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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to you under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    * http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.hadoop.hbase.quotas;
18  
19  import java.util.Collections;
20  import java.util.HashMap;
21  import java.util.Map;
22  import java.util.Objects;
23  
24  import org.apache.hadoop.hbase.TableName;
25  import org.apache.hadoop.hbase.classification.InterfaceAudience;
26  import org.apache.hadoop.hbase.classification.InterfaceStability;
27  import org.apache.hadoop.hbase.regionserver.Region;
28  import org.apache.hadoop.hbase.regionserver.RegionServerServices;
29  
30  /**
31   * A class to ease dealing with tables that have and do not have violation policies
32   * being enforced. This class is immutable, expect for {@code locallyCachedPolicies}.
33   *
34   * The {@code locallyCachedPolicies} are mutable given the current {@code activePolicies}
35   * and {@code snapshots}. It is expected that when a new instance of this class is
36   * instantiated, we also want to invalidate those previously cached policies (as they
37   * may now be invalidate if we received new quota usage information).
38   */
39  @InterfaceAudience.Private
40  @InterfaceStability.Evolving
41  public class ActivePolicyEnforcement {
42    private final Map<TableName,SpaceViolationPolicyEnforcement> activePolicies;
43    private final Map<TableName,SpaceQuotaSnapshot> snapshots;
44    private final RegionServerServices rss;
45    private final SpaceViolationPolicyEnforcementFactory factory;
46    private final Map<TableName,SpaceViolationPolicyEnforcement> locallyCachedPolicies;
47  
48    public ActivePolicyEnforcement(Map<TableName,SpaceViolationPolicyEnforcement> activePolicies,
49        Map<TableName,SpaceQuotaSnapshot> snapshots, RegionServerServices rss) {
50      this(activePolicies, snapshots, rss, SpaceViolationPolicyEnforcementFactory.getInstance());
51    }
52  
53    public ActivePolicyEnforcement(Map<TableName,SpaceViolationPolicyEnforcement> activePolicies,
54        Map<TableName,SpaceQuotaSnapshot> snapshots, RegionServerServices rss,
55        SpaceViolationPolicyEnforcementFactory factory) {
56      this.activePolicies = activePolicies;
57      this.snapshots = snapshots;
58      this.rss = rss;
59      this.factory = factory;
60      // Mutable!
61      this.locallyCachedPolicies = new HashMap<>();
62    }
63  
64    /**
65     * Returns the proper {@link SpaceViolationPolicyEnforcement} implementation for the given table.
66     * If the given table does not have a violation policy enforced, a "no-op" policy will
67     * be returned which always allows an action.
68     *
69     * @see #getPolicyEnforcement(TableName)
70     */
71    public SpaceViolationPolicyEnforcement getPolicyEnforcement(Region r) {
72      return getPolicyEnforcement(Objects.requireNonNull(r).getTableDesc().getTableName());
73    }
74  
75    /**
76     * Returns the proper {@link SpaceViolationPolicyEnforcement} implementation for the given table.
77     * If the given table does not have a violation policy enforced, a "no-op" policy will
78     * be returned which always allows an action.
79     *
80     * @param tableName The table to fetch the policy for.
81     * @return A non-null {@link SpaceViolationPolicyEnforcement} instance.
82     */
83    public SpaceViolationPolicyEnforcement getPolicyEnforcement(TableName tableName) {
84      SpaceViolationPolicyEnforcement policy = activePolicies.get(Objects.requireNonNull(tableName));
85      if (policy == null) {
86        synchronized (locallyCachedPolicies) {
87          // When we don't have an policy enforcement for the table, there could be one of two cases:
88          //  1) The table has no quota defined
89          //  2) The table is not in violation of its quota
90          // In both of these cases, we want to make sure that access remains fast and we minimize
91          // object creation. We can accomplish this by locally caching policies instead of creating
92          // a new instance of the policy each time.
93          policy = locallyCachedPolicies.get(tableName);
94          // We have already created/cached the enforcement, use it again. `activePolicies` and
95          // `snapshots` are immutable, thus this policy is valid for the lifetime of `this`.
96          if (policy != null) {
97            return policy;
98          }
99          // Create a PolicyEnforcement for this table and snapshot. The snapshot may be null
100         // which is OK.
101         policy = factory.createWithoutViolation(rss, tableName, snapshots.get(tableName));
102         // Cache the policy we created
103         locallyCachedPolicies.put(tableName, policy);
104       }
105     }
106     return policy;
107   }
108 
109   /**
110    * Returns an unmodifiable version of the active {@link SpaceViolationPolicyEnforcement}s.
111    */
112   public Map<TableName,SpaceViolationPolicyEnforcement> getPolicies() {
113     return Collections.unmodifiableMap(activePolicies);
114   }
115 
116   /**
117    * Returns an unmodifiable version of the policy enforcements that were cached because they are
118    * not in violation of their quota.
119    */
120   Map<TableName,SpaceViolationPolicyEnforcement> getLocallyCachedPolicies() {
121     return Collections.unmodifiableMap(locallyCachedPolicies);
122   }
123 
124   @Override
125   public String toString() {
126     return getClass().getSimpleName() + ": " + activePolicies;
127   }
128 }