frontend: add listing all existing labels

Motivation
This is the second part of correction of existing an issues  #7727;

the API call `/labels` was not working

Modifiction
New message has been added to list exitig labels together with a new handler.

Result

now it is possible to call API for `/labels` with result listing all existing labels

{
  "labels" : [ "red11", "red18" ]
}

Target: master
Require-book: yes
Acked-by: Tigran Mkrtchyan
Patch: https://rb.dcache.org/r/14423/

Author: mksahakyan

modules/chimera/src/main/java/org/dcache/chimera/FileSystemProvider.java

@@ -174,6 +174,19 @@ DirectoryStreamB<ChimeraDirectoryEntry> newDirectoryStream(FsInode dir)
     DirectoryStreamB<ChimeraDirectoryEntry> virtualDirectoryStream(FsInode dir, String labelname)
           throws ChimeraFsException;
 
+    /**
+     * Returns {@link DirectoryStreamB} of ChimeraDirectoryEntry in the directory.
+     * <p>
+     * The returned stream may keep system resources allocated. The try-with-resources construct
+     * should be used to ensure that the stream's close method is invoked after the stream
+     * operations are completed.
+     *
+     * @param dir inode of "collection" node
+     * @return stream of directory entries
+     */
+    DirectoryStreamB<ChimeraDirectoryEntry> listLabelsStream(FsInode dir)
+            throws ChimeraFsException;
+
     void remove(String path) throws ChimeraFsException;
 
     /**

modules/chimera/src/main/java/org/dcache/chimera/FsInode.java

@@ -435,6 +435,10 @@ public DirectoryStreamB<ChimeraDirectoryEntry> virtualDirectoryStream(String lab
         return _fs.virtualDirectoryStream(this, labelname);
     }
 
+    public DirectoryStreamB<ChimeraDirectoryEntry> listLabelsStream() throws ChimeraFsException {
+        return _fs.listLabelsStream(this);
+    }
+
     public String getId() throws ChimeraFsException {
         Stat stat = _stat;
         return (stat != null) ? stat.getId() : _fs.inode2id(this);

modules/chimera/src/main/java/org/dcache/chimera/JdbcFs.java

@@ -563,6 +563,14 @@ public DirectoryStreamB<ChimeraDirectoryEntry> virtualDirectoryStream(FsInode di
         return _sqlDriver.virtualDirectoryStream(dir, labelname);
     }
 
+
+    @Override
+    public DirectoryStreamB<ChimeraDirectoryEntry> listLabelsStream(FsInode dir) throws ChimeraFsException {
+        return _sqlDriver.labelsDirectoryStream(dir);
+    }
+
+
+
     @Override
     public void remove(String path) throws ChimeraFsException {
 

modules/dcache-chimera/src/main/java/org/dcache/chimera/namespace/ChimeraNameSpaceProvider.java

@@ -98,12 +98,13 @@
 import org.dcache.chimera.FileSystemProvider;
 import org.dcache.chimera.FileSystemProvider.SetXattrMode;
 import org.dcache.chimera.FsInode;
-import org.dcache.chimera.FsInode_LABEL;
+import org.dcache.chimera.NoLabelChimeraException;
 import org.dcache.chimera.NoXdataChimeraException;
 import org.dcache.chimera.NotDirChimeraException;
 import org.dcache.chimera.StorageGenericLocation;
 import org.dcache.chimera.StorageLocatable;
 import org.dcache.chimera.UnixPermission;
+
 import org.dcache.chimera.posix.Stat;
 import org.dcache.commons.stats.MonitoringProxy;
 import org.dcache.commons.stats.RequestCounters;
@@ -1391,6 +1392,46 @@ public void listVirtualDirectory(Subject subject, String path, Range<Integer> ra
         }
     }
 
+
+    @Override
+    public void listLabels(Subject subject, Range<Integer> range,
+                           Set<FileAttribute> attrs, ListHandler handler)
+            throws CacheException
+    {
+        try {
+            int counter = 0;
+            //TODO check permissions
+            try (DirectoryStreamB<ChimeraDirectoryEntry> dirStream = FsInode.getRoot(_fs)
+                    .listLabelsStream()) {
+                for (ChimeraDirectoryEntry entry : dirStream) {
+                    try {
+                        String name = entry.getName();
+
+                        // FIXME: actually, ChimeraDirectoryEntry
+                        // already contains most of attributes
+
+                        FileAttributes fa =
+                                attrs.isEmpty()
+                                        ? null
+                                        : getFileAttributes(new ExtendedInode(_fs, entry.getInode()), attrs);
+                        handler.addEntry(name, fa);
+
+                    } catch (NoLabelChimeraException e) {
+                        /* Not an error; files may be deleted during the
+                         * list operation.
+                         */
+                    }
+                }
+            }
+
+        } catch (FileNotFoundChimeraFsException e) {
+            throw new FileNotFoundCacheException("there are no any labels added to files : ");
+        } catch (IOException e) {
+            LOGGER.error("Exception in list: {}", e.getMessage());
+            throw new CacheException(CacheException.UNEXPECTED_SYSTEM_EXCEPTION, e.getMessage());
+        }
+    }
+
     private ExtendedInode mkdir(Subject subject, ExtendedInode parent, String name, int uid,
           int gid, int mode)
           throws ChimeraFsException, CacheException {

modules/dcache-frontend/src/main/java/org/dcache/restful/providers/JsonListLabels.java

