python - 为什么 cqlsh 失败并出现 LookupError : unknown encoding?

Question

我刚刚在 Mac OS X 10.9.4 上使用 brew 安装了 Cassandra:

➜  ~  brew info cassandra
cassandra: stable 2.1.0
http://cassandra.apache.org
/usr/local/Cellar/cassandra/2.0.9 (3466 files, 79M) *
  Built from source
From: https://github.com/Homebrew/homebrew/blob/master/Library/Formula/cassandra.rb
==> Caveats
If you plan to use the CQL shell (cqlsh), you will need the Python CQL library
installed. Since Homebrew prefers using pip for Python packages, you can
install that using:

  pip install cql

To have launchd start cassandra at login:
    ln -sfv /usr/local/opt/cassandra/*.plist ~/Library/LaunchAgents
Then to load cassandra now:
    launchctl load ~/Library/LaunchAgents/homebrew.mxcl.cassandra.plist
➜  ~  uname -a
Darwin xxx 13.3.0 Darwin Kernel Version 13.3.0: Tue Jun  3 21:27:35 PDT 2014; root:xnu-2422.110.17~1/RELEASE_X86_64 x86_64

按照上面信息消息中的建议，为了安装 cql，我执行了 sudo easy_install pip，然后是 pip install cql。

安装软件后，在执行 cqlsh 时我遇到了错误:

➜  ~  cqlsh
Traceback (most recent call last):
  File "/usr/local/bin/cqlsh", line 2084, in <module>
    main(*read_options(sys.argv[1:], os.environ))
  File "/usr/local/bin/cqlsh", line 2067, in main
    single_statement=options.execute)
  File "/usr/local/bin/cqlsh", line 509, in __init__
    self.output_codec = codecs.lookup(encoding)
LookupError: unknown encoding:

我该如何解决？

Answer 1

经过一些谷歌搜索和调试后，事实证明对 locale.getpreferredencoding() 的调用需要正确的 LC_ALL，如 22.2. locale — Internationalization services 中所述。 :

To maintain compatibility with other platforms, not only the LANG variable is tested, but a list of variables given as envvars parameter. The first found to be defined will be used. envvars defaults to the search path used in GNU gettext; it must always contain the variable name LANG. The GNU gettext search path contains 'LANGUAGE', 'LC_ALL', 'LC_CTYPE', and 'LANG', in that order.

在我的系统上 LC_ALL 被设置为 pl_PL:

➜  ~  echo $LC_ALL
pl_PL

将 LC_ALL 更改为 pl 或 pl_pl.utf-8 后，Cassandra shell cqlsh 启动正常:

➜  ~  export LC_ALL=pl_pl.utf-8
➜  ~  cqlsh
Connected to Test Cluster at localhost:9160.
[cqlsh 4.1.1 | Cassandra 2.0.9 | CQL spec 3.1.1 | Thrift protocol 19.39.0]
Use HELP for help.
cqlsh>

查看主题 Problem start cqlsh on OSX - Lion用于检查语言环境的示例 Python 应用程序:

python -c 'import locale, codecs; encoding = locale.getpreferredencoding(); print encoding; print codecs.lookup(encoding)'

一旦运行正常，问题就可以认为已经解决了。