SOLR-16470: Create v2 replication "fetch file" API (#2734)

New v2 API is available at `GET /api/cores/coreName/replication/files/fileName`

---------

Co-authored-by: Matthew Biscocho <mbiscocho@bloomberg.net>
Co-authored-by: Jason Gerlowski <gerlowskija@apache.org>

solr/CHANGES.txt

@@ -172,6 +172,9 @@ Improvements
   New APIs for listing-all and fetching-single cluster props are also now available at `GET /api/cluster/properties` and
   `GET /api/cluster/properties/somePropName`, respectively. (Carlos Ugarte via Jason Gerlowski)
 
+* SOLR-16470: Replication "fetch file" API now has a v2 equivalent, available at `GET /api/cores/coreName/replication/files/fileName`
+  (Matthew Biscocho via Jason Gerlowski)
+
 
 Optimizations
 ---------------------

solr/api/src/java/org/apache/solr/client/api/endpoint/ReplicationApis.java

@@ -16,11 +16,18 @@
  */
 package org.apache.solr.client.api.endpoint;
 
+import static org.apache.solr.client.api.util.Constants.OMIT_FROM_CODEGEN_PROPERTY;
+
 import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.Parameter;
+import io.swagger.v3.oas.annotations.extensions.Extension;
+import io.swagger.v3.oas.annotations.extensions.ExtensionProperty;
+import jakarta.ws.rs.DefaultValue;
 import jakarta.ws.rs.GET;
 import jakarta.ws.rs.Path;
+import jakarta.ws.rs.PathParam;
 import jakarta.ws.rs.QueryParam;
+import jakarta.ws.rs.core.StreamingOutput;
 import java.io.IOException;
 import org.apache.solr.client.api.model.FileListResponse;
 import org.apache.solr.client.api.model.IndexVersionResponse;
@@ -47,4 +54,43 @@ FileListResponse fetchFileList(
       @Parameter(description = "The generation number of the index", required = true)
           @QueryParam("generation")
           long gen);
+
+  @GET
+  @CoreApiParameters
+  @Operation(
+      summary = "Get a stream of a specific file path of a core",
+      tags = {"core-replication"},
+      extensions = { // TODO Remove as a part of SOLR-17562
+        @Extension(
+            properties = {@ExtensionProperty(name = OMIT_FROM_CODEGEN_PROPERTY, value = "true")})
+      })
+  @Path("/files/{filePath}")
+  StreamingOutput fetchFile(
+      @PathParam("filePath") String filePath,
+      @Parameter(
+              description =
+                  "Directory type for specific filePath (cf or tlogFile). Defaults to Lucene index (file) directory if empty",
+              required = true)
+          @QueryParam("dirType")
+          String dirType,
+      @Parameter(description = "Output stream read/write offset", required = false)
+          @QueryParam("offset")
+          String offset,
+      @Parameter(required = false) @QueryParam("len") String len,
+      @Parameter(description = "Compress file output", required = false)
+          @QueryParam("compression")
+          @DefaultValue("false")
+          Boolean compression,
+      @Parameter(description = "Write checksum with output stream", required = false)
+          @QueryParam("checksum")
+          @DefaultValue("false")
+          Boolean checksum,
+      @Parameter(
+              description = "Limit data write per seconds. Defaults to no throttling",
+              required = false)
+          @QueryParam("maxWriteMBPerSec")
+          double maxWriteMBPerSec,
+      @Parameter(description = "The generation number of the index", required = false)
+          @QueryParam("generation")
+          Long gen);
 }

solr/core/src/java/org/apache/solr/cloud/ReplicateFromLeader.java

@@ -27,6 +27,7 @@
 import org.apache.solr.core.SolrCore;
 import org.apache.solr.handler.IndexFetcher;
 import org.apache.solr.handler.ReplicationHandler;
+import org.apache.solr.handler.admin.api.ReplicationAPIBase;
 import org.apache.solr.request.LocalSolrQueryRequest;
 import org.apache.solr.request.SolrQueryRequest;
 import org.apache.solr.update.CommitUpdateCommand;
@@ -89,7 +90,7 @@ public void startReplication(boolean switchTransactionLog) {
       NamedList<Object> followerConfig = new NamedList<>();
       followerConfig.add(ReplicationHandler.FETCH_FROM_LEADER, Boolean.TRUE);
       followerConfig.add(ReplicationHandler.SKIP_COMMIT_ON_LEADER_VERSION_ZERO, Boolean.TRUE);
-      followerConfig.add(ReplicationHandler.POLL_INTERVAL, pollIntervalStr);
+      followerConfig.add(ReplicationAPIBase.POLL_INTERVAL, pollIntervalStr);
       NamedList<Object> replicationConfig = new NamedList<>();
       replicationConfig.add("follower", followerConfig);
 

