Mercurial > hg > blitz_condensed
comparison src/org/dancres/blitz/entry/WriteBuffer.java @ 0:3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
author | Dan Creswell <dan.creswell@gmail.com> |
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date | Sat, 21 Mar 2009 11:00:06 +0000 |
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1 package org.dancres.blitz.entry; | |
2 | |
3 import java.io.IOException; | |
4 | |
5 import java.util.TreeMap; | |
6 import java.util.ArrayList; | |
7 import java.util.Map; | |
8 import java.util.HashMap; | |
9 | |
10 import java.util.logging.Level; | |
11 | |
12 import EDU.oswego.cs.dl.util.concurrent.Mutex; | |
13 | |
14 import org.dancres.blitz.oid.OID; | |
15 | |
16 import org.dancres.blitz.disk.WriteDaemon; | |
17 | |
18 import org.dancres.blitz.stats.StatsBoard; | |
19 import org.dancres.blitz.stats.StatGenerator; | |
20 import org.dancres.blitz.stats.Stat; | |
21 import org.dancres.blitz.stats.DirtyBufferStat; | |
22 import org.dancres.blitz.entry.ci.CacheIndexer; | |
23 | |
24 /** | |
25 <p> Writes to disk from Storage are done asynchronously. With this being | |
26 the case, it's possible for SleeveCache to flush an EntrySleeveImpl in | |
27 favour of another and then reload it later with a resultant loss of accurate | |
28 state due to the fact that the write has yet to be done. </p> | |
29 | |
30 <p> WriteBuffer tracks all pending writes and ensures that "dirty" state | |
31 that has yet to reach disk is always available to SleeveCache so that | |
32 on-disk state appears to be correct. This works because we also persistently | |
33 log such changes and ensure they've been applied at recovery or an | |
34 intermediate checkpoint. </p> | |
35 | |
36 <p> It's possible that several updates for one EntrySleeveImpl will | |
37 be submitted to WriteBuffer. Rather than handle each update separately, | |
38 WriteBuffer consolidates them all into a single disk op which improves | |
39 performance and reduces latency.</p> | |
40 */ | |
41 class WriteBuffer { | |
42 private Map theJobInfo = new HashMap(); | |
43 private EntryEditor theEditor; | |
44 | |
45 WriteBuffer(EntryEditor anEditor) { | |
46 theEditor = anEditor; | |
47 StatsBoard.get().add(new DirtyBufferGenerator(theEditor.getType(), theJobInfo)); | |
48 } | |
49 | |
50 void add(EntrySleeveImpl aSleeve) throws IOException { | |
51 try { | |
52 OID myUid = aSleeve.getOID(); | |
53 | |
54 if (aSleeve.getState().test(SleeveState.PINNED)) | |
55 throw new RuntimeException("Panic, shouldn't be seeing PINNED"); | |
56 | |
57 // We must duplicate to ensure that further changes by the | |
58 // upper layer, don't pollute us. | |
59 // | |
60 WriteRequest myRequest = new WriteRequest(aSleeve.getState().get(), | |
61 aSleeve.getPersistentRep().duplicate()); | |
62 | |
63 boolean schedule = false; | |
64 | |
65 synchronized(theJobInfo) { | |
66 ArrayList myUpdates = | |
67 (ArrayList) theJobInfo.get(myUid); | |
68 | |
69 // Queue exists? | |
70 if (myUpdates == null) { | |
71 | |
72 /* | |
73 MULTI-THREAD WRITING: | |
74 | |
75 At this point, go to WriteDaemon and ask for a queue | |
76 to dispatch to. Stamp this onto the myUpdates | |
77 (which can therefore no longer be a simple ArrayList) | |
78 */ | |
79 myUpdates = new ArrayList(); | |
80 theJobInfo.put(myUid, myUpdates); | |
81 } | |
82 | |
83 synchronized(myUpdates) { | |
84 // If nothing is pending, buffer it and indicate we need | |
85 // a job scheduled. | |
86 if (myUpdates.size() == 0) { | |
87 myUpdates.add(myRequest); | |
88 schedule = true; | |
89 } else { | |
90 // Recover last update (there should be only one?) | |
91 WriteRequest myLast = (WriteRequest) | |
92 myUpdates.get(myUpdates.size() - 1); | |
93 | |
94 try { | |
95 boolean wasActive; | |
96 | |
97 myLast.lock(); | |
98 | |
99 wasActive = myLast.isActive(); | |
