huaxingao commented on code in PR #4659:
URL: https://github.com/apache/polaris/pull/4659#discussion_r3392658403


##########
runtime/service/src/main/java/org/apache/polaris/service/idempotency/IdempotencyHandlerSupport.java:
##########
@@ -0,0 +1,334 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.polaris.service.idempotency;
+
+import jakarta.annotation.Nonnull;
+import jakarta.annotation.Nullable;
+import jakarta.enterprise.context.RequestScoped;
+import jakarta.inject.Inject;
+import jakarta.ws.rs.core.HttpHeaders;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.time.Clock;
+import java.time.Instant;
+import java.util.Locale;
+import java.util.Optional;
+import java.util.TreeSet;
+import java.util.UUID;
+import java.util.regex.Pattern;
+import org.apache.polaris.core.auth.PolarisPrincipal;
+import org.apache.polaris.core.context.RealmContext;
+import org.apache.polaris.core.entity.IdempotencyRecord;
+import org.apache.polaris.core.persistence.IdempotencyStore;
+import org.apache.polaris.core.persistence.IdempotencyStoreFactory;
+
+/**
+ * Handler-side helper for the single-transaction ("optimistic commit") 
idempotency model.
+ *
+ * <p>Responsibilities:
+ *
+ * <ul>
+ *   <li>Read and validate the {@code Idempotency-Key} request header (UUIDv7 
only).
+ *   <li>Compute the principal/resource hashes that form the binding stored 
alongside each record.
+ *   <li>Pre-flight: look up an existing record for the same {@code (realm, 
key)} and dispatch into
+ *       {@link Outcome#owned()} or {@link 
Outcome#duplicate(IdempotencyRecord)} for the handler.
+ *   <li>Record the terminal outcome after a successful operation, returning 
{@link Outcome#owned()}
+ *       on win and {@link Outcome#duplicate(IdempotencyRecord)} on a 
race-driven duplicate.
+ * </ul>
+ *
+ * <p>This bean is {@link RequestScoped}: a single request operates within one 
realm, so the
+ * realm-scoped {@link IdempotencyStore} is resolved once (lazily) from {@link
+ * IdempotencyStoreFactory} for the request's {@link RealmContext}. When 
idempotency is disabled the
+ * store is never resolved — the bean is an inert shell. No response body is 
stored; duplicate
+ * responses are rebuilt from authoritative catalog state by the handler 
itself.
+ */
+@RequestScoped
+public class IdempotencyHandlerSupport {
+
+  // RFC 9562 UUID v7 has version nibble 7 in time_hi_and_version.
+  private static final Pattern UUID_V7_PATTERN =
+      Pattern.compile(
+          
"^[0-9a-f]{8}-[0-9a-f]{4}-7[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$",
+          Pattern.CASE_INSENSITIVE);
+
+  @Inject IdempotencyConfiguration configuration;
+  @Inject IdempotencyStoreFactory storeFactory;
+  @Inject RealmContext realmContext;
+  @Inject Clock clock;
+
+  // Resolved lazily on first use within the request; never resolved when 
idempotency is disabled.
+  private IdempotencyStore store;
+
+  /**
+   * Returns an instance with idempotency permanently disabled. Useful for 
test fixtures that need a
+   * non-null {@code IdempotencyHandlerSupport} but exercise non-idempotent 
code paths.
+   */
+  public static IdempotencyHandlerSupport disabled() {
+    IdempotencyHandlerSupport instance = new IdempotencyHandlerSupport();
+    instance.configuration = DisabledConfiguration.INSTANCE;
+    return instance;
+  }
+
+  /** Returns {@code true} if handler-level idempotency is enabled. */
+  public boolean isEnabled() {
+    return configuration != null && configuration.enabled();
+  }
+
+  /**
+   * Reads and validates the idempotency key from the request headers using 
the deploy-time
+   * configured header name from {@link IdempotencyConfiguration#keyHeader()}.
+   *
+   * @return validated key, or {@link Optional#empty()} if {@code httpHeaders} 
is null, the header
+   *     is absent / blank, or idempotency is disabled
+   * @throws IllegalArgumentException if the header is present but not a valid 
UUIDv7 (callers
+   *     translate this into a 400 Bad Request)
+   */
+  public Optional<String> validatedKey(@Nullable HttpHeaders httpHeaders) {
+    if (httpHeaders == null) {
+      return Optional.empty();
+    }
+    return 
validatedKey(httpHeaders.getHeaderString(configuration.keyHeader()));
+  }
+
+  /**
+   * Validates a raw header value. UUIDv7 is required so that the key has 
enough entropy to be a
+   * meaningful idempotency boundary.
+   */
+  public Optional<String> validatedKey(@Nullable String headerValue) {
+    if (!isEnabled() || headerValue == null) {
+      return Optional.empty();
+    }
+    String trimmed = headerValue.trim();
+    if (trimmed.isEmpty()) {
+      return Optional.empty();
+    }
+    if (!UUID_V7_PATTERN.matcher(trimmed).matches()) {
+      throw new IllegalArgumentException(
+          "Idempotency-Key must be a UUIDv7; got: " + summarizeKey(trimmed));
+    }
+    try {
+      UUID.fromString(trimmed);
+    } catch (IllegalArgumentException e) {
+      throw new IllegalArgumentException("Idempotency-Key must be a valid 
