Loopback: "Unhandled rejection Error: The transaction is not active" when begin 10 transactions at the same time

Question

I have a nodejs project using loopback and postgressql.

I got a function handleTrade like this, simply start the transaction with timeout 30s, query the Trade by id and do some updates:

async function handleTrade(id) {
  const { Trade } = app.models;
  const transaction = await Trade.beginTransaction({
    timeout: 30000 // 30 seconds
  });

  try {
    console.log(`${id} - 1`);
    const trade = await Trade.findById(id, { transaction });
    console.log(`${id} - 2`);

    if (trade) {
      // Do some updates with the trade
    }
    transaction.commit();
  } catch (e) {
    console.log(`${id} - 3`, e);
    transaction.rollback();
  }
}

I have a list of 10 ids, I want to handle all of them asynchronously and print Done when everything is done.

async function test(ids) {
  const promises = ids.map(id => handleTrade(id));
  await Promise.all(promises);
  console.log('Done');
  process.exit(0);
}

test([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);

And here's the log:

2 - Step 1
3 - Step 1
1 - Step 1
4 - Step 1
6 - Step 1
5 - Step 1
10 - Step 1
9 - Step 1
8 - Step 1
7 - Step 1

-- The process stuck here for 30 seconds (which is the timeout value of the transaction)

2 - Step 2
Unhandled rejection Error: The transaction is not active: 914ca760-b804-11e8-bb6c-094b32725638
    at process.nextTick (/Users/admin/Work/NIX/nix-project/engine/node_modules/loopback-datasource-juggler/lib/transaction.js:202:12)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

9 - Step 2
1 - Step 2
3 - Step 2
6 - Step 2
4 - Step 2
5 - Step 2
10 - Step 2
8 - Step 2
Unhandled rejection Error: The transaction is not active: 914e5510-b804-11e8-bb6c-094b32725638
    at process.nextTick (/Users/admin/Work/NIX/nix-project/engine/node_modules/loopback-datasource-juggler/lib/transaction.js:202:12)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

Unhandled rejection Error: The transaction is not active: 914cce71-b804-11e8-bb6c-094b32725638
    at process.nextTick (/Users/admin/Work/NIX/nix-project/engine/node_modules/loopback-datasource-juggler/lib/transaction.js:202:12)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

Unhandled rejection Error: The transaction is not active: 914cce70-b804-11e8-bb6c-094b32725638
    at process.nextTick (/Users/admin/Work/NIX/nix-project/engine/node_modules/loopback-datasource-juggler/lib/transaction.js:202:12)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

Unhandled rejection Error: The transaction is not active: 914cf581-b804-11e8-bb6c-094b32725638
    at process.nextTick (/Users/admin/Work/NIX/nix-project/engine/node_modules/loopback-datasource-juggler/lib/transaction.js:202:12)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

Unhandled rejection Error: The transaction is not active: 914cf580-b804-11e8-bb6c-094b32725638
    at process.nextTick (/Users/admin/Work/NIX/nix-project/engine/node_modules/loopback-datasource-juggler/lib/transaction.js:202:12)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

Unhandled rejection Error: The transaction is not active: 914cf582-b804-11e8-bb6c-094b32725638
    at process.nextTick (/Users/admin/Work/NIX/nix-project/engine/node_modules/loopback-datasource-juggler/lib/transaction.js:202:12)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

Unhandled rejection Error: The transaction is not active: 914cf583-b804-11e8-bb6c-094b32725638
    at process.nextTick (/Users/admin/Work/NIX/nix-project/engine/node_modules/loopback-datasource-juggler/lib/transaction.js:202:12)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

Unhandled rejection Error: The transaction is not active: 914e5511-b804-11e8-bb6c-094b32725638
    at process.nextTick (/Users/admin/Work/NIX/nix-project/engine/node_modules/loopback-datasource-juggler/lib/transaction.js:202:12)
    at _combinedTickCallback (internal/process/next_tick.js:131:7)
    at process._tickCallback (internal/process/next_tick.js:180:9)

7 - Step 2
Done

The processes got stuck for 30 seconds after step 1, then when transaction timeout, it return the Error The transaction is not active

And this only happen when I have 10 ids, if I only use 9, it run smoothly

test([1, 2, 3, 4, 5, 6, 7, 8, 9]);

// Logs
2 - Step 1
4 - Step 1
5 - Step 1
9 - Step 1
7 - Step 1
8 - Step 1
6 - Step 1
1 - Step 1
3 - Step 1
2 - Step 2
4 - Step 2
9 - Step 2
8 - Step 2
1 - Step 2
5 - Step 2
7 - Step 2
6 - Step 2
3 - Step 2
Done

If you have any idea please help me. Thanks

Answer 1

try edit your datasource file.

example: my dataresources.json

old:

{   
  "db": {
    "url": "${DATABASE_URL}",
    "name": "db",
    "connector": "postgresql"
  }
}

new:

{
  "db": {
    "url": "${DATABASE_URL}",
    "name": "db",
    "connector": "postgresql",
    "max": 100
  }
}

explanation: your problem mainly like you're running out of connection pool, this will increase it. (100 is just a example number, you can change from 0 to the max number defined in your postgresql config)