feat: Vercel Edge Config Adapter (#896)

Co-authored-by: emmawillis <[email protected]>

lib/shared/config-manager/__tests__/environmentConfigManager.spec.ts

@@ -172,7 +172,7 @@ describe('EnvironmentConfigManager Unit Tests', () => {
         expect(trackSDKConfigEvent_mock).toBeCalledWith(
             'https://config-cdn.devcycle.com/config/v1/server/sdkKey.json',
             expect.any(Number),
-            expect.objectContaining({ status: 200 }),
+            expect.objectContaining({ resStatus: 200 }),
             undefined,
             undefined,
             undefined,
@@ -211,7 +211,7 @@ describe('EnvironmentConfigManager Unit Tests', () => {
 
         const envConfig = getConfigManager(logger, 'sdkKey', {})
         expect(envConfig.fetchConfigPromise).rejects.toThrow(
-            'Invalid SDK key provided:',
+            'Invalid SDK key provided',
         )
         expect(setInterval_mock).toHaveBeenCalledTimes(0)
     })

lib/shared/config-manager/src/CDNConfigSource.ts

@@ -0,0 +1,78 @@
+import { ConfigBody, DVCLogger } from '@devcycle/types'
+import { ConfigSource } from './ConfigSource'
+import { getEnvironmentConfig } from './request'
+import { ResponseError, UserError } from '@devcycle/server-request'
+
+export class CDNConfigSource extends ConfigSource {
+    constructor(
+        private cdnURI: string,
+        private logger: DVCLogger,
+        private requestTimeoutMS: number,
+    ) {
+        super()
+    }
+
+    async getConfig(
+        sdkKey: string,
+        kind: 'server' | 'bootstrap',
+        lastModifiedThreshold?: string,
+    ): Promise<[ConfigBody | null, Record<string, unknown>]> {
+        let res: Response
+        try {
+            res = await getEnvironmentConfig({
+                logger: this.logger,
+                url: this.getConfigURL(sdkKey, kind),
+                requestTimeout: this.requestTimeoutMS,
+                currentEtag: this.configEtag,
+                currentLastModified: this.configLastModified,
+                sseLastModified: lastModifiedThreshold,
+            })
+        } catch (e) {
+            if (e instanceof ResponseError && e.status === 403) {
+                throw new UserError(`Invalid SDK key provided: ${sdkKey}`)
+            }
+            throw e
+        }
+
+        const metadata = {
+            resEtag: res.headers.get('etag') ?? undefined,
+            resLastModified: res.headers.get('last-modified') ?? undefined,
+            resRayId: res.headers.get('cf-ray') ?? undefined,
+            resStatus: res.status ?? undefined,
+        }
+
+        const projectConfig = (await res.json()) as unknown
+
+        this.logger.debug(
+            `Downloaded config, status: ${
+                res?.status
+            }, etag: ${res?.headers.get('etag')}`,
+        )
+
+        if (res.status === 304) {
+            this.logger.debug(
+                `Config not modified, using cache, etag: ${this.configEtag}` +
+                    `, last-modified: ${this.configLastModified}`,
+            )
+        } else if (res.status === 200 && projectConfig) {
+            const lastModifiedHeader = res.headers.get('last-modified')
+            if (this.isLastModifiedHeaderOld(lastModifiedHeader ?? null)) {
+                this.logger.debug(
+                    'Skipping saving config, existing last modified date is newer.',
+                )
+                return [null, metadata]
+            }
+            this.configEtag = res.headers.get('etag') || ''
+            this.configLastModified = lastModifiedHeader || ''
+            return [projectConfig as ConfigBody, metadata]
+        }
+        return [null, metadata]
+    }
+
+    getConfigURL(sdkKey: string, kind: 'server' | 'bootstrap'): string {
+        if (kind === 'bootstrap') {
+            return `${this.cdnURI}/config/v1/server/bootstrap/${sdkKey}.json`
+        }
+        return `${this.cdnURI}/config/v1/server/${sdkKey}.json`
+    }
+}

lib/shared/config-manager/src/ConfigSource.ts

@@ -0,0 +1,44 @@
+import { ConfigBody } from '@devcycle/types'
+import { isValidDate } from './request'
+
+export abstract class ConfigSource {
+    configEtag?: string
+    configLastModified?: string
+
+    /**
+     * Method to get the config from the source.
+     * Should return null if the config has not changed, and throw an error if it could not be retrieved.
+     * @param sdkKey
+     * @param kind
+     * @param lastModifiedThreshold
+     */
+    abstract getConfig(
+        sdkKey: string,
+        kind: 'server' | 'bootstrap',
+        lastModifiedThreshold?: string,
+    ): Promise<[ConfigBody | null, Record<string, unknown>]>
+
+    /**
+     * Return the URL (or path or storage key etc.) that will be used to retrieve the config for the given SDK key
+     * @param sdkKey
+     * @param kind
+     */
+    abstract getConfigURL(sdkKey: string, kind: 'server' | 'bootstrap'): string
+
+    protected isLastModifiedHeaderOld(
+        lastModifiedHeader: string | null,
+    ): boolean {
+        const lastModifiedHeaderDate = lastModifiedHeader
+            ? new Date(lastModifiedHeader)
+            : null
+        const configLastModifiedDate = this.configLastModified
+            ? new Date(this.configLastModified)
+            : null
+
+        return (
+            isValidDate(configLastModifiedDate) &&
+            isValidDate(lastModifiedHeaderDate) &&
+            lastModifiedHeaderDate <= configLastModifiedDate
+        )
+    }
+}