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

@@ -106,9 +106,9 @@
 import org.apache.solr.core.snapshots.SolrSnapshotMetaDataManager;
 import org.apache.solr.core.snapshots.SolrSnapshotMetaDataManager.SnapshotMetaData;
 import org.apache.solr.handler.IndexFetcher;
-import org.apache.solr.handler.ReplicationHandler;
 import org.apache.solr.handler.RequestHandlerBase;
 import org.apache.solr.handler.SolrConfigHandler;
+import org.apache.solr.handler.admin.api.ReplicationAPIBase;
 import org.apache.solr.handler.api.V2ApiUtils;
 import org.apache.solr.handler.component.HighlightComponent;
 import org.apache.solr.handler.component.SearchComponent;
@@ -3018,7 +3018,7 @@ public PluginBag<QueryResponseWriter> getResponseWriters() {
     m.put("schema.xml", new SchemaXmlResponseWriter());
     m.put("smile", new SmileResponseWriter());
     m.put(PROMETHEUS_METRICS_WT, new PrometheusResponseWriter());
-    m.put(ReplicationHandler.FILE_STREAM, getFileStreamWriter());
+    m.put(ReplicationAPIBase.FILE_STREAM, getFileStreamWriter());
     DEFAULT_RESPONSE_WRITERS = Collections.unmodifiableMap(m);
     try {
       m.put(
@@ -3037,7 +3037,7 @@ private static BinaryResponseWriter getFileStreamWriter() {
       @Override
       public void write(OutputStream out, SolrQueryRequest req, SolrQueryResponse response)
           throws IOException {
-        RawWriter rawWriter = (RawWriter) response.getValues().get(ReplicationHandler.FILE_STREAM);
+        RawWriter rawWriter = (RawWriter) response.getValues().get(ReplicationAPIBase.FILE_STREAM);
         if (rawWriter != null) {
           rawWriter.write(out);
           if (rawWriter instanceof Closeable) ((Closeable) rawWriter).close();
@@ -3046,7 +3046,7 @@ public void write(OutputStream out, SolrQueryRequest req, SolrQueryResponse resp
 
       @Override
       public String getContentType(SolrQueryRequest request, SolrQueryResponse response) {
-        RawWriter rawWriter = (RawWriter) response.getValues().get(ReplicationHandler.FILE_STREAM);
+        RawWriter rawWriter = (RawWriter) response.getValues().get(ReplicationAPIBase.FILE_STREAM);
         if (rawWriter != null) {
           return rawWriter.getContentType();
         } else {

solr/core/src/java/org/apache/solr/filestore/NodeFileStore.java

@@ -17,7 +17,7 @@
 package org.apache.solr.filestore;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
-import static org.apache.solr.handler.ReplicationHandler.FILE_STREAM;
+import static org.apache.solr.handler.admin.api.ReplicationAPIBase.FILE_STREAM;
 import static org.apache.solr.response.RawResponseWriter.CONTENT;
 import static org.apache.solr.security.PermissionNameProvider.Name.FILESTORE_READ_PERM;
 

