Traffic Router

Introduction

Traffic Router is a Java Tomcat application that routes clients to the closest available cache on the CDN using both HTTP and DNS. Cache availability is determined by Traffic Monitor; consequently Traffic Router polls Traffic Monitor for its configuration and cache health state information, and uses this data to make routing decisions. HTTP routing is performed by localizing the client based on the request’s source IP address (IPv4 or IPv6), and issues an HTTP 302 redirect to the nearest cache. HTTP routing utilizes consistent hashing on request URLs to optimize cache performance and request distribution. DNS routing is performed by localizing clients, resolvers in most cases, requesting A and AAAA records for a configurable name such as foo.deliveryservice.somecdn.net. Traffic Router is comprised of seven separate Maven modules:

  • shared - A reusable utility JAR for defining Delivery Service Certificates
  • configuration - A resuable JAR defining the ConfigurationListener interface
  • connector - A JAR that overrides Tomcat’s standard Http11Protocol Connector class and allows Traffic Router to delay opening listen sockets until it is in a state suitable for routing traffic
  • geolocation - Submodule for defining geolocation services
  • neustar - A Jar that provides a bean “neustarGeolocationService” that implements the GeolocationService interface defined in the geolocation maven submodule, which can optionally be added to the build of Traffic Router
  • core - Services DNS and HTTP requests, performs localization on routing requests, and is deployed as a WAR to a Service (read: connector/listen port) within Tomcat which is separate from api
  • build - A simple Maven project which gathers the artifacts from the modules and builds an RPM

Software Requirements

To work on Traffic Router you need a *nix (MacOS and Linux are most commonly used) environment that has the following installed:

  • Eclipse >= Kepler SR2 (or another Java IDE)
  • Maven >= 3.3.1
  • JDK >= 8.0
  • OpenSSL >= 1.0.2
  • APR (Apache Portable Runtime) >= 1.4.8-3
  • Tomcat Native >= 1.2.16
  • Not Tomcat - You do not need a Tomcat installation for development. An embedded version is launched for development testing instead.

Traffic Router Project Tree Overview

  • traffic_control/traffic_traffic_router/ - base directory for Traffic Router

    • connector/ - Source code for Traffic Router Connector;

      • src/main/java - Java source directory for Traffic Router Connector
    • core/ - Source code for Traffic Router Core, which is built as its own deployable WAR file and communicates with Traffic Router API using JMX

      • src/main - Main source directory for Traffic Router Core

        • lib/systemd/system/traffic_router.service - Unit script for launching the Traffic Router with Tomcat
        • conf/ - All of the required configuration files for running the traffic_router web application, including those needed for Tomcat
        • java/ - Java source code for Traffic Router Core
        • resources/ - Resources pulled in during an RPM build
        • scripts/ - Scripts used by the RPM build process
        • webapp/ - Java webapp resources
        • var/log/ - location of all the Traffic Router runtime logs
      • src/test - Test source directory for Traffic Router Core

        • conf/ - Minimal Configuration files that make it possible to run junit tests

        • db/ - Files downloaded by unit tests

        • java/ - JUnit based unit tests for Traffic Router Core

        • resources/ - Example data files used by junit tests

          • var/auto-zones - BIND formatted zone files generated by Traffic Router Core during unit testing

Java Formatting Conventions

None at this time. The codebase will eventually be formatted per Java standards.

Installing The Developer Environment

To install the Traffic Router Developer environment:

  1. Clone the traffic_control repository using Git.
  2. Change directories into traffic_control/traffic_router.
  3. Follow the instructions in “README.DNSSEC” for DNSSEC support.
  4. Set the environment variable TRAFFIC_MONITOR_HOSTS to be a semicolon delimited list of Traffic Monitors that can be accessed during integration tests OR install the traffic_monitor.properties file as described below.
  5. Additional configuration is set using the below files:
  • core/src/test/conf/dns.properties - copy from core/src/main/conf

  • core/src/test/conf/http.properties - copy from core/src/main/conf

  • core/src/test/conf/log4j.properties - copy from core/src/main/conf

  • core/src/test/conf/traffic_monitor.properties - copy from core/src/main/conf and then edit the ‘traffic_monitor.bootstrap.hosts’ property.

  • core/src/test/conf/traffic_ops.properties file holds the credentials for accessing Traffic Ops. - copy from core/src/main/conf and then edit the credentials as approriate for the Traffic Ops instance you will be using.

  • Default configuration values now reside in core/src/main/webapp/WEB-INF/applicationContext.xml

  • The above values may be overridden by creating and/or modifying the property files listed in core/src/main/resources/applicationProperties.xml

  • Pre-existing properties files are still honored by Traffic Router. For example traffic_monitor.properties:

    Parameter Value
    traffic_monitor.bootstrap.hosts FQDN and port of the Traffic Monitor instance(s), separated by semicolons as necessary (do not include http://).
  1. Import the existing git repo as projects into your IDE (Eclipse):

    1. File -> Import -> Git -> Projects from Git; Next
    2. Existing local repository; Next
    3. Add -> browse to find traffic_control; Open
    4. Select traffic_control; Next
    5. Ensure “Import existing projects” is selected, expand traffic_control, select traffic_router; Next
    6. Ensure traffic_router_api, traffic_router_connector, and traffic_router_core are checked; Finish (this step can take several minutes to complete)
    7. Ensure traffic_router_api, traffic_router_connector, and traffic_router_core have been opened by Eclipse after importing
  2. From the terminal or your IDE, run mvn clean verify from the traffic_router directory. This will run a series of integration tests and will temporarily start and embeded version of Traffic Router and a ‘fake’ simulated instance of Traffic Monitor.

  3. Start the embedded Tomcat instance for Core from within your IDE by following these steps:

    1. In the package explorer, expand traffic_router_core

    2. Expand src/test/java

    3. Expand the package com.comcast.cdn.traffic_control.traffic_router.core

    4. Open and run TrafficRouterStart.java

      Note

      If an error is displayed in the Console, run mvn clean verify from the traffic_router directory

9. Traffic Router Core should now be running; the Traffic Router API is available at http://localhost:3333, the HTTP routing interface is available on http://localhost:8888 and HTTPS is available on http://localhost:8443. The DNS server and routing interface is available on localhost:1053 via TCP and UDP.

Manual Testing

Look up the URL for your test ‘http’ Delivery Service in Traffic Ops and then:

curl -vs -H [Delivery Service FQDN] http://localhost:8888/x

or to test an ‘https’ enabled service:

curl -vs -k –resolve [Delivery Serice FQDN]:8443:127.0.0.1 https://[Delivery Service FQDN]:8443/x

Test Cases

  • Unit tests can be executed using Maven by running mvn test at the root of the traffic_router project.
  • Unit and Integration tests can be executed using Maven by running mvn verify at the root of the traffic_router project.

RPM Packaging

Running mvn package on a Linux based distribution will trigger the build process to create the Traffic Router rpm and the Traffic Router .war file, but will not run the integration tests, so it is a good way to update those artifacts quickly during development. But the prefered way to build the Traffic Router RPMs is to navigate to the root of the Traffic Control source tree and run:

./pkg -v traffic_router_build

This will create the traffic_router.rpm and the tomcat.rpm and copy them to the ./dist directory.