Add etcd proxy as sidecar to Cloud Foundry applications

You will know that etcd is a distributed, reliable key-value store. This buildpack does not install or run an etcd cluster, instead to runs an etcd proxy as a sidecar next to your application. Your application need only connect to localhost2379 and get the full benefits of connecting to a secure, highly-available, multi-node etcd cluster.

From etcd proxy docs:

The gRPC proxy is a stateless etcd reverse proxy operating at the gRPC layer (L7). The proxy is designed to reduce the total processing load on the core etcd cluster. For horizontal scalability, it coalesces watch and lease API requests. To protect the cluster against abusive clients, it caches key range requests.

The gRPC proxy supports multiple etcd server endpoints. When the proxy starts, it randomly picks one etcd server endpoint to use. This endpoint serves all requests until the proxy detects an endpoint failure. If the gRPC proxy detects an endpoint failure, it switches to a different endpoint, if available, to hide failures from its clients. Other retry policies, such as weighted round-robin, may be supported in the future.

The etcd proxy is distributed within the etcd binary, which is packaged and installed into your Cloud Foundry application using this supply buildpack.

You configure your Cloud Foundry application to both:

1. Use this supply buildpack, in addition to your application's primary buildpack.
2. Run etcd proxy start as a sidecar within your application containers.

Example usage

There is a sample application within fixtures/rubyapp that can be installed. To use sidecars we need the cf v3-xyz commands:

cf7 create-buildpack etcdproxy_buildpack etcdproxy_buildpack-*.zip 1
cf7 create-app app-using-etcd
cf7 apply-manifest -f fixtures/rubyapp/manifest.cfdev.yml
cf7 push app-using-etcd -p $PWD/fixtures/rubyapp -f $PWD/fixtures/rubyapp/manifest.cfdev.yml

During deployment staging of cf7 push you will see the latest etcd version being installed into the application droplet:

$ cf7 push
...
[STG/0] OUT -----> Etcdproxy Buildpack version 1.0.0
[STG/0] OUT -----> Supplying etcd
[STG/0] OUT        Using etcd version 3.3.13
[STG/0] OUT -----> Installing etcd 3.3.13
[STG/0] OUT        Copy [/tmp/buildpacks/3d4ba95f26291321f5c6633264c1c6bb/dependencies/02866fcde1388c50c101a96ed2d1cfdb/etcd-v3.3.13-linux-amd64.ta

The application container logs will show etcd proxy output with ETCDPROXY/0 prefix:

$ cf7 logs app-with-etcd
...
[APP/PROC/WEB/SIDECAR/ETCDPROXY/0] ERR | etcdmain: listening for grpc-proxy client requests on 127.0.0.1:2379

Your application only needs to connect to localhost:2379 or 127.0.0.1:2379 without any other configuration requirements.

Buildpack User Documentation

Building the Buildpack

To build this buildpack, run the following command from the buildpack's directory:

1. Source the .envrc file in the buildpack directory.

   source .envrc

   To simplify the process in the future, install direnv which will automatically source .envrc when you change directories.

2. Install buildpack-packager

   ./scripts/install_tools.sh

3. Build the buildpack

   buildpack-packager build -stack cflinuxfs3 -cached

4. Use in Cloud Foundry

   Upload the buildpack to your Cloud Foundry.

   cf7 create-buildpack etcdproxy_buildpack etcdproxy_buildpack-*.zip 1
   cf7 create-app app-using-etcd
   cf7 apply-manifest -f fixtures/rubyapp/manifest.cfdev.yml
   cf7 push app-using-etcd -p $PWD/fixtures/rubyapp -f $PWD/fixtures/rubyapp/manifest.cfdev.yml

   As buildpack that delivers a sidecar, you'll need an explicit manifest.yml that describes the startup of the sidecar. For example, running an app within CFDev, and proxying to an etcd server on your host machine (host.cfdev.sh:2379):

   applications:
   - name: app-using-etcd
     instances: 1
     memory: 128M
     disk_quota: 512M
     stack: cflinuxfs3
     buildpacks:
     - etcdproxy_buildpack
     - staticfile_buildpack
     sidecars:
     - name: etcdproxy
       process_types:
       - web
       command: etcd grpc-proxy start --endpoints=host.cfdev.sh:2379 --listen-addr=127.0.0.1:2379
     routes:
     - route: app-using-etcd.dev.cfdev.sh

Testing

Buildpacks use the Cutlass framework for running integration tests.

To test this buildpack, run the following command from the buildpack's directory:

1. Source the .envrc file in the buildpack directory.

   source .envrc

   To simplify the process in the future, install direnv which will automatically source .envrc when you change directories.

2. Run integration tests

   ./scripts/integration.sh

   More information can be found on Github cutlass.

Reporting Issues

Open an issue on this project