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https://issues.apache.org/jira/browse/HADOOP-18671?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17718670#comment-17718670
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ASF GitHub Bot commented on HADOOP-18671:
-----------------------------------------
taklwu commented on code in PR #5553:
URL: https://github.com/apache/hadoop/pull/5553#discussion_r1182859537
##########
hadoop-common-project/hadoop-common/src/site/markdown/filesystem/safemode.md:
##########
@@ -0,0 +1,45 @@
+<!---
+ 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.
+-->
+
+# <a name="SafeMode"></a> interface `SafeMode`
+
+The `SafeMode` interface provides a way to perform safe mode actions and
obtain the
+status after such actions performed to the `FileSystem`.
+
+This is admin only interface, should be implemented accordingly when necessary
to
+Filesystem that support safe mode, e.g. `DistributedFileSystem` (HDFS) and
+`ViewDistributedFileSystem`.
+
+```java
+public interface SafeMode {
+ default boolean setSafeMode(SafeModeAction action) throws IOException {
+ return setSafeMode(action, false);
+ }
+ boolean setSafeMode(SafeModeAction action, boolean isChecked) throws
IOException;
+}
+```
+
+The goals of this interface is allow any file system implementation to share
the
+same concept of safe mode with the following actions and states
+
+Safe mode actions
+1. `GET`, get the safe mode status of the file system.
+1. `ENTER`, enter the safe mode for the file system.
+1. `LEAVE`, exit safe mode for the file system gracefully.
+1. `FORCE_EXIT`, exit safe mode for the file system even if there is any
ongoing data process.
+
+Safe mode states
+1. `ON`, when safe mode is on.
+1. `OFF`, when safe mode is off, usually it's the result of safe mode actions
+with `GET`, `LEAVE`, `FORCE_EXIT`
Review Comment:
safe mode does not have `hasPathCapability` because it is a filesystem admin
interface and the input for the `setSafeMode` does not include any direct path
(see below)
```
boolean setSafeMode(SafeModeAction action, boolean isChecked) throws
IOException;
```
so I think you're referring to the `LeaseRecoverable` interface, and I
should have missed that at the beginning, let me add it back
> Add recoverLease(), setSafeMode(), isFileClosed() APIs to FileSystem
> --------------------------------------------------------------------
>
> Key: HADOOP-18671
> URL: https://issues.apache.org/jira/browse/HADOOP-18671
> Project: Hadoop Common
> Issue Type: New Feature
> Components: fs
> Reporter: Wei-Chiu Chuang
> Priority: Major
> Labels: pull-request-available
>
> We are in the midst of enabling HBase and Solr to run on Ozone.
> An obstacle is that HBase relies heavily on HDFS APIs and semantics for its
> Write Ahead Log (WAL) file (similarly, for Solr's transaction log). We
> propose to push up these HDFS APIs, i.e. recoverLease(), setSafeMode(),
> isFileClosed() to FileSystem abstraction so that HBase and other applications
> do not need to take on Ozone dependency at compile time. This work will
> (hopefully) enable HBase to run on other storage system implementations in
> the future.
> There are other HDFS features that HBase uses, including hedged read and
> favored nodes. Those are FS-specific optimizations and are not critical to
> enable HBase on Ozone.
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