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https://issues.apache.org/jira/browse/HDFS-15621?focusedWorklogId=581824&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-581824
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ASF GitHub Bot logged work on HDFS-15621:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 13/Apr/21 14:52
Start Date: 13/Apr/21 14:52
Worklog Time Spent: 10m
Work Description: jojochuang commented on a change in pull request #2849:
URL: https://github.com/apache/hadoop/pull/2849#discussion_r612493208
##########
File path:
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeSpi.java
##########
@@ -297,23 +281,18 @@ private static String getSuffix(File f, String prefix) {
* @param metaFile the path to the block meta-data file
Review comment:
need a @param for basePath. Also add that metaFile stores only the
suffix.
##########
File path:
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeSpi.java
##########
@@ -227,27 +227,27 @@
*/
public static class ScanInfo implements Comparable<ScanInfo> {
private final long blockId;
-
/**
- * The block file path, relative to the volume's base directory.
- * If there was no block file found, this may be null. If 'vol'
- * is null, then this is the full path of the block file.
+ * The full path to the folder containing the block / meta files.
*/
- private final String blockSuffix;
-
+ private final File basePath;
/**
- * The suffix of the meta file path relative to the block file.
- * If blockSuffix is null, then this will be the entire path relative
- * to the volume base directory, or an absolute path if vol is also
- * null.
+ * The block file name, with no path
*/
- private final String metaSuffix;
+ private final String blockFile;
+ /**
+ * Holds the meta file name, with no path, only if blockFile is null.
+ * If blockFile is not null, the meta file will be named identically to
+ * the blockFile, but with a suffix like "_1234.meta". If the blockFile
+ * is present, we store only the meta file suffix.
+ */
Review comment:
it would also make sense to copy this comment to the constructor
parameters.
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Issue Time Tracking
-------------------
Worklog Id: (was: 581824)
Time Spent: 50m (was: 40m)
> Datanode DirectoryScanner uses excessive memory
> -----------------------------------------------
>
> Key: HDFS-15621
> URL: https://issues.apache.org/jira/browse/HDFS-15621
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Affects Versions: 3.4.0
> Reporter: Stephen O'Donnell
> Assignee: Stephen O'Donnell
> Priority: Major
> Labels: pull-request-available
> Attachments: Screenshot 2020-10-09 at 14.11.36.png, Screenshot
> 2020-10-09 at 15.20.56.png
>
> Time Spent: 50m
> Remaining Estimate: 0h
>
> We generally work a rule of 1GB heap on a datanode per 1M blocks. For nodes
> with a lot of blocks, this can mean a lot of heap.
> We recently captured a heapdump of a DN with about 22M blocks and found only
> about 1.5GB was occupied by the ReplicaMap. Another 9GB of the heap is taken
> by the DirectoryScanner ScanInfo objects. Most of this memory was alloated to
> strings.
> Checking the strings in question, we can see two strings per scanInfo,
> looking like:
> {code}
> /current/BP-671271071-10.163.205.13-1552020401842/current/finalized/subdir28/subdir17/blk_1180438785
> _106716708.meta
> {code}
> I will update a screen shot from MAT showing this.
> For the first string especially, the part
> "/current/BP-671271071-10.163.205.13-1552020401842/current/finalized/" will
> be the same for every block in the block pool as the scanner is only
> concerned about finalized blocks.
> We can probably also store just the subdir indexes "28" and "27" rather than
> "subdir28/subdir17" and then construct the path when it is requested via the
> getter.
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