Logbook: HTTP request and response logging

Logbook is an extensible Java library to enable complete request and response logging for different client- and server-side technologies. It satisfies a special need by a) allowing web application developers to log any HTTP traffic that an application receives or sends b) in a way that makes it easy to persist and analyze it later. This can be useful for traditional log analysis, meeting audit requirements or investigating individual historic traffic issues.

Logbook is ready to use out of the box for most common setups. Even for uncommon applications and technologies, it should be simple to implement the necessary interfaces to connect a library/framework/etc. to it.

Features

• Logging: of HTTP requests and responses, including the body; partial logging (no body) for unauthorized requests
• Customization: of logging format, logging destination, and conditions that request to log
• Support: for Servlet containers, Apache’s HTTP client, and (via its elegant API) other frameworks
• Optional obfuscation of sensitive data
• Spring Boot Auto Configuration
• Sensible defaults

Dependencies

• Java 8
• Any build tool using Maven Central, or direct download
• Servlet Container (optional)
• Apache HTTP Client (optional)
• Spring Boot (optional)

Installation

Selectively add the following dependencies to your project:

<dependency>
    <groupId>org.zalando</groupId>
    <artifactId>logbook-core</artifactId>
    <version>${logbook.version}</version>
</dependency>
<dependency>
    <groupId>org.zalando</groupId>
    <artifactId>logbook-servlet</artifactId>
    <version>${logbook.version}</version>
</dependency>
<dependency>
    <groupId>org.zalando</groupId>
    <artifactId>logbook-httpclient</artifactId>
    <version>${logbook.version}</version>
</dependency>
<dependency>
    <groupId>org.zalando</groupId>
    <artifactId>logbook-spring-boot-starter</artifactId>
    <version>${logbook.version}</version>
</dependency>

Usage

All integrations require an instance of Logbook which holds all configuration and wires all necessary parts together. You can either create one using all the defaults:

Logbook logbook = Logbook.create();

or create a customized version using the LogbookBuilder:

Logbook logbook = Logbook.builder()
    .condition(new CustomCondition())
    .queryObfuscator(new CustomQueryObfuscator())
    .headerObfuscator(new CustomHeaderObfuscator())
    .bodyObfuscator(new CustomBodyObfuscator())
    .requestObfuscator(new CustomRequestObfuscator())
    .responseObfuscator(new CustomResponseObfuscator())
    .formatter(new CustomHttpLogFormatter())
    .writer(new CustomHttpLogWriter())
    .build();

Phases

Logbook works in several different phases:

1. Conditional,
2. Obfuscation,
3. Formatting and
4. Writing

Each phase is represented by one or more interfaces that can be used for customization. Every phase has a sensible default.

Conditional

Logging HTTP messages and including their bodies is a rather expensive task, so it makes a lot of sense to disable logging for certain requests. A common use case would be to ignore health check requests from a load balancer, or any request to management endpoints typically created by developers.

Defining a condition is as easy as writing a special Predicate that decides whether a request (and its corresponding response) should be logged or not. Alternatively you can use and combine predefined predicates:

Logbook logbook = Logbook.builder()
    .condition(exclude(
        requestTo("/health"),
        requestTo("/admin/**"),
        contentType("application/octet-stream"),
        header("X-Secret", newHashSet("1", "true")::contains)))
    .build();

Exclusion patterns, e.g. /admin/**, are loosely following Ant's style of path patterns without taking the the query string of the URL into consideration.

Obfuscation

The goal of Obfuscation is to prevent the logging of certain sensitive parts of HTTP requests and responses. This usually includes the Authorization header, but could also apply to certain plaintext query or form parameters — e.g. password.

Logbook supports different types of obfuscators:

Type	Operates on	Applies to	Default
QueryObfuscator	Query string	request	access_token
HeaderObfuscator	Header (single key-value pair)	both	Authorization
BodyObfuscator	Content-Type and body	both	n/a
RequestObfuscator	HttpRequest	request	n/a
ResponseObfuscator	HttpResponse	response	n/a

QueryObfuscator, HeaderObfuscator and BodyObfuscator are relatively high-level and should cover all needs in ~90% of all cases. For more complicated setups one should fallback to the low-level variants, i.e. RequestObfuscator and ResponseObfuscator (in conjunction with ObfuscatedHttpRequest and ObfuscatedHttpResponse).

