A hierarchical config using yaml in Python.
Latest version is: 0.15.2
A python module which allows you to merge hierarchical config files using YAML syntax. It offers deep merge, variable interpolation and secrets retrieval from secrets managers.
It is ideal if you want to structure your hierarchy in such a way that you avoid duplication. You can define a structure for your configuration using a hierarchy such environment/project/cluster/app. It is up to you what layers you want to use in this hierarchy. The tool will read all yaml files starting from the root (where default values would be) all the way to the leaf (where most specific values would be, which will take precedence).
Idea came from puppet's hiera.
pip install himldocker run ghcr.io/adobe/himl:latest himl-config-merger --helpSee all docker tags at: https://github.com/adobe/himl/pkgs/container/himl/versions
git clone https://github.com/adobe/himl
cd himl
sudo python install -e .
This will merge simple/default.yaml with simple/production/env.yaml
from himl import ConfigProcessor
config_processor = ConfigProcessor()
path = "examples/simple/production"
filters = () # can choose to output only specific keys
exclude_keys = () # can choose to remove specific keys
output_format = "yaml" # yaml/json
config_processor.process(path=path, filters=filters, exclude_keys=exclude_keys,
output_format=output_format, print_data=True)The above example will merge simple/default.yaml with simple/production/env.yaml:
$ tree examples/simple
examples/simple
├── default.yaml
└── production
└── env.yaml
The example also showcases deep merging of lists and maps.
examples/simple/default.yaml
---
env: default
deep:
key1: v1
key2: v2
deep_list:
- item1
- item2examples/simple/production/env.yaml
---
env: prod
deep:
key3: v3
deep_list:
- item3Result:
env: prod
deep:
key1: v1
key2: v2
key3: v3
deep_list:
- item1
- item2
- item3A cli tool called himl is automatically installed via pip. You can use it to parse a tree of yamls and it will either output the combined configuration at standard output or write it to a file.
usage: himl [-h] [--output-file OUTPUT_FILE] [--format OUTPUT_FORMAT]
[--filter FILTER] [--exclude EXCLUDE]
[--skip-interpolation-validation]
[--skip-interpolation-resolving] [--enclosing-key ENCLOSING_KEY]
[--cwd CWD]
[--list-merge-strategy {append,override,prepend,append_unique}]
pathhiml examples/complex/env=dev/region=us-east-1/cluster=cluster2Based on the configuration tree from the examples/complex folder, the output of the above command will be the following:
cluster:
description: 'This is cluster: cluster2. It is using c3.2xlarge instance type.'
name: cluster2
node_type: c3.2xlarge
region:
location: us-east-1
env: dev
Where the examples folder looks something like this:
$ tree examples/complex
examples/complex
├── default.yaml
├── env=dev
│ ├── env.yaml
│ ├── region=us-east-1
│ │ ├── cluster=cluster1
│ │ │ └── cluster.yaml
│ │ ├── cluster=cluster2
│ │ │ └── cluster.yaml
│ │ └── region.yaml
│ └── region=us-west-2
│ ├── cluster=cluster1
│ │ └── cluster.yaml
│ └── region.yaml
└── env=prod
├── env.yaml
└── region=eu-west-2
├── cluster=ireland1
│ └── cluster.yaml
└── region.yaml
In order to avoid repetition, we wanted to make it possible to define a value once and reuse it in other parts of the yaml config. Unlike yaml anchors, these interpolations work across multiple files.
data/default.yaml:
allowed_roles:
- "arn:aws:iam::{{account.id}}:role/myrole"data/dev/env.yaml:
account:
id: "123456"
projects:
webapp1:
tagging:
Owner: "Web Service Team"
Environment: "dev"
CostCenter: "123"
data-store:
Owner: "Backend Team"
Environment: "dev"
CostCenter: "455"
# this will copy the whole projects.webapp1.tagging dict to this key
tagging: "{{projects.webapp1.tagging}}"
# or even a double interpolation
tagging: "{{projects.{{project.name}}.tagging}}"It's possible to have the same key (eg. a dict/list) in multiple files and combine them using a deep merge. See an example here.
passphrase: "{{ssm.path(/key/coming/from/aws/secrets/store/manager).aws_profile(myprofile)}}"my_value: "{{s3.bucket(my-bucket).path(path/to/file.txt).base64encode(true).aws_profile(myprofile)}}"Use vault cli to authenticate, fallback method via LDAP.
