node js应用程序中的knex迁移错误

Question

I am using knew to connect with postgres in my application. I am getting following error when I run

knex migrate:latest

TimeoutError: Knex: Timeout acquiring a connection. The pool is probably full. Are you missing a .transacting(trx) call?
    at Timeout._onTimeout 

Referring some thread , I understand that I have to add transacting call but Do I need to add in all the sql calls of my app ?

In documentation , It do not give me details about when to add this ? why is must ? My queries are mostly of type "GET", hence not sure if those queries needs to apply transacting?

Answer 1

It seems a library bug, probably.

Generally speaking, any behaviors including SELECT also need a transaction with read locking. DB will organize the resource locking sequence according to the transaction isolation level setting and mostly READ COMMITTED is default. Rows in a table cannot be deleted while a user is reading it until finished the action. Delete (exclusive locking) waits until the Select (read shared lock) release it, even if we didn't mention a begin transaction.

In this reason, most of the database connection libraries are supporting "auto commit" option like this , this and this to automatically wrap with a transaction by default if there is no explicit transaction made (or supported by the DBMS session option natively), so all the request run on a transaction block.

Knex seems not have this option explicitly. I can find it may differ to the DBMS types. Oracle dialect . While reading the code, I found Oracle implementation have it here but Postgresql implementation here does not have auto commit. It looks incomplete to me.

The document also says it could select query without transacting call. If it leaks many open session, then it's obviously a bug. Please file a bug report with a sample code to reproduce this issue.

Or you could inspect what queries in the pending list from the database side. All the modern database system could list up the sessions and locking status. I suppose you have mixed with the naive select call and the transacting() call and then the naive select calls may appended to an uncommitted open transaction. You can watch what is happening from the DB admin feature like this .