|
8 | 8 |
|
9 | 9 | package org.opensearch.common.cache.stats;
|
10 | 10 |
|
11 |
| -import java.util.Collections; |
12 |
| -import java.util.HashMap; |
13 | 11 | import java.util.List;
|
14 |
| -import java.util.Map; |
15 |
| -import java.util.TreeMap; |
16 |
| -import java.util.concurrent.ConcurrentHashMap; |
17 |
| -import java.util.concurrent.locks.Lock; |
18 |
| -import java.util.concurrent.locks.ReentrantLock; |
19 |
| -import java.util.function.Consumer; |
20 | 12 |
|
21 | 13 | /**
|
22 |
| - * A class ICache implementations use to internally keep track of their stats across multiple dimensions. |
23 |
| - * Not intended to be exposed outside the cache; for this, caches use getImmutableCacheStatsHolder() to create an immutable |
24 |
| - * copy of the current state of the stats. |
25 |
| - * Currently, in the IRC, the stats tracked in a CacheStatsHolder will not appear for empty shards that have had no cache |
26 |
| - * operations done on them yet. This might be changed in the future, by exposing a method to add empty nodes to the |
27 |
| - * tree in CacheStatsHolder in the ICache interface. |
28 |
| - * |
29 |
| - * @opensearch.experimental |
| 14 | + * An interface extended by DefaultCacheStatsHolder and NoopCacheStatsHolder. |
30 | 15 | */
|
31 |
| -public class CacheStatsHolder { |
32 |
| - |
33 |
| - // The list of permitted dimensions. Should be ordered from "outermost" to "innermost", as you would like to |
34 |
| - // aggregate them in an API response. |
35 |
| - private final List<String> dimensionNames; |
36 |
| - // A tree structure based on dimension values, which stores stats values in its leaf nodes. |
37 |
| - // Non-leaf nodes have stats matching the sum of their children. |
38 |
| - // We use a tree structure, rather than a map with concatenated keys, to save on memory usage. If there are many leaf |
39 |
| - // nodes that share a parent, that parent's dimension value will only be stored once, not many times. |
40 |
| - private final Node statsRoot; |
41 |
| - // To avoid sync problems, obtain a lock before creating or removing nodes in the stats tree. |
42 |
| - // No lock is needed to edit stats on existing nodes. |
43 |
| - private final Lock lock = new ReentrantLock(); |
44 |
| - |
45 |
| - public CacheStatsHolder(List<String> dimensionNames) { |
46 |
| - this.dimensionNames = Collections.unmodifiableList(dimensionNames); |
47 |
| - this.statsRoot = new Node("", true); // The root node has the empty string as its dimension value |
48 |
| - } |
49 |
| - |
50 |
| - public List<String> getDimensionNames() { |
51 |
| - return dimensionNames; |
52 |
| - } |
53 |
| - |
54 |
| - // For all these increment functions, the dimensions list comes from the key, and contains all dimensions present in dimensionNames. |
55 |
| - // The order has to match the order given in dimensionNames. |
56 |
| - public void incrementHits(List<String> dimensionValues) { |
57 |
| - internalIncrement(dimensionValues, Node::incrementHits, true); |
58 |
| - } |
59 |
| - |
60 |
| - public void incrementMisses(List<String> dimensionValues) { |
61 |
| - internalIncrement(dimensionValues, Node::incrementMisses, true); |
62 |
| - } |
63 |
| - |
64 |
| - public void incrementEvictions(List<String> dimensionValues) { |
65 |
| - internalIncrement(dimensionValues, Node::incrementEvictions, true); |
66 |
| - } |
67 |
| - |
68 |
| - public void incrementSizeInBytes(List<String> dimensionValues, long amountBytes) { |
69 |
