add a `fallback` input

action.yml

@@ -7,6 +7,9 @@ branding:
   color: 'blue'
 
 inputs:
+  nofallback:
+    description: "Fail the build if the remote builder is not available; defaults to false"
+    required: false
   add-hosts:
     description: "List of a customs host-to-IP mapping (e.g., docker:10.180.0.1)"
     required: false

src/context.ts

@@ -40,6 +40,7 @@ export interface Inputs {
   target: string;
   ulimit: string[];
   'github-token': string;
+  nofallback: boolean;
 }
 
 export async function getInputs(): Promise<Inputs> {
@@ -75,7 +76,8 @@ export async function getInputs(): Promise<Inputs> {
     tags: Util.getInputList('tags'),
     target: core.getInput('target'),
     ulimit: Util.getInputList('ulimit', {ignoreComma: true}),
-    'github-token': core.getInput('github-token')
+    'github-token': core.getInput('github-token'),
+    nofallback: core.getBooleanInput('nofallback')
   };
 }
 

src/main.ts

@@ -97,7 +97,9 @@ async function getRemoteBuilderAddr(inputs: context.Inputs): Promise<string | nu
     return null;
   } catch (error) {
     if (error.response && error.response.status === 404) {
+      if (!inputs.nofallback) {
         core.warning('No builder instances were available, falling back to a local build');
+      }
     } else {
       core.warning(`Error in getBuildkitdAddr: ${error.message}`);
     }
@@ -171,8 +173,12 @@ actionsToolkit.run(
     await core.group(`Starting Blacksmith remote builder`, async () => {
       remoteBuilderAddr = await getRemoteBuilderAddr(inputs);
       if (!remoteBuilderAddr) {
+        if (inputs.nofallback) {
+          core.setFailed('Failed to obtain Blacksmith builder. Failing the build');
+        } else {
           core.warning('Failed to obtain Blacksmith remote builder address. Falling back to a local build.');
         }
+      }
     });
 
     if (remoteBuilderAddr) {