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Walter is a tiny deployment pipeline template.



Walter automates the deployment process of applications or servers from configuration to software deployment.

Getting Started


  • Go 1.3 or greater
  • Mercurial 2.9 or greater

How to Build

You can build Walter with the following commands.

$ git clone
$ cd walter
$ ./build

How to contribute

We welcome any contributions through Github pull requests.
When you make changes such as new features and the add the tests, please run test before throw the pull request.
You can run test with the script.

$ sh

Configuration setting

Walter has one configuration file, which specifies a set of tasks needed to build or deploy target application or service.
More specifically, users specify the order of the tasks for the deployment. Each task is called as stage, and the flow is called pipeline in Walter.

Pipeline setting

The configuration format of Walter is Yaml. The yaml configuration file need to have one pipeline block, which has more
than one stage element.

The following is a sample configuration of Walter.

  - name: command_stage_1
    type: command
    command: echo "hello, world"
  - name: command_stage_2
    type: command
    command: echo "hello, world, command_stage_2"
  - name: command_stage_3
    type: command
    command: echo "hello, world, command_stage_3"

As we see, the pipeline block has three stages and the stage type is command, each of which run echo command and has the stage name
(such as command_stage_1). User can name arbitrary name of each stage. The commands are executed with the same order as the pipeline configuration.

Stage setting

Stage in pipeline has three elements, name, type and configurations. configuration elements are optional. The elements of configurations depend on the type.
For example command_stage type has command configuration, which specify the shell command run in the stage.
The following is the table on the type and the parameters.

Command stage

Command stage executes one command. Users specify Command stage adding command in type.

The following is the parameter of Command stage.

Configuration Optional meaning
command false shell command run in the stage
only_if true run specified command on when the condition written in only_if is satisfied
directory true the directory where walter runs the specified command

Shell script stage

Shell script stage executes specified shell script file. Users specify Shell script stage adding shell in type.

The following is the parameter of Shell script stage.

Configuration Optional meaning
file false shell script file run in the stage

Parallel stages

You can set child stages and run these stages in parallel like this.

  - name: parallel stages
      - name: parallel command 1
        type: command
        command: parallel command 1
      - name: parallel command 2
        type: command
        command: parallel command 2
      - name: parallel command 3
        type: command
        command: parallel command 3

In the above setting, parallel command 1, parallel command 2 and parallel command 3 are executed in parallel.

Import predefined stages

Walter provides the feature to import predefined stages in specified files.
To import stages to pipeline configuration file, we use require block and
add the list of file names into the block.

For example, the following example import the stages defined in conf/mystage.yml

    - conf/mystages.yml

  - call: mypackage::hello
  - call: mypackage::goodbye

In the above setting, the stages ("mypacakge::hello" and "mypackage::goodbye") which are defined in "mystage.yml" are specified.

The files specified in pipeline configuration file need to have two blocks namespace and stages.
In namespace, we add the package name, the package name is need to avoid collisions of the stage names in multiple required files.
The stages block contains the list of stage definitions. We can define the stages same as the stages in pipeline configurations.

For example, the following configuration is the content of conf/mystages.yml imported from the above pipeline configuration file.

namespace: mypackage

  - def:
      name: hello
      command: echo "May I help you majesty!"
  - def:
      name: goodbye
      command: echo "Goobye majesty."

As we see that stages hello and goodbye are defined in the file.

Cleanup pipeline

Walter configuraiton can have one cleanup block; cleanup is another pipeline which needs to be executed after a pipeline has either failed or passed.
In the cleanup block, we can add command or shell script stages. The below example create a log file in pipeline and then cleanup the log file in the cleaup steps.

  - name: start pipeline
    command: echo “pipeline” > log/log.txt
  - name: cleanup
    command:  rm log/*

Reporting function

Walter supports to submits the messages to messaging services.

Report configuration

To submit a message, users need to add a messenger block into the configuration file. The following is a sample of the yaml block with HipChat.

  type: hipchat2
  base_url: BASE_URL
  room_id: ROOM_ID
  token: TOKEN
  from: USER_NAME

To report the full output of stage execution to the specified messenger service added with the above setting,
users add report_full_output attribute with true into the stage they want to know the command outputs.

