feat(scaffolder): implementing a basic API for the processor to mutate the entity state

plugins/scaffolder-backend/src/scaffolder/jobs/index.ts

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+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+export * from './processor';

plugins/scaffolder-backend/src/scaffolder/jobs/processor.ts

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+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { Processor, Job, ProcessorContstructorArgs } from './types';
+import { JsonValue } from '@backstage/config';
+import { TemplateEntityV1alpha1 } from '@backstage/catalog-model';
+import { PassThrough, Writable } from 'stream';
+import uuid from 'uuid';
+import winston from 'winston';
+import { RequiredTemplateValues } from '../templater';
+import { createNewRootLogger } from '@backstage/backend-common';
+
+export class JobProcessor implements Processor {
+  private preparers: ProcessorContstructorArgs['preparers'];
+  private templater: ProcessorContstructorArgs['templater'];
+  private dockerClient: ProcessorContstructorArgs['dockerClient'];
+  private jobs = new Map<string, Job>();
+
+  constructor({
+    preparers,
+    templater,
+    dockerClient,
+  }: ProcessorContstructorArgs) {
+    this.preparers = preparers;
+    this.templater = templater;
+    this.dockerClient = dockerClient;
+    return this;
+  }
+
+  create(
+    entity: TemplateEntityV1alpha1,
+    values: RequiredTemplateValues & Record<string, JsonValue>,
+  ): Job {
+    const id = uuid.v4();
+    const log: string[] = [];
+    const logStream = new PassThrough();
+    logStream.on('data', chunk => log.push(chunk.toString()));
+
+    const logger = createNewRootLogger();
+    logger.add(new winston.transports.Stream({ stream: logStream }));
+
+    const job: Job = {
+      id,
+      logStream,
+      logger,
+      log,
+      status: 'PENDING',
+      metadata: {
+        entity,
+        values,
+      },
+    };
+
+    this.jobs.set(job.id, job);
+    return job;
+  }
+  get(id: string): Job | undefined {
+    return this.jobs.get(id);
+  }
+  async run(job: Job) {
+    if (job.status !== 'PENDING') {
+      throw new Error('Job is not in pending state');
+    }
+
+    const { logger, logStream } = job;
+
+    try {
+      logger.debug('Prepare started');
+      job.status = 'PREPARING';
+      const entity = job.metadata.entity;
+      const preparer = this.preparers.get(entity);
+      const skeletonPath = await preparer.prepare(entity);
+      logger.debug('Prepare finished', {
+        skeletonPath,
+      });
+
+      logger.debug('Templating started');
+      job.status = 'TEMPLATING';
+      // Run the templater on the mock directory with values from the post body
+      const templatedPath = await this.templater.run({
+        directory: skeletonPath,
+        values: job.metadata.values,
+        dockerClient: this.dockerClient,
+        logStream,
+      });
+      logger.debug('Template finished', { templatedPath });
+
+      job.status = 'STORING';
+      // TODO(blam): Implement VCS Push here
+
+      job.status = 'COMPLETE';
+    } catch (ex) {
+      job.error = ex;
+      job.status = 'FAILED';
+      logger.error(`job ${job.id} failed with reason`, { ex });
+    }
+  }
+}

plugins/scaffolder-backend/src/scaffolder/jobs/types.ts

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+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import type { Writable } from 'stream';
+import { TemplateEntityV1alpha1 } from '@backstage/catalog-model';
+import { JsonValue } from '@backstage/config';
+import { PreparerBuilder } from '../prepare';
+import Docker from 'dockerode';
+import { TemplaterBase, RequiredTemplateValues } from '../templater';
+import { Logger } from 'winston';
+
+export type Job = {
+  id: string;
+  metadata: {
+    entity: TemplateEntityV1alpha1;
+    values: RequiredTemplateValues & Record<string, JsonValue>;
+  };
+  status:
+    | 'PENDING'
+    | 'PREPARING'
+    | 'TEMPLATING'
+    | 'STORING'
+    | 'COMPLETE'
+    | 'FAILED';
+  logStream: Writable;
+  log: string[];
+  logger: Logger;
+  error?: Error;
+};
+
+export type ProcessorContstructorArgs = {
+  preparers: PreparerBuilder;
+  templater: TemplaterBase;
+  logger: Logger;
+  dockerClient: Docker;
+};
+
+export type Processor = {
+  create(
+    entity: TemplateEntityV1alpha1,
+    values: RequiredTemplateValues & Record<string, JsonValue>,
+  ): Job;
+
+  get(id: string): Job | undefined;
+};