feat: binfmt image local cached

.gitignore

@@ -51,3 +51,6 @@ jspm_packages/
 .yarn/build-state.yml
 .yarn/install-state.gz
 .pnp.*
+
+# IDE
+.idea/

__tests__/context.test.ts

@@ -23,6 +23,7 @@ describe('getInputs', () => {
         image: 'docker.io/tonistiigi/binfmt:latest',
         platforms: 'all',
         cacheImage: true,
+        localCachePath: ''
       } as context.Inputs
     ],
     [
@@ -36,6 +37,7 @@ describe('getInputs', () => {
         image: 'docker/binfmt:latest',
         platforms: 'arm64,riscv64,arm',
         cacheImage: false,
+        localCachePath: ''
       } as context.Inputs
     ],
     [
@@ -48,6 +50,21 @@ describe('getInputs', () => {
         image: 'docker.io/tonistiigi/binfmt:latest',
         platforms: 'arm64,riscv64,arm',
         cacheImage: true,
+        localCachePath: ''
+      } as context.Inputs
+    ],
+    [
+      3,
+      new Map<string, string>([
+        ['platforms', 'arm64'],
+        ['cache-image', 'false'],
+        ['local-cache-path', '/tmp/cache'],
+      ]),
+      {
+        image: 'docker.io/tonistiigi/binfmt:latest',
+        platforms: 'arm64',
+        cacheImage: false,
+        localCachePath: '/tmp/cache'
       } as context.Inputs
     ]
   ])(

action.yml

@@ -19,6 +19,12 @@ inputs:
     description: 'Cache binfmt image to GitHub Actions cache backend'
     default: 'true'
     required: false
+  local-cache-path:
+    description: >
+      Local path to store the binfmt image. Using this enables local caching instead of GitHub Actions cache.
+      Note: The "latest" tag won't auto-update - delete the cached file to fetch updates.
+    default: ''
+    required: false
 
 outputs:
   platforms:

src/context.ts

@@ -5,12 +5,14 @@ export interface Inputs {
   image: string;
   platforms: string;
   cacheImage: boolean;
+  localCachePath: string;
 }
 
 export function getInputs(): Inputs {
   return {
     image: core.getInput('image') || 'docker.io/tonistiigi/binfmt:latest',
     platforms: Util.getInputList('platforms').join(',') || 'all',
-    cacheImage: core.getBooleanInput('cache-image')
+    cacheImage: core.getBooleanInput('cache-image'),
+    localCachePath: core.getInput('local-cache-path') || ''
   };
 }

src/local-cache.ts

@@ -0,0 +1,57 @@
+import * as fs from 'fs';
+import * as path from 'path';
+import * as core from '@actions/core';
+import {Docker} from '@docker/actions-toolkit/lib/docker/docker';
+
+function getImageCacheFileName(imageName: string): string {
+  return `${imageName.replace(/[\/\:]/g, '-')}.tar`;
+}
+
+export async function loadDockerImageFromCache(localCachePath: string, imageName: string): Promise<void> {
+  const cacheFilePath = path.join(localCachePath, getImageCacheFileName(imageName));
+
+  try {
+    if (fs.existsSync(cacheFilePath)) {
+      await Docker.getExecOutput(['load', '-i', cacheFilePath], {
+        ignoreReturnCode: true
+      }).then(res => {
+        if (res.stderr.length > 0 && res.exitCode != 0) {
+          throw new Error(res.stderr.match(/(.*)\s*$/)?.[0]?.trim() ?? 'unknown error');
+        }
+        core.info(`Loaded image from ${cacheFilePath}`);
+      });
+    } else {
+      core.info(`Cache file not found at ${cacheFilePath}, pulling image instead`);
+      await Docker.pull(imageName);
+    }
+  } catch (error) {
+    core.warning(`Failed to check/load cache file: ${error}`);
+    await Docker.pull(imageName);
+  }
+}
+
+export async function saveDockerImageToCache(localCachePath: string, imageName: string): Promise<void> {
+  const cacheFilePath = path.join(localCachePath, getImageCacheFileName(imageName));
+
+  try {
+    if (!fs.existsSync(localCachePath)) {
+      fs.mkdirSync(localCachePath, {recursive: true});
+    }
+
+    if (fs.existsSync(cacheFilePath)) {
+      core.info(`Cache file already exists at ${cacheFilePath}, skipping save`);
+      return;
+    }
+
+    await Docker.getExecOutput(['save', '-o', cacheFilePath, imageName], {
+      ignoreReturnCode: true
+    }).then(res => {
+      if (res.stderr.length > 0 && res.exitCode != 0) {
+        throw new Error(res.stderr.match(/(.*)\s*$/)?.[0]?.trim() ?? 'unknown error');
+      }
+      core.info(`Saved image to ${cacheFilePath}`);
+    });
+  } catch (error) {
+    core.warning(`Failed to save image to cache file: ${error}`);
+  }
+}

src/main.ts

@@ -3,6 +3,7 @@ import * as core from '@actions/core';
 import * as actionsToolkit from '@docker/actions-toolkit';
 
 import {Docker} from '@docker/actions-toolkit/lib/docker/docker';
+import {loadDockerImageFromCache, saveDockerImageToCache} from './local-cache';
 
 interface Platforms {
   supported: string[];
@@ -19,9 +20,15 @@ actionsToolkit.run(
       await Docker.printInfo();
     });
 
-    await core.group(`Pulling binfmt Docker image`, async () => {
-      await Docker.pull(input.image, input.cacheImage);
-    });
+    if (input.localCachePath !== '') {
+      await core.group(`Pulling binfmt Docker image`, async () => {
+        await loadDockerImageFromCache(input.localCachePath, input.image);
+      });
+    } else {
+      await core.group(`Pulling binfmt Docker image`, async () => {
+        await Docker.pull(input.image, input.cacheImage);
+      });
+    }
 
     await core.group(`Image info`, async () => {
       await Docker.getExecOutput(['image', 'inspect', input.image], {
@@ -56,5 +63,15 @@ actionsToolkit.run(
         core.setOutput('platforms', platforms.supported.join(','));
       });
     });
+  },
+
+  // post
+  async () => {
+    const input: context.Inputs = context.getInputs();
+    if (input.localCachePath !== '') {
+      await core.group(`Saving binfmt Docker image`, async () => {
+        await saveDockerImageToCache(input.localCachePath, input.image);
+      });
+    }
   }
 );