  - name: command_stage_1
    type: command
    command: echo "hello, world"
    report_full_output: true # If you put this option, messenger sends the command output "hello, world"
  - name: command_stage_2
    type: command
    command: echo "hello, world, command_stage_2"
    # By default, report_full_output is false

Report types

Walter supports HipChat API v1 and v2 as the messenger type.

Messenger Type meaning
hipchat HipChat (API v1)
hipchat2 HipChat (API v2)
slack Slack Incoming Webhook integration

Report configuration

To activate the report function, we need to specify the properties for messenger type. The needed properties are different in each messenger type.

hipchat and hipchat2

Property Name meaning
room_id Room name
token HipChat token
from Account name
base_url Base API URL (for private servers; hipchat2 only)


Property Name meaning
channel Channel name
username User name

Service coordination

Walter provides a coordination function to a project hosting service, GitHub. Specifically the service function provides two roles

  • Check if a new commit or pull requests from the repository
  • Run pipeline to the latest commit and pull requests when there are newer ones than the last update

Service configuration

To activate service coordination function, we add a "service" block to the Walter configuration file. "service" block contains several elements (type, token, repo, from, update).

  type: github
  token: ADD_YOUR_KEY

The following shows the description of each element.

Element description
type Service type (currently Walter supports github only)
token GitHub token
repo Repository name
from Account or organization name (if the repository is own by a organization)
update Update file which contains the result and time of the last execution (default .walter)
branch Branch name pattern (When this value is filled, Walter only checks the branches who name is matched with the filled regex pattern)

Embedding Environment Variables

Users add environment variables in Walter configuration files. The names of environment variables are expanted into the the values of environment variables.
Environment variables in the configuration files are valuable when we need to write the sensitive information such as
tokens of messenger service or passwords of a external systems.

The following is the format of embedding of the environment variables.


We write the envrionment variable into ENV_NAME. The following configuration file specify the GitHub Token by embedding the environment variable, GITHUB_TOKEN.

  type: github
  token: $GITHUB_TOKEN
  repo: my-service-repository
  from: service-group
  update: .walter

Reusing the results from stages

Walter stores the results of preceding stages. The stages can make use of the results of finished stages using the three special
variables (OUT, ERR, COMBINED and RESULT) in Walter configuration files.

  • __OUT - output flushed to standard output
  • __ERR - output flushed to standard error
  • __COMBINED - combined output of stdout and stderr
  • __RESULT - execution result (true or false)

The three variables are maps whose keys are stage names and the value are results of the stages. For example, we want the standard output
result of the stage named "stage1", we write __OUT["stage1"].

The following is a sample configuration with a specical value.

  - name: stage_1
    command: echo "hello world"
  - name: stage_2
    command: echo __OUT["stage_1"]

Walter with the above configuraiton outputs "hello world" twice, since the second stage (stage_2) flushes the standard output result of first stage (stage_1).

Wait running stages until the conditions are satisfied

Walter stage starts imidiately after the previous stage finish, but some stages need to wait for some action such as port is ready or file are created.
wait_for feature supports the actions which need to be ready before the stages begin.

wait_for is defined as a property of stage.

  - name: launch solr
    command: bin/solr start
  - name: post data to solr index
    command: bin/post -d ~/tmp/foobar.js
    wait_for: host=localhost port=8983 state=ready

The wait_for property takes the key value pairs. Key has sevaral variations. The value depends on the key type. The following table shows the supported key value pairs and the description.

Key Value (value type) Description
delay second (float) The second to wait after the previous stage finish
port port number (int) Port number
file file name (string) File to be created in the previous stages
host host (string) IP address or host name
state state of the other key (string) Four types of states are supported. The possible value is dependent to the other Keys.

State values

There are seveal state values and possible state values are depend on the other key.

State value Description
present / ready Specified port is ready or file is created.
absent / unready port is not active or file does not exist
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