@@ -0,0 +1,44 @@
+/*
+ * dCache - http://www.dcache.org/
+ *
+ * Copyright (C) 2025 Deutsches Elektronen-Synchrotron
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.dcache.restful.providers;
+
+import io.swagger.annotations.ApiModel;
+import io.swagger.annotations.ApiModelProperty;
+import java.util.HashSet;
+import java.util.Set;
+
+@ApiModel(description = "Specifies all existing lables")
+public class JsonListLabels {
+
+
+    @ApiModelProperty("All existing labels.")
+    private Set<String> labels = new HashSet();
+
+    public void setLabels(Set<String> labelnames) {
+        if (labelnames == null) {
+            return;
+        }
+
+        labels.addAll(labelnames);
+    }
+
+    public Set<String> getLabels() {
+        return labels;
+    }
+}

modules/dcache-frontend/src/main/java/org/dcache/restful/resources/labels/LabelsResources.java

@@ -33,6 +33,7 @@
 import io.swagger.annotations.ApiResponses;
 import io.swagger.annotations.Authorization;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 import javax.inject.Inject;
@@ -56,12 +57,13 @@
 import org.dcache.namespace.FileAttribute;
 import org.dcache.poolmanager.PoolMonitor;
 import org.dcache.restful.providers.JsonFileAttributes;
+import org.dcache.restful.providers.JsonListLabels;
 import org.dcache.restful.util.HttpServletRequests;
 import org.dcache.restful.util.RequestUser;
 import org.dcache.restful.util.namespace.NamespaceUtils;
 import org.dcache.util.list.DirectoryEntry;
 import org.dcache.util.list.DirectoryStream;
-import org.dcache.util.list.ListDirectoryHandler;
+import org.dcache.util.list.LabelsListHandler;
 import org.dcache.util.list.VirtualDirectoryListHandler;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -96,14 +98,83 @@ public class LabelsResources {
     private VirtualDirectoryListHandler virtualDirectoryListHandler;
 
     @Inject
-    @Named("pool-manager-stub")
-    private CellStub poolmanager;
+    private LabelsListHandler labelsListHandler;
 
     @Inject
     @Named("pinManagerStub")
     private CellStub pinmanager;
 
+    @GET
+    @ApiOperation(value = "List all existing labels.",
+            notes = "The method offers the possibility to query of all existing labels.")
+    @ApiResponses({
+            @ApiResponse(code = 401, message = "Unauthorized"),
+            @ApiResponse(code = 403, message = "Forbidden"),
+            @ApiResponse(code = 404, message = "Not Found"),
+            @ApiResponse(code = 500, message = "Internal Server Error"),
+    })
+    @Produces(MediaType.APPLICATION_JSON)
+    public JsonListLabels getListLabels(
+            @ApiParam("Limit number of replies in labels listing.")
+            @QueryParam("limit") String limit,
+            @ApiParam("Number of entries to skip in labels listing.")
+            @QueryParam("offset") String offset) throws CacheException {
+
+        JsonListLabels labels = new JsonListLabels();
 
+        Set<FileAttribute> attributes =
+                NamespaceUtils.getRequestedAttributes(false,
+                        false,
+                        false,
+                        false,
+                        false);
+
+        FsPath path = pathMapper.asDcachePath(request, "/", ForbiddenException::new);
+
+
+        Range<Integer> range;
+        try {
+            int lower = (offset == null) ? 0 : Integer.parseInt(offset);
+            int ceiling = (limit == null) ? Integer.MAX_VALUE : Integer.parseInt(limit);
+            if (ceiling < 0 || lower < 0) {
+                throw new BadRequestException("limit and offset can not be less than zero.");
+            }
+            range = (Integer.MAX_VALUE - lower < ceiling) ? Range.atLeast(lower)
+                    : Range.closedOpen(lower, lower + ceiling);
+        } catch (NumberFormatException e) {
+            throw new BadRequestException("limit and offset must be an integer value.");
+        }
+        try {
+            DirectoryStream stream = labelsListHandler.listLabels(
+                    HttpServletRequests.roleAwareSubject(request),
+                    HttpServletRequests.roleAwareRestriction(request),
+                    range,
+                    attributes);
+
+
+            Set<String> labelsList = new HashSet<>();
+
+            for (DirectoryEntry entry : stream) {
+                String labelName = entry.getName();
+                labelsList.add(labelName);
+            }
+
+
+            labels.setLabels(labelsList);
+
+        }
+        catch (PermissionDeniedCacheException e) {
+            if (RequestUser.isAnonymous()) {
+                throw new NotAuthorizedException(e);
+            } else {
+                throw new ForbiddenException(e);
+            }
+        } catch (CacheException | InterruptedException ex) {
+            LOGGER.warn(Exceptions.meaningfulMessage(ex));
+            throw new InternalServerErrorException(ex);
+        }
+        return labels;
+    }
 
     @GET
     @ApiOperation(value = "Find metadata and optionally virtual directory contents.",
@@ -161,6 +232,8 @@ public JsonFileAttributes getFileAttributes(@ApiParam("Path of file or directory
             throw new BadRequestException("limit and offset must be an integer value.");
         }
         try {
+
+
             List<JsonFileAttributes> children = new ArrayList<>();
 
             DirectoryStream stream = virtualDirectoryListHandler.listVirtualDirectory(

modules/dcache-frontend/src/main/resources/org/dcache/frontend/frontend.xml

@@ -97,6 +97,15 @@
             </bean>
         </constructor-arg>
     </bean>
+
+    <bean id="labels-list-handler" class="org.dcache.util.list.LabelsListHandler">
+        <description>Client stub for directory listing</description>
+        <constructor-arg>
+            <bean class="diskCacheV111.util.PnfsHandler">
+                <constructor-arg ref="pnfs-stub"/>
+            </bean>
+        </constructor-arg>
+    </bean>
     <bean id="path-mapper" class="org.dcache.http.PathMapper">
         <description>Mapping between request paths and dCache paths</description>
         <property name="rootPath" value="${frontend.root}"/>