solr/core/src/java/org/apache/solr/handler/BlobHandler.java

@@ -58,6 +58,7 @@
 import org.apache.solr.core.PluginInfo;
 import org.apache.solr.core.SolrCore;
 import org.apache.solr.handler.admin.api.GetBlobInfoAPI;
+import org.apache.solr.handler.admin.api.ReplicationAPIBase;
 import org.apache.solr.handler.admin.api.UploadBlobAPI;
 import org.apache.solr.request.LocalSolrQueryRequest;
 import org.apache.solr.request.SolrQueryRequest;
@@ -194,7 +195,7 @@ public void handleRequestBody(final SolrQueryRequest req, SolrQueryResponse rsp)
           return;
         }
       }
-      if (ReplicationHandler.FILE_STREAM.equals(req.getParams().get(CommonParams.WT))) {
+      if (ReplicationAPIBase.FILE_STREAM.equals(req.getParams().get(CommonParams.WT))) {
         if (blobName == null) {
           throw new SolrException(
               SolrException.ErrorCode.NOT_FOUND,
@@ -211,7 +212,7 @@ public void handleRequestBody(final SolrQueryRequest req, SolrQueryResponse rsp)
                       new Sort(new SortField("version", SortField.Type.LONG, true)));
           if (docs.totalHits.value > 0) {
             rsp.add(
-                ReplicationHandler.FILE_STREAM,
+                ReplicationAPIBase.FILE_STREAM,
                 new SolrCore.RawWriter() {
 
                   @Override

solr/core/src/java/org/apache/solr/handler/ExportHandler.java

@@ -31,6 +31,7 @@
 import org.apache.solr.common.params.SolrParams;
 import org.apache.solr.core.CoreContainer;
 import org.apache.solr.core.SolrCore;
+import org.apache.solr.handler.admin.api.ReplicationAPIBase;
 import org.apache.solr.handler.component.SearchHandler;
 import org.apache.solr.handler.export.ExportWriter;
 import org.apache.solr.handler.export.ExportWriterStream;
@@ -125,10 +126,10 @@ public void handleRequestBody(SolrQueryRequest req, SolrQueryResponse rsp) throw
     }
     String wt = req.getParams().get(CommonParams.WT, JSON);
     if ("xsort".equals(wt)) wt = JSON;
-    Map<String, String> map = Map.of(CommonParams.WT, ReplicationHandler.FILE_STREAM);
+    Map<String, String> map = Map.of(CommonParams.WT, ReplicationAPIBase.FILE_STREAM);
     req.setParams(SolrParams.wrapDefaults(new MapSolrParams(map), req.getParams()));
     rsp.add(
-        ReplicationHandler.FILE_STREAM,
+        ReplicationAPIBase.FILE_STREAM,
         new ExportWriter(
             req, rsp, wt, initialStreamContext, solrMetricsContext, writerMetricsPath));
   }

solr/core/src/java/org/apache/solr/handler/IndexFetcher.java

@@ -19,27 +19,25 @@
 import static org.apache.solr.common.params.CommonParams.JAVABIN;
 import static org.apache.solr.common.params.CommonParams.NAME;
 import static org.apache.solr.handler.ReplicationHandler.ALIAS;
-import static org.apache.solr.handler.ReplicationHandler.CHECKSUM;
 import static org.apache.solr.handler.ReplicationHandler.CMD_DETAILS;
 import static org.apache.solr.handler.ReplicationHandler.CMD_GET_FILE;
 import static org.apache.solr.handler.ReplicationHandler.CMD_GET_FILE_LIST;
 import static org.apache.solr.handler.ReplicationHandler.CMD_INDEX_VERSION;
 import static org.apache.solr.handler.ReplicationHandler.COMMAND;
-import static org.apache.solr.handler.ReplicationHandler.COMPRESSION;
 import static org.apache.solr.handler.ReplicationHandler.CONF_FILES;
-import static org.apache.solr.handler.ReplicationHandler.CONF_FILE_SHORT;
-import static org.apache.solr.handler.ReplicationHandler.EXTERNAL;
 import static org.apache.solr.handler.ReplicationHandler.FETCH_FROM_LEADER;
-import static org.apache.solr.handler.ReplicationHandler.FILE;
-import static org.apache.solr.handler.ReplicationHandler.FILE_STREAM;
-import static org.apache.solr.handler.ReplicationHandler.GENERATION;
-import static org.apache.solr.handler.ReplicationHandler.INTERNAL;
 import static org.apache.solr.handler.ReplicationHandler.LEADER_URL;
 import static org.apache.solr.handler.ReplicationHandler.LEGACY_LEADER_URL;
 import static org.apache.solr.handler.ReplicationHandler.LEGACY_SKIP_COMMIT_ON_LEADER_VERSION_ZERO;
-import static org.apache.solr.handler.ReplicationHandler.OFFSET;
 import static org.apache.solr.handler.ReplicationHandler.SIZE;
 import static org.apache.solr.handler.ReplicationHandler.SKIP_COMMIT_ON_LEADER_VERSION_ZERO;
+import static org.apache.solr.handler.admin.api.ReplicationAPIBase.CHECKSUM;
+import static org.apache.solr.handler.admin.api.ReplicationAPIBase.COMPRESSION;
+import static org.apache.solr.handler.admin.api.ReplicationAPIBase.CONF_FILE_SHORT;
+import static org.apache.solr.handler.admin.api.ReplicationAPIBase.FILE;
+import static org.apache.solr.handler.admin.api.ReplicationAPIBase.FILE_STREAM;
+import static org.apache.solr.handler.admin.api.ReplicationAPIBase.GENERATION;
+import static org.apache.solr.handler.admin.api.ReplicationAPIBase.OFFSET;
 
