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Posted to issues@solr.apache.org by "liangkaiwen (via GitHub)" <gi...@apache.org> on 2026/09/22 22:36:54 UTC
[PR] SOLR-18476: Support file suffix based MMapDirectory preload [solr]
liangkaiwen opened a new pull request, #4935:
URL: https://github.com/apache/solr/pull/4935
https://issues.apache.org/jira/browse/SOLR-18476
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# Description
Existing usage of `preload=true` will attempt to load the entire index (filesystem) directory into OS page cache indiscriminately. This can be a problematic take on a good idea in 2 ways: 1) you may not want to run this long synchronous preload over the entire index and 2) you may not have enough physical memory to fit the whole index, so having the ability to prioritize some index files over others would be more practical/useful.
# Solution
Coded using Claude 5.0 Opus
* Added "preloadExtensions" to MMapDirectoryFactory config definition, which allows a comma separate list of file extensions to be provided (does not need to be used in conjunction with preload=true)
* MMapDirectoryFactory's create function uses a preload predicate depending on the configuration. Extensions predicate matches files with extension (after last .) matching any of the provided in the configuration
* When preload=true is provided and preloadExtensions is provided, preloadExtensions behavior will take precedence (whole index not preloaded)
# Tests
* Add unit tests for MMapDirectoryFactory
* Check OS off-heap memory metrics
# Checklist
Please review the following and check all that apply:
- [X] I have reviewed the guidelines for [How to Contribute](https://github.com/apache/solr/blob/main/CONTRIBUTING.md) and my code conforms to the standards described there to the best of my ability.
- [X] I have created a Jira issue and added the issue ID to my pull request title.
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- [X] I have developed this patch against the `main` branch.
- [X] I have run `./gradlew check`.
- [X] I have added tests for my changes.
- [X] I have added documentation for the [Reference Guide](https://github.com/apache/solr/tree/main/solr/solr-ref-guide)
- [X] I have added a [changelog entry](https://github.com/apache/solr/blob/main/dev-docs/changelog.adoc) for my change
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Re: [PR] SOLR-18476: Support file suffix based MMapDirectory preload [solr]
Posted by "sigram (via GitHub)" <gi...@apache.org>.
sigram commented on code in PR #4935:
URL: https://github.com/apache/solr/pull/4935#discussion_r4153762665
##########
solr/core/src/java/org/apache/solr/core/StandardDirectoryFactory.java:
##########
@@ -42,14 +50,77 @@
* behavior.
*
* <p>File based DirectoryFactory implementations generally extend this class.
+ *
+ * <p>Can set the following parameters:
+ *
+ * <ul>
+ * <li>preload -- Whether to load each index file into the OS page cache when that file is opened.
+ * <li>preloadExtensions -- Comma separated file extensions, such as {@code vex,vec}. Only files
+ * whose name ends with a listed extension are loaded into the OS page cache when those files
+ * are opened. Takes precedence over {@code preload}.
+ * </ul>
+ *
+ * <p>Both parameters only apply when the underlying directory is an {@link MMapDirectory}, which is
+ * what {@link FSDirectory#open} selects on most platforms.
*/
public class StandardDirectoryFactory extends CachingDirectoryFactory {
private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
+ private boolean preload;
+ private Set<String> preloadExtensions = Set.of();
+
+ @Override
+ public void init(NamedList<?> args) {
+ super.init(args);
+ SolrParams params = args.toSolrParams();
+ preload = params.getBool("preload", false); // default turn-off
+ preloadExtensions = parsePreloadExtensions(params.get("preloadExtensions"));
+ if (preload && !preloadExtensions.isEmpty()) {
+ log.info(
+ "Ignoring preload=true because preloadExtensions was provided, so only loading files with extensions: {}",
+ preloadExtensions);
+ }
+ }
+
+ private static Set<String> parsePreloadExtensions(String value) {
+ if (value == null) {
+ return Set.of();
+ }
+ Set<String> extensions = new LinkedHashSet<>();
Review Comment:
Why not a plain HashSet? I wouldn't expect the iteration order to matter here.
