Document log file endpoint's support for using Range header

Closes gh-5062

Author: wilkinsona

spring-boot-actuator-docs/src/main/asciidoc/index.adoc

@@ -34,6 +34,19 @@ include::{generated}/logfile/http-request.adoc[]
 Example HTTP response:
 include::{generated}/logfile/http-response.adoc[]
 
+==== Partial content
+
+You can use the `Range` header to retrieve part of the log file's content.
+
+Example curl request:
+include::{generated}/partial-logfile/curl-request.adoc[]
+
+Example HTTP request:
+include::{generated}/partial-logfile/http-request.adoc[]
+
+Example HTTP response:
+include::{generated}/partial-logfile/http-response.adoc[]
+
 
 
 === /docs

spring-boot-actuator-docs/src/restdoc/java/org/springframework/boot/actuate/hypermedia/EndpointDocumentation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -40,6 +40,7 @@
 import org.springframework.boot.actuate.endpoint.mvc.MvcEndpoint;
 import org.springframework.boot.actuate.endpoint.mvc.MvcEndpoints;
 import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
 import org.springframework.restdocs.RestDocumentation;
 import org.springframework.test.annotation.DirtiesContext;
@@ -104,6 +105,15 @@ public void logfile() throws Exception {
 				.andExpect(status().isOk()).andDo(document("logfile"));
 	}
 
+	@Test
+	public void partialLogfile() throws Exception {
+		this.mockMvc
+				.perform(get("/logfile").accept(MediaType.TEXT_PLAIN)
+						.header(HttpHeaders.RANGE, "bytes=0-1024"))
+				.andExpect(status().isPartialContent())
+				.andDo(document("partial-logfile"));
+	}
+
 	@Test
 	public void endpoints() throws Exception {
 

spring-boot-actuator-docs/src/restdoc/resources/org/springframework/restdocs/templates/http-response.snippet

@@ -0,0 +1,8 @@
+[source,http,options="nowrap"]
+----
+HTTP/1.1 {{statusCode}} {{statusReason}}
+{{#headers}}
+{{name}}: {{value}}
+{{/headers}}
+{{responseBody}}
+----

spring-boot-docs/src/main/asciidoc/production-ready-features.adoc

@@ -118,7 +118,8 @@ unauthenticated connection or full message details when authenticated).
 
 |`logfile`
 |Returns the contents of the logfile (if `logging.file` or `logging.path` properties have
-been set). Only available via MVC.
+been set). Only available via MVC. Supports the use of the HTTP `Range` header to retrieve
+part of the log file's content.
 |true
 
 |`metrics`