You can configure obfuscators like this:

Logbook logbook = Logbook.builder()
    .queryObfuscator(accessToken())
    .queryObfuscator(obfuscate("password", "<secret>"))
    .headerObfuscator(authorization()) 
    .headerObfuscator(obfuscate("X-Secret"::equalsIgnoreCase, "<secret>"))
    .build();

You can configure as many obfuscators as you want - they will run consecutively.

Correlation

Logbook uses a correlation id to correlate requests and responses. This allows match-related requests and responses that would usually be located in different places in the log file.

Formatting

Formatting defines how requests and responses will be transformed to strings basically. Formatters do not specify where requests and responses are logged to — writers do that work.

Logbook comes with two different default formatters: HTTP and JSON.

HTTP

HTTP is the default formatting style, provided by the DefaultHttpLogFormatter. It is primarily designed to be used for local development and debugging, not for production use. This is because it’s not as readily machine-readable as JSON.

Request

Incoming Request: 2d66e4bc-9a0d-11e5-a84c-1f39510f0d6b
GET http://example.org/test HTTP/1.1
Accept: application/json
Host: localhost
Content-Type: text/plain

Hello world!

Response

Outgoing Response: 2d66e4bc-9a0d-11e5-a84c-1f39510f0d6b
HTTP/1.1 200
Content-Type: application/json

{"value":"Hello world!"}

JSON

JSON is an alternative formatting style, provided by the JsonHttpLogFormatter. Unlike HTTP, it is primarily designed for production use — parsers and log consumers can easily consume it.

Request

{
  "origin": "remote",
  "type": "request",
  "correlation": "2d66e4bc-9a0d-11e5-a84c-1f39510f0d6b",
  "protocol": "HTTP/1.1",
  "sender": "127.0.0.1",
  "method": "GET",
  "path": "http://example.org/test",
  "headers": {
    "Accept": ["application/json"],
    "Content-Type": ["text/plain"]
  },
  "body": "Hello world!"
}

Response

{
  "origin": "local",
  "type": "response",
  "correlation": "2d66e4bc-9a0d-11e5-a84c-1f39510f0d6b",
  "protocol": "HTTP/1.1",
  "status": 200,
  "headers": {
    "Content-Type": ["text/plain"]
  },
  "body": "Hello world!"
}

Note: Bodies of type application/json (and application/*+json) will be inlined into the resulting JSON tree. I.e., a JSON response body will not be escaped and represented as a string:

{
  "origin": "local",
  "type": "response",
  "correlation": "2d66e4bc-9a0d-11e5-a84c-1f39510f0d6b",
  "protocol": "HTTP/1.1",
  "status": 200,
  "headers": {
    "Content-Type": ["application/json"]
  },
  "body": {
    "greeting": "Hello, world!"
  }
}

Writing

Writing defines where formatted requests and responses are written to. Logbook comes with two implementations: Logger and Stream.

Logger

By default, requests and responses are logged with an slf4j logger that uses the org.zalando.logbook.Logbook category and the log level trace. This can be customized:

Logbook logbook = Logbook.builder()
    .writer(new DefaultHttpLogWriter(
        LoggerFactory.getLogger("http.wire-log"), 
        Level.DEBUG))
    .build();

Stream

An alternative implementation is to log requests and responses to a PrintStream, e.g. System.out or System.err. This is usually a bad choice for running in production, but can sometimes be useful for short-term local development and/or investigation.

Logbook logbook = Logbook.builder()
    .writer(new StreamHttpLogWriter(System.err))
    .build();

Servlet

You’ll have to register the LogbookFilter as a Filter in your filter chain — either in your web.xml file (please note that the xml approach will use all the defaults and is not configurable):

<filter>
    <filter-name>LogbookFilter</filter-name>
    <filter-class>org.zalando.logbook.LogbookFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>LogbookFilter</filter-name>
    <url-pattern>/*</url-pattern>
    <dispatcher>REQUEST</dispatcher>
    <dispatcher>ASYNC</dispatcher>
    <dispatcher>ERROR</dispatcher>
</filter-mapping>

or programmatically, via the ServletContext:

context.addFilter("LogbookFilter", new LogbookFilter(logbook))
    .addMappingForUrlPatterns(EnumSet.of(REQUEST, ASYNC, ERROR), true, "/*"); 

Security

Secure applications usually need a slightly different setup. You should generally avoid logging unauthorized requests, especially the body, because it quickly allows attackers to flood your logfile — and, consequently, your precious disk space. Assuming that your application handles authorization inside another filter, you have two choices:

