世界の総水産量は年間約9000万トン(養殖含め)だそうですが、世界の鯨が1年に食べる魚類の量は2.8億トンから5億トンになると試算されており(1)、人間の数倍もの水産物が鯨によって消費されているそうです。ヒトの生物量でもせいぜい3億トンかそこら(50kg*70億人=3.5億トン)ですから、すごい量です。とはいえオキアミや微生物など水産物として競合しないものもあるので単純な比較はできませんが。

さて、rails開発していて、見たことのないこんなエラーに遭遇しました。

% rake -T
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:2: warning: already initialized constant Rake::VERSION
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:2: warning: previous definition of VERSION was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:5: warning: already initialized constant Rake::Version::MAJOR
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:5: warning: previous definition of MAJOR was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:5: warning: already initialized constant Rake::Version::MINOR
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:5: warning: previous definition of MINOR was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:5: warning: already initialized constant Rake::Version::BUILD
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:5: warning: previous definition of BUILD was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:5: warning: already initialized constant Rake::Version::OTHER
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:5: warning: previous definition of OTHER was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:7: warning: already initialized constant Rake::Version::NUMBERS
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/version.rb:7: warning: previous definition of NUMBERS was here
WARNING: Possible conflict with Rake extension: String#ext already exists
WARNING: Possible conflict with Rake extension: String#pathmap already exists

...(つらつら続きます)...

/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/task_arguments.rb:107: warning: already initialized constant Rake::EMPTY_TASK_ARGS
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/task_arguments.rb:107: warning: previous definition of EMPTY_TASK_ARGS was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/invocation_chain.rb:54: warning: already initialized constant Rake::InvocationChain::EMPTY
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/invocation_chain.rb:54: warning: previous definition of EMPTY was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/early_time.rb:20: warning: already initialized constant Rake::EARLY
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/early_time.rb:20: warning: previous definition of EARLY was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/late_time.rb:16: warning: already initialized constant Rake::LATE
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/late_time.rb:16: warning: previous definition of LATE was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/backtrace.rb:3: warning: already initialized constant Rake::Backtrace::SYS_KEYS
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/backtrace.rb:3: warning: previous definition of SYS_KEYS was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/backtrace.rb:4: warning: already initialized constant Rake::Backtrace::SYS_PATHS
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/backtrace.rb:4: warning: previous definition of SYS_PATHS was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/backtrace.rb:7: warning: already initialized constant Rake::Backtrace::SUPPRESSED_PATHS
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/backtrace.rb:7: warning: previous definition of SUPPRESSED_PATHS was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/backtrace.rb:11: warning: already initialized constant Rake::Backtrace::SUPPRESSED_PATHS_RE
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/backtrace.rb:11: warning: previous definition of SUPPRESSED_PATHS_RE was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/backtrace.rb:15: warning: already initialized constant Rake::Backtrace::SUPPRESS_PATTERN
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake/backtrace.rb:15: warning: previous definition of SUPPRESS_PATTERN was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake.rb:69: warning: already initialized constant FileList
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake.rb:69: warning: previous definition of FileList was here
/Users/foo/bar/hoge/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake.rb:70: warning: already initialized constant RakeFileUtils
/Users/foo/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/rake-12.0.0/lib/rake.rb:70: warning: previous definition of RakeFileUtils was here

自分の場合はrbenvを使っていたので、rubyの処理系を一旦消した上でもっかい入れ直し、さらにvendor/bundleを消したらなおりました。

% rbenv uninstall 2.4.1
% rbenv install 2.4.1
% rbenv rehash
% rm -rf vendor/bundle
% gem install bundler
% bundle install
% rake -T
rake about                              # List versions of all Rails frameworks and the environment
rake app:template                       # Applies the template supplied by LOCATION=(/path/to/template) or URL
rake app:update                         # Update configs and some other initially generated files (or use just update:configs or update:bin)
rake assets:clean[keep]                 # Remove old compiled assets
rake assets:clobber                     # Remove compiled assets
...

原因は、rails newしたあと一回普通にbundle installしたのですが、その後でbundle install –path=vendor/bundleをしてしまったため、rbenvの下のrubyの中にgemがどばどば入ったのと、railsアプリ内のvendor/bundleの下に入ったgemが一緒にロードされてしまったためです。

上の対処法では両方消した形になりますが、本当は片方だけで良いはず。
自分はついでに.bundle/configの中からBUNDLE_PATHを除去し、vendor/bundleではなくruby処理系の中に入れることにしました（自分のruby使用頻度だとそれであんま困らないので）

備忘録でした。