 import java.io.File;
 import java.io.FileNotFoundException;
@@ -121,7 +119,7 @@
 import org.apache.solr.core.DirectoryFactory.DirContext;
 import org.apache.solr.core.IndexDeletionPolicyWrapper;
 import org.apache.solr.core.SolrCore;
-import org.apache.solr.handler.ReplicationHandler.FileInfo;
+import org.apache.solr.handler.admin.api.ReplicationAPIBase;
 import org.apache.solr.request.LocalSolrQueryRequest;
 import org.apache.solr.request.SolrQueryRequest;
 import org.apache.solr.search.SolrIndexSearcher;
@@ -303,8 +301,8 @@ public IndexFetcher(
 
     this.replicationHandler = handler;
     String compress = (String) initArgs.get(COMPRESSION);
-    useInternalCompression = INTERNAL.equals(compress);
-    useExternalCompression = EXTERNAL.equals(compress);
+    useInternalCompression = ReplicationHandler.INTERNAL.equals(compress);
+    useExternalCompression = ReplicationHandler.EXTERNAL.equals(compress);
     connTimeout = getParameter(initArgs, HttpClientUtil.PROP_CONNECTION_TIMEOUT, 30000, null);
 
     // allow a leader override for tests - you specify this in /replication follower section of
@@ -1575,7 +1573,7 @@ private String getDateAsStr(Date d) {
     return new SimpleDateFormat(SnapShooter.DATE_FMT, Locale.ROOT).format(d);
   }
 
-  private final Map<String, FileInfo> confFileInfoCache = new HashMap<>();
+  private final Map<String, ReplicationHandler.FileInfo> confFileInfoCache = new HashMap<>();
 
   /**
    * The local conf files are compared with the conf files in the leader. If they are same (by
@@ -1723,7 +1721,7 @@ private interface FileInterface {
    * The class acts as a client for ReplicationHandler.FileStream. It understands the protocol of
    * wt=filestream
    *
-   * @see org.apache.solr.handler.ReplicationHandler.DirectoryFileStream
+   * <p>see org.apache.solr.handler.admin.api.ReplicationAPIBase.DirectoryFileStream
    */
   private class FileFetcher {
     private final FileInterface file;
@@ -1750,7 +1748,7 @@ private class FileFetcher {
       this.file = file;
       this.fileName = (String) fileDetails.get(NAME);
       this.size = (Long) fileDetails.get(SIZE);
-      buf = new byte[(int) Math.min(this.size, ReplicationHandler.PACKET_SZ)];
+      buf = new byte[(int) Math.min(this.size, ReplicationAPIBase.PACKET_SZ)];
       this.solrParamOutput = solrParamOutput;
       this.saveAs = saveAs;
       indexGen = latestGen;
@@ -2047,7 +2045,7 @@ public void delete() throws Exception {
     }
   }
 
-  private class DirectoryFileFetcher extends FileFetcher {
+  protected class DirectoryFileFetcher extends FileFetcher {
     DirectoryFileFetcher(
         Directory tmpIndexDir,
         Map<String, Object> fileDetails,
@@ -2107,7 +2105,7 @@ public void delete() throws Exception {
     }
   }
 
-  private class LocalFsFileFetcher extends FileFetcher {
+  protected class LocalFsFileFetcher extends FileFetcher {
     LocalFsFileFetcher(
         File dir,
         Map<String, Object> fileDetails,