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https://issues.apache.org/jira/browse/HADOOP-16202?focusedWorklogId=536032&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-536032
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ASF GitHub Bot logged work on HADOOP-16202:
-------------------------------------------
Author: ASF GitHub Bot
Created on: 14/Jan/21 14:58
Start Date: 14/Jan/21 14:58
Worklog Time Spent: 10m
Work Description: steveloughran commented on a change in pull request
#2168:
URL: https://github.com/apache/hadoop/pull/2168#discussion_r557456802
##########
File path:
hadoop-common-project/hadoop-common/src/site/markdown/filesystem/openfile.md
##########
@@ -0,0 +1,290 @@
+<!---
+ 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. See accompanying LICENSE file.
+-->
+
+# `openFile()`
+
+Create a builder to open a file, supporting options
+both standard and filesystem specific. The return
+value of the `build()` call is a `Future<FSDataInputStream>`,
+which must be waited on. The file opening may be
+asynchronous, and it may actually be postponed (including
+permission/existence checks) until reads are actually
+performed.
+
+This API call was added to `FileSystem` and `FileContext` in
+Hadoop 3.3.0; it was tuned in Hadoop 3.3.1 as follows.
+
+* Support `opt(key, long)` and `must(key, long)`.
+* Declare that `withFileStatus(null)` is allowed.
+* Declare that `withFileStatus(status)` only checks
+ the filename of the path, not the full path.
+ This is needed to support passthrough/mounted filesystems.
+
+
+### <a name="openfile(path)"></a> `FSDataInputStreamBuilder openFile(Path
path)`
Review comment:
oops. Will do. I won't rename the fsdatainputstreambuilder.md file
though -it's already shipped and I don't want to break links across versions.
Will change all text references
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Issue Time Tracking
-------------------
Worklog Id: (was: 536032)
Time Spent: 7.5h (was: 7h 20m)
> Stabilize openFile() and adopt internally
> -----------------------------------------
>
> Key: HADOOP-16202
> URL: https://issues.apache.org/jira/browse/HADOOP-16202
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs, fs/s3, tools/distcp
> Affects Versions: 3.3.0
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Priority: Major
> Labels: pull-request-available
> Time Spent: 7.5h
> Remaining Estimate: 0h
>
> The {{openFile()}} builder API lets us add new options when reading a file
> Add an option {{"fs.s3a.open.option.length"}} which takes a long and allows
> the length of the file to be declared. If set, *no check for the existence of
> the file is issued when opening the file*
> Also: withFileStatus() to take any FileStatus implementation, rather than
> only S3AFileStatus -and not check that the path matches the path being
> opened. Needed to support viewFS-style wrapping and mounting.
> and Adopt where appropriate to stop clusters with S3A reads switched to
> random IO from killing download/localization
> * fs shell copyToLocal
> * distcp
> * IOUtils.copy
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