🎈 Welcome to linkerd! 👋

linkerd is a transparent service mesh, designed to make modern applications safe and sane by transparently adding service discovery, load balancing, failure handling, instrumentation, and routing to all inter-service communication.

linkerd (pronouned "linker-DEE") acts as a transparent HTTP/gRPC/thrift/etc proxy, and can usually be dropped into existing applications with a minimum of configuration, regardles of what language they're written in. It works with many common protocols and service discovery backends, including scheduled environments like Mesos and Kubernetes.

linkerd is built on top of Netty and Finagle, a production-tested RPC framework used by high-traffic companies like Twitter, Pinterest, Tumblr, PagerDuty, and others.

Want to try it?

We distribute binaries which you can download from the linkerd releases page.

For instructions on how to configure and run linkerd, see the user documentation on linkerd.io.

Want to build it?

The rest of this document will help you build linkerd from source and how to contribute code.

This repo contains two main projects: linkerd itself and namerd, a service for centrally managing routing policy and fronting service discovery.

• linkerd
• namerd

Development quickstart

Boot linkerd

$ ./sbt linkerd-examples/http:run # build and run linkerd
$ open http://localhost:9990      # open linkerd's admin interface in a browser

More details at linkerd's quickstart

Boot namerd

$ ./sbt namerd-examples/basic:run # build and run namerd
$ open http://localhost:9991      # open namerd's admin interface in a browser
$ curl :4180/api/1/dtabs          # test namerd's http interface

More details at namerd's quickstart

Working in this repository

sbt is used to build and test linkerd. Developers should not use a system-installed version of sbt, and should instead use the ./sbt script, which ensures that a compatible version of sbt is available.

./sbt accepts commands on the command line, or if it is invoked with no arguments it loads an interactive sbt shell:

$ ./sbt
>

The sbt project consists of many sub-projects. To list all projects run:

> projects

These projects are configured in project/LinkerdBuild.scala, which may be edited to include additional sub-projects, build configurations, etc. project/Base.scala is used to augment sbt's api.

You may run commands, for instance, compile on the aggregate project, all, by invoking:

> compile

Commands may be scoped by project, as in:

> router-http/test

Or by configuration as in:

> e2e:test

or

> router-http/e2e:test

The inspect command helps describe how a command is configured:

> inspect tree examples/http:run
[info] examples/http:run = InputTask[Unit]
[info]   +-examples/http:configFile = examples/http.yaml
[info]   | +-examples/http:configuration = http
[info]   |
[info]   +-examples/http:runtimeConfiguration = minimal
[info]   +-*/*:settingsData = Task[sbt.Settings[sbt.Scope]]
[info]

Tests

There are several supported test configurations:

• test: pure unit tests that do not require system or network
• e2e: tests that compose multiple modules; may allocate random ephemeral ports and write temporary files
• integration: tests that rely on external services or programs that require external installation and/or configuration.

Both unit and end-to-end tests are run as part of our Continuous Integration setup.

Tests may be run with:

> test
...
[success] Total time: 14 s, completed Jan 29, 2016 4:24:16 PM

> e2e:test
...
[success] Total time: 8 s, completed Jan 29, 2016 4:25:18 PM

sbt also provides a testQuick command which is especially useful when actively editing code:

> ~testQuick

The validator project provides an integration test that operates on assembled artifacts. It may be run with:

> validator/validateAssembled

Writing tests

Test files for each of the above test configurations are stored in a per-configuration directory structure, e.g.:

$ ls -l router/http/src
e2e
main
test

Tests are written using the ScalaTest testing framework, and specifically the FunSuite mixin, which supports xUnit-like semantics. We avoid using mocking frameworks when testing our own code, as they tend to introduce as many problems as they solve. Tests may leverage the test-util project, which provides some helpers for writing tests against Finagle's asynchronous APIs.

Packaging

Building an executable

linkerd provides a plugin system so that features may be chosen at packaging time. To this end, there are multiple configurations for running and packaging linkerd executables.

