SOLR-17932: Remove deprecated Solr Transient Cores (#3699)

* Remove transient cores
* .lazy is no longer a metric, removed from various tests related to metrics
* Remove (Core) CloserThread  and remove SolrCores.pendingCloses

---------

Co-authored-by: David Smiley <[email protected]>

Author: epugh

solr/CHANGES.txt

@@ -165,6 +165,8 @@ Deprecation Removals
  for that (which will be removed eventually), and many tests still use it.  Also, there were server metrics
  relating to HTTP client connection pools that no longer exist.  (David Smiley)
 
+* SOLR-17932: Remove transient Solr cores capability. (Eric Pugh, David Smiley)
+
 Dependency Upgrades
 ---------------------
 

solr/api/src/java/org/apache/solr/client/api/model/CreateCoreParams.java

@@ -17,7 +17,6 @@
 package org.apache.solr.client.api.model;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
-import io.swagger.v3.oas.annotations.media.Schema;
 import java.util.Map;
 
 public class CreateCoreParams {
@@ -38,10 +37,6 @@ public class CreateCoreParams {
 
   @JsonProperty public Boolean loadOnStartup;
 
-  @Schema(name = "isTransient")
-  @JsonProperty("transient")
-  public Boolean isTransient;
-
   @JsonProperty public String shard;
 
   @JsonProperty public String collection;

solr/core/src/java/org/apache/solr/core/CoreContainer.java

@@ -239,7 +239,6 @@ public JerseyAppHandlerCache getJerseyAppHandlerCache() {
 
   protected volatile LogWatcher<?> logging = null;
 
-  private volatile CloserThread backgroundCloser = null;
   protected final NodeConfig cfg;
   protected final SolrResourceLoader loader;
 
@@ -894,12 +893,6 @@ private void loadInternal() {
         "loaded",
         SolrInfoBean.Category.CONTAINER.toString(),
         "cores");
-    solrMetricsContext.gauge(
-        solrCores::getNumLoadedTransientCores,
-        true,
-        "lazy",
-        SolrInfoBean.Category.CONTAINER.toString(),
-        "cores");
     solrMetricsContext.gauge(
         solrCores::getNumUnloadedCores,
         true,
@@ -1028,7 +1021,7 @@ private void loadInternal() {
       status |= CORE_DISCOVERY_COMPLETE;
 
       for (final CoreDescriptor cd : cds) {
-        if (cd.isTransient() || !cd.isLoadOnStartup()) {
+        if (!cd.isLoadOnStartup()) {
           solrCores.addCoreDescriptor(cd);
         } else if (asyncSolrCoreLoad) {
           solrCores.markCoreAsLoading(cd);
@@ -1069,10 +1062,6 @@ private void loadInternal() {
         }
       }
 
-      // Start the background thread
-      backgroundCloser = new CloserThread(this, solrCores, cfg);
-      backgroundCloser.start();
-
     } finally {
       coreLoadExecutor.shutdown(); // doesn't block
       if (!asyncSolrCoreLoad) {
@@ -1259,31 +1248,6 @@ public void shutdown() {
 
       ExecutorUtil.shutdownAndAwaitTermination(coreLoadExecutor); // actually already shutdown
 
-      // First wake up the closer thread, it'll terminate almost immediately since it checks
-      // isShutDown.
-      synchronized (solrCores.getModifyLock()) {
-        solrCores.getModifyLock().notifyAll(); // wake up anyone waiting
-      }
-      if (backgroundCloser
-          != null) { // Doesn't seem right, but tests get in here without initializing the core.
-        try {
-          while (true) {
-            backgroundCloser.join(15000);
-            if (backgroundCloser.isAlive()) {
-              synchronized (solrCores.getModifyLock()) {
-                solrCores.getModifyLock().notifyAll(); // there is a race we have to protect against
-              }
-            } else {
-              break;
-            }
-          }
-        } catch (InterruptedException e) {
-          Thread.currentThread().interrupt();
-          if (log.isDebugEnabled()) {
-            log.debug("backgroundCloser thread was interrupted before finishing");
-          }
-        }
-      }
       // Now clear all the cores that are being operated upon.
       solrCores.close();
 
@@ -1877,13 +1841,8 @@ public List<SolrCore> getCores() {
   }
 
   /**
-   * Gets the permanent and transient cores that are currently loaded, i.e. cores that have 1:
-   * loadOnStartup=true and are either not-transient or, if transient, have been loaded and have not
-   * been aged out 2: loadOnStartup=false and have been loaded but are either non-transient or have
-   * not been aged out.
-   *
-   * <p>Put another way, this will not return any names of cores that are lazily loaded but have not
-   * been called for yet or are transient and either not loaded or have been swapped out.
+   * Gets the cores that are currently loaded, i.e. cores that have 1: loadOnStartup=true and have
+   * been loaded and 2: loadOnStartup=false and have been subsequently loaded.
    *
    * <p>For efficiency, prefer to check {@link #isLoaded(String)} instead of {@link
    * #getLoadedCoreNames()}.contains(coreName).
@@ -1896,8 +1855,7 @@ public List<String> getLoadedCoreNames() {
   }
 
