How to use other repos in a transactions - node.js

Question

I have several repos with methods and some of these methods use transaction (.tx).
For example, in my DevicesRepository below, the 'add' method have to insert a new Device, which means:
1. Insert a System and return the ID (SystemsRepository)
2. insert the device with the returner systemId and get the new id
3. Insert other pieces (other repos) that uses the deviceId
My problem is that in that transaction I don't know how to access to the other repo methods.
I could use the other repos from my Database object (Database.systems.add, Database.OtherRepo.add, [...]), but if I do that
tx doc
When invoked on the root Database object, the method allocates the connection from the pool, executes the callback, and once finished - releases the connection back to the pool. However, when invoked inside another task or transaction, the method reuses the parent connection.
task doc
When executing more than one request at a time, one should allocate and release the connection only once, while executing all the required queries within the same connection session. More importantly, a transaction can only work within a single connection.
Thanks! :)
P.S : I can add how I initialize the DB and repos
./db/repos/devices.js
'use strict';
var Database = null, pgp = null, Collections = null;
async function add(params) {
// I can use Database.systems.add
return Database.tx('Insert-New-Device', async function(transaction) {
let device = params.data.device;
const system = await transaction.systems.add(params);
device.systemid = system.systemId;
const query = pgp.helpers.insert(device, Collections.insert);
query += " RETURNING deviceId";
device.deviceId = await transaction.one(query);
const OtherRepoInsert = await transaction.otherRepos.add(params);
device.otherRepos.id = OtherRepoInsert.otherReposId;
return device
})
.then(data => { return data; })
.catch(ex => { throw new Error(ex); });
}
function createColumnsets() { /* hidden for brevity (almost the same as the pg-promise-demo */ }
const DevicesRepository = {
add: add
};
module.exports = (db) => {
Database = db;
pgp = db.$config.pgp;
Collections = createColumnsets();
return DevicesRepository;
}
./db/repos/systems.js
'use strict';
var Database = null, pgp = null, Collections = null;
async function add(params) {
var system = params.data.system;
system.archid=2;
system.distributionid=3;
var query = pgp.helpers.insert(system, Collections.insert);
if(params.return) query += " RETURNING *";
return Database.any(query)
.then(data => { return data; })
.catch(ex => { throw new Error(ex); });
}
function createColumnsets() { /* hidden for brevity (almost the same as the pg-promise-demo */ }
const SystemsRepository = {
add: add
};
module.exports = (db) => {
Database = db;
pgp = db.$config.pgp;
Collections = createColumnsets();
return SystemsRepository;
}

Answer 1

I found the real problem.
If you go to my first post, you can see that each of my repo exports an initialization function :
1. which is called by the pg-promise 'extend' event
2. which takes one param : the context
3. which uses this param to initialize the 'pgp' variable in the repo with db.$config.pgp
As explained in the demo, this event occurs when the db is loaded for the first time in the appl and for every task and transaction.
In my case :
The first time the event occurs (full app initialization), the event's param 'obj' is the database context (containing $config, $pool, ...) so it works
When the event occurs for a task or transaction, the event's param 'obj' is a Task context, where $config does not exists so the event can not extend the context with my repo. An exception 'can not read property helpers of undefined' is thrown but does not appear and does not crash my app, I don't know why, maybe catched in the event. That is why I could not use my repo in the transaction.
I modified my code like it and it works :
./db/index.js
'use strict';
/* hidden for brevity */
// pg-promise initialization options:
const initOptions = {
promiseLib: promise,
extend(obj, dc) {
obj.roles = repos.Roles(obj, pgp);
obj.shells = repos.Shells(obj, pgp);
obj.systems = repos.Systems(obj, pgp);
obj.devices = repos.Devices(obj, pgp);
}
};
const pgp = require('pg-promise')(initOptions);
const db = pgp(config);
/* hidden for brevity */
./db/index.js
'use strict';
/* hidden for brevity */
// pg-promise initialization options:
const initOptions = {
promiseLib: promise,
extend(obj, dc) {
obj.roles = repos.Roles(obj, pgp);
obj.shells = repos.Shells(obj, pgp);
obj.systems = repos.Systems(obj, pgp);
obj.devices = repos.Devices(obj, pgp);
}
};
const pgp = require('pg-promise')(initOptions);
const db = pgp(config);
/* hidden for brevity */
./db/repos/{repoFiles}.js
/* hidden for brevity */
module.exports = (db, pgpLib) => {
Database = db;
pgp = pgpLib;
Collections = createColumnsets();
return DevicesRepository;
}

Answer 2

Property $config is there for integration purposes. That's why it exists only on the root Database level, and not inside tasks or transactions.
In order to make use of the helpers namespace, you should pass pgp into repositories when you initialize them, as shown within pg-promise-demo:
extend(obj, dc) {
obj.users = new repos.Users(obj, pgp);
obj.products = new repos.Products(obj, pgp);
}

Answer 3

You can establish the transaction outside the calls, then pass it in to those functions to have them use it.
That said, I'd recommend looking into a slightly higher-level query builder library such as Knex.js to save you from some of these (and future) headaches.