• Don't log unauthorized requests
• Log unauthorized requests without the request body

You can easily achieve the former setup by placing the LogbookFilter after your security filter. The latter is a little bit more sophisticated. You’ll need two LogbookFilter instances — one before your security filter, and one after it:

context.addFilter("unauthorizedLogbookFilter", new LogbookFilter(logbook, Strategy.SECURITY))
    .addMappingForUrlPatterns(EnumSet.of(REQUEST, ASYNC, ERROR), true, "/*");
context.addFilter("securityFilter", new SecurityFilter())
    .addMappingForUrlPatterns(EnumSet.of(REQUEST), true, "/*");
context.addFilter("authorizedLogbookFilter", new LogbookFilter(logbook))
    .addMappingForUrlPatterns(EnumSet.of(REQUEST, ASYNC, ERROR), true, "/*");

The first logbook filter will log unauthorized requests only. The second filter will log authorized requests, as always.

HTTP Client

The logbook-httpclient module contains both an HttpRequestInterceptor and an HttpResponseInterceptor to use with the HttpClient:

CloseableHttpClient client = HttpClientBuilder.create()
        .addInterceptorFirst(new LogbookHttpRequestInterceptor(logbook))
        .addInterceptorFirst(new LogbookHttpResponseInterceptor())
        .build();

Since the LogbookHttpResponseInterceptor is incompatible with the HttpAsyncClient there is another way to log responses:

CloseableHttpAsyncClient client = HttpAsyncClientBuilder.create()
        .addInterceptorFirst(new LogbookHttpRequestInterceptor(logbook))
        .build();
        
// and then wrap your response consumer
client.execute(producer, new LogbookHttpAsyncResponseConsumer<>(consumer), callback)

Spring Boot Starter

Logbook comes with a convenient auto configuration for Spring Boot users. It sets up all of the following parts automatically with sensible defaults:

• Servlet filter
• Second Servlet filter for unauthorized requests (if Spring Security is detected)
• Header-/Parameter-/Body-Obfuscators
• HTTP-/JSON-style formatter
• Logging writer

Type	Name	Default
FilterRegistrationBean	unauthorizedLogbookFilter	Based on LogbookFilter
FilterRegistrationBean	authorizedLogbookFilter	Based on LogbookFilter
Logbook		Based on condition, obfuscators, formatter and writer
Predicate<RawHttpRequest>	requestCondition	No filter; is later combined with logbook.exclude
HeaderObfuscator		Based on logbook.obfuscate.headers
QueryObfuscator		Based on logbook.obfuscate.parameters
BodyObfuscator		BodyObfuscator.none()
RequestObfuscator		RequestObfuscator.none()
ResponseObfuscator		ResponseObfuscator.none()
HttpLogFormatter		JsonHttpLogFormatter
HttpLogWriter		DefaultHttpLogWriter

Multiple obfuscators are merged into one.

Configuration

The following tables show the available configuration:

Configuration	Description	Default
logbook.exclude	Exclude certain URLs	[]
logbook.filter.enabled	Enable the LogbookFilter(s)	true
logbook.format.style	Formatting style (http or json)	json
logbook.obfuscate.headers	List of header names that need obfuscation	[Authorization]
logbook.obfuscate.parameters	List of parameter names that need obfuscation	[access_token]
logbook.write.category	Changes the category of the DefaultHttpLogWriter	org.zalando.logbook.Logbook
logbook.write.level	Changes the level of the DefaultHttpLogWriter	TRACE

Example configuration

logbook:
    exclude:
        - /health
        - /admin/**
    filter.enabled: true
    format.style: http
    obfuscate:
        headers:
            - Authorization
            - X-Secret
        parameters:
            - access_token
            - password
    write:
        category: http.wire-log
        level: INFO

Known Issues

The Logbook servlet integration is incompatible with incoming POST requests that use application/x-www-form-urlencoded form parameters and use any of the HttpServletRequest.getParameter*(..) methods. See issue #94 for details.

Getting Help with Logbook

If you have questions, concerns, bug reports, etc., please file an issue in this repository's Issue Tracker.

Getting Involved/Contributing

To contribute, simply make a pull request and add a brief description (1-2 sentences) of your addition or change. For more details, check the contribution guidelines.

Credits and References

Grand Turk, a replica of a three-masted 6th rate frigate from Nelson's days - logbook and charts by JoJan is licensed under a Creative Commons (Attribution-Share Alike 3.0 Unported).