| - internalIncrement(dimensionValues, (node) -> node.incrementSizeInBytes(amountBytes), true); |
70 |
| - } |
71 |
| - |
72 |
| - // For decrements, we should not create nodes if they are absent. This protects us from erroneously decrementing values for keys |
73 |
| - // which have been entirely deleted, for example in an async removal listener. |
74 |
| - public void decrementSizeInBytes(List<String> dimensionValues, long amountBytes) { |
75 |
| - internalIncrement(dimensionValues, (node) -> node.decrementSizeInBytes(amountBytes), false); |
76 |
| - } |
77 |
| - |
78 |
| - public void incrementEntries(List<String> dimensionValues) { |
79 |
| - internalIncrement(dimensionValues, Node::incrementEntries, true); |
80 |
| - } |
81 |
| - |
82 |
| - public void decrementEntries(List<String> dimensionValues) { |
83 |
| - internalIncrement(dimensionValues, Node::decrementEntries, false); |
84 |
| - } |
85 |
| - |
86 |
| - /** |
87 |
| - * Reset number of entries and memory size when all keys leave the cache, but don't reset hit/miss/eviction numbers. |
88 |
| - * This is in line with the behavior of the existing API when caches are cleared. |
89 |
| - */ |
90 |
| - public void reset() { |
91 |
| - resetHelper(statsRoot); |
92 |
| - } |
93 |
| - |
94 |
| - private void resetHelper(Node current) { |
95 |
| - current.resetSizeAndEntries(); |
96 |
| - for (Node child : current.children.values()) { |
97 |
| - resetHelper(child); |
98 |
| - } |
99 |
| - } |
100 |
| - |
101 |
| - public long count() { |
102 |
| - // Include this here so caches don't have to create an entire CacheStats object to run count(). |
103 |
| - return statsRoot.getEntries(); |
104 |
| - } |
105 |
| - |
106 |
| - private void internalIncrement(List<String> dimensionValues, Consumer<Node> adder, boolean createNodesIfAbsent) { |
107 |
| - assert dimensionValues.size() == dimensionNames.size(); |
108 |
| - // First try to increment without creating nodes |
109 |
| - boolean didIncrement = internalIncrementHelper(dimensionValues, statsRoot, 0, adder, false); |
110 |
| - // If we failed to increment, because nodes had to be created, obtain the lock and run again while creating nodes if needed |
111 |
| - if (!didIncrement && createNodesIfAbsent) { |
112 |
| - try { |
113 |
| - lock.lock(); |
114 |
| - internalIncrementHelper(dimensionValues, statsRoot, 0, adder, true); |
115 |
| - } finally { |
116 |
| - lock.unlock(); |
117 |
| - } |
118 |
| - } |
119 |
| - } |
120 |
| - |
121 |
| - /** |
122 |
| - * Use the incrementer function to increment/decrement a value in the stats for a set of dimensions. |
123 |
| - * If createNodesIfAbsent is true, and there is no stats for this set of dimensions, create one. |
124 |
| - * Returns true if the increment was applied, false if not. |
125 |
| - */ |
126 |
| - private boolean internalIncrementHelper( |
127 |
| - List<String> dimensionValues, |
128 |
| - Node node, |
129 |
| - int depth, // Pass in the depth to avoid having to slice the list for each node. |
130 |
| - Consumer<Node> adder, |
131 |
| - boolean createNodesIfAbsent |
132 |
| - ) { |
133 |
| - if (depth == dimensionValues.size()) { |
134 |
| - // This is the leaf node we are trying to reach |
135 |
| - adder.accept(node); |
136 |
| - return true; |
137 |
| - } |
138 |
| - |
139 |
| - Node child = node.getChild(dimensionValues.get(depth)); |
140 |
| - if (child == null) { |
141 |
| - if (createNodesIfAbsent) { |
142 |
| - boolean createMapInChild = depth < dimensionValues.size() - 1; |
