Ruby on Rails / PostgreSQL - 启动服务器时库未加载错误

Question

Heyo. I apologize in advance if this question has been answered in another thread. I've searched through the site but I didn't find an answer. However, the closest related issue was Ruby on Rails / PostgreSQL - Library not Loaded error when starting server- libq.5.dylib , but it was never resolved, and the answer doesn't help me.

I'm trying to get PostgreSQL running on my Mac OSX 10.6.8. I already have Ruby 1.9.3p392 and Rails 3.2.13 installed.

Since I've 10.6.8, and PostGresApp requires 10.7+, I tried installing PG using the manual installer (v9.2.3) available here: http://www.enterprisedb.com/products-services-training/pgdownload

I first installed it to its default path at: /Library/PostgreSQL/9.2/. I then installed the pg gem ( PATH=$PATH:/Library/PostgreSQL/9.2/bin sudo gem install pg ). When I tried rails s to launch my localhost, I got the error below.

After some reading, I guessed it might be a path error, so I removed the pg gem, and then used the postgresql uninstaller. I then reinstalled pg in /users/stewartmccoy/Library/PostgreSQL/9.2/...and then reinstalled the pg gem. But I still get the same error.

Any thoughts on how I might correctly install PostgreSQL and get my rails server running?

stewart-mccoys-macbook:footy_subs stewartmccoy$ rails s
/Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.14.1/lib/pg.rb:4:in `require': dlopen(/Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.14.1/lib/pg_ext.bundle, 9): Library not loaded: libpq.5.dylib (LoadError)
  Referenced from: /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.14.1/lib/pg_ext.bundle
  Reason: image not found - /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.14.1/lib/pg_ext.bundle
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.14.1/lib/pg.rb:4:in `<top (required)>'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:72:in `require'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:72:in `block (2 levels) in require'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:70:in `each'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:70:in `block in require'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:59:in `each'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:59:in `require'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler.rb:132:in `require'
    from /Users/stewartmccoy/Code/footy_subs/config/application.rb:13:in `<top (required)>'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/commands.rb:53:in `require'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/commands.rb:53:in `block in <top (required)>'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/commands.rb:50:in `tap'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/commands.rb:50:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'
stewart-mccoys-macbook:footy_subs stewartmccoy$ gem uninstall pgSuccessfully uninstalled pg-0.14.1
stewart-mccoys-macbook:footy_subs stewartmccoy$ PATH=$PATH:/users/stewartmccoy/Library/PostgreSQL/9.2/bin sudo gem install pg
Password:
Fetching: pg-0.14.1.gem (100%)
Building native extensions.  This could take a while...
Successfully installed pg-0.14.1
1 gem installed
Installing ri documentation for pg-0.14.1...
Installing RDoc documentation for pg-0.14.1...
stewart-mccoys-macbook:footy_subs stewartmccoy$ rails s
/Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.14.1/lib/pg.rb:4:in `require': dlopen(/Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.14.1/lib/pg_ext.bundle, 9): Library not loaded: libpq.5.dylib (LoadError)
  Referenced from: /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.14.1/lib/pg_ext.bundle
  Reason: image not found - /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.14.1/lib/pg_ext.bundle
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/pg-0.14.1/lib/pg.rb:4:in `<top (required)>'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:72:in `require'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:72:in `block (2 levels) in require'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:70:in `each'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:70:in `block in require'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:59:in `each'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler/runtime.rb:59:in `require'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392@global/gems/bundler-1.3.4/lib/bundler.rb:132:in `require'
    from /Users/stewartmccoy/Code/footy_subs/config/application.rb:13:in `<top (required)>'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/commands.rb:53:in `require'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/commands.rb:53:in `block in <top (required)>'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/commands.rb:50:in `tap'
    from /Users/stewartmccoy/.rvm/gems/ruby-1.9.3-p392/gems/railties-3.2.13/lib/rails/commands.rb:50:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

Answer 1

The key part of the error is:

Library not loaded: libpq.5.dylib (LoadError)

This suggests that ruby can't find libpq at runtime. To address that you should probably set the DYLD_LIBRARY_PATH environment variable to point to the lib directory of your PostgreSQL install, either globally or in a wrapper script you use to start Rails. See this superuser question for some more info.

The Pg gem can find the library during compilation and installation because the pg_config executable is on the PATH and it uses that to find libpq . It appears that it doesn't store the path for use at runtime so you have to set the runtime dynamic linker up yourself.

A simple wrapper script (in case you don't want to modify your global environment) is something like:

#!/bin/bash
export DYLD_LIBRARY_PATH=/path/to/pg/lib 
exec rails "$@"

The "$@" basically means "pass all arguments to this script through as if they were passed here directly". It preserves quoting correctly and essentially means that the rails command can't tell you didn't run it directly.

Answer 2

A similar stackoverflow answer proposed removing Postgres.app from your PATH, uninstalling the pg gem, and installing the pg gem again.

(I'm not taking the time to check carefully if that applies to this problem, but it solved a problem I had and I want to spread that solution around since I had trouble finding it.)

Answer 3

I wanted to put my two cents here to answers above.

Sometimes it's enough to just reinstall pg gem.

gem uninstall pg && gem install pg

In my case I upgraded postgresql server from 9.6 up to 14.x and dylib paths were changed.

/opt/local/lib/postgresql96/libpq.5.dylib -> /opt/local/lib/postgresql14/libpq.5.dylib

The gem uses pg_config to determine paths to /opt/local/lib/postgresql[version] folder (named PKGLIBDIR ). To build native library for the gem rake sets paths to dynamic libs by fetching them from pg_config in compile. Once pg gem is compiled the paths are linked forever. So, the reinstallation recompiles and relinks path to the new libraries.