CloudRover serves as configuration entry-point for instances running in the cloud. CloudRover provides an easy way to dynamically re-configure a running instance. Tools like Puppet and Chef serve a similar purpose, but those are based on a "pull" model, while CloudRover allows configuration to be "pushed" to an instance. That approach provides more transparency in regard to the state of a running instance.
CloudRover serves two distinct use-cases:
- Provides an external HTTP-based API to execute shell-scripts locally. Example: "Deploy war file to a Tomcat service running on that box/instance"
- Provides a key/value store that can serve as a lookup service for configuration information for locally installed apps. Example: "Get me the address for the system-wide message queue"
Some architectural decisions made:
- CloudRover stores configuration in memory only. All configuration has to be re-set after every reboot of an instance.
- For authentication and security purposes a CloudRover-ID has to be sent to the CloudRover for every write and execute operation. That ID is part of the URL. The ID has to be set every time either the CloudRover or the the instance gets restarted. The ID can only be set once.
- Shell-scripts get pulled down from a Git repository. The URL for the Git repository can only be set once.
- No ID is require to retrieve any of the values. Exceptions are ID and URL for the Git repository, those values can't be read/retrieved.
CloudRover is written in Erlang based on [webmachine] (https://github.com/basho/webmachine).
CloudRover was developed and tested using Erlang R14B03.
Build
git clone git://github.com/neuhausler/CloudRover.git
cd CloudRover
make
Run
Run in Erlang console mode
./start.sh
Set CloudRover ID
A CloudRover ID has to be set first via a PUT request. That ID will be used later as part of the URL. That ID can only be set once.
Example: Set ID of local CloudRover to A123B345:
curl -X PUT http://localhost:8000/base/key \
-H 'Content-Type: application/json' \
-d '{"accesskey":"A123B345"}'
Set Git repository
The CloudRover can execute scripts that are available via a Git repository. The URL for the Git repository can only be set once. The CloudRover ID defined in the previous step (A123B345) has to be part of the URL used to set the Git repository.
If the Git repository requires username/password those can be passed in via the URL: https://username:[email protected]/username/test.
Example: Set the URL for the Git repository to the test repository https://github.com/neuhausler/cloudrover_test_config.git
curl -X PUT http://localhost:8000/base/A123B345/gitsh \
-H 'Content-Type: application/json' \
-d '{"gitsh":"https://github.com/neuhausler/cloudrover_test_config.git"}'
Execute a shell command remotely
Shell commands can be executed via CloudRover. The CloudRover ID has to be part of the URL. Only shell scripts in the previously defined Git repository can be executed. CloudRover does a git clone/pull before every execution of a command. Shell scripts are "packaged" in folders.
Example: Execute ls_tmp.sh defined in the playground folder in the test Git repository
curl http://localhost:8000/base/A123B345/sh/playground/ls_tmp.sh
The output of a command gets returned as a JSON object: {"Output":"8 lrwxr-xr-x@ 1 root wheel 11 Aug 20 2011 /tmp -> private/tmp"}
Optional environment variables can be passed in via the URL as regular URL parameters.
Example: Execute ls.sh in the playground folder with $cdpath set to / (URL encoded: %2F)
curl http://localhost:8000/base/A123B345/sh/playground/ls.sh?cdpath=%2F
Set a configuration parameter
CloudRover serves as a generic Key/Value store. This can be used to store/exchange configuration information. The CloudRover ID defined at startup (A123B345) has to be used to set a value.
Example: Set the host for the message queue mq_hostname to mq.test.com and the port mq_portnumber of the queue to 5672
curl -X PUT http://localhost:8000/base/A123B345/dict/mq_hostname \
-H 'Content-Type: application/json' \
-d '{"value":"mq.test.com"}'
curl -X PUT http://localhost:8000/base/A123B345/dict/mq_portnumber \
-H 'Content-Type: application/json' \
-d '{"value":"5672"}'
Retrieve a configuration parameter
Configuration information stored in the previous step can be retrieved by local applications. No CloudRover ID is needed to retrieve information.
curl http://localhost:8000/base/get/dict/mq_hostname
curl http://localhost:8000/base/get/dict/mq_portnumber
The value gets returned as a JSON object: {"mq_hostname":"mq.test.com"} and {"mq_portnumber":"5672"}
CloudRover Configuration
The configuration for the CloudRover itself is stored in ./priv/cloudrover.conf and can be adjusted as needed.
{port, 8000}.
{log_dir, "priv/log/"}.
{work_dir, "priv/var/work/"}.
{pid_file, "priv/var/cloudrover.pid"}.