Something strange in transaction()

[alxndrsn]

Node version:
Sails version (sails): 1.2.3
ORM hook version (sails-hook-orm): 2.1.1
Sockets hook version (sails-hook-sockets):
Organics hook version (sails-hook-organics):
Grunt hook version (sails-hook-grunt):
Uploads hook version (sails-hook-uploads):
DB adapter & version (e.g. sails-mysql@5.55.5): sails-postgresql 1.0.2
Skipper adapter & version (e.g. skipper-s3@5.55.5):

---

Steps to recreate:

git clone git@github.com:alxndrsn/sailsjs-bug-6805.git
cd sailsjs-bug-6805
yarn
yarn start &
curl localhost:1337

Observed:

Transaction never completes for this controller:

const fn = function() {};                                                                                                                                                    
                                                                                                                                                                             
module.exports = {                                                                                                                                                           
  fn: async function (inputs, exits) {                                                                                                                                       
    await sails.getDatastore()                                                                                                                                               
      .transaction(async db => {                                                                                                                                             
        fn(true, true);                                                                                                                                                      
      });                                                                                                                                                                    
                                                                                                                                                                             
    return exits.success();                                                                                                                                                  
  }                                                                                                                                                                          
}; 

Adding a console.log() inside the controller allows the transaction to complete:

const fn = function() {};                                                                                                                                                    
                                                                                                                                                                             
module.exports = {                                                                                                                                                           
  fn: async function (inputs, exits) {                                                                                                                                       
    await sails.getDatastore()                                                                                                                                               
      .transaction(async db => {              
        console.log();                                                                                                                               
        fn(true, true);                                                                                                                                                      
      });                                                                                                                                                                    
                                                                                                                                                                             
    return exits.success();                                                                                                                                                  
  }                                                                                                                                                                          
}; 

Another way of fixing the problem is to remove one of the arguments from fn(...):

const fn = function() {};                                                                                                                                                    
                                                                                                                                                                             
module.exports = {                                                                                                                                                           
  fn: async function (inputs, exits) {                                                                                                                                       
    await sails.getDatastore()                                                                                                                                               
      .transaction(async db => {                                                                                                                                             
        fn(true);                                                                                                                                                      
      });                                                                                                                                                                    
                                                                                                                                                                             
    return exits.success();                                                                                                                                                  
  }                                                                                                                                                                          
}; 

or, changing the argument to a string:

const fn = function() {};                                                                                                                                                    
                                                                                                                                                                             
module.exports = {                                                                                                                                                           
  fn: async function (inputs, exits) {                                                                                                                                       
    await sails.getDatastore()                                                                                                                                               
      .transaction(async db => {                                                                                                                                             
        fn(true, '');                                                                                                                                                      
      });                                                                                                                                                                    
                                                                                                                                                                             
    return exits.success();                                                                                                                                                  
  }                                                                                                                                                                          
}; 

Another fix is to remove the argument for the transaction callback:

const fn = function() {};                                                                                                                                                    
                                                                                                                                                                             
module.exports = {                                                                                                                                                           
  fn: async function (inputs, exits) {                                                                                                                                       
    await sails.getDatastore()                                                                                                                                               
      .transaction(async () => {                                                                                                                                             
        fn(true, true);                                                                                                                                                      
      });                                                                                                                                                                    
                                                                                                                                                                             
    return exits.success();                                                                                                                                                  
  }                                                                                                                                                                          
}; 

?!?!?!?!?!

Conclusion

If there is a single function call inside a transaction with two or fewer arguments of certain values, then the transaction is never completed.

[sailsbot]

@alxndrsn Thanks for posting! We'll take a look as soon as possible.

In the mean time, there are a few ways you can help speed things along:

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---

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[johnabrams7]

@alxndrsn Thanks a lot for bringing attention to this logic curiosity. Will bring it up with the team for analysis of the best approach to have transaction() complete. Appreciate the handful of workarounds I'll get back with you with the decision 👍 Any further community feedback / experiences are welcome for this one.

[alxndrsn]

@mikermcneil @MadisonHicks Just in case you haven't seen it, I think this is my favourite bug 😉

[alxndrsn]

If there is a single function call inside a transaction with two or fewer arguments of certain values, then the transaction is never completed.

I've just run into this again with a three-argument function preceded by await.

[alxndrsn]

This can be avoided by replacing:

await sails.getDatastore().transaction(

with

await withDbTx(

and defining the additional function:

function withDbTx(fn) {
  return sails
      .getDatastore()
      .transaction(db => fn(db));
}

[mikermcneil]

https://github.com/balderdashy/sails-hook-orm/blob/86e431ec88aad828e4aaa0b9a9eea3b13bd405a7/lib/datastore-method-utils/help-run-transaction.js#L70-L78

[alxndrsn]

😱

@mikermcneil what's that code doing? Checking if the during function has more than one arguments? Could you just use:

var seemsToExpectCallback = options.during.length > 1;

?

[alxndrsn]

For reference if facing similar mysteries, this code's repeated in:

• waterline/lib/waterline/methods/stream.js
• sails/lib/hooks/index.js
• sails/lib/app/private/bootstrap.js
• sails-hook-orm/lib/datastore-method-utils/help-run-transaction.js (linked above)
• sails-hook-orm/lib/datastore-method-utils/private/do-with-connection.js

[alxndrsn]

Example PR for the core sails instances: #7017