100 | |
101 // If the last request is not active we can merge | |
102 // without queue'ing another job. | |
103 if (!wasActive) { | |
104 myLast.merge(myRequest); | |
105 } | |
106 | |
107 myLast.unlock(); | |
108 | |
109 // Last request was active, queue a new one and | |
110 // ask for a job to be scheduled. | |
111 if (wasActive) { | |
112 myUpdates.add(myRequest); | |
113 schedule = true; | |
114 } | |
115 | |
116 } catch (InterruptedException anIE) { | |
117 EntryStorage.theLogger.log(Level.SEVERE, | |
118 "Failed to lock previous request", anIE); | |
119 } | |
120 } | |
121 } | |
122 | |
123 /* | |
124 Make sure we flip NOT_ON_DISK because we're really | |
125 writing. This might seem odd - for example, what would | |
126 happen if we had a Sleeve with NOT_ON_DISK | DELETE? | |
127 Well, because the Sleeve is DELETE, no other thread | |
128 should dirty the cache entry again. Were it to do so | |
129 if will cause a write problem but it would also be a bug. | |
130 */ | |
131 aSleeve.getState().clear(SleeveState.NOT_ON_DISK); | |
132 | |
133 if (schedule) { | |
134 Job myJob = new Job(myUid, this); | |
135 | |
136 /* | |
137 MULTI-THREAD WRITING: | |
138 | |
139 Use the queue id gathered from the list of updates | |
140 above as an argument to this method. | |
141 | |
142 In this way, we can ensure all updates for one | |
143 UID are dispatched in the same queue which ensures | |
144 FIFO ordering. | |
145 */ | |
146 WriteDaemon.get().queue(myJob); | |
147 } | |
148 } | |
149 | |
150 } catch (Exception anE) { | |
151 EntryStorage.theLogger.log(Level.SEVERE, | |
152 "Failed to add write to cache: " + | |
153 theEditor, anE); | |
154 } | |
155 } | |
156 | |
157 /** | |
158 @return copy of the entry sleeve or <code>null</code> if | |
159 there is no entry in the cache. | |
160 */ | |
161 EntrySleeveImpl dirtyRead(OID aUID) { | |
162 EntrySleeveImpl myResult = null; | |
163 | |
164 synchronized(theJobInfo) { | |
165 ArrayList myStates = (ArrayList) theJobInfo.get(aUID); | |
166 | |
167 if (myStates != null) { | |
168 synchronized(myStates) { | |
169 WriteRequest myRequest = (WriteRequest) | |
170 myStates.get(myStates.size() - 1); | |
171 | |
172 try { | |
173 myRequest.lock(); | |
174 | |
175 myResult = myRequest.newSleeve(); | |
176 | |
177 myRequest.unlock(); | |
178 } catch (InterruptedException anIE) { | |
179 EntryStorage.theLogger.log(Level.SEVERE, | |
180 "Failed to copy sleeve", | |
181 anIE); | |
182 } | |
183 } | |
184 } | |
185 } | |
186 | |
187 return myResult; | |
188 } | |
189 | |
190 /** | |
191 Callback for the Job when it is executed by the WriteDaemon | |
192 */ | |
193 void update(OID aUID) { | |
194 try { | |
195 ArrayList myQueue; | |
196 | |
197 synchronized(theJobInfo) { | |
198 myQueue = (ArrayList) theJobInfo.get(aUID); | |
199 } | |
200 | |
201 WriteRequest myRequest; | |
202 | |
203 synchronized(myQueue) { | |
204 myRequest = (WriteRequest) myQueue.get(0); | |
205 | |
206 try { | |
207 myRequest.lock(); | |
208 | |
209 myRequest.markActive(); | |
210 | |
211 myRequest.unlock(); | |
212 } catch (InterruptedException anIE) { | |
213 EntryStorage.theLogger.log(Level.SEVERE, | |
214 "Failed to lock request for processing", anIE); | |
215 } | |
216 } | |
217 | |
218 myRequest.flush(theEditor); | |
219 | |
220 /* | |
221 Regardless of which write this is, once we've done one, the | |
222 indexes on disk contain any search material we require and | |
223 thus we can clear the CacheIndexer. | |
224 */ | |
225 if ((myRequest.getStateFlags() & SleeveState.NOT_ON_DISK) != 0) { | |
226 /* | |
227 If it's not also marked as deleted (in which case the | |
228 indexer will already be updated) | |
229 */ | |
230 if ((myRequest.getStateFlags() & SleeveState.DELETED) == 0) { | |
231 CacheIndexer.getIndexer( | |