UUID");
+    }
+    return Optional.of(trimmed.toLowerCase(Locale.ROOT));
+  }
+
+  /**
+   * SHA-256 (hex) of the calling principal's identity, bound to the realm. 
The input is the
+   * principal name, the realm id, and the activated role set, canonicalised 
so the hash is
+   * deterministic and order-independent.
+   *
+   * <p>Roles are part of the binding so two callers that share a name but 
differ in activated roles
+   * do not collide. Principal properties are intentionally excluded: they are 
admin-mutable and not
+   * authentication context.
+   */
+  public String principalHash(PolarisPrincipal principal, String realmId) {
+    StringBuilder sb = new StringBuilder();
+    sb.append("name=").append(principal.getName()).append('|');
+    sb.append("realm=").append(realmId).append('|');
+    sb.append("roles=");
+    new TreeSet<>(principal.getRoles()).forEach(r -> sb.append(r).append(','));
+    return sha256Hex(sb.toString());
+  }
+
+  /**
+   * SHA-256 hex of an arbitrary string used as the resource binding 
component. The caller supplies
+   * a stable resource identity (e.g. operation, namespace, name and 
access-delegation modes); the
+   * request payload itself is intentionally not part of the binding.
+   */
+  public String resourceHash(String value) {
+    return sha256Hex(value);
+  }
+
+  /**
+   * Pre-flight: look up an existing record for {@code (realm, key)} and 
dispatch the handler.
+   *
+   * <p>If an existing record is found, the binding is validated against the 
current request and a
+   * mismatch raises {@link ConflictException} (handler maps to HTTP 422). If 
the binding matches,
+   * the existing record is returned as a {@link Outcome.Duplicate} so the 
handler can rebuild the
+   * response from current catalog state.
+   *
+   * <p>If no record exists, this returns {@link Outcome.Owned}; the handler 
should perform the
+   * operation and then call {@link #recordOutcome(String, String, String, 
String, int, String)} to
+   * commit a record.
+   */
+  public Outcome preflight(
+      String idempotencyKey, String operationType, String resourceHash, String 
principalHash) {
+    Optional<IdempotencyRecord> existing =
+        store().load(realmContext.getRealmIdentifier(), idempotencyKey);
+    if (existing.isEmpty()) {
+      return Outcome.owned();
+    }
+    return matchOrConflict(existing.get(), operationType, resourceHash, 
principalHash);
+  }
+
+  /**
+   * Records the terminal outcome of an operation that just completed.
+   *
+   * <p>The insert is atomic on {@code (realm, key)}; if another caller raced 
ahead and inserted
+   * first, the returned {@link Outcome} carries that existing record so the 
handler can rebuild an
+   * equivalent response from current state.
+   */
+  public Outcome recordOutcome(
+      String idempotencyKey,
+      String operationType,
+      String resourceHash,
+      String principalHash,
+      int httpStatus,
+      @Nullable String metadataLocation) {
+    Instant now = clock.instant();
+    Instant expiresAt = now.plus(configuration.ttl());
+    IdempotencyStore.RecordResult result =
+        store()
+            .recordIfAbsent(
+                realmContext.getRealmIdentifier(),
+                idempotencyKey,
+                operationType,
+                resourceHash,
+                principalHash,
+                httpStatus,
+                metadataLocation,
+                now,
+                expiresAt);
+    if (result.type() == IdempotencyStore.RecordResultType.OWNED) {
+      return Outcome.owned();
+    }
+    IdempotencyRecord existing =
+        result
+            .existing()
+            .orElseThrow(() -> new IllegalStateException("DUPLICATE result 
without record"));
+    return matchOrConflict(existing, operationType, resourceHash, 
principalHash);
+  }
+
+  /**
+   * Resolves (once per request) the realm-scoped {@link IdempotencyStore} for 
the request's realm.
+   * Only called from the idempotency code paths, so it is never invoked when 
the feature is
+   * disabled.
+   */
+  private IdempotencyStore store() {
+    if (store == null) {
+      store = storeFactory.getOrCreateIdempotencyStore(realmContext);
+    }
+    return store;
+  }
+
+  private static Outcome matchOrConflict(
+      IdempotencyRecord existing,
+      String expectedOperationType,
+      String expectedResourceHash,
+      String expectedPrincipalHash) {
+    if (!expectedPrincipalHash.equals(existing.principalHash())) {
+      throw new ConflictException(
+          "Idempotency-Key already used by a different caller for the same 
key");
+    }
+    if (!expectedResourceHash.equals(existing.resourceHash())
+        || !expectedOperationType.equals(existing.operationType())) {
+      throw new ConflictException(
+          "Idempotency-Key already used for a different operation or 
resource");
+    }
+    return Outcome.duplicate(existing);
+  }
+
+  private static String sha256Hex(@Nonnull String input) {