143 |
| - child = node.createChild(dimensionValues.get(depth), createMapInChild); |
144 |
| - } else { |
145 |
| - return false; |
146 |
| - } |
147 |
| - } |
148 |
| - if (internalIncrementHelper(dimensionValues, child, depth + 1, adder, createNodesIfAbsent)) { |
149 |
| - // Function returns true if the next node down was incremented |
150 |
| - adder.accept(node); |
151 |
| - return true; |
152 |
| - } |
153 |
| - return false; |
154 |
| - } |
155 |
| - |
156 |
| - /** |
157 |
| - * Produce an immutable version of these stats. |
158 |
| - */ |
159 |
| - public ImmutableCacheStatsHolder getImmutableCacheStatsHolder() { |
160 |
| - return new ImmutableCacheStatsHolder(statsRoot.snapshot(), dimensionNames); |
161 |
| - } |
162 |
| - |
163 |
| - public void removeDimensions(List<String> dimensionValues) { |
164 |
| - assert dimensionValues.size() == dimensionNames.size() : "Must specify a value for every dimension when removing from StatsHolder"; |
165 |
| - // As we are removing nodes from the tree, obtain the lock |
166 |
| - lock.lock(); |
167 |
| - try { |
168 |
| - removeDimensionsHelper(dimensionValues, statsRoot, 0); |
169 |
| - } finally { |
170 |
| - lock.unlock(); |
171 |
| - } |
172 |
| - } |
173 |
| - |
174 |
| - // Returns a CacheStatsCounterSnapshot object for the stats to decrement if the removal happened, null otherwise. |
175 |
| - private ImmutableCacheStats removeDimensionsHelper(List<String> dimensionValues, Node node, int depth) { |
176 |
| - if (depth == dimensionValues.size()) { |
177 |
| - // Pass up a snapshot of the original stats to avoid issues when the original is decremented by other fn invocations |
178 |
| - return node.getImmutableStats(); |
179 |
| - } |
180 |
| - Node child = node.getChild(dimensionValues.get(depth)); |
181 |
| - if (child == null) { |
182 |
| - return null; |
183 |
| - } |
184 |
| - ImmutableCacheStats statsToDecrement = removeDimensionsHelper(dimensionValues, child, depth + 1); |
185 |
| - if (statsToDecrement != null) { |
186 |
| - // The removal took place, decrement values and remove this node from its parent if it's now empty |
187 |
| - node.decrementBySnapshot(statsToDecrement); |
188 |
| - if (child.getChildren().isEmpty()) { |
189 |
| - node.children.remove(child.getDimensionValue()); |
190 |
| - } |
191 |
| - } |
192 |
| - return statsToDecrement; |
193 |
| - } |
194 |
| - |
195 |
| - // pkg-private for testing |
196 |
| - Node getStatsRoot() { |
197 |
| - return statsRoot; |
198 |
| - } |
199 |
| - |
200 |
| - static class Node { |
201 |
| - private final String dimensionValue; |
202 |
| - // Map from dimensionValue to the DimensionNode for that dimension value. |
203 |
| - final Map<String, Node> children; |
204 |
| - // The stats for this node. If a leaf node, corresponds to the stats for this combination of dimensions; if not, |
205 |
| - // contains the sum of its children's stats. |
206 |
| - private CacheStats stats; |
207 |
| - |
208 |
| - // Used for leaf nodes to avoid allocating many unnecessary maps |
209 |
| - private static final Map<String, Node> EMPTY_CHILDREN_MAP = new HashMap<>(); |
210 |
| - |
211 |
| - Node(String dimensionValue, boolean createChildrenMap) { |
212 |
| - this.dimensionValue = dimensionValue; |
213 |
| - if (createChildrenMap) { |
214 |
| - this.children = new ConcurrentHashMap<>(); |
215 |
| - } else { |
216 |
| - this.children = EMPTY_CHILDREN_MAP; |
217 |
| - } |
218 |
