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paramsync

Paramsync is a simple, straightforward CLI tool for synchronizing data from the filesystem to the AWS parameter store KV store and vice-versa.

Basic Usage

Run paramsync check to see what differences exist, and paramsync push to synchronize the changes from the filesystem to parameter store.

$ paramsync check
=====================================================================================
myapp-private
local:path/private => ssm:us-east-1:private/myapp
  Keys scanned: 37
No changes to make for this sync target.

=====================================================================================
myapp-config
local:path/config => ssm:us-east-1:config/myapp
  Keys scanned: 80

UPDATE config/myapp/prod/ip-allowlist.json
-------------------------------------------------------------------------------------
-["10.8.0.0/16"]
+["10.8.0.0/16","10.9.10.0/24"]
-------------------------------------------------------------------------------------

Keys to update: 1
~ config/myapp/prod/ip-allowlist.json

You can also limit your command to specific synchronization targets by using the --target flag:

$ paramsync push --target myapp-config
=====================================================================================
myapp-config
local:path/config => ssm:us-east-1:config/myapp
  Keys scanned: 80

UPDATE config/myapp/prod/ip-allowlist.json
-------------------------------------------------------------------------------------
-["10.8.0.0/16"]
+["10.8.0.0/16","10.9.10.0/24"]
-------------------------------------------------------------------------------------

Keys to update: 1
~ config/myapp/prod/ip-allowlist.json

Do you want to push these changes?
  Enter 'yes' to continue: yes

UPDATE config/myapp/prod/ip-allowlist.json   OK

Run paramsync --help for additional options and commands.

Pull Mode

Paramsync can also sync from parameter store to the local filesystem. This can be particularly useful for seeding a git repo with the current contents of a parameter store config.

Run paramsync check --pull to get a summary of changes, and paramsync pull to actually sync the changes to the local filesystem. Additional arguments such as --target <name> work in pull mode as well.

Configuration

Paramsync will automatically configure itself using the first paramsync.yml file it comes across when searching backwards through the directory tree from the current working directory. So, typically you may wish to place the config file in the root of your git repository or the base directory of your config file tree.

You can also specify a config file using the --config <filename> command line argument.

Configuration file structure

The configuration file is a Hash represented in YAML format with three possible top-level keys: paramsync, ssm, and sync. The paramsync section sets global defaults and app options. The ssm section specifies the roles to assume for aws. And the sync section lists the directories and ssm prefixes you wish to synchronize. Only the sync section is strictly required. An example paramsync.yml is below including explanatory comments:

# paramsync.yml

paramsync:
  # verbose - defaults to `false`
  #   Set this to `true` for more verbose output.
  verbose: false

  # chomp - defaults to `true`
  #   Automatically runs `chomp` on the strings read in from files to
  #   eliminate a single trailing newline character (commonly inserted
  #   by text editors). Set to `false` to disable this by default for
  #   all sync targets (it can be overridden on a per-target basis).
  chomp: true

  # delete - defaults to `false`
  #   Set this to `true` to make the default for all sync targets to
  #   delete any keys found in parameter store that do not have a corresponding
  #   file on disk. By default, extraneous remote keys will be ignored.
  #   If `verbose` is set to `true` the extraneous keys will be named
  #   in the output.
  delete: false

  # color - defaults to `true`
  #   Set this to `false` to disable colorized output (eg when running
  #   with an automated tool).
  color: true

ssm:
  accounts:
    account1:
      role: arn:aws:iam::123456789012:role/admin

sync:
  # sync is an array of hashes of sync target configurations
  #   Fields:
  #     name - The arbitrary friendly name of the sync target. Only
  #       required if you wish to target specific sync targets using
  #       the `--target` CLI flag.
  #     prefix - (required) The parameter store prefix to synchronize to.
  #     type - (default: "dir") The type of local file storage. Either
  #       'dir' to indicate a directory tree of files corresponding to
  #       parameter store keys; or 'file' to indicate a single YAML file with a
  #       map of relative key paths to values.
  #     region - (required) The aws region to synchronize to
  #     path - (required) The relative filesystem path to either the
  #       directory containing the files with content to synchronize
  #       to parameter store if this sync target has type=dir, or the local file
  #       containing a hash of remote keys if this sync target has
  #       type=file. This path is calculated relative to the directory
  #       containing the configuration file.
  #     account - (account) The account from the ssm block to use
  #     delete - Whether or not to delete remote keys that do not exist
  #       in the local filesystem. This inherits the setting from the
  #       `paramsync` section, or if not specified, defaults to `false`.
  #     chomp - Whether or not to chomp a single newline character off
  #       the contents of local files before synchronizing to parameter store.
  #       This inherits the setting from the `paramsync` section, or if
  #       not specified, defaults to `true`.
  #     exclude - An array of parameter store paths to exclude from the
  #       sync process. These exclusions will be noted in output if the
  #       verbose mode is in effect, otherwise they will be silently
  #       ignored. At this time there is no provision for specifying
  #       prefixes or patterns. Each key must be fully and explicitly
  #       specified.
  #     erb_enabled - Whether or not to run the local content through
  #       ERB parsing before attempting to sync to the remote. Defaults
  #       to `false`.
  - name: myapp-config
    prefix: config/myapp
    region: us-east-1
    path: path/config
    exclude:
      - config/myapp/beta.cowboy-yolo
      - config/myapp/prod.cowboy-yolo
    account: account1
  - name: myapp-private
    prefix: private/myapp
    type: dir
    region: us-east-1
    path: path/private
    account: account1
    delete: true
  - name: yourapp-config
    prefix: config/yourapp
    type: file
    region: us-east-1
    path: path/yourapp.yml
    delete: true
    erb_enabled: true

