UKHomeOffice / dropwizard-smart-logging-bundle

Prepend a configured header to log messages in Dropwizard. Useful for identifying API users.

Dropwizard Smart Logging Bundle

Changelog

• v0.9.0: Update to java 17, dropwizard 4.0.0, junit 5
• v0.8.0: Dependency updates including dropwizard 2.0.28 and bring in dependency check and spotbugs plugins
• v0.7.0: Update to dropwizard 2.0.20 and replace deprecated io.dropwizard.Bundle interface
• v0.6.0: Update to dropwizard 1.3.13 and to be a java 11 project
• v0.5.0: Update dropwizard to 1.1.1
• v0.4.9: Considering only GET requests for healthcheck URLs
• v0.4.8: Configurable healthcheck URLs
• v0.4.6: Not swallowing root cause of exception

Why

APIs are great. Microservices are great. But how do we keep track of a user who uses multiple APIs throughout a session? One approach is to add an additional value to each request i.e. user_id or session_id. This forces every API call to have an additional id attached to it (if available) and somewhere in the code we need to assign this to a log message.

Wouldn't it be easier to let an API client send identifiable information to the host via a header?

It would also be nice to be able to configure some extra fields to appear in every log message.

How

Add the corresponding configuration to your config file (MyServiceConfiguration in this example) and implement interface

    public class MyServiceConfiguration extends Configuration implements PrependLogConfiguration
    
    @JsonProperty
    private SmartLogging smartLogging;

Specify what header and any extra fields you want to log in your requests by adding this to your configuration:

smartLogging:
    useHeader: X-REQ-ID
    extraFields:
      someExtraKey: someExtraValue
    
    requestLoggingFilter:
      excluded: 
        - "^/healthcheck$"

This bundle can be added to a dropwizard app using:

    @Override
    public void initialize(Bootstrap<MyServiceConfiguration> bootstrap) {
        bootstrap.addBundle(new PrependLogBundle());
    }

Clearing MDC on each request

This is important to avoid MDC context leaking through request threads.

    @Override
    public void initialize(Bootstrap<MyServiceConfiguration> bootstrap) {
        bootstrap.addBundle(new MdcClearingBundle());
    }

Json logging

This bundle now includes (as of version 0.4.3) a json logging encoder which produces logs formatted for logstash. To use simply define a json appender in your dropwizard config file as follows.

Add your new log format to your chosen appender

- 
    type: json
    appname: my-name
    apphostname: localhost
    appsecurityzone: dap
    apptype: dropwizard
    appenvironment: dev
    threshold: DEBUG
    currentLogFilename: ./logs/rest-dap-application-store.log
    archivedLogFilenamePattern: ./logs/rest-dap-application-store-%d.log.gz
    archivedFileCount: 5

Security

Be careful of what you log, make sure you validate headers to ensure your logs don't become a potential attack vector.