ajfabbri commented on a change in pull request #568: HADOOP-15691 Add PathCapabilities to FS and FC to complement StreamCapabilities URL: https://github.com/apache/hadoop/pull/568#discussion_r326426940
########## File path: hadoop-common-project/hadoop-common/src/site/markdown/filesystem/pathcapabilities.md ########## @@ -0,0 +1,158 @@ +<!--- + 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="PathCapabilities"></a> interface `PathCapabilities` + +The `PathCapabilities` interface provides a way to programmatically query the +operations offered under a given path by an instance of `FileSystem`, `FileContext` +or other implementing class. + +```java +public interface PathCapabilities { + boolean hasPathCapability(Path path, String capability) + throws IOException; +} +``` + +There are a number of goals here: + +1. Allow callers to probe for optional filesystem operations without actually +having to invoke them. +1. Allow filesystems with their own optional per-instance features to declare +whether or not they are active for the specific instance. +1. Allow for fileystem connectors which work with object stores to expose the +fundamental difference in semantics of these stores (e.g: files not visible +until closed, file rename being `O(data)`), directory rename being non-atomic, +etc. + +### Available Capabilities + +Capabilities are defined as strings and split into "Common Capabilites" +and non-standard ones for a specific store. + +The common capabilities are all defined under the prefix `fs.capability.` + +Consult the javadocs for `org.apache.hadoop.fs.CommonPathCapabilities` for these. + + +Individual filesystems MAY offer their own set of capabilities which +can be probed for. These MUST begin with `fs.` + the filesystem schema + Review comment: /schema/scheme/ ? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