You can run paramsync config to get a summary of the defined configuration and to double-check config syntax.

File sync targets

When using type: file for a sync target (see example above), the local path should be a YAML (or JSON) file containing a hash of relative key paths to the contents of those keys. So for example, given this configuration:

sync:
  - name: config
    prefix: config/yourapp
    type: file
    region: us-east-1
    path: yourapp.yml

If the file yourapp.yml has the following content:

---
prod/dbname: yourapp
prod/message: |
  Hello, world. This is a multiline message.
  Thanks.
prod/app/config.json: |
  {
    "port": 8080,
    "enabled": true
  }

Then paramsync push will attempt to create and/or update the following keys with the corresponding content from yourapp.yml:

Key Value
config/yourapp/prod/dbname yourapp
config/yourapp/prod/message Hello, world. This is a multiline message.\nThanks.
config/yourapp/prod/app/config.json {\n "port": 8080,\n "enabled": true\n}

In addition to specifying the entire relative path in each key, you may also reference paths via your file's YAML structure directly. For example:

---
prod:
  redis:
    port: 6380
    host: redis.example.com

When pushed, this document will create and/or update the following keys:

Key Value
config/yourapp/prod/redis/port 6380
config/yourapp/prod/redis/host redis.example.com

You may mix and match relative paths and document hierarchy to build paths as you would like. And you may also use the special key _ to embed a value for a particular prefix while also nesting values underneath it. For example, given this local file target content:

---
prod/postgres:
  host: db.myproject.example.com
  port: 10001

prod:
  redis:
    _: Embedded Value
    port: 6380

prod/redis/host: cache.myproject.example.com

This file target content would correspond to the following values, when pushed:

Key Value
config/yourapp/prod/postgres/host db.myproject.example.com
config/yourapp/prod/postgres/port 10001
config/yourapp/prod/redis Embedded Value
config/yourapp/prod/redis/port 6380
config/yourapp/prod/redis/host cache.myproject.example.com

A paramsync pull operation against a file type target will work in reverse, and pull values from any keys under config/yourapp/ into the file yourapp.yml, overwriting whatever values are there.

NOTE: Values in local file targets are converted to strings before comparing with or uploading to the parameter store. However, because YAML parsing converts some values (such as yes or no) to boolean types, the effective value of a key with a value of a bare yes will be true when converted to a string. If you need the actual values yes or no, use quotes around the value to force the YAML parser to interpret it as a string.

IMPORTANT NOTES ABOUT PULL MODE WITH FILE TARGETS

Against a file target, the structure of the local file can vary in a number of ways while still producing the same remote structure. Thus, in pull mode, Paramsync must necessarily choose one particular rendering format, and will not be able to retain the exact structure of the local file if you alternate push and pull operations.

Specifically, the following caveats are important to note, when pulling a target to a local file:

  • The local file will be written out as YAML, even if it was originally provided locally as a JSON file, and even if the extension is .json.

  • Any existing comments in the local file will be lost.

  • The document structure will be that of a flat hash will fully-specified relative paths as the keys.

Future versions of Paramsync may provide options to modify the behavior for pull operations on a per-target basis. Pull requests are always welcome.

Dynamic configuration

The configuration file will be rendered through ERB before being parsed as YAML. This can be useful for avoiding repetitive configuration across multiple prefixes or regions, eg:

sync:
<% %w( us-east-1 us-west-2 ).each do |region| %>
  - name: <%= dc %>:myapp-private
    prefix: private/myapp
    region: <%= region %>
    path: path/<%= region %>/private
    delete: true
<% end %>

It's a good idea to sanity-check your ERB by running paramsync config after making any changes.

Dynamic content

You can also choose to enable ERB parsing for local content as well, by setting erb_enabled: true on any sync targets you wish to populate in this way.

Environment configuration

Paramsync may be partially configured using environment variables:

  • PARAMSYNC_VERBOSE - set this variable to any value to enable verbose mode

Contributing

I'm happy to accept suggestions, bug reports, and pull requests through Github.

License

This software is public domain. No rights are reserved. See LICENSE for more information.

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