This repository contains the code for the Droplet Execution Agent (DEA) and related components.
The DEA itself is written in Ruby and takes care of managing an application instance's lifecycle. It can be instructed by the Cloud Controller to start and stop application instances. It keeps track of all started instances, and periodically broadcasts messages about their state over NATS (meant to be picked up by the Health Manager).
The advantages of this generation of the DEA over the previous (and first) generation DEA is that is more modular and has better test coverage. A breaking change between the two is that this version of the DEA depends on Warden to run application instances.
The directory server is written in Go and can be found in the
directory. It is a replacement for the older directory server that was
embedded in the DEA itself.
Requests for directories/files are handled by the DEA, which responds with a HTTP redirect to a URL that hits the directory server directly. The URL is signed by the DEA, and the directory server checks the validity of the URL with the DEA before serving it.
You can run the dea executable at the command line by passing the path to a YAML configuration file:
The following is a partial list of the keys that are read from the YAML file:
logging- a Steno configuration
nats_servers- an array of URIs of the form
nats://host:portthat the DEA will use to connect to NATS.
warden_socket- the path to a unix domain socket that the DEA will use to communicate to a warden server.
instance.nproc_limit- sets the system ulimit for the number of processes within an application container
Running the DEA in the provided Vagrant VM
When contributing to DEA it is useful to run it as a standalone component.
In the following examples, we assume that you have cloned the
cf-release repository into
If you use a different path, you need to adjust the path in the DEA
to point to the correct location of
cf-release, otherwise you will most likely get this error when you try
to create the Vagrant VM:
vm: * The host path of the shared folder is missing: ~/workspace/cf-release
In this case, simply edit the
Vagrantfile to insert the correct path and retry creating the VM.
If you are able to bring up the VM, but the tests terminate quickly with this error message:
bash: /var/cf-release/src/dea-hm-workspace/src/dea_next/bin/start_warden_and_run_specs.sh: No such file or directory
then either the repository is incomplete/corrupted, or the directory mounted simply does not actually point to
the cloned repository. Check that the location into which you've cloned
cf-release matches the source path
for the mount in the
Vagrantfile, remove the existing VM with
vagrant destroy (be sure to run this from the
dea_next directory so that you do not accidentally delete other VMs you may have running), and then retry
VM creation and test execution.
The DEA integration tests run against real Warden, directory, and NATS servers, so they must be run
in a Vagrant VM. The
bin directory contains a helper script that runs the entire DEA test suite:
bash # Checkout the required repos mkdir ~/workspace cd ~/workspace git clone https://github.com/cloudfoundry/cf-release cd cf-release scripts/update bosh sync blobs # required to download rootfs blob cd src/dea-hm-workspace git checkout master git submodule update --init --recursive cd src/dea_next; git checkout master # Verify that Vagrant version is at least 1.5 vagrant --version # Ensure the guest additions plugin is installed vagrant plugin install vagrant-vbguest # Run test suite in Vagrant vm bin/run_specs_in_vm.sh
This will stand up the test virtual machine (if it is not already running) and run both the unit and integration suites. Note that the integration tests stage and run real applications, which requires an internet connection. They take 5-10 minutes to run, depending on your connection speed.
To run tests individually, there is a bit of setup:
#start vagrant vagrant up #shell into the VM vagrant ssh #create rootfs mkdir -p /tmp/warden/rootfs sudo tar -xvf /var/cf-release/.blobs/`basename $(readlink /var/cf-release/blobs/rootfs/*)` -C /tmp/warden/rootfs > /dev/null #start warden cd /var/cf-release/src/warden/warden sudo bundle install bundle exec rake setup:bin sudo bundle exec rake warden:start[config/linux.yml] &> /tmp/warden.log & # start the DEA's dependencies cd /var/cf-release/src/dea_next export GOPATH=$PWD/go go get github.com/nats-io/gnatsd sudo bundle install sudo bundle exec foreman start &> /tmp/foreman.log & #To run the tests (unit or integration - these must be run separately if run as suites): bundle install bundle exec rspec spec/unit bundle exec rspec spec/integration
To watch the internal NATS traffic while the tests run, do this in another ssh session:
nats-sub ">" -s nats://localhost:4222
Testing the directory server
Running the dea unit and integration tests via the
will also run the directory server tests, but if you want to run tests against just the directory
server, you can do the following once you have checked out the repository (replace
$DEA_REPO_ROOT with the location of the
dea_ng repo - in the above examples, it is
cd $DEA_REPO_ROOT export GOPATH=$PWD/go go test -i -race directoryserver go test -v -race directoryserver
See staging.rb for staging flow.
staging.advertise: Stagers (now DEA's) broadcast their capacity/capability
staging.locate: Stagers respond to any message on this subject with a
staging.advertisemessage (CC uses this to bootstrap)
staging.<uuid>.start: Stagers respond to requests on this subject to stage apps
For details about how to use and update the Warden rootfs, see the stacks documentation.
The DEA's logging is handled by Steno. The DEA can be configured to log to a file, a syslog server or both. If neither is provided, it will log to its stdout.
The following log levels exist, shown with an example of what they are used for:
error- DEA failed to download builpack cache, cannot create PID file
warn- DEA failed to destroy a warden container, DEA received invalid JSON message over NATS
info- DEA is shutting down, DEA received a request to stage/run an app, but didn't have the resources
debug2- DEA received request for instance information, but was not running the specified app
debug- DEA saved a snapshot, downloaded a droplet
- droplet.* - logging relevant to an app's instance
- staging.* - logging relevant to the staging of an app's bits
- dea.* - component-level logging for the DEA itself
Please read the contributors' guide