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child-processor.ts
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child-processor.ts
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import { JobJson, ParentCommand, SandboxedJob } from '../interfaces';
import { errorToJSON } from '../utils';
enum ChildStatus {
Idle,
Started,
Terminating,
Errored,
}
/**
* ChildProcessor
*
* This class acts as the interface between a child process and it parent process
* so that jobs can be processed in different processes.
*
*/
export class ChildProcessor {
public status?: ChildStatus;
public processor: any;
public currentJobPromise: Promise<unknown> | undefined;
constructor(private send: (msg: any) => Promise<void>) {}
public async init(processorFile: string): Promise<void> {
let processor;
try {
processor = require(processorFile);
if (processor.default) {
// support es2015 module.
processor = processor.default;
}
if (typeof processor !== 'function') {
throw new Error('No function is exported in processor file');
}
} catch (err) {
this.status = ChildStatus.Errored;
return this.send({
cmd: ParentCommand.InitFailed,
err: errorToJSON(err),
});
}
const origProcessor = processor;
processor = function (job: SandboxedJob, token?: string) {
try {
return Promise.resolve(origProcessor(job, token));
} catch (err) {
return Promise.reject(err);
}
};
this.processor = processor;
this.status = ChildStatus.Idle;
await this.send({
cmd: ParentCommand.InitCompleted,
});
}
public async start(jobJson: JobJson, token?: string): Promise<void> {
if (this.status !== ChildStatus.Idle) {
return this.send({
cmd: ParentCommand.Error,
err: errorToJSON(new Error('cannot start a not idling child process')),
});
}
this.status = ChildStatus.Started;
this.currentJobPromise = (async () => {
try {
const job = wrapJob(jobJson, this.send);
//console.log('el token', token, job.id)
const result = (await this.processor(job, token)) || {};
await this.send({
cmd: ParentCommand.Completed,
value: result,
});
} catch (err) {
await this.send({
cmd: ParentCommand.Failed,
value: errorToJSON(!(<Error>err).message ? new Error(<any>err) : err),
});
} finally {
this.status = ChildStatus.Idle;
this.currentJobPromise = undefined;
}
})();
}
public async stop(): Promise<void> {}
async waitForCurrentJobAndExit(): Promise<void> {
this.status = ChildStatus.Terminating;
try {
await this.currentJobPromise;
} finally {
process.exit(process.exitCode || 0);
}
}
}
/**
* Enhance the given job argument with some functions
* that can be called from the sandboxed job processor.
*
* Note, the `job` argument is a JSON deserialized message
* from the main node process to this forked child process,
* the functions on the original job object are not in tact.
* The wrapped job adds back some of those original functions.
*/
function wrapJob(
job: JobJson,
send: (msg: any) => Promise<void>,
): SandboxedJob {
let progressValue = job.progress;
const updateProgress = async (progress: number | object) => {
// Locally store reference to new progress value
// so that we can return it from this process synchronously.
progressValue = progress;
// Send message to update job progress.
await send({
cmd: ParentCommand.Progress,
value: progress,
});
};
return {
...job,
data: JSON.parse(job.data || '{}'),
opts: job.opts,
returnValue: JSON.parse(job.returnvalue || '{}'),
/*
* Emulate the real job `updateProgress` function, should works as `progress` function.
*/
updateProgress,
/*
* Emulate the real job `log` function.
*/
log: async (row: any) => {
send({
cmd: ParentCommand.Log,
value: row,
});
},
/*
* Emulate the real job `moveToDelayed` function.
*/
moveToDelayed: async (timestamp: number, token?: string) => {
send({
cmd: ParentCommand.MoveToDelayed,
value: { timestamp, token },
});
},
/*
* Emulate the real job `updateData` function.
*/
updateData: async (data: any) => {
send({
cmd: ParentCommand.Update,
value: data,
});
},
};
}