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Merge Generator¶
The Merge generator combines parameters produced by the base (first) generator with matching parameter sets produced by subsequent generators. A matching parameter set has the same values for the configured merge keys. Non-matching parameter sets are discarded. Override precedence is bottom-to-top: the values from a matching parameter set produced by generator 3 will take precedence over the values from the corresponding parameter set produced by generator 2.
Using a Merge generator is appropriate when a subset of parameter sets require overriding.
Example: Base Cluster generator + override Cluster generator + List generator¶
As an example, imagine that we have two clusters:
- A
stagingcluster (athttps://1.2.3.4) - A
productioncluster (athttps://2.4.6.8)
yaml
apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
name: cluster-git
spec:
generators:
# merge 'parent' generator
- merge:
mergeKeys:
- server
generators:
- clusters:
values:
kafka: 'true'
redis: 'false'
# For clusters with a specific label, enable Kafka.
- clusters:
selector:
matchLabels:
use-kafka: 'false'
values:
kafka: 'false'
# For a specific cluster, enable Redis.
- list:
elements:
- server: https://2.4.6.8
values.redis: 'true'
template:
metadata:
name: '{{name}}'
spec:
project: '{{metadata.labels.environment}}'
source:
repoURL: https://github.com/argoproj/applicationset.git
targetRevision: HEAD
path: app
helm:
parameters:
- name: kafka
value: '{{values.kafka}}'
- name: redis
value: '{{values.redis}}'
destination:
server: '{{server}}'
namespace: default
The base Cluster generator scans the set of clusters defined in Argo CD, finds the staging and production cluster secrets, and produces two corresponding sets of parameters: ```yaml - name: staging server: https://1.2.3.4 values.kafka: 'true' values.redis: 'false'
- name: production server: https://2.4.6.8 values.kafka: 'true' values.redis: 'false' ```
The override Cluster generator scans the set of clusters defined in Argo CD, finds the staging cluster secret (which has the required label), and produces the following parameters:
yaml
- name: staging
server: https://1.2.3.4
values.kafka: 'false'
When merged with the base generator's parameters, the values.kafka value for the staging cluster is set to 'false'.
```yaml
- name: staging
server: https://1.2.3.4
values.kafka: 'false'
values.redis: 'false'
- name: production server: https://2.4.6.8 values.kafka: 'true' values.redis: 'false' ```
Finally, the List cluster generates a single set of parameters:
yaml
- server: https://2.4.6.8
values.redis: 'true'
When merged with the updated base parameters, the values.redis value for the production cluster is set to 'true'. This is the merge generator's final output:
```yaml
- name: staging
server: https://1.2.3.4
values.kafka: 'false'
values.redis: 'false'
- name: production server: https://2.4.6.8 values.kafka: 'true' values.redis: 'true' ```
Restrictions¶
- You should specify only a single generator per array entry. This is not valid: ```yaml
- merge:
generators:
- list: # (...) git: # (...) ```
- While this will be accepted by Kubernetes API validation, the controller will report an error on generation. Each generator should be specified in a separate array element, as in the examples above.
- The Merge generator does not support
templateoverrides specified on child generators. Thistemplatewill not be processed: ```yaml - merge:
generators:
- list: elements: - # (...) template: { } # Not processed ```
- Combination-type generators (Matrix or Merge) can only be nested once. For example, this will not work: ```yaml
- merge:
generators:
- merge: generators: - merge: # This third level is invalid. generators: - list: elements: - # (...) ```