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:description: Helidon Reactive Webserver Access Log
:keywords: helidon, webserver, access log

= WebServer Access Log

Access logging in Helidon is done by a dedicated module that can be
added to WebServer and configured.

Access logging is a Helidon WebServer `Service` and as such is executed
in the order it is registered with WebServer routing.
This implies that if you register it last and another `Service` or
`Handler` finishes the request, the service will not be invoked.


== Configuring Access Log in your code

Access log is configured in your code by registering it as a service with `Routing`

[source,java]
----
Routing.builder()
    .register(AccessLogSupport.create(config.get("server.access-log")))
    .get("/greet", myService)
----

The order of registration is significant - make sure `AccessLogSupport` is registered first (even before security, tracing etc.).

== Configuring Access Log in a configuration file

Access log can be configured as follows:

[source, yaml]
.Access Log configuration file
----
server:
  port: 8080
  access-log:
    format: "%h %l %u %t %r %s %b %{Referer}i"
----

All options shown above are also available programmatically when using builder.

== Configuration options

The following configuration options can be defined:

|===
|Config key     |Default value      |Builder method     |Description

|`enabled`      |`true`             |`enabled(boolean)`          |When this option is set to `false`, access logging will be disabled
|`logger-name`  |`io.helidon.webserver.AccessLog` |`loggerName(String)` |Name of the logger to use when writing log entries
|`format`       |`helidon`          |`helidonLogFormat()`, `commonLogFormat()`, `add(AccessLogEntry entry)` |Configuration of access log output,
                                                        when `helidon` is defined, the Helidon log format (see below) is used.
                                                        Can be configured to explicitly define log entries (see below as well)

|===

== Supported Log Formats

=== Supported Log Entries

The following log entries are supported in Helidon:

|===
|Config format  |Class (to use with builder)    |Description

|%h                 |`HostLogEntry`                 |IP address of the remote host
|%l                 |`UserIdLogEntry`               |Client identity, always undefined in Helidon
|%u                 |`UserLogEntry`                 |The username of logged-in user (when Security is used)
|%t                 |`TimestampLogEntry`            |The current timestamp
|%r                 |`RequestLineLogEntry`          |The request line (method, path and HTTP version)
|%s                 |`StatusLogEntry`               |The HTTP status returned to the client
|%b                 |`SizeLogEntry`                 |The response entity size (if available)
|%D                 |`TimeTakenLogEntry`            |The time taken in microseconds
|%T                 |`TimeTakenLogEntry`            |The time taken in seconds
|%{`header-name`}i  |`HeaderLogEntry`               |Value of a header (can have multiple such specification to write
                                                     multiple headers)
|===

Currently we only support the entries defined above, with NO support for free text.

=== Helidon Log Format
When format is set to `helidon`, the format used is:

`"%h %u %t %r %s %b %D"`

The entries logged:

1. IP Address
2. Username of a logged-in user
3. Timestamp
4. Request Line
5. HTTP Status code
6. Entity size
7. Time taken (microseconds)

Access log example:

----
192.168.0.104 - [18/Jun/2019:22:28:55 +0200] "GET /greet/test HTTP/1.1" 200 53
0:0:0:0:0:0:0:1 - [18/Jun/2019:22:29:00 +0200] "GET /metrics/vendor HTTP/1.1" 200 1658
0:0:0:0:0:0:0:1 jack [18/Jun/2019:22:29:07 +0200] "PUT /greet/greeting HTTP/1.1" 200 21
0:0:0:0:0:0:0:1 jill [18/Jun/2019:22:29:12 +0200] "PUT /greet/greeting HTTP/1.1" 403 0
0:0:0:0:0:0:0:1 - [18/Jun/2019:22:29:17 +0200] "PUT /greet/greeting HTTP/1.1" 401 0
----


=== Common Log Format
When format is set to `common`, the format used is:

`"%h %l %u %t %r %s %b"`

The entries logged:

1. IP Address
2. Client identity
3. Username of a logged-in user
4. Timestamp
5. Request Line
6. HTTP Status code
7. Entity size

Access log example:

----
192.168.0.104   - - [18/Jun/2019:22:28:55 +0200] "GET /greet/test HTTP/1.1" 200 53
0:0:0:0:0:0:0:1 - - [18/Jun/2019:22:29:00 +0200] "GET /metrics/vendor HTTP/1.1" 200 1658
0:0:0:0:0:0:0:1 - jack [18/Jun/2019:22:29:07 +0200] "PUT /greet/greeting HTTP/1.1" 200 21
0:0:0:0:0:0:0:1 - jill [18/Jun/2019:22:29:12 +0200] "PUT /greet/greeting HTTP/1.1" 403 0
0:0:0:0:0:0:0:1 - - [18/Jun/2019:22:29:17 +0200] "PUT /greet/greeting HTTP/1.1" 401 0
----

== Configuring Access Log with Java util logging

To support a separate file for Access log entries, Helidon provides a custom
log handler, that extends the `FileHandler`.

To log to a file `access.log` with appending records after restart, you can use the
 following configuration in `logging.properties`:

[source, properties]
.Logging configuration file
----
io.helidon.webserver.accesslog.AccessLogHandler.level=INFO
io.helidon.webserver.accesslog.AccessLogHandler.pattern=access.log
io.helidon.webserver.accesslog.AccessLogHandler.append=true

io.helidon.webserver.AccessLog.level=INFO
io.helidon.webserver.AccessLog.useParentHandlers=false
io.helidon.webserver.AccessLog.handlers=io.helidon.webserver.accesslog.AccessLogHandler
----