Review Comment:
   commons-codec is only a transitive dependency here, so to avoid adding a new 
declared dependency I used Guava's Hashing.sha256() (Guava is already a direct 
dependency) 



##########
runtime/service/src/main/java/org/apache/polaris/service/catalog/iceberg/IcebergCatalogHandler.java:
##########
@@ -509,6 +689,64 @@ public LoadTableResponse createTableDirect(
     throw new IllegalStateException("Cannot wrap catalog that does not produce 
BaseTable");
   }
 
+  /**
+   * Replay path for an idempotent {@code createTableDirect}: load the 
existing table and rebuild a
+   * response with freshly-vended credentials for the current caller. No 
credentials from the
+   * original call are stored or returned.
+   *
+   * <p>Authorization is not repeated here: {@link 
#authorizeCreateTableDirect} already ran for the
+   * current caller in {@link #createTableDirect} before the idempotency 
lookup, and the duplicate
+   * was matched on the same {@code principalHash} and request binding.
+   *
+   * <p>The replay reflects <em>current</em> catalog state rather than the 
original response bytes
+   * (no response body is stored). To avoid silently returning a materially 
different table, if the
+   * table has advanced beyond the metadata location captured when the key was 
recorded, this raises
+   * 422 instead of returning divergent state.
+   */
+  private LoadTableResponse replayCreateTableDirect(
+      Namespace namespace,
+      CreateTableRequest request,
+      Optional<AccessDelegationMode> resolvedMode,
+      Optional<String> refreshCredentialsEndpoint,
+      IdempotencyRecord existing) {
+    TableIdentifier tableIdentifier = TableIdentifier.of(namespace, 
request.name());
+    // If the original create succeeded but the table is no longer there 
(manual drop, retention,
+    // etc.), loadTable raises NoSuchTableException, surfacing the same 
not-found the client would
+    // get from a regular load.
+    Table table = baseCatalog.loadTable(tableIdentifier);
+    if (table instanceof BaseTable baseTable) {
+      TableMetadata tableMetadata = baseTable.operations().current();
+      if (existing.metadataLocation() != null
+          && 
!existing.metadataLocation().equals(tableMetadata.metadataFileLocation())) {
+        throw new UnprocessableEntityException(
+            "Idempotency-Key replay failed: table %s has changed since it was 
created with this key",
+            tableIdentifier);
+      }
+      return buildLoadTableResponseWithDelegationCredentials(
+              tableIdentifier,
+              tableMetadata,
+              resolvedMode,
+              Set.of(
+                  PolarisStorageActions.READ,
+                  PolarisStorageActions.WRITE,
+                  PolarisStorageActions.LIST),
+              refreshCredentialsEndpoint)
+          .build();
+    }
+    if (table instanceof BaseMetadataTable) {
+      throw notFoundExceptionForTableLikeEntity(
+          tableIdentifier, PolarisEntitySubType.ICEBERG_TABLE);
+    }
+    throw new IllegalStateException("Cannot wrap catalog that does not produce 
BaseTable");
+  }
+
+  private static String delegationModesToken(EnumSet<AccessDelegationMode> 
delegationModes) {

Review Comment:
   Moved into `IdempotencyHandlerSupport`



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