   /**
-   * Gets a collection of all the cores, permanent and transient, that are currently known, whether
-   * they are loaded or not.
+   * Gets a collection of all the cores that are currently known, whether they are loaded or not.
    *
    * <p>For efficiency, prefer to check {@link #getCoreDescriptor(String)} != null instead of {@link
    * #getAllCoreNames()}.contains(coreName).
@@ -1910,8 +1868,8 @@ public List<String> getAllCoreNames() {
   }
 
   /**
-   * Gets the total number of cores, including permanent and transient cores, loaded and unloaded
-   * cores. Faster equivalent for {@link #getAllCoreNames()}.size().
+   * Gets the total number of cores, including both loaded and unloaded cores. Faster equivalent to
+   * {@link #getAllCoreNames()}.size().
    */
   public int getNumAllCores() {
     return solrCores.getNumAllCores();
@@ -2143,16 +2101,11 @@ private void unloadWithoutCoreOp(
           ErrorCode.BAD_REQUEST, "Cannot unload non-existent core [" + name + "]");
     }
 
-    boolean close = solrCores.isLoadedNotPendingClose(name);
+    boolean close = solrCores.isLoaded(name);
     SolrCore core = solrCores.remove(name);
 
     solrCores.removeCoreDescriptor(cd);
     coresLocator.delete(this, cd);
-    if (core == null) {
-      // transient core
-      SolrCore.deleteUnloadedCore(cd, deleteDataDir, deleteInstanceDir);
-      return;
-    }
 
     // delete metrics specific to this core
     metricManager.removeRegistry(core.getCoreMetricManager().getRegistryName());
@@ -2264,16 +2217,13 @@ public SolrCore getCore(String name, UUID id) {
     // if there was an error initializing this core, throw a 500
     // error with the details for clients attempting to access it.
     CoreLoadFailure loadFailure = getCoreInitFailures().get(name);
-    if (null != loadFailure) {
+    if (loadFailure != null) {
       throw new SolrCoreInitializationException(name, loadFailure.exception);
     }
-    // This is a bit of awkwardness where SolrCloud and transient cores don't play nice together.
-    // For transient cores, we have to allow them to be created at any time there hasn't been a core
-    // load failure (use reload to cure that). But for
-    // TestConfigSetsAPI.testUploadWithScriptUpdateProcessor, this needs to _not_ try to load the
-    // core if the core is null and there was an error. If you change this, be sure to run both
-    // TestConfigSetsAPI and TestLazyCores
-    if (desc == null || zkSys.getZkController() != null) return null;
+
+    if (desc == null || zkSys.getZkController() != null) {
+      return null;
+    }
 
     // This will put an entry in pending core ops if the core isn't loaded. Here's where moving the
     // waitAddPendingCoreOps to createFromDescriptor would introduce a race condition.
@@ -2574,45 +2524,3 @@ public void addKeyVal(Object map, Object key, Object val) throws IOException {
         });
   }
 }
-
-class CloserThread extends Thread {
-  CoreContainer container;
-  SolrCores solrCores;
-  NodeConfig cfg;
-
-  CloserThread(CoreContainer container, SolrCores solrCores, NodeConfig cfg) {
-    super("CloserThread");
-    this.container = container;
-    this.solrCores = solrCores;
-    this.cfg = cfg;
-  }
-
-  // It's important that this be the _only_ thread removing things from pendingDynamicCloses!
-  // This is single-threaded, but I tried a multithreaded approach and didn't see any performance
-  // gains, so there's no good justification for the complexity. I suspect that the locking on
-  // things like DefaultSolrCoreState essentially create a single-threaded process anyway.
-  @Override
-  public void run() {
-    while (!container.isShutDown()) {
-      synchronized (solrCores.getModifyLock()) { // need this so we can wait and be awoken.
-        try {
-          solrCores.getModifyLock().wait();
-        } catch (InterruptedException e) {
-          // Well, if we've been told to stop, we will. Otherwise, continue on and check to see if
-          // there are any cores to close.
-        }
-      }
-
-      SolrCore core;
-      while (!container.isShutDown() && (core = solrCores.getCoreToClose()) != null) {
-        assert core.getOpenCount() == 1;
-        try {
-          MDCLoggingContext.setCore(core);
-          core.close(); // will clear MDC
-        } finally {
-          solrCores.removeFromPendingOps(core.getName());
-        }
-      }
-    }
-  }
-}

