[catapult] - Copy Telemetry's gsutilz over to third_party.

third_party/gsutil/gslib/addlhelp/metadata.py

+# -*- coding: utf-8 -*-
+# Copyright 2012 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Additional help about object metadata."""
+
+from __future__ import absolute_import
+
+from gslib.help_provider import HelpProvider
+
+_DETAILED_HELP_TEXT = ("""
+<B>OVERVIEW OF METADATA</B>
+  Objects can have associated metadata, which control aspects of how
+  GET requests are handled, including Content-Type, Cache-Control,
+  Content-Disposition, and Content-Encoding (discussed in more detail in
+  the subsections below). In addition, you can set custom metadata that
+  can be used by applications (e.g., tagging that particular objects possess
+  some property).
+
+  There are two ways to set metadata on objects:
+
+  - at upload time you can specify one or more headers to associate with
+    objects, using the gsutil -h option.  For example, the following command
+    would cause gsutil to set the Content-Type and Cache-Control for each
+    of the files being uploaded:
+
+      gsutil -h "Content-Type:text/html" \\
+             -h "Cache-Control:public, max-age=3600" cp -r images \\
+             gs://bucket/images
+
+    Note that -h is an option on the gsutil command, not the cp sub-command.
+
+  - You can set or remove metadata fields from already uploaded objects using
+    the gsutil setmeta command. See "gsutil help setmeta".
+
+  More details about specific pieces of metadata are discussed below.
+
+
+<B>CONTENT TYPE</B>
+  The most commonly set metadata is Content-Type (also known as MIME type),
+  which allows browsers to render the object properly.
+  gsutil sets the Content-Type automatically at upload time, based on each
+  filename extension. For example, uploading files with names ending in .txt
+  will set Content-Type to text/plain. If you're running gsutil on Linux or
+  MacOS and would prefer to have content type set based on naming plus content
+  examination, see the use_magicfile configuration variable in the gsutil/boto
+  configuration file (See also "gsutil help config"). In general, using
+  use_magicfile is more robust and configurable, but is not available on
+  Windows.
+
+  If you specify a Content-Type header with -h when uploading content (like the
+  example gsutil command given in the previous section), it overrides the
+  Content-Type that would have been set based on filename extension or content.
+  This can be useful if the Content-Type detection algorithm doesn't work as
+  desired for some of your files.
+
+  You can also completely suppress content type detection in gsutil, by
+  specifying an empty string on the Content-Type header:
+
+    gsutil -h 'Content-Type:' cp -r images gs://bucket/images
+
+  In this case, the Google Cloud Storage service will not attempt to detect
+  the content type. In general this approach will work better than using
+  filename extension-based content detection in gsutil, because the list of
+  filename extensions is kept more current in the server-side content detection
+  system than in the Python library upon which gsutil content type detection
+  depends. (For example, at the time of writing this, the filename extension
+  ".webp" was recognized by the server-side content detection system, but
+  not by gsutil.)
+
+
+<B>CACHE-CONTROL</B>
+  Another commonly set piece of metadata is Cache-Control, which allows
+  you to control whether and for how long browser and Internet caches are
+  allowed to cache your objects. Cache-Control only applies to objects with
+  a public-read ACL. Non-public data are not cacheable.
+
+  Here's an example of uploading an object set to allow caching:
+
+    gsutil -h "Cache-Control:public,max-age=3600" cp -a public-read \\
+           -r html gs://bucket/html
+
+  This command would upload all files in the html directory (and subdirectories)
+  and make them publicly readable and cacheable, with cache expiration of
+  one hour.
+
+  Note that if you allow caching, at download time you may see older versions
+  of objects after uploading a newer replacement object. Note also that because
+  objects can be cached at various places on the Internet there is no way to
+  force a cached object to expire globally (unlike the way you can force your
+  browser to refresh its cache).
+
+  Another use of the Cache-Control header is through the "no-transform" value,
+  which instructs Google Cloud Storage to not apply any content transformations
+  based on specifics of a download request, such as removing gzip
+  content-encoding for incompatible clients.  Note that this parameter is only
+  respected by the XML API. The Google Cloud Storage JSON API respects only the
+  no-cache and max-age Cache-Control parameters.
