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 edge.deliveryservice.somecdn.net
. Traffic Router is comprised of four separate Maven modules:
- api - Provides a simple JSON interface into certain aspects of core and is deployed as a WAR to a Service (read: connector/listen port) within Tomcat which is separate from core
- 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
- 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
- rpm - A simple Maven project which gathers the artifacts from the prior three 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 >= 6.0
Traffic Router Project Tree Overview¶
traffic_control/traffic_traffic_router/
- base directory for Traffic Routerapi/
- Source code for Traffic Router API, which is built as its own deployable WAR file and communicates with Traffic Router Core using JMXsrc/main
- Main source directory for Traffic Router APIjava/
- Java source code for Traffic Router APIresources/
- Spring resources pulled in during an RPM buildwebapp/
- Java webapp resources
src/test
- Test source directory for Traffic Router APIjava/
- JUnit based unit tests for Traffic Router APIresources/
- Resources pulled in by unit tests
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 JMXsrc/main
- Main source directory for Traffic Router Coreetc/init.d
- Init script for Tomcatconf/
- 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 Coredb
- Files downloaded by unit testsjava/
- JUnit based unit tests for Traffic Router Coreresources/
- Configuration files used by unit 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
. - If you are not running Traffic Monitor locally (http://localhost:8080) from within Eclipse, edit the following parameter in core/src/test/resources/traffic_monitor.properties and point it to an instance, or instances of Traffic Monitor for your chosen CDN:
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 Jetty instance for Core from within Eclipse
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
Traffic Router Core should now be running; the HTTP routing interface is available on http://localhost:8081, while the DNS server and routing interface is available on localhost:1053 via TCP and UDP.
Test Cases¶
Unit tests can be executed using Maven by running mvn test
at the root of the traffic_router
project.