solr/core/src/java/org/apache/solr/core/CoreDescriptor.java

@@ -56,7 +56,6 @@ public class CoreDescriptor {
   public static final String CORE_COLLECTION = "collection";
   public static final String CORE_PROPERTIES = "properties";
   public static final String CORE_LOADONSTARTUP = "loadOnStartup";
-  public static final String CORE_TRANSIENT = "transient";
   public static final String CORE_NODE_NAME = "coreNodeName";
   public static final String CORE_CONFIGSET = "configSet";
   public static final String CORE_CONFIGSET_PROPERTIES = "configSetProperties";
@@ -89,7 +88,6 @@ public Properties getPersistableUserProperties() {
           CORE_SCHEMA, "schema.xml",
           CORE_CONFIGSET_PROPERTIES, ConfigSetProperties.DEFAULT_FILENAME,
           CORE_DATADIR, "data" + FileSystems.getDefault().getSeparator(),
-          CORE_TRANSIENT, "false",
           CORE_LOADONSTARTUP, "true");
 
   private static final List<String> requiredProperties = List.of(CORE_NAME);
@@ -104,7 +102,6 @@ public Properties getPersistableUserProperties() {
           CORE_PROPERTIES,
           CORE_CONFIGSET_PROPERTIES,
           CORE_LOADONSTARTUP,
-          CORE_TRANSIENT,
           CORE_CONFIGSET,
           // cloud props
           CORE_SHARD,
@@ -338,11 +335,6 @@ public boolean isLoadOnStartup() {
     return Boolean.parseBoolean(stringValue);
   }
 
-  public boolean isTransient() {
-    String stringValue = coreProperties.getProperty(CORE_TRANSIENT, "false");
-    return PropertiesUtil.toBoolean(stringValue);
-  }
-
   public String getUlogDir() {
     return coreProperties.getProperty(CORE_ULOGDIR);
   }

solr/core/src/java/org/apache/solr/core/NodeConfig.java

@@ -107,8 +107,6 @@ public class NodeConfig {
 
   private final int indexSearcherExecutorThreads;
 
-  @Deprecated private final int transientCacheSize;
-
   private final boolean useSchemaCache;
 
   private final String managementPath;
@@ -147,7 +145,6 @@ private NodeConfig(
       Integer coreLoadThreads,
       int replayUpdatesThreads,
       int indexSearcherExecutorThreads,
-      int transientCacheSize,
       boolean useSchemaCache,
       String managementPath,
       Path solrHome,
@@ -187,7 +184,6 @@ private NodeConfig(
     this.coreLoadThreads = coreLoadThreads;
     this.replayUpdatesThreads = replayUpdatesThreads;
     this.indexSearcherExecutorThreads = indexSearcherExecutorThreads;
-    this.transientCacheSize = transientCacheSize;
     this.useSchemaCache = useSchemaCache;
     this.managementPath = managementPath;
     this.solrHome = solrHome;
@@ -401,10 +397,6 @@ public CloudConfig getCloudConfig() {
     return cloudConfig;
   }
 
-  public int getTransientCacheSize() {
-    return transientCacheSize;
-  }
-
   protected final Path solrHome;
   protected final SolrResourceLoader loader;
   protected final Properties solrProperties;
@@ -607,7 +599,6 @@ public static class NodeConfigBuilder {
     private int coreLoadThreads = DEFAULT_CORE_LOAD_THREADS;
     private int replayUpdatesThreads = Runtime.getRuntime().availableProcessors();
     private int indexSearcherExecutorThreads = DEFAULT_INDEX_SEARCHER_EXECUTOR_THREADS;
-    @Deprecated private int transientCacheSize = -1;
     private boolean useSchemaCache = false;
     private String managementPath;
     private Properties solrProperties = new Properties();
@@ -773,14 +764,6 @@ public NodeConfigBuilder setIndexSearcherExecutorThreads(int indexSearcherExecut
       return this;
     }
 
-    // Remove in Solr 10.0
-
-    @Deprecated
-    public NodeConfigBuilder setTransientCacheSize(int transientCacheSize) {
-      this.transientCacheSize = transientCacheSize;
-      return this;
-    }
-
     public NodeConfigBuilder setUseSchemaCache(boolean useSchemaCache) {
       this.useSchemaCache = useSchemaCache;
       return this;
@@ -915,7 +898,6 @@ public NodeConfig build() {
           coreLoadThreads,
           replayUpdatesThreads,
           indexSearcherExecutorThreads,
-          transientCacheSize,
           useSchemaCache,
           managementPath,
           solrHome,