Merge "i18n enabablement"
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specs/juno/i18n-enablement.rst
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specs/juno/i18n-enablement.rst
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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==========================================
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i18n Enablement for Nova
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==========================================
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https://blueprints.launchpad.net/nova/+spec/i18n-enablement
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This BluePrint/Spec proposes completing the enablement of i18n
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(internationalization) support for Nova by turning on the "lazy" translation
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support from Oslo i18n and updating Nova to adhere to the restrictions this
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adds to translatable strings.
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Internationalization implementation has been an on-going effort in OpenStack
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during recent releases. The original blueprint for the Oslo support was
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included in Havana:
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https://blueprints.launchpad.net/oslo/+spec/delayed-message-translation
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Blueprints for this support in Nova have been approved and worked on in
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previous releases
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(https://blueprints.launchpad.net/nova/+spec/user-locale-api).
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During the Icehouse release, the foundational support for internationalization
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was merged into Nova. Specifically the update of Oslo's gettextutils and the
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pre-existing work of explicitly importing '_' from gettextutils.
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To finalize this work in Juno we need to enable the "lazy" translation
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provided in gettextutils and change how messages are manipulated. Enablement
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of lazy translation will allow end users to not only have logs produced in
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multiple languages, but adds the ability for REST API messages to also be
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returned in the language chosen by the user. This functionality is important
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to support the use of OpenStack by the international community.
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Problem description
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===================
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Today all users of Nova must agree on a common locale to use to translate
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messages. This is because messages are translated when they are created.
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There is a need for different Nova users to be able to use different
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translations simultaneously.
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Proposed change
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===============
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This proposal is to use the i18n support provided as part of Oslo in order
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to enable "lazy" translation of messages. This support, instead of
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immediately translating the messages, creates a Message object which
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holds the message and replacement text until the message can be translated
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using the locale associated with the Accept-Language Header from the
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user request.
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The code changes will be done as a series of patches that culminate in a
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patch that adds a call to 'gettextutils.enable_lazy()' in
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nova/cmd/__init__.py.
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A few prepratory patches will be required due to the limitations of the
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i18n support:
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* The Message class does not support str(), so use of str() on translatable
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messages must be removed. The most common case being when it is used on an
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exception that is being put into another translatable message or logged.
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This is due to the requirement by logging in Python 2.6 that str() return
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a UnicodeError.
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* The Message class does not support concatenation of translatable messages,
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so concatenation of translatable messages must be replaced with formatting.
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This is due to the complexity caused by trying to concatenate two
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independent Message instances potentially with overlapping replacement keys.
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There are very few of these and the use of formatting allows for better
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translation by translators.
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Alternatives
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------------
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None.
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Data model impact
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-----------------
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None.
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REST API impact
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---------------
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There is no additional changes to the REST API other than the fact
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that the change enables the user to specify the language they
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wish REST API responses to be returned in using the Accept-Language
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option.
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Security impact
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---------------
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None.
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Notifications impact
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--------------------
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None.
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Other end user impact
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---------------------
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None.
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Performance Impact
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------------------
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None.
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Other deployer impact
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---------------------
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Once merged this feature is immediately available to users.
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Developer impact
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----------------
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The developer impacts have already been in place for some time. Developers
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have been using _() around messages that need translation.
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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<jecarey@us.ibm.com>
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Other contributors:
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Work Items
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----------
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I am planning to implement this as three patches in this order:
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* Remove concatenations of translatable messages
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* Remove use of str() on translatable messages
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* Add enable_lazy to nova/cmd/__init__.py
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* Investigate and add hacking checks to catch i18n unfriendly practices
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Dependencies
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============
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None.
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* Note that gettextutil was synced with the latest oslo-incubator via
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commit 185e4562df47a101cf41d1e66d75de2644c78022.
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Testing
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=======
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* There will be a tempest test added for Nova that will ensure that
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lazy translation is working properly.
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* Hacking checks will be investigated and added for failures caused when
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enabling lazy translation.
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* For example the changes in
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https://review.openstack.org/#/q/status:abandoned+project:openstack/
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nova+branch:master+topic:bp/i18n--messages,n,z>
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which includes using str() (or six.text_type) on an exception used
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as replacement text.
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Documentation Impact
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====================
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None.
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References
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==========
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* Mailing list discussion initiated by FFE rejected request for adding i18n to
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Icehouse:
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https://www.mail-archive.com/openstack-dev@lists.openstack.org/msg18617.html
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* Accept-Language header: http://www.w3.org/International/questions/qa-accept-lang-locale
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