[
https://issues.apache.org/jira/browse/SSHD-1220?focusedWorklogId=672472&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-672472
]
ASF GitHub Bot logged work on SSHD-1220:
----------------------------------------
Author: ASF GitHub Bot
Created on: 31/Oct/21 17:58
Start Date: 31/Oct/21 17:58
Worklog Time Spent: 10m
Work Description: lgoldstein commented on a change in pull request #207:
URL: https://github.com/apache/mina-sshd/pull/207#discussion_r739855590
##########
File path: docs/sftp.md
##########
@@ -532,7 +530,27 @@ if (directoryPath instanceof SftpPath) {
// Not an SFTP path -- get the directory listing in whatever other way is
appropriate.
}
```
-So even if an `SftpFileSystem` fulfills the general contract of a
`FileSystem`, a client still has to be aware that
+Alternatively, one can also use the fact that Apache MINA sshd caches the SFTP
file attributes on the `SftpPath` objects it
+returns from a `DirectoryStream`:
+
+```java
+public void processSftpDirectory(SftpPath directoryPath, BiConsumer<Path,
SftpClient.Attributes> process) throws IOException {
+ try (DirectoryStream<Path> dir = Files.newDirectoryStream(directoryPath)) {
+ for (Path path : dir) {
+ if (path instanceof SftpPath) {
+ SftpClient.Attributes attributes = ((SftpPath) path).getAttributes();
+ process.accept(path, attributes);
+ } else {
+ // A DirectoryStream on a directory given by an SftpPath always
returns SftpPath instances as elements.
+ throw new IllegalStateException();
Review comment:
Let's add a message to exception along the lines of "Iterated directory
entry=" + path + " is not an SftpPath as expected"
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Issue Time Tracking
-------------------
Worklog Id: (was: 672472)
Time Spent: 2.5h (was: 2h 20m)
> SFTP: too many LSTAT calls
> --------------------------
>
> Key: SSHD-1220
> URL: https://issues.apache.org/jira/browse/SSHD-1220
> Project: MINA SSHD
> Issue Type: Improvement
> Affects Versions: 2.7.0
> Reporter: Thomas Wolf
> Assignee: Thomas Wolf
> Priority: Major
> Time Spent: 2.5h
> Remaining Estimate: 0h
>
> While looking at an alternate solution for SSHD-1217 I noticed that the
> {{AbstractSftpSubsystemHelper}} makes several LSTAT calls for a single
> {{FileSystem.readAttributes()}} invocation.
> Basically it makes one LSTAT call per supported attributes view; only to
> collect the returned items then in one single map anyway.
> This doesn't make any sense. SFTP file attributes are a single, defined
> structure. If {{AbstractSftpSubsystemHelper.getAttributes()}} needs to
> collect all these different views ({{BasicFileAttributes}},
> {{PosixFileAttributes}}, and so on) on these underlying SFTP attributes, then
> all these views should build upon the same single {{SftpClient.Attributes}}
> gotten exactly _once_.
> This could be solved with careful temporary caching of SFTP attributes on the
> {{SftpPath}} once read while in
> {{AbstractSftpSubsystemHelper.getAttributes()}} and clearing that cache at
> the end.
> The problem is more general, though. The code in several places makes
> up-front checks whether a file exists, is a directory, and so on. This is a
> questionable pattern anyway, since the result of a {{Files.exists()}} is
> outdated immediately; one cannot rely on the file being still there on the
> next access. With an {{SftpPath}}, this {{exists()}} call is an (L)STAT
> remote call getting the attributes. Now look at
> {{AbstractSftpSubsystemHelper.resolveFileAttributes}}: here getting the
> attributes themselves is so guarded, so it makes at least _two_ LSTAT calls.
> This should also be improved.
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