Retrieve only one key value from a secret, the path tail is used as key:
my_value: "{{vault.key(/path/from/vault/key)}}"Retrieve all key/value pairs from a vault path:
my_dict: "{{vault.path(/path/from/vault)}}"Generate a token for a policy:
my_token: "{{vault.token_policy(my_vault_policy)}}"Merge with Terraform remote state
### Terraform remote states ###
remote_states:
- name: cluster_composition
type: terraform
aws_profile: "my_aws_profile"
s3_bucket: "my_terraform_bucket"
s3_key: "mycluster.tfstate"
endpoint: "{{outputs.cluster_composition.output.value.redis_endpoint}}"kubeconfig_location: "{{env(KUBECONFIG)}}"The himl-config-merger script, contains logic of merging a hierarchical config directory and creating the end result YAML files.
himl-config-merger examples/complex --output-dir merged_output --levels env region cluster --leaf-directories clusterINFO:__main__:Found input config directory: examples/complex/env=prod/region=eu-west-2/cluster=ireland1
INFO:__main__:Storing generated config to: merged_output/prod/eu-west-2/ireland1.yaml
INFO:__main__:Found input config directory: examples/complex/env=dev/region=us-west-2/cluster=cluster1
INFO:__main__:Storing generated config to: merged_output/dev/us-west-2/cluster1.yaml
INFO:__main__:Found input config directory: examples/complex/env=dev/region=us-east-1/cluster=cluster1
INFO:__main__:Storing generated config to: merged_output/dev/us-east-1/cluster1.yaml
INFO:__main__:Found input config directory: examples/complex/env=dev/region=us-east-1/cluster=cluster2
INFO:__main__:Storing generated config to: merged_output/dev/us-east-1/cluster2.yaml
Input example:
> tree examples/complex
examples/complex
├── default.yaml
├── env=dev
│ ├── env.yaml
│ ├── region=us-east-1
│ │ ├── cluster=cluster1
│ │ │ └── cluster.yaml
│ │ ├── cluster=cluster2
│ │ │ └── cluster.yaml
│ │ └── region.yaml
│ └── region=us-west-2
│ ├── cluster=cluster1
│ │ └── cluster.yaml
│ └── region.yaml
└── env=prod
├── env.yaml
└── region=eu-west-2
├── cluster=ireland1
│ └── cluster.yaml
└── region.yaml
Output:
merged_output
├── dev
│ ├── us-east-1
│ │ ├── cluster1.yaml
│ │ └── cluster2.yaml
│ └── us-west-2
│ └── cluster1.yaml
└── prod
└── eu-west-2
└── ireland1.yaml
Leveraging HIML, the config-merger script loads the configs tree structure and deep-merges all keys from all YAML files found from a root path to an edge. For each leaf directory, a file will be created under --output-dir.
Under each level, there is a mandatory "level key" that is used by config-merger for computing the end result. This key should be present in one of the files under each level. (eg. env.yaml under env).
Some configs that are specified in the higher levels of the directory tree might not be needed in the end (leaf) result. For this reason, the config-merger script can apply a set of filter rules that are specified via the --filter-rules-key parameter. This property must be present in the config and contains rules for removing root level keys from the output. The filter is applied if the selector object matches a subset of the output keys and will keep the keys specified in the values list or the keys that match the regex pattern.
# intermediate config after hierarchical merge
env: dev
cluster: cluster1
region: us-east-1
key1: persisted
key2: dropped
keep_1: persisted
tags:
cost_center: 123
_filters:
- selector:
env: "dev"
keys:
values:
- key1
regex: "keep_.*"
- selector:
cluster:
regex: "cluster1"
keys:
values:
- tagsBuild the output with filtering:
himl-config-merger examples/filters --output-dir merged_output --levels env region cluster --leaf-directories cluster --filter-rules-key _filters# output after filtering
env: dev
cluster: cluster1
region: us-east-1
key1: persisted
keep_1: persisted
tags:
cost_center: 123Rule selectors and keys filtering only works at the root level of the config. It is not possible to filter nested keys.
Apart from the standard features found in the PyYaml library, the himl-config-merger component also implements a custom YAML tag called !include.
Example:
VA7: !include configs/env=int/region=va7/kafka-brokers.yaml regionBrokers.VA7This will replace the value after interpolation with the value of the regionBrokers.VA7 found under the configs/env=int/region=va7/kafka-brokers.yaml path.
An optional parameter type_strategies can be passed into ConfigProcessor to define custom merging behavior. It could be custom functions that fit your needs.
Your function should take the arguments of (config, path, base, nxt) and return the merged result.
Example:
from himl import ConfigProcessor
def strategy_merge_override(config, path, base, nxt):
"""merge list of dicts. if objects have same id, nxt replaces base."""
"""if remove flag is present in nxt item, remove base and not add nxt"""
result = deepcopy(base)
for nxto in nxt:
for baseo in result:
# if list is not a list of dicts, bail out and let the next strategy to execute
if not isinstance(baseo,dict) or not isinstance(nxto,dict):
return STRATEGY_END
if 'id' in baseo and 'id' in nxto and baseo['id'] == nxto['id']:
result.remove(baseo) #same id, remove previous item
if 'remove' not in nxto:
result.append(nxto)
return result
config_processor = ConfigProcessor()
path = "examples/simple/production"
filters = () # can choose to output only specific keys
exclude_keys = () # can choose to remove specific keys
output_format = "yaml" # yaml/json
config_processor.process(path=path, filters=filters, exclude_keys=exclude_keys,
output_format=output_format, print_data=True,
type_strategies= [(list, [strategy_merge_override,'append']), (dict, ["merge"])] ))
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