Mercurial > hg > blitz_condensed
comparison src/org/dancres/blitz/disk/DiskTxn.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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-1:000000000000 | 0:3dc0c5604566 |
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1 package org.dancres.blitz.disk; | |
2 | |
3 import java.io.IOException; | |
4 | |
5 import java.util.Stack; | |
6 import java.util.logging.Level; | |
7 | |
8 import com.sleepycat.je.Transaction; | |
9 import com.sleepycat.je.DatabaseException; | |
10 import com.sleepycat.je.Database; | |
11 | |
12 import EDU.oswego.cs.dl.util.concurrent.LockReleaser; | |
13 | |
14 /** | |
15 Disk operations are encapsulated in transactions for the purposes of | |
16 recovery etc. DiskTxn represents such transactions. No DiskTxn means | |
17 no disk update. | |
18 */ | |
19 public class DiskTxn { | |
20 private static ThreadLocal ACTIVE_TXN = new ThreadLocal(); | |
21 | |
22 private Transaction theTxn; | |
23 | |
24 private boolean amStandalone = false; | |
25 | |
26 private DiskTxn(Transaction aTxn) { | |
27 theTxn = aTxn; | |
28 } | |
29 | |
30 private DiskTxn(Transaction aTxn, boolean isStandalone) { | |
31 theTxn = aTxn; | |
32 amStandalone = isStandalone; | |
33 } | |
34 | |
35 /** | |
36 Create a new txn and make it part of the current thread's context. | |
37 <B>Warning</B> if there's another Txn already associated with this | |
38 thread (i.e. a non-standalone txn) then it will be overwritten by | |
39 this one with the resultant loss of the old transaction which will | |
40 remain open forever - this would be bad! Under circumstances where | |
41 it's necessary to nest txns, use newStandlone(). | |
42 */ | |
43 public static DiskTxn newTxn() throws IOException { | |
44 Transaction myDbTxn; | |
45 | |
46 try { | |
47 myDbTxn = Disk.newTxn(); | |
48 } catch (DatabaseException aDbe) { | |
49 Disk.theLogger.log(Level.SEVERE, "Got DatabaseException", aDbe); | |
50 throw new IOException("DatabaseException"); | |
51 } | |
52 | |
53 DiskTxn myTxn = new DiskTxn(myDbTxn); | |
54 | |
55 ACTIVE_TXN.set(myTxn); | |
56 | |
57 return myTxn; | |
58 } | |
59 | |
60 /** | |
61 Create a new txn but don't make it a part of the current thread's | |
62 context. | |
63 */ | |
64 public static DiskTxn newStandalone() throws IOException { | |
65 Transaction myDbTxn; | |
66 | |
67 try { | |
68 myDbTxn = Disk.newTxn(); | |
69 } catch (DatabaseException aDbe) { | |
70 Disk.theLogger.log(Level.SEVERE, "Got DatabaseException", aDbe); | |
71 throw new IOException("DatabaseException"); | |
72 } | |
73 | |
74 DiskTxn myTxn = new DiskTxn(myDbTxn, true); | |
75 | |
76 return myTxn; | |
77 } | |
78 | |
79 /** | |
80 If you choose to use a non-blocking transaction, you must be prepared | |
81 to handle (for Db) <code>DatabaseException</code> with an errno of | |
82 <code>Db.DB_LOCK_NOTGRANTED</code> during any operations performed under | |
83 that transaction. This breaks encapsulation of Db a little. | |
84 Note that Db documentation for 4.1.25 would lead a programmer to | |
85 believe they need to handle DbLockNotGrantedException - unfortunately, | |
86 that never seems to be thrown - sigh. | |
87 | |
88 @todo Fix API leakage. | |
89 */ | |
90 public static DiskTxn newNonBlockingStandalone() throws IOException { | |
91 Transaction myDbTxn; | |
92 | |
93 try { | |
94 myDbTxn = Disk.newNonBlockingTxn(); | |
95 } catch (DatabaseException aDbe) { | |
96 Disk.theLogger.log(Level.SEVERE, "Got DatabaseException", aDbe); | |
97 throw new IOException("DatabaseException"); | |
98 } | |
99 | |
100 DiskTxn myTxn = new DiskTxn(myDbTxn, true); | |
101 | |
102 return myTxn; | |
103 } | |
104 | |
105 public static DiskTxn getActiveTxn() { | |
106 return (DiskTxn) ACTIVE_TXN.get(); | |
107 } | |
108 | |
109 public static Transaction getActiveDbTxn() { | |
110 return getActiveTxn().getDbTxn(); | |
111 } | |
112 | |
113 public Transaction getDbTxn() { | |
114 return theTxn; | |
115 } | |
116 | |
117 /** | |
118 Commit the transaction with no forced logging. If you want forced | |
119 logging invoke <code>commit(true)</code>. | |
120 */ | |
121 public void commit() throws IOException { | |
122 commit(false); | |
123 } | |
124 | |
125 public void commit(boolean shouldSync) throws IOException { | |
126 try { | |
127 if (shouldSync) | |
128 theTxn.commitSync(); | |
129 else | |
130 theTxn.commitNoSync(); | |
131 } catch (DatabaseException aDbe) { | |
132 Disk.theLogger.log(Level.SEVERE, "Got DatabaseException", aDbe); | |
133 throw new IOException("DatabaseException"); | |
134 } | |
135 | |
136 release(); | |
137 | |
138 if (!amStandalone) | |
139 ACTIVE_TXN.set(null); | |
140 } | |
141 | |
142 public void abort() throws IOException { | |
143 try { | |
144 theTxn.abort(); | |
145 } catch (DatabaseException aDbe) { | |
146 Disk.theLogger.log(Level.SEVERE, "Got DatabaseException", aDbe); | |
147 throw new IOException("DatabaseException"); | |
148 } | |
149 | |
150 release(); | |
151 | |
152 if (!amStandalone) | |
153 ACTIVE_TXN.set(null); | |
154 } | |
155 | |
156 private void release() { | |
157 } | |
158 } |