Add custom metadata to snapshots (#41281)

Adds a metadata field to snapshots which can be used to store arbitrary
key-value information. This may be useful for attaching a description of
why a snapshot was taken, tagging snapshots to make categorization
easier, or identifying the source of automatically-created snapshots.

client/rest-high-level/src/test/java/org/elasticsearch/client/SnapshotIT.java

@@ -41,9 +41,13 @@
 import org.elasticsearch.repositories.fs.FsRepository;
 import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.snapshots.RestoreInfo;
+import org.elasticsearch.snapshots.SnapshotInfo;
 
 import java.io.IOException;
 import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
 import java.util.stream.Collectors;
 
 import static org.hamcrest.Matchers.contains;
@@ -139,6 +143,9 @@ public void testCreateSnapshot() throws IOException {
         CreateSnapshotRequest request = new CreateSnapshotRequest(repository, snapshot);
         boolean waitForCompletion = randomBoolean();
         request.waitForCompletion(waitForCompletion);
+        if (randomBoolean()) {
+            request.userMetadata(randomUserMetadata());
+        }
         request.partial(randomBoolean());
         request.includeGlobalState(randomBoolean());
 
@@ -167,6 +174,8 @@ public void testGetSnapshots() throws IOException {
         CreateSnapshotResponse putSnapshotResponse1 = createTestSnapshot(createSnapshotRequest1);
         CreateSnapshotRequest createSnapshotRequest2 = new CreateSnapshotRequest(repository, snapshot2);
         createSnapshotRequest2.waitForCompletion(true);
+        Map<String, Object> originalMetadata = randomUserMetadata();
+        createSnapshotRequest2.userMetadata(originalMetadata);
         CreateSnapshotResponse putSnapshotResponse2 = createTestSnapshot(createSnapshotRequest2);
         // check that the request went ok without parsing JSON here. When using the high level client, check acknowledgement instead.
         assertEquals(RestStatus.OK, putSnapshotResponse1.status());
@@ -186,6 +195,15 @@ public void testGetSnapshots() throws IOException {
         assertEquals(2, response.getSnapshots().size());
         assertThat(response.getSnapshots().stream().map((s) -> s.snapshotId().getName()).collect(Collectors.toList()),
             contains("test_snapshot1", "test_snapshot2"));
+        Optional<Map<String, Object>> returnedMetadata = response.getSnapshots().stream()
+            .filter(s -> s.snapshotId().getName().equals("test_snapshot2"))
+            .findFirst()
+            .map(SnapshotInfo::userMetadata);
+        if (returnedMetadata.isPresent()) {
+            assertEquals(originalMetadata, returnedMetadata.get());
+        } else {
+            assertNull("retrieved metadata is null, expected non-null metadata", originalMetadata);
+        }
     }
 
     public void testSnapshotsStatus() throws IOException {
@@ -231,6 +249,9 @@ public void testRestoreSnapshot() throws IOException {
         CreateSnapshotRequest createSnapshotRequest = new CreateSnapshotRequest(testRepository, testSnapshot);
         createSnapshotRequest.indices(testIndex);
         createSnapshotRequest.waitForCompletion(true);
+        if (randomBoolean()) {
+            createSnapshotRequest.userMetadata(randomUserMetadata());
+        }
         CreateSnapshotResponse createSnapshotResponse = createTestSnapshot(createSnapshotRequest);
         assertEquals(RestStatus.OK, createSnapshotResponse.status());
 
@@ -261,6 +282,9 @@ public void testDeleteSnapshot() throws IOException {
 
         CreateSnapshotRequest createSnapshotRequest = new CreateSnapshotRequest(repository, snapshot);
         createSnapshotRequest.waitForCompletion(true);
+        if (randomBoolean()) {
+            createSnapshotRequest.userMetadata(randomUserMetadata());
+        }
         CreateSnapshotResponse createSnapshotResponse = createTestSnapshot(createSnapshotRequest);
         // check that the request went ok without parsing JSON here. When using the high level client, check acknowledgement instead.
         assertEquals(RestStatus.OK, createSnapshotResponse.status());
@@ -270,4 +294,28 @@ public void testDeleteSnapshot() throws IOException {
 
