ReferenceBlueprint spec

Dry run

A dry run shows the plan of an apply and writes nothing.

ferry.yaml (edited)

 envVarGroups:
   - name: shared-settings
     envVars:
       - key: APP_ENV
-        value: production
+        value: staging
 …
   - type: redis
     name: cache
-    plan: starter            # 256 MiB of memory
+    plan: standard
 …
-    numInstances: 2
-    plan: starter            # 512 MiB / 0.5 CPU per instance
+    numInstances: 1
+    plan: standard

A dry run makes the same plan as an apply, with the same validation and the same warnings. It writes nothing.

Use it before each apply to a server that runs real work.

The output

ferry blueprint apply ferry.yaml --dry-run

Blueprint ferry.yaml — dry run, nothing was changed

Would update:
  ~ env group shared-settings
      - env APP_ENV: updated
  ~ datastore cache
      - memory_limit: 256 MiB → 1 GiB
  ~ service hello
      - memory_limit: 512 MiB → 2 GiB
      - cpu_limit: 0.5 CPU → 1 CPU
      - instances: 2 → 1

Unchanged:
  = datastore app-db
  = service nightly

Run without --dry-run to apply.

The real apply of this file

The container of cache gets 1 GiB in place.
Ferry scales hello to one instance.
Ferry restarts hello (trigger restart) with its new limits and the new variable of the group.
Ferry builds nothing.

Guarantees

An apply deletes nothing, changes nothing the second time, and writes nothing if the file is not valid.

The result of an apply

The API answers with a BlueprintResult. It has the actions, the deploys and the warnings.

On this page

The output The real apply of this file