:13:55:36 -0700`) Refer to Customizing timestamp format for more information.
`%r`	Yes	the request line from the client (for example, `GET /path h2`)
`%s`	No	the HTTP status code returned to the client
`%b`	Yes	the size of the object returned to the client, measured in bytes
`%{HEADER_NAME}i`	Yes	the value of the specified HTTP request header name
`%{HEADER_NAME}o`	Yes	the value of the specified HTTP response header name
`%{ATTRIBUTE_NAME}j`	Yes	the value of the specified attribute name
`%{REQUEST_LOG_NAME}L`	Yes	the value of the specified variable of the `RequestLog`. Refer to Retrieving values from RequestLog for more information.

Some tokens can have a condition of the response status code and the log message can be omitted with the condition.

Example of a condition	Description
`%200b`	Write the size of the object returned to the client only if the response code is `200`.
`%200,304{User-Agent}i`	Write `User-Agent` header value only if the response code is `200` or `304`.
`%!200,304{com.example.armeria.Attribute#KEY}j`	Write the value of the specified attribute only if the response code is neither `200` nor `304`.

Retrieving values from `RequestLog`

RequestLog holds information about the request, so a user may want to write these values to his or her access log file. To write them in a simple way, %{variable}L token is provided with the following supported variable:

Name	Description
`method`	the HTTP method value of the request
`path`	the absolute path part of the HTTP request URI
`query`	the query part of the HTTP request URI
`requestStartTimeMillis`	the time when the processing of the request started, in milliseconds since the epoch
`requestDurationMillis`	the duration that was taken to consume or produce the request completely, in milliseconds
`requestDurationNanos`	the duration that was taken to consume or produce the request completely, in nanoseconds
`requestLength`	the length of the request content
`requestCause`	the cause of request processing failure. The class name of the cause and the detail message of it will be contained if exists.
`requestContentPreview`	the preview of the request content
`responseStartTimeMillis`	the time when the processing of the response started, in milliseconds since the epoch
`responseDurationMillis`	the duration that was taken to consume or produce the response completely, in milliseconds
`responseDurationNanos`	the duration that was taken to consume or produce the response completely, in nanoseconds
`responseLength`	the length of the response content
`responseCause`	the cause of response processing failure. The class name of the cause and the detail message of it will be contained if exists.
`responseContentPreview`	the preview of the response content
`totalDurationMillis`	the amount of time taken since the request processing started and until the response processing ended, in milliseconds
`totalDurationNanos`	the amount of time taken since the request processing started and until the response processing ended, in nanoseconds
`sessionProtocol`	the session protocol of the request. e.g. `h1`, `h2`, `h1c` or `h2c`
`serializationFormat`	the serialization format of the request. e.g. `tbinary`, `ttext`, `tcompact`, `tjson` or `none`
`scheme`	the scheme value printed as `serializationFormat+sessionProtocol`
`host`	the host name of the request
`status`	the status code and its reason phrase of the response. e.g. `200 OK`
`statusCode`	the status code of the response. e.g. `200`

Customizing timestamp format

You can specify a new date/time format for the %t token with DateTimeFormatter. You can use one of the following formatters which is provided by JDK as a variable of the %t token, e.g. %{BASIC_ISO_DATE}t. If you want to use your own pattern, you can specify it as the variable, e.g. %{yyyy MM dd}t.

Formatter	Description	Example
`BASIC_ISO_DATE`	Basic ISO date	`20111203`
`ISO_LOCAL_DATE`	ISO Local Date	`2011-12-03`
`ISO_OFFSET_DATE`	ISO Date with offset	`2011-12-03+01:00`
`ISO_DATE`	ISO Date with or without offset	`2011-12-03+01:00`; `2011-12-03`
`ISO_LOCAL_TIME`	Time without offset	`10:15:30`
`ISO_OFFSET_TIME`	Time with offset	`10:15:30+01:00`
`ISO_TIME`	Time with or without offset	`10:15:30+01:00`; `10:15:30`
`ISO_LOCAL_DATE_TIME`	ISO Local Date and Time	`2011-12-03T10:15:30`
`ISO_OFFSET_DATE_TIME`	Date Time with Offset	`2011-12-03T10:15:30+01:00`
`ISO_ZONED_DATE_TIME`	Zoned Date Time	`2011-12-03T10:15:30+01:00[Europe/Paris]`
`ISO_DATE_TIME`	Date and time with ZoneId	`2011-12-03T10:15:30+01:00[Europe/Paris]`
`ISO_ORDINAL_DATE`	Year and day of year	`2012-337`
`ISO_WEEK_DATE`	Year and Week	`2012-W48-6`
`ISO_INSTANT`	Date and Time of an Instant	`2011-12-03T10:15:30Z`
`RFC_1123_DATE_TIME`	RFC 1123 / RFC 822	`Tue, 3 Jun 2008 11:05:30 GMT`

Customizing an access log writer

You can specify your own log writer which implements a Consumer of RequestLog.

ServerBuilder sb = Server.builder();
sb.accessLogWriter(requestLog -> {
    // Write your access log with the given RequestLog instance.
    ...
}, true);

Customizing an access logger

Armeria uses an SLF4J logger whose name is based on a reversed domain name of each virtual host by default, e.g.

com.linecorp.armeria.logging.access.com.example for *.example.com
com.linecorp.armeria.logging.access.com.linecorp for *.linecorp.com

Alternatively, you can specify your own mapper or logger for a VirtualHost, e.g.

ServerBuilder sb = Server.builder();

// Using the specific logger name.
sb.accessLogger("com.example.my.access.logs");
...

// Using your own logger.
Logger logger = LoggerFactory.getLogger("com.example2.my.access.logs");
sb.accessLogger(Logger);
...

// Using the mapper which sets an access logger with the given VirtualHost instance.
sb.accessLogger(virtualHost -> {
    // Return the logger.
    // Do not return null. Otherwise, it will raise an IllegalStateException.
    return LoggerFactory.getLogger("com.example.my.access.logs." + virtualHost.defaultHostname());
});
...

You can also specify your own logger for the specific VirtualHost. In this case, the mapper or logger you set for a specific VirtualHost will override the access logger set via ServerBuilder.accessLogger().

// Using the specific logger name.
sb.virtualHost("*.example.com")
  .accessLogger("com.example.my.access.logs")
  .and()
...

// Using your own logger.
Logger logger = LoggerFactory.getLogger("com.example2.my.access.logs");
sb.virtualHost("*.example2.com")
  .accessLogger(Logger)
  .and()
...

// Using the mapper which sets an access logger with the given VirtualHost instance.
sb.virtualHost("*.example3.com")
  .accessLogger(virtualHost -> {
    // Return the logger.
    // Do not return null. Otherwise, it will raise an IllegalStateException.
    return LoggerFactory.getLogger("com.example.my.access.logs." + virtualHost.defaultHostname());
  })
...