Synchronous architecture with asynchronous repository
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Adam
Oct 21, 2015, 11:01:32 AM10/21/15
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In order to keep clean architecture of my node.js microservice I have controllers, services and e.g. repositories.
I want a synchronous data flow: controller -> service -> repository -> service -> controller. In this flow (in simple user story) repository returns data to service and service to controller. But repository should process requests to external storage in a asynchronous way. All asynchronous code should exist only in repository, service should obtain raw data.
My current implementation:
UserController.js
module.exports.create = function() {
console.log("In controller: before service call");
let userDto = JSON.parse(this.request.body);
let savedUser = userService.createUser(userDto);
console.log("In controller: after service call");
};
UserService.js
module.exports.createUser = function createUser(userDto) {
let user = require('../domain/user/User');
user.login = userDto.login;
user.password = userDto.password;
let userRepository = require('../infrastructure/user/UserRepository');
Q.spawn(function* () {
console.log("In service before promise resolve");
let savedUser = yield userRepository.createUser(user);
console.log("In service after promise resolve");
return savedUser;
});
console.log("In service: after repository call");
};
UserRepository.js
module.exports.createUser = function createUser(user) {
console.log("In repository: before save call");
return new Q.Promise(function(resolve, reject) {
userEntity.save(function(err, savedUser) {
console.log("In repository: inside callback after save call");
if (err) {
console.log("In repository: inside callback before reject");
reject(Error('Błąd zapisu danych!'));
} else {
console.log("In repository: inside callback before resolve");
resolve(savedUser);
}
});
});
};
Logs:
- In controller: before service call
- In service before promise resolve
- In repository: before save call
- In service: after repository call
- In controller: after service call
- In repository: inside callback after save call
- In repository: inside callback before resolve
- In service after promise resolve
I would like to get the following sequence of logs:
- In controller: before service call
- In service before promise resolve
- In repository: before save call
- In repository: inside callback after save call
- In repository: inside callback before resolve
- In service after promise resolve
- In controller: after service call
stephane chretien
Oct 26, 2015, 4:11:06 PM10/26/15
to nodejs
Hi Adam,
there is several way to achieve this.
first you should know Q.spawn return a promise, so you can chain it as follow:
UserService.js
module.exports.createUser = function createUser(userDto) {
let user = require('../domain/user/User');
user.login = userDto.login;
user.password = userDto.password;
let userRepository = require('../infrastructure/user/UserRepository');
return Q.spawn(function* () {
console.log("In service before promise resolve");
let savedUser = yield userRepository.createUser(user);
console.log("In service after promise resolve");
return savedUser;
}).then(function(savedUser){
console.log("In service: after repository call");
return savedUser;
});
};
now you must also update UserController.js to use generator or promise an example with generator
module.exports.create = function() {
return q.spawn(function *(){
console.log("In controller: before service call");
let userDto = JSON.parse(this.request.body);
let savedUser = yield userService.createUser(userDto);
console.log("In controller: after service call");
});
};
please notice that now create will also return a promise
now more generator based solution using yield *:
UserController.js
module.exports.create = function() {
return Q.spawn(function* () {
console.log("In controller: before service call");
let userDto = JSON.parse(this.request.body);
let savedUser = yield * userService.createUser(userDto);
console.log("In controller: after service call");
});
};
UserService.js
module.exports.createUser = function createUser(userDto) {
let user = require('../domain/user/User');
user.login = userDto.login;
user.password = userDto.password;
let userRepository = require('../infrastructure/user/UserRepository');
console.log("In service before promise resolve");
let savedUser = yield userRepository.createUser(user);
console.log("In service after promise resolve");
return savedUser;
};
again UserController.create return a promise
Br
stephane
stephane chretien
Oct 27, 2015, 1:02:36 PM10/27/15
to nodejs
Hi Adam,
I've a mistake on the 'generator oriented' solution:
UserController.js
module.exports.create = function() {
return Q.spawn(function* () {
console.log("In controller: before service call");
let userDto = JSON.parse(this.request.body);
let savedUser = yield * userService.createUser(userDto);
console.log("In controller: after service call");
});
};
UserService.js
module.exports.createUser = function * createUser(userDto) {
let user = require('../domain/user/User');
user.login = userDto.login;
user.password = userDto.password;
let userRepository = require('../infrastructure/user/UserRepository');
console.log("In service before promise resolve");
let savedUser = yield userRepository.createUser(user);
console.log("In service after promise resolve");
return savedUser;
};
On Wednesday, October 21, 2015 at 5:01:32 PM UTC+2, Adam wrote:
Alexey Petrushin
Nov 8, 2015, 11:34:59 AM11/8/15
to nodejs
Use fibers, it would allow you to write plain good old Ruby / Python like code without callbacks & at the same time preserve non-blocking node.js features.
Here's an example of Controller https://github.com/sinizinairina/mono-example/blob/master/controllers/Posts.coffee
it looks like synchronous code, but it's not blocking.
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