Today I Learned

A Hashrocket project

Transactions can timeout in Elixir

In Ecto, transactions can timeout. So this type of code:

  Repo.transaction fn -> 
    # Many thousands of expensive queries
    # And inserts
  end

This type of code might fail after 15 seconds, which is the default timeout.

In Ecto you can specify what the timeout should be for each operation. All functions that make a request to the database have the same same shared options of which :timeout is one.

Repo.all(massive_query, timeout: 20_000)

The above query now times out after 20 seconds.

These shared options apply to a transaction as well. If you don’t care that a transaction is taking a long time you can set the timeout to :infinity.

  Repo.transaction(fn -> 
    # Many thousands of expensive queries
    # And inserts
  end, timeout: :infinity)

Now this operation will be allowed to finish, despite the time it takes.

Looking for help? Elixir is quickly gaining momentum for web applications that need concurrency, performance, and the ability to connect to many different clients. The developers at Hashrocket are learning along with the rest of the development community that Elixir and Phoenix are viable Rails alternatives for the right application. Check out the source code for Today I Learned, written in Elixir, and contact us if you need help with your Elixir project.