232 theEditor.getType()).flushed(myRequest.getSleeve()); | |
233 } | |
234 } | |
235 | |
236 synchronized(theJobInfo) { | |
237 synchronized(myQueue) { | |
238 | |
239 // Remove the consolidated image stored previously | |
240 myQueue.remove(0); | |
241 | |
242 if (myQueue.size() == 0) { | |
243 theJobInfo.remove(aUID); | |
244 } | |
245 } | |
246 } | |
247 | |
248 } catch (Exception anE) { | |
249 EntryStorage.theLogger.log(Level.SEVERE, | |
250 "Failed to sync cache: " + theEditor, | |
251 anE); | |
252 } | |
253 } | |
254 | |
255 private static final class Job implements Runnable { | |
256 private OID theUID; | |
257 private WriteBuffer theBuffer; | |
258 | |
259 Job(OID aUID, WriteBuffer aBuffer) { | |
260 theUID = aUID; | |
261 theBuffer = aBuffer; | |
262 } | |
263 | |
264 public void run() { | |
265 theBuffer.update(theUID); | |
266 } | |
267 } | |
268 | |
269 private static final class WriteRequest { | |
270 /* | |
271 For performance measurement only | |
272 */ | |
273 private static final Object theLockObject = new Object(); | |
274 private static int numMerges; | |
275 | |
276 private int theStateFlags; | |
277 | |
278 private boolean isActive; | |
279 | |
280 private PersistentEntry theEntry; | |
281 | |
282 private Mutex theLock = new Mutex(); | |
283 | |
284 WriteRequest(int aState, PersistentEntry anEntry) { | |
285 theEntry = anEntry; | |
286 theStateFlags = aState; | |
287 } | |
288 | |
289 void markActive() { | |
290 isActive = true; | |
291 } | |
292 | |
293 boolean isActive() { | |
294 return isActive; | |
295 } | |
296 | |
297 void lock() throws InterruptedException { | |
298 theLock.acquire(); | |
299 } | |
300 | |
301 void unlock() { | |
302 theLock.release(); | |
303 } | |
304 | |
305 int getStateFlags() { | |
306 return theStateFlags; | |
307 } | |
308 | |
309 EntrySleeveImpl getSleeve() { | |
310 EntrySleeveImpl mySleeve = new EntrySleeveImpl(theEntry); | |
311 | |
312 mySleeve.getState().setExplicit(theStateFlags); | |
313 mySleeve.getState().clear(SleeveState.NOT_ON_DISK); | |
314 | |
315 return mySleeve; | |
316 } | |
317 | |
318 void merge(WriteRequest anOther) { | |
319 /* | |
320 synchronized(theLockObject) { | |
321 ++numMerges; | |
322 System.err.println("Coalesce: " + numMerges); | |
323 } | |
324 */ | |
325 | |
326 theStateFlags |= anOther.theStateFlags; | |
327 | |
328 theEntry = anOther.getSleeve().getPersistentRep(); | |
329 } | |
330 | |
331 EntrySleeveImpl newSleeve() { | |
332 EntrySleeveImpl mySleeve = | |
333 new EntrySleeveImpl(theEntry.duplicate()); | |
334 | |
335 mySleeve.getState().setExplicit(theStateFlags); | |
336 mySleeve.getState().clear(SleeveState.NOT_ON_DISK); | |
337 | |
338 return mySleeve; | |
339 } | |
340 | |
341 void flush(EntryEditor anEditor) throws IOException { | |
342 if ((theStateFlags & SleeveState.DELETED) != 0) { | |
343 if ((theStateFlags & SleeveState.NOT_ON_DISK) == 0) { | |
344 anEditor.delete(theEntry); | |
345 } | |
346 } else if ((theStateFlags & SleeveState.NOT_ON_DISK) != 0){ | |
347 anEditor.write(theEntry); | |
348 } else { | |
349 anEditor.update(theEntry); | |
350 } | |
351 } | |
352 } | |
353 | |
354 public class DirtyBufferGenerator implements StatGenerator { | |
355 private long _id = StatGenerator.UNSET_ID; | |
356 | |
357 private Map _jobInfo; | |
358 private String _type; | |
359 | |
360 public DirtyBufferGenerator(String aType, Map aJobInfo) { | |
361 _type = aType; | |
362 _jobInfo = aJobInfo; | |
363 } | |
364 | |
365 public long getId() { | |
366 return _id; | |
367 } | |
368 | |
369 public void setId(long anId) { | |
370 _id = anId; | |
371 } | |
372 | |
373 public Stat generate() { | |
374 int myBufferSize; | |
375 | |
376 synchronized(_jobInfo) { | |
377 myBufferSize = _jobInfo.size(); | |
378 } | |
379 | |
380 return new DirtyBufferStat(_id, _type, myBufferSize); | |
381 } | |
382 } | |
383 } |