[Fleet][EPM] Move SO work from getFileHandler to service method (#85594)

## Summary

 - Move registry URL details from handler to Registry service 
 - rename `archive/save_to_es` to `archive/storage` to better reflect its role
 - Move SO handling from http into new  `getAsset` method in `archive/storage`
 - Rearrange code in HTTP handler to be more easily moved to one or two service method(s) which deal with the logic for getting the asset.


### Checklist

- [ ] [Unit or functional tests](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#cross-browser-compatibility) were updated or added to match the most common scenarios

x-pack/plugins/fleet/server/routes/epm/handlers.ts

@@ -17,7 +17,6 @@ import {
   BulkInstallPackageInfo,
   BulkInstallPackagesResponse,
   IBulkInstallPackageHTTPError,
-  ASSETS_SAVED_OBJECT_TYPE,
 } from '../../../common';
 import {
   GetCategoriesRequestSchema,
@@ -48,7 +47,7 @@ import { defaultIngestErrorHandler, ingestErrorToResponseOptions } from '../../e
 import { splitPkgKey } from '../../services/epm/registry';
 import { licenseService } from '../../services';
 import { getArchiveEntry } from '../../services/epm/archive/cache';
-import { PackageAsset, assetPathToObjectId } from '../../services/epm/archive/save_to_es';
+import { getAsset } from '../../services/epm/archive/storage';
 
 export const getCategoriesHandler: RequestHandler<
   undefined,
@@ -113,45 +112,50 @@ export const getFileHandler: RequestHandler<TypeOf<typeof GetFileRequestSchema.p
     const useLocalFile = pkgVersion === installation?.version;
 
     if (useLocalFile) {
-      const archiveKey = `${pkgName}-${pkgVersion}/${filePath}`;
-      const archiveEntry = getArchiveEntry(archiveKey);
-      const assetSavedObject = await savedObjectsClient.get<PackageAsset>(
-        ASSETS_SAVED_OBJECT_TYPE,
-        assetPathToObjectId(archiveKey)
-      );
+      const assetPath = `${pkgName}-${pkgVersion}/${filePath}`;
+      const fileBuffer = getArchiveEntry(assetPath);
+      // only pull local installation if we don't have it cached
+      const storedAsset = !fileBuffer && (await getAsset({ savedObjectsClient, path: assetPath }));
 
-      if (!archiveEntry && !assetSavedObject) {
+      // error, if neither is available
+      if (!fileBuffer && !storedAsset) {
         return response.custom({
           body: `installed package file not found: ${filePath}`,
           statusCode: 404,
         });
       }
 
-      const headerContentType =
-        assetSavedObject.attributes.media_type || mime.contentType(path.extname(archiveKey));
-      if (!headerContentType) {
+      // if storedAsset is not available, fileBuffer *must* be
+      // b/c we error if we don't have at least one, and storedAsset is the least likely
+      const { buffer, contentType } = storedAsset
+        ? {
+            contentType: storedAsset.media_type,
+            buffer: storedAsset.data_utf8
+              ? Buffer.from(storedAsset.data_utf8, 'utf8')
+              : Buffer.from(storedAsset.data_base64, 'base64'),
+          }
+        : {
+            contentType: mime.contentType(path.extname(assetPath)),
+            buffer: fileBuffer,
+          };
+
+      if (!contentType) {
         return response.custom({
           body: `unknown content type for file: ${filePath}`,
           statusCode: 400,
         });
       }
 
-      const { data_base64: base64, data_utf8: utf8 } = assetSavedObject.attributes;
-      // if we have a local Buffer, use that
-      // else, create one from the saved object (try utf8 first)
-      const responseBody =
-        archiveEntry || utf8 ? Buffer.from(utf8, 'utf8') : Buffer.from(base64, 'base64');
-
       return response.custom({
-        body: responseBody,
+        body: buffer,
         statusCode: 200,
         headers: {
           'cache-control': 'max-age=10, public',
-          'content-type': headerContentType,
+          'content-type': contentType,
         },
       });
     } else {
-      const registryResponse = await getFile(`/package/${pkgName}/${pkgVersion}/${filePath}`);
+      const registryResponse = await getFile(pkgName, pkgVersion, filePath);
       const headersToProxy: KnownHeaders[] = ['content-type', 'cache-control'];
       const proxiedHeaders = headersToProxy.reduce((headers, knownHeader) => {
         const value = registryResponse.headers.get(knownHeader);

x-pack/plugins/fleet/server/services/epm/archive/save_to_es.ts → x-pack/plugins/fleet/server/services/epm/archive/storage.ts

@@ -121,3 +121,20 @@ export async function archiveEntryToBulkCreateObject(opts: {
     attributes: doc,
   };
 }
+
+export async function getAsset(opts: {
+  savedObjectsClient: SavedObjectsClientContract;
+  path: string;
+}) {
+  const { savedObjectsClient, path } = opts;
+  const assetSavedObject = await savedObjectsClient.get<PackageAsset>(
+    ASSETS_SAVED_OBJECT_TYPE,
+    assetPathToObjectId(path)
+  );
+  const storedAsset = assetSavedObject?.attributes;
+  if (!storedAsset) {
+    return;
+  }
+
+  return storedAsset;
+}

x-pack/plugins/fleet/server/services/epm/packages/_install_package.ts

@@ -29,7 +29,7 @@ import { updateCurrentWriteIndices } from '../elasticsearch/template/template';
 import { deleteKibanaSavedObjectsAssets } from './remove';
 import { installTransform } from '../elasticsearch/transform/install';
 import { createInstallation, saveKibanaAssetsRefs, updateVersion } from './install';
-import { saveArchiveEntries } from '../archive/save_to_es';
+import { saveArchiveEntries } from '../archive/storage';
 
 // this is only exported for testing
 // use a leading underscore to indicate it's not the supported path

x-pack/plugins/fleet/server/services/epm/packages/get.ts

@@ -18,7 +18,7 @@ import * as Registry from '../registry';
 import { createInstallableFrom, isRequiredPackage } from './index';
 import { getArchivePackage } from '../archive';
 
-export { fetchFile as getFile, SearchParams } from '../registry';
+export { getFile, SearchParams } from '../registry';
 
 function nameAsTitle(name: string) {
   return name.charAt(0).toUpperCase() + name.substr(1).toLowerCase();

x-pack/plugins/fleet/server/services/epm/packages/remove.ts

@@ -23,7 +23,7 @@ import { deleteTransforms } from '../elasticsearch/transform/remove';
 import { packagePolicyService, appContextService } from '../..';
 import { splitPkgKey } from '../registry';
 import { deletePackageCache } from '../archive';
-import { removeArchiveEntries } from '../archive/save_to_es';
+import { removeArchiveEntries } from '../archive/storage';
 
 export async function removeInstallation(options: {
   savedObjectsClient: SavedObjectsClientContract;

x-pack/plugins/fleet/server/services/epm/registry/index.ts

@@ -110,6 +110,15 @@ export async function fetchInfo(pkgName: string, pkgVersion: string): Promise<Re
   return fetchUrl(`${registryUrl}/package/${pkgName}/${pkgVersion}`).then(JSON.parse);
 }
 
+export async function getFile(
+  pkgName: string,
+  pkgVersion: string,
+  relPath: string
+): Promise<Response> {
+  const filePath = `/package/${pkgName}/${pkgVersion}/${relPath}`;
+  return fetchFile(filePath);
+}
+
 export async function fetchFile(filePath: string): Promise<Response> {
   const registryUrl = getRegistryUrl();
   return getResponse(`${registryUrl}${filePath}`);