linkerd-tcp

linkerd-tcp

This directory contains a docker-compose environment that runs a demo that you can use to try out linkerd-tcp.

Startup

The docker-compose.yml file that's included in this directory is configured to run the demo. Start everything with:

$ docker-compose build && docker-compose up -d

That command will start linkerd-viz on port 3000 on your Docker host, which you can use to view the demo in action. Set the DOCKER_IP environment variable to your Docker IP (e.g. DOCKER_IP=localhost for Docker For Mac, or DOCKER_IP=$(docker-machine ip) for Docker Toolkit), and then open the dashboard with:

$ open http://$DOCKER_IP:3000 # on OS X

It will look like this:

The docker environment is also running all of the following containers:

• namerd: namerd is configured via the provided namerd.yml file, which defines a default namespace that can be used to route traffic using the io.l5d.fs namer in conjunction with the files in the disco directory.

• linkerd: linkerd is configured via the provided linkerd.yml, which specifies 1 HTTP router running on port 4140, routing HTTP traffic via namerd.

• linkerd-tcp: linkerd-tcp is configured via the provided linkerd-tcp.yml, which specifies 1 TCP proxy running on port 7474, routing redis traffic via namerd.

• redis: Two redis clusters are configured to run on port 6379. The default namerd namespace is setup to send all redis traffic to the first redis cluster, but that routing decision can be changed by modifying namerd's dtab.

• web service: The web service is composed of 10 instances of the HTTP web service defined in web.go. The web service responds to HTTP requests with the string "hello", caches its responses in redis. If the response is found in cache, it returns immediately. On cache miss, it sleeps for 300 milliseconds before returning.

• slow_cooker: Traffic to linkerd is generated using slow_cooker. slow_cooker is configured to send 500 requests per second to the linkerd HTTP router, which load balances the requests over all 10 instances of the web service.

• linkerd-viz: linkerd, linkerd-tcp, and redis expose metrics data in a format that can be read by Prometheus. Those metrics are collected by the linkerd-viz container and displayed on dashboards using Grafana. The linkerd-viz UI is running on port 3000.

Traffic shifting

Once the demo is up and running, you can shift traffic between the two redis clusters by updating the default routing rules that are stored in namerd. To do this, use the namerctl command line utility. Install it with:

$ go get -u github.com/linkerd/namerctl

namerctl uses namerd's HTTP API, which is running on port 4180 on your Docker host. Set the DOCKER_IP environment variable as described above, and then configure namerctl to talk to namerd by setting the NAMERCTL_BASE_URL environment variable:

$ export NAMERCTL_BASE_URL=http://$DOCKER_IP:4180

Fetch namerd's current routing configuration:

$ namerctl dtab get default
# version AAAAAAAAAAE=
/cluster    => /#/io.l5d.fs ;
/svc        => /cluster ;
/svc/redis  => /cluster/redis1 ;

You can see that the final dtab entry is routing all redis traffic to the first redis cluster. Use namerctl to route all traffic to the second cluster:

$ namerctl dtab get default | sed 's/redis1/redis2/' > default.dtab
$ namerctl dtab update default default.dtab
Updated default

The linkerd-viz dashboard will show traffic switching from redis1 to redis2.

Namerctl without a Go environment

Alternatively, if you do not have a working Go environment, you can run namerctl from a Docker container.

export NAMERCTL_BASE_URL=http://$DOCKER_IP:4180

# get dtab
docker run --network=host -e NAMERCTL_BASE_URL=$NAMERCTL_BASE_URL linkerd/namerctl:0.8.6 dtab get default

# edit dtab
docker run --network=host -e NAMERCTL_BASE_URL=$NAMERCTL_BASE_URL linkerd/namerctl:0.8.6 dtab get default | sed 's/redis1/redis2/' > default.dtab

# update dtab
docker run --network=host -e NAMERCTL_BASE_URL=$NAMERCTL_BASE_URL -v `pwd`:/dtab linkerd/namerctl:0.8.6 dtab update default /dtab/default.dtab

Troubleshooting

If you have any issues getting the demo up and running, pop into linkerd's Slack and we'll help you get it sorted out.

Thanks! 👋