         assertTrue(response.isAcknowledged());
     }
+
+    private static Map<String, Object> randomUserMetadata() {
+        if (randomBoolean()) {
+            return null;
+        }
+
+        Map<String, Object> metadata = new HashMap<>();
+        long fields = randomLongBetween(0, 4);
+        for (int i = 0; i < fields; i++) {
+            if (randomBoolean()) {
+                metadata.put(randomValueOtherThanMany(metadata::containsKey, () -> randomAlphaOfLengthBetween(2,10)),
+                    randomAlphaOfLengthBetween(5, 5));
+            } else {
+                Map<String, Object> nested = new HashMap<>();
+                long nestedFields = randomLongBetween(0, 4);
+                for (int j = 0; j < nestedFields; j++) {
+                    nested.put(randomValueOtherThanMany(nested::containsKey, () -> randomAlphaOfLengthBetween(2,10)),
+                        randomAlphaOfLengthBetween(5, 5));
+                }
+                metadata.put(randomValueOtherThanMany(metadata::containsKey, () -> randomAlphaOfLengthBetween(2,10)), nested);
+            }
+        }
+        return metadata;
+    }
 }

docs/reference/modules/snapshots.asciidoc

@@ -349,7 +349,11 @@ PUT /_snapshot/my_backup/snapshot_2?wait_for_completion=true
 {
   "indices": "index_1,index_2",
   "ignore_unavailable": true,
-  "include_global_state": false
+  "include_global_state": false,
+  "_meta": {
+    "taken_by": "kimchy",
+    "taken_because": "backup before upgrading"
+  }
 }
 -----------------------------------
 // CONSOLE
@@ -363,6 +367,9 @@ By setting `include_global_state` to false it's possible to prevent the cluster
 the snapshot. By default, the entire snapshot will fail if one or more indices participating in the snapshot don't have
 all primary shards available. This behaviour can be changed by setting `partial` to `true`.
 
+The `_meta` field can be used to attach arbitrary metadata to the snapshot. This may be a record of who took the snapshot,
+why it was taken, or any other data that might be useful.
+
 Snapshot names can be automatically derived using <<date-math-index-names,date math expressions>>, similarly as when creating
 new indices. Note that special characters need to be URI encoded.
 

rest-api-spec/src/main/resources/rest-api-spec/test/snapshot.get/10_basic.yml

@@ -87,6 +87,7 @@ setup:
   - is_false: snapshots.0.failures
   - is_false: snapshots.0.shards
   - is_false: snapshots.0.version
+  - is_false: snapshots.0._meta
 
   - do:
       snapshot.delete:
@@ -152,3 +153,41 @@ setup:
       snapshot.delete:
         repository: test_repo_get_1
         snapshot: test_snapshot_without_include_global_state
+
+---
+"Get snapshot info with metadata":
+  - skip:
+      version: " - 7.9.99"
+      reason: "https://github.com/elastic/elasticsearch/pull/41281 not yet backported to 7.x"
+
+  - do:
+      indices.create:
+        index: test_index
+        body:
+          settings:
+            number_of_shards:   1
+            number_of_replicas: 0
+
+  - do:
+      snapshot.create:
+        repository: test_repo_get_1
+        snapshot: test_snapshot_with_metadata
+        wait_for_completion: true
+        body: |
+          { "metadata": {"taken_by": "test", "foo": {"bar": "baz"}} }
+
+  - do:
+      snapshot.get:
+        repository: test_repo_get_1
+        snapshot: test_snapshot_with_metadata
+
+  - is_true: snapshots
+  - match: { snapshots.0.snapshot: test_snapshot_with_metadata }
+  - match: { snapshots.0.state: SUCCESS }
+  - match: { snapshots.0.metadata.taken_by: test }
+  - match: { snapshots.0.metadata.foo.bar: baz }
+
+  - do:
+      snapshot.delete:
+        repository: test_repo_get_1
+        snapshot: test_snapshot_with_metadata

server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/create/CreateSnapshotRequest.java

@@ -19,12 +19,14 @@
 
 package org.elasticsearch.action.admin.cluster.snapshots.create;
 
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.ElasticsearchGenerationException;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.IndicesRequest;
 import org.elasticsearch.action.support.IndicesOptions;
 import org.elasticsearch.action.support.master.MasterNodeRequest;
 import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.settings.Settings;
@@ -46,6 +48,7 @@
 import static org.elasticsearch.common.settings.Settings.readSettingsFromStream;
 import static org.elasticsearch.common.settings.Settings.writeSettingsToStream;
 import static org.elasticsearch.common.xcontent.support.XContentMapValues.nodeBooleanValue;
+import static org.elasticsearch.snapshots.SnapshotInfo.METADATA_FIELD_INTRODUCED;
 
 /**
  * Create snapshot request
@@ -63,6 +66,7 @@
  */
 public class CreateSnapshotRequest extends MasterNodeRequest<CreateSnapshotRequest>
         implements IndicesRequest.Replaceable, ToXContentObject {
+    public static int MAXIMUM_METADATA_BYTES = 1024; // chosen arbitrarily
 
     private String snapshot;
 
@@ -80,6 +84,8 @@ public class CreateSnapshotRequest extends MasterNodeRequest<CreateSnapshotReque
 
     private boolean waitForCompletion;
 
