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
Traffic Router Project Tree Overview¶
traffic_control/traffic_traffic_router/
- base directory for Traffic Routerconnector/
- 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 JMXsrc/main
- Main source directory for Traffic Router Coreetc/init.d
- Init script for Tomcatconf/
- Minimum required configuration filesjava/
- Java source code for Traffic Router Coreopt/tomcat/conf
- Contains Tomcat configuration file(s) pulled in during an RPM buildresources/
- Resources pulled in during an RPM buildscripts/
- Scripts used by the RPM build processwebapp/
- Java webapp resources
src/test
- Test source directory for Traffic Router Coreconf/
- Minimal Configuration files that make it possible to run junit testsdb/
- Files downloaded by unit testsjava/
- JUnit based unit tests for Traffic Router Coreresources/
- Example data files used by junit testsvar/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:
- Clone the traffic_control repository using Git.
- Change directories into
traffic_control/traffic_router
. - Follow the instructions in “README.DNSSEC” for DNSSEC support.
- Set the environment variable TRAFFIC_MONITOR_HOSTS to be a semicolon delimited list of Traffic Monitors that can be accessed during integration tests
- 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
core/src/test/conf/traffic_ops.properties file holds the credentials for accessing Traffic Ops. - copy from core/src/main/conf
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://).
Import the existing git repo into Eclipse:
- File -> Import -> Git -> Projects from Git; Next
- Existing local repository; Next
- Add -> browse to find
traffic_control
; Open - Select
traffic_control
; Next - Ensure “Import existing projects” is selected, expand
traffic_control
, selecttraffic_router
; Next - Ensure
traffic_router_api
,traffic_router_connector
, andtraffic_router_core
are checked; Finish (this step can take several minutes to complete) - Ensure
traffic_router_api
,traffic_router_connector
, andtraffic_router_core
have been opened by Eclipse after importing
From the terminal, run
mvn clean verify
from thetraffic_router
directoryStart the embedded Tomcat instance for Core from within your IDE by following these steps:
In the package explorer, expand
traffic_router_core
Expand
src/test/java
Expand the package
com.comcast.cdn.traffic_control.traffic_router.core
Open and run
TrafficRouterStart.java
Note
If an error is displayed in the Console, run
mvn clean verify
from thetraffic_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 “Host: <Delivery Service URL>” http://localhost:8888/x
Test Cases¶
- Unit tests can be executed using Maven by running
mvn test
at the root of thetraffic_router
project. - Unit and Integration tests can be executed using Maven by running
mvn verify
at the root of thetraffic_router
project.
RPM Packaging¶
Running mvn package
on a Linux based distribution will trigger the build process to create the Traffic Router rpm.