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https://issues.apache.org/jira/browse/ASTERIXDB-3407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17850211#comment-17850211
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ASF subversion and git services commented on ASTERIXDB-3407:
------------------------------------------------------------
Commit 2941a842e2b7758aa7f647477134c8ce1b9ea285 in asterixdb's branch
refs/heads/master from Wail Alkowaileet
[ https://gitbox.apache.org/repos/asf?p=asterixdb.git;h=2941a842e2 ]
[ASTERIXDB-3407][STO] Increment page counter for valid pages
- user model changes: no
- storage format changes: no
- interface changes: no
Details:
When reading a valid page from the buffer cache,
the page counter in CloudMegaPageReadContext should
be incremented.
Change-Id: I7cfa419d216cf875a4e403c8b90b5a0007bf9bfc
Reviewed-on: https://asterix-gerrit.ics.uci.edu/c/asterixdb/+/18323
Integration-Tests: Jenkins <[email protected]>
Tested-by: Jenkins <[email protected]>
Reviewed-by: Murtadha Hubail <[email protected]>
> Increment page counter when skipping a valid page's cloud bytes
> ---------------------------------------------------------------
>
> Key: ASTERIXDB-3407
> URL: https://issues.apache.org/jira/browse/ASTERIXDB-3407
> Project: Apache AsterixDB
> Issue Type: Bug
> Components: STO - Storage
> Affects Versions: 0.9.10
> Reporter: Wail Y. Alkowaileet
> Assignee: Wail Y. Alkowaileet
> Priority: Critical
> Fix For: 0.9.10
>
>
> An issue was observed when testing cloud caching:
> {noformat}
> Failure while trying to read a page from disk
> org.apache.hyracks.api.exceptions.HyracksDataException: java.io.IOException:
> FAILED_TO_UNCOMPRESS(5) {noformat}
>
> Given the following code snippet in
> [CloudMegaPageReadContext.java|https://github.com/apache/asterixdb/blob/master/hyracks-fullstack/hyracks/hyracks-storage-am-lsm-btree-column/src/main/java/org/apache/hyracks/storage/am/lsm/btree/column/cloud/buffercache/read/CloudMegaPageReadContext.java]
> {noformat}
> @Override
> public void onPin(ICachedPage page) throws HyracksDataException {
> CloudCachedPage cachedPage = (CloudCachedPage) page;
> if (gapStream != null && cachedPage.skipCloudStream()) {
> /*
> * This page is requested but the buffer cache has a valid copy
> in memory. Also, the page itself was
> * requested to be read from the cloud. Since this page is valid,
> no buffer cache read() will be performed.
> * As the buffer cache read() is also responsible for persisting
> the bytes read from the cloud, we can end
> * up writing the bytes of this page in the position of another
> page. Therefore, we should skip the bytes
> * for this particular page to avoid placing the bytes of this
> page into another page's position.
> */
> try {
> long remaining = cachedPage.getCompressedPageSize();
> while (remaining > 0) {
> remaining -= gapStream.skip(remaining);
> }
> } catch (IOException e) {
> throw HyracksDataException.create(e);
> }
> }
> } {noformat}
>
> The issue appeared when the following sequence is performed to read a range
> of columnar pages
> 1- Reading N *valid* from the buffer cache (i.e., the buffer cache has those
> pages cached in memory)
> 2- Doing a read of a page that requires to be retrieved from the cloud. A
> stream will be created. However,
> [pageCounter|https://github.com/apache/asterixdb/blob/7b3f1eb481a54119529d1372df148468613dd69e/hyracks-fullstack/hyracks/hyracks-storage-am-lsm-btree-column/src/main/java/org/apache/hyracks/storage/am/lsm/btree/column/cloud/buffercache/read/CloudMegaPageReadContext.java#L53]
> was never incremented when the N valid pages where pinned.
> 3- The [created
> stream|https://github.com/apache/asterixdb/blob/7b3f1eb481a54119529d1372df148468613dd69e/hyracks-fullstack/hyracks/hyracks-storage-am-lsm-btree-column/src/main/java/org/apache/hyracks/storage/am/lsm/btree/column/cloud/buffercache/read/CloudMegaPageReadContext.java#L191]
> will start from the page that requires to be read from the cloud in addition
> to
> [numberOfContiguousPages|https://github.com/apache/asterixdb/blob/7b3f1eb481a54119529d1372df148468613dd69e/hyracks-fullstack/hyracks/hyracks-storage-am-lsm-btree-column/src/main/java/org/apache/hyracks/storage/am/lsm/btree/column/cloud/buffercache/read/CloudMegaPageReadContext.java#L52]
> -
> [pageCounter|https://github.com/apache/asterixdb/blob/7b3f1eb481a54119529d1372df148468613dd69e/hyracks-fullstack/hyracks/hyracks-storage-am-lsm-btree-column/src/main/java/org/apache/hyracks/storage/am/lsm/btree/column/cloud/buffercache/read/CloudMegaPageReadContext.java#L53C17-L53C28].
> The issue is
> [pageCounter|https://github.com/apache/asterixdb/blob/7b3f1eb481a54119529d1372df148468613dd69e/hyracks-fullstack/hyracks/hyracks-storage-am-lsm-btree-column/src/main/java/org/apache/hyracks/storage/am/lsm/btree/column/cloud/buffercache/read/CloudMegaPageReadContext.java#L53C17-L53C28]
> was never incremented (i.e., it is 0). Thus, we will request more pages than
> we suppose to read. This will be OK if the component has those pages.
> However, if the requested range of pages exceeds the component's pages, then
> an undefined behavior will occur. In the case with compressed pages, we got
> an incompressible page.
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