Setting config for libraries inside Livebook

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In elixir, when you are working with libraries that require setting some configurations such as access keys, the traditional way is to put configs inside the config/ directory.

For example, using ex_aws library, we need to set access_key_id and secret_access_key in the config.

So, inside our config/dev.exs(or config/prod.exs), we put the following code:

import Config config :ex_aws, access_key_id: [{:system, "AWS_ACCESS_KEY_ID"}, :instance_role], secret_access_key: [{:system, "AWS_SECRET_ACCESS_KEY"}, :instance_role]

and it works as intended. The problem arises when you want to use this library(or similar ones that require setting config) inside livebook. You can't really use the above code to set the configurations.

Well, it turns out livebook(or rather Mix) has a different way to set these configs.

Let's see an example:

Imagine a library named very_cool_library that requires cool_name to be set through config. Lets use Mix.install to install this library.


Now, we need to set cool_name through config. To do that, Mix.install takes an optional keyword list argument named config(how convenient). The value of config should be a keyword list, and the keyword list must contain the library's name for which we want to add config.

Mix.install([:very_cool_library], config: [ very_cool_library: [] ])

The value of this library name key is another keyword list. We can put in the key and value of the config that the library requires. Here's the full code:

Mix.install([:very_cool_library], config: [ very_cool_library: [ cool_name: "Mario" ] ])

And that's it! Everything should work as flawlessley.

Taking our previous example of ex_aws library which requires access_key_id and secret_access_key to be set through config, here's the equivalent for livebook:

Mix.install([:ex_aws], config: [ ex_aws: [ access_key_id: [{:system, "<AWS_ACCESS_KEY_ID>"}, :instance_role], # or key as a string secret_access_key: [{:system, "<AWS_SECRET_ACCESS_KEY>"}, :instance_role] # or key as a string ] ])

Setting config with new livebook secrets feature

With release of livebook 0.7, you can using secrets within your livebook without exposing it to others(which one would've easily done with the above approach).

Set the livebook secret with keys "AWS_ACCESS_KEY_ID" and "AWS_SECRET_ACCESS_KEY".

Now, just use this key with prefix "LB_" inside the config(livebook fills in the secrets that start with "LB" automatically):

Mix.install([:ex_aws], config: [ ex_aws: [ access_key_id: [{:system, "LB_AWS_ACCESS_KEY_ID"}, :instance_role], secret_access_key: [{:system, "LB_AWS_SECRET_ACCESS_KEY"}, :instance_role] ] ])

and everything should work as expected! No more accidental secret sharing with others.

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