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Re: [PR] SOLR-18476: Support file suffix based MMapDirectory preload [solr]
Posted by "sigram (via GitHub)" <gi...@apache.org>.
sigram commented on code in PR #4935:
URL: https://github.com/apache/solr/pull/4935#discussion_r4153768653
##########
solr/core/src/java/org/apache/solr/core/StandardDirectoryFactory.java:
##########
@@ -42,14 +50,77 @@
* behavior.
*
* <p>File based DirectoryFactory implementations generally extend this class.
+ *
+ * <p>Can set the following parameters:
Review Comment:
Hmm, maybe change this to "The following parameters are supported" ?
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Re: [PR] SOLR-18476: Support file suffix based MMapDirectory preload [solr]
Posted by "sigram (via GitHub)" <gi...@apache.org>.
sigram commented on PR #4935:
URL: https://github.com/apache/solr/pull/4935#issuecomment-5928538444
The case when the underlying directory is not a MMapDirectory is untested.
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Re: [PR] SOLR-18476: Support file suffix based MMapDirectory preload [solr]
Posted by "alessandrobenedetti (via GitHub)" <gi...@apache.org>.
alessandrobenedetti commented on code in PR #4935:
URL: https://github.com/apache/solr/pull/4935#discussion_r4229799092
##########
solr/core/src/java/org/apache/solr/core/StandardDirectoryFactory.java:
##########
@@ -42,14 +50,77 @@
* behavior.
*
* <p>File based DirectoryFactory implementations generally extend this class.
+ *
+ * <p>Can set the following parameters:
+ *
+ * <ul>
+ * <li>preload -- Whether to load each index file into the OS page cache when that file is opened.
+ * <li>preloadExtensions -- Comma separated file extensions, such as {@code vex,vec}. Only files
+ * whose name ends with a listed extension are loaded into the OS page cache when those files
+ * are opened. Takes precedence over {@code preload}.
+ * </ul>
+ *
+ * <p>Both parameters only apply when the underlying directory is an {@link MMapDirectory}, which is
+ * what {@link FSDirectory#open} selects on most platforms.
*/
public class StandardDirectoryFactory extends CachingDirectoryFactory {
private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
+ private boolean preload;
+ private Set<String> preloadExtensions = Set.of();
+
+ @Override
+ public void init(NamedList<?> args) {
+ super.init(args);
+ SolrParams params = args.toSolrParams();
+ preload = params.getBool("preload", false); // default turn-off
+ preloadExtensions = parsePreloadExtensions(params.get("preloadExtensions"));
+ if (preload && !preloadExtensions.isEmpty()) {
+ log.info(
+ "Ignoring preload=true because preloadExtensions was provided, so only loading files with extensions: {}",
+ preloadExtensions);
+ }
+ }
+
+ private static Set<String> parsePreloadExtensions(String value) {
+ if (value == null) {
+ return Set.of();
+ }
+ Set<String> extensions = new LinkedHashSet<>();
+ for (String extension : value.split(",")) {
+ extension = extension.trim().toLowerCase(Locale.ROOT);
+ if (!extension.isEmpty()) {
+ extensions.add(extension.startsWith(".") ? extension : "." + extension);
+ }
+ }
+ return Collections.unmodifiableSet(extensions);
+ }
+
+ @VisibleForTesting
+ BiPredicate<String, IOContext> preloadPredicate() {
+ if (preloadExtensions.isEmpty()) {
+ return preload ? MMapDirectory.ALL_FILES : MMapDirectory.NO_FILES;
+ }
+ Set<String> extensions = preloadExtensions;
+ return (name, ioContext) -> {
+ int dot = name.lastIndexOf('.');
+ return dot >= 0 && extensions.contains(name.substring(dot).toLowerCase(Locale.ROOT));
+ };
+ }
+
+ /** Applies the configured preload settings, if the given directory supports them. */
+ protected void applyPreload(Directory directory) {
+ if (directory instanceof MMapDirectory mMapDirectory) {
Review Comment:
This defeats the idea of polymorphism, I have to dedicate more mental time on this, but I'm wondering if this should seat here if only affect a MMapDirectory or maybe directly in the MMapDirectory?
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