+    private Map<String, Object> userMetadata;
+
     public CreateSnapshotRequest() {
     }
 
@@ -104,6 +110,9 @@ public CreateSnapshotRequest(StreamInput in) throws IOException {
         includeGlobalState = in.readBoolean();
         waitForCompletion = in.readBoolean();
         partial = in.readBoolean();
+        if (in.getVersion().onOrAfter(METADATA_FIELD_INTRODUCED)) {
+            userMetadata = in.readMap();
+        }
     }
 
     @Override
@@ -117,6 +126,9 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeBoolean(includeGlobalState);
         out.writeBoolean(waitForCompletion);
         out.writeBoolean(partial);
+        if (out.getVersion().onOrAfter(METADATA_FIELD_INTRODUCED)) {
+            out.writeMap(userMetadata);
+        }
     }
 
     @Override
@@ -144,9 +156,28 @@ public ActionRequestValidationException validate() {
         if (settings == null) {
             validationException = addValidationError("settings is null", validationException);
         }
+        final int metadataSize = metadataSize(userMetadata);
+        if (metadataSize > MAXIMUM_METADATA_BYTES) {
+            validationException = addValidationError("metadata must be smaller than 1024 bytes, but was [" + metadataSize + "]",
+                validationException);
+        }
         return validationException;
     }
 
+    private static int metadataSize(Map<String, Object> userMetadata) {
+        if (userMetadata == null) {
+            return 0;
+        }
+        try (XContentBuilder builder = XContentFactory.jsonBuilder()) {
+            builder.value(userMetadata);
+            int size = BytesReference.bytes(builder).length();
+            return size;
+        } catch (IOException e) {
+            // This should not be possible as we are just rendering the xcontent in memory
+            throw new ElasticsearchException(e);
+        }
+    }
+
     /**
      * Sets the snapshot name
      *
@@ -378,6 +409,15 @@ public boolean includeGlobalState() {
         return includeGlobalState;
     }
 
+    public Map<String, Object> userMetadata() {
+        return userMetadata;
+    }
+
+    public CreateSnapshotRequest userMetadata(Map<String, Object> userMetadata) {
+        this.userMetadata = userMetadata;
+        return this;
+    }
+
     /**
      * Parses snapshot definition.
      *
@@ -405,6 +445,11 @@ public CreateSnapshotRequest source(Map<String, Object> source) {
                 settings((Map<String, Object>) entry.getValue());
             } else if (name.equals("include_global_state")) {
                 includeGlobalState = nodeBooleanValue(entry.getValue(), "include_global_state");
+            } else if (name.equals("metadata")) {
+                if (entry.getValue() != null && (entry.getValue() instanceof Map == false)) {
+                    throw new IllegalArgumentException("malformed metadata, should be an object");
+                }
+                userMetadata((Map<String, Object>) entry.getValue());
             }
         }
         indicesOptions(IndicesOptions.fromMap(source, indicesOptions));
@@ -433,6 +478,7 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         if (indicesOptions != null) {
             indicesOptions.toXContent(builder, params);
         }
+        builder.field("metadata", userMetadata);
         builder.endObject();
         return builder;
     }
@@ -460,12 +506,14 @@ public boolean equals(Object o) {
             Arrays.equals(indices, that.indices) &&
             Objects.equals(indicesOptions, that.indicesOptions) &&
             Objects.equals(settings, that.settings) &&
-            Objects.equals(masterNodeTimeout, that.masterNodeTimeout);
+            Objects.equals(masterNodeTimeout, that.masterNodeTimeout) &&
+            Objects.equals(userMetadata, that.userMetadata);
     }
 
     @Override
     public int hashCode() {
-        int result = Objects.hash(snapshot, repository, indicesOptions, partial, settings, includeGlobalState, waitForCompletion);
+        int result = Objects.hash(snapshot, repository, indicesOptions, partial, settings, includeGlobalState,
+            waitForCompletion, userMetadata);
         result = 31 * result + Arrays.hashCode(indices);
         return result;
     }
@@ -482,6 +530,7 @@ public String toString() {
             ", includeGlobalState=" + includeGlobalState +
             ", waitForCompletion=" + waitForCompletion +
             ", masterNodeTimeout=" + masterNodeTimeout +
+            ", metadata=" + userMetadata +
             '}';
     }
 }

server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/GetSnapshotsResponse.java

@@ -21,6 +21,7 @@
 
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.common.ParseField;
+import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.xcontent.ConstructingObjectParser;
@@ -117,4 +118,9 @@ public boolean equals(Object o) {
     public int hashCode() {
         return Objects.hash(snapshots);
     }
+
+    @Override
+    public String toString() {
+        return Strings.toString(this);
+    }
 }