Fix Double Rainbow #552
Closed
Fix Double Rainbow #552
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
We mistakenly added yarn to the path even when it was not on the system.
This is super UGHHH. There are cases when a `json` gem has been installed already. One case is when two ruby buildpacks run. Here's what I think is happening: The first buildpack sets the PATH so that future buildpacks can execute Ruby code. This means that now all ruby gems installed from the customer app are on GEM_PATH. Now when the next invocation of building ruby comes up it fires `require 'json'` ruby sees that there's a gem installed and tries to load it, unfortunately it's for a different version of ruby than the one the buildpack is running on. One option to solve is by not requiring `json` but to vendor in a json library such as https://github.com/kr/okjson.
|
Tested, it does fix the example app mentioned in #551. |
|
I agree with the sentiment here... ugh. Weird stuff is weird. Thanks for figuring it out. |
|
Rather than using a different gem should the buildpack try to isolate itself from changes in the build environment? Could it set the appropriate |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
A "double rainbow" deploy is when someone is using the same buildpack twice. Normally this is by accident. There are failure conditions defined in #511 the app has to have a
jsongem and a version of Ruby that is different from the version of Ruby being used by the buildpacks.When this happens, this exception will occur when the second buildpack tries to execute:
If you look at the output, the failure is happening extremely early, this indicated that it was happening before any significant code had been run, otherwise we would have expected to see
The exception only occurred when using
v155of the buildpack as the second buildpack (viaheroku buildpacks:add).Here's what was happening: The first buildpack runs and installs the app's
jsongem. The buildpacks are designed so that they make their contents available for the next buildpack. I.e. if you installnodevia a buildpack, then the next buildpack to execute is expected to havenodeon thePATH. The same is true of ruby and any gems installed.So now the second buildpack executes. To do this it's own source code is loaded into memory, when it does this it hits a
require "json"call that was introduced inv155and tries find thejsonlibrary. While this library ships with Ruby it is also a gem, if the gem is present on the system it will prefer the gem. So it loads thejsongem from a different version of Ruby that is currently executing, it can't because the symbols are different, it errors out.We can avoid this completely by not loading the
jsonlibrary, instead we can vendor in https://github.com/kr/okjson.