The assembly plugin can be used to produce an executable containing all library dependencies. The linkerd subproject has several build configurations to support packaging:

> linkerd/assembly
[info] SHA-1: 5599e65540ebe6122da114be4a8b9a763475b789
[info] Packaging ...linkerd/target/scala-2.11/linkerd-0.0.10-SNAPSHOT-exec ...
[info] Done packaging.
[success] Total time: 14 s, completed Jan 29, 2016 4:29:40 PM

minimal build configuration

The 'minimal' sbt configuration, supporting only the http protocol and the io.l5d.fs namer, is useful for running linkerd during development. This configuration may be specified explicitly to scope build commands:

> linkerd/minimal:assembly
[info] Packaging ...linkerd/target/scala-2.11/linkerd-minimal-0.0.10-SNAPSHOT-exec ...
[info] Done packaging.
[success] Total time: 13 s, completed Jan 29, 2016 4:30:58 PM

Similarly, a namerd executable can be produced with the command:

> namerd/assembly

Releasing

Before releasing ensure that CHANGES.md is updated to include the version that you're trying to release.

By default, the -SNAPSHOT suffix is appended to the version number when building linkerd. In order to build a non-snapshot (i.e. releasable) version of linkerd, the build must occur from a release tag in git.

For example, in order to build the 0.0.10 release of linkerd:

1. Ensure that the head version is 0.0.10
2. git tag 0.0.10 && git push origin 0.0.10
3. ./sbt linkerd/assembly namerd/assembly will produce executables in linkerd/target/scala-2.11/linkerd-0.0.10-exec and namerd/target/scala-2.11/namerd-0.0.10-exec.

Docker

Each of these configurations may be used to build a docker image.

> ;linkerd/docker ;namerd/docker
...
[info] Tagging image 94ab0793addf with name: buoyantio/linkerd:0.0.10-SNAPSHOT

The produced image does not contain any configuration. It's expected that configuration is provided by another docker layer or volume. For example, if you have linkerd configuration in path/to/myapp/linkerd.yml, you could start linkerd in docker with the following command:

$ docker run -p 4140:4140 -p 9990:9990 -v /absolute/path/to/myapp:/myapp buoyantio/linkerd:0.0.10-SNAPSHOT /myapp/linkerd.yml

For local testing convenience, we supply a config that routes to a single backend on localhost:8080.

$ docker run -p 4140:4140 -p 9990:9990 -v /path/to/linkerd/linkerd/examples:/config buoyantio/linkerd:0.8.3-SNAPSHOT /config/static_namer.yaml

The list of image names may be changed with a command like:

> set imageNames in docker in (linkerd, Bundle) += ImageName("gcr.io/gce-project/linkerd:v"+version.value)
...
> show linkerd/bundle:docker::imageNames
[info] List(buoyantio/linkerd:0.0.10-SNAPSHOT, gcr.io/gce-project/linkerd:v0.0.10-SNAPSHOT)

DCOS

Namerd supports a DCOS-specific configuration. When used in conjunction with namerd's io.l5d.zk dtab storage, this configuration provides bootstrapping of the ZooKeeper pathPrefix, along with a default dtab.

Run locally

This executes only the namerd-dcos-bootstrap command, it does not boot namerd.

$ ./sbt "namerd/dcos:run-main io.buoyant.namerd.DcosBootstrap namerd/examples/zk.yaml"

Run assembly script locally

The assembly script executes two commands serially:

1. runs namerd-dcos-bootstrap
2. boots namerd

$ ./sbt namerd/dcos:assembly
$ namerd/target/scala-2.11/namerd-0.8.3-SNAPSHOT-dcos-exec namerd/examples/zk.yaml

Run assembly script in docker

$ ./sbt namerd/dcos:docker
$ docker run -p 2181:2181 -p 4180:4180 -v /path/to/repo:/myapp -w /myapp buoyantio/namerd:0.8.3-SNAPSHOT-dcos namerd/examples/zk.yaml

Contributing

See CONTRIBUTING.md for more details about how to contribute.

Style

We generally follow Effective Scala and the Scala Style Guide. When in doubt, we try to use Finagle's idioms.

License

Copyright 2016, Buoyant Inc. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use these files except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.