| - this.stats = new CacheStats(); |
219 |
| - } |
220 |
| - |
221 |
| - public String getDimensionValue() { |
222 |
| - return dimensionValue; |
223 |
| - } |
224 |
| - |
225 |
| - protected Map<String, Node> getChildren() { |
226 |
| - // We can safely iterate over ConcurrentHashMap without worrying about thread issues. |
227 |
| - return children; |
228 |
| - } |
229 |
| - |
230 |
| - // Functions for modifying internal CacheStatsCounter without callers having to be aware of CacheStatsCounter |
231 |
| - |
232 |
| - void incrementHits() { |
233 |
| - this.stats.incrementHits(); |
234 |
| - } |
235 |
| - |
236 |
| - void incrementMisses() { |
237 |
| - this.stats.incrementMisses(); |
238 |
| - } |
239 |
| - |
240 |
| - void incrementEvictions() { |
241 |
| - this.stats.incrementEvictions(); |
242 |
| - } |
243 |
| - |
244 |
| - void incrementSizeInBytes(long amountBytes) { |
245 |
| - this.stats.incrementSizeInBytes(amountBytes); |
246 |
| - } |
| 16 | +public interface CacheStatsHolder { |
| 17 | + void incrementHits(List<String> dimensionValues); |
247 | 18 |
|
248 |
| - void decrementSizeInBytes(long amountBytes) { |
249 |
| - this.stats.decrementSizeInBytes(amountBytes); |
250 |
| - } |
| 19 | + void incrementMisses(List<String> dimensionValues); |
251 | 20 |
|
252 |
| - void incrementEntries() { |
253 |
| - this.stats.incrementEntries(); |
254 |
| - } |
| 21 | + void incrementEvictions(List<String> dimensionValues); |
255 | 22 |
|
256 |
| - void decrementEntries() { |
257 |
| - this.stats.decrementEntries(); |
258 |
| - } |
| 23 | + void incrementSizeInBytes(List<String> dimensionValues, long amountBytes); |
259 | 24 |
|
260 |
| - long getEntries() { |
261 |
| - return this.stats.getEntries(); |
262 |
| - } |
| 25 | + void decrementSizeInBytes(List<String> dimensionValues, long amountBytes); |
263 | 26 |
|
264 |
| - ImmutableCacheStats getImmutableStats() { |
265 |
| - return this.stats.immutableSnapshot(); |
266 |
| - } |
| 27 | + void incrementEntries(List<String> dimensionValues); |
267 | 28 |
|
268 |
| - void decrementBySnapshot(ImmutableCacheStats snapshot) { |
269 |
| - this.stats.subtract(snapshot); |
270 |
| - } |
| 29 | + void decrementEntries(List<String> dimensionValues); |
271 | 30 |
|
272 |
| - void resetSizeAndEntries() { |
273 |
| - this.stats.resetSizeAndEntries(); |
274 |
| - } |
| 31 | + void reset(); |
275 | 32 |
|
276 |
| - Node getChild(String dimensionValue) { |
277 |
| - return children.get(dimensionValue); |
278 |
| - } |
| 33 | + long count(); |
279 | 34 |
|
280 |
| - Node createChild(String dimensionValue, boolean createMapInChild) { |
281 |
| - return children.computeIfAbsent(dimensionValue, (key) -> new Node(dimensionValue, createMapInChild)); |
282 |
| - } |
| 35 | + void removeDimensions(List<String> dimensionValues); |
283 | 36 |
|
284 |
| - ImmutableCacheStatsHolder.Node snapshot() { |
285 |
| - TreeMap<String, ImmutableCacheStatsHolder.Node> snapshotChildren = null; |
286 |
| - if (!children.isEmpty()) { |
287 |
| - snapshotChildren = new TreeMap<>(); |
288 |
| - for (Node child : children.values()) { |
289 |
| - snapshotChildren.put(child.getDimensionValue(), child.snapshot()); |
290 |
| - } |
291 |
| - } |
292 |
| - return new ImmutableCacheStatsHolder.Node(dimensionValue, snapshotChildren, getImmutableStats()); |
293 |
| - } |
294 |
| - } |
| 37 | + ImmutableCacheStatsHolder getImmutableCacheStatsHolder(); |
295 | 38 | }
|
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