+
+  Note that if you upload an object with a public-read ACL and don't include a
+  Cache-Control header, it will be served with a Cache-Control header allowing
+  the object to be cached for 3600 seconds. This will not happen if the object
+  is uploaded with a non-public ACL and then changed to public. Moreover, if you
+  upload an object with a public-read ACL and later change the ACL not to be
+  public-read, the object will no longer be served with the default
+  Cache-Control header noted above (so will be served as not cacheable).
+  
+  For details about how to set the Cache-Control header see
+  "gsutil help setmeta".
+
+
+<B>CONTENT-ENCODING</B>
+  You can specify a Content-Encoding to indicate that an object is compressed
+  (for example, with gzip compression) while maintaining its Content-Type.
+  You will need to ensure that the files have been compressed using the
+  specified Content-Encoding before using gsutil to upload them. Consider the
+  following example for Linux:
+
+    echo "Highly compressible text" | gzip > foo.txt
+    gsutil -h "Content-Encoding:gzip" -h "Content-Type:text/plain" \\
+      cp foo.txt gs://bucket/compressed
+
+  Note that this is different from uploading a gzipped object foo.txt.gz with
+  Content-Type: application/x-gzip because most browsers are able to
+  dynamically decompress and process objects served with Content-Encoding: gzip
+  based on the underlying Content-Type.
+
+  For compressible content, using Content-Encoding: gzip saves network and
+  storage costs, and improves content serving performance. However, for content
+  that is already inherently compressed (archives and many media formats, for
+  instance) applying another level of compression via Content-Encoding is
+  typically detrimental to both object size and performance and should be
+  avoided.
+
+  Note also that gsutil provides an easy way to cause content to be compressed
+  and stored with Content-Encoding: gzip: see the -z option in "gsutil help cp".
+
+
+<B>CONTENT-DISPOSITION</B>
+  You can set Content-Disposition on your objects, to specify presentation
+  information about the data being transmitted. Here's an example:
+
+    gsutil -h 'Content-Disposition:attachment; filename=filename.ext' \\
+      cp -r attachments gs://bucket/attachments
+
+  Setting the Content-Disposition allows you to control presentation style
+  of the content, for example determining whether an attachment should be
+  automatically displayed vs should require some form of action from the user to
+  open it.  See http://www.w3.org/Protocols/rfc2616/rfc2616-sec19.html#sec19.5.1
+  for more details about the meaning of Content-Disposition.
+
+
+<B>CUSTOM METADATA</B>
+  You can add your own custom metadata (e.g,. for use by your application)
+  to an object by setting a header that starts with "x-goog-meta", for example:
+
+    gsutil -h x-goog-meta-reviewer:jane cp mycode.java gs://bucket/reviews
+
+  You can add multiple differently named custom metadata fields to each object.
+
+
+<B>SETTABLE FIELDS; FIELD VALUES</B>
+  You can't set some metadata fields, such as ETag and Content-Length. The
+  fields you can set are:
+
+  - Cache-Control
+  - Content-Disposition
+  - Content-Encoding
+  - Content-Language
+  - Content-MD5
+  - Content-Type
+  - Any field starting with a matching Cloud Storage Provider
+    prefix, such as x-goog-meta- (i.e., custom metadata).
+
+  Header names are case-insensitive.
+
+  x-goog-meta- fields can have data set to arbitrary Unicode values. All
+  other fields must have ASCII values.
+
+
+<B>VIEWING CURRENTLY SET METADATA</B>
+  You can see what metadata is currently set on an object by using:
+
+    gsutil ls -L gs://the_bucket/the_object
+""")
+
+
+class CommandOptions(HelpProvider):
+  """Additional help about object metadata."""
+
+  # Help specification. See help_provider.py for documentation.
+  help_spec = HelpProvider.HelpSpec(
+      help_name='metadata',
+      help_name_aliases=[
+          'cache-control', 'caching', 'content type', 'mime type', 'mime',
+          'type'],
+      help_type='additional_help',
+      help_one_line_summary='Working With Object Metadata',
+      help_text=_DETAILED_HELP_TEXT,
+      subcommand_help_text={},
+  )