Mercurial > hg > blitz_condensed
annotate src/org/dancres/blitz/oid/Allocator.java @ 33:0b9265358617
Added tag 2.1.1 for changeset a77f0a9ed93c
author | Dan Creswell <dan.creswell@gmail.com> |
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date | Sat, 12 Jun 2010 10:52:10 +0100 |
parents | 3dc0c5604566 |
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1 package org.dancres.blitz.oid; |
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Initial checkin of blitz 2.0 fcs - no installer yet.
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2 |
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3 import java.io.IOException; |
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4 |
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Initial checkin of blitz 2.0 fcs - no installer yet.
Dan Creswell <dan.creswell@gmail.com>
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5 /** |
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6 <p>An Allocator generates a series of UIDImpl's each of which is |
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Initial checkin of blitz 2.0 fcs - no installer yet.
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7 guarenteed to be unique within the scope of the Allocator. Note that |
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Initial checkin of blitz 2.0 fcs - no installer yet.
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8 allocated id's are not re-used so an Allocator can, potentially, become |
3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
Dan Creswell <dan.creswell@gmail.com>
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9 exhausted. This can be avoided by allowing the allocator sufficient |
3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
Dan Creswell <dan.creswell@gmail.com>
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10 space to allocate from by increasing the maximum number of available |
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11 allocator ids.</p> |
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12 |
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13 <p>Allocator's are self-recovering. They check <code>BootContext</code> |
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Initial checkin of blitz 2.0 fcs - no installer yet.
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14 for the presence of a <code>SyncBarrier</code> instance which indicates |
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15 the maximum number of log operations between checkpoints. This number |
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16 represents the maximum number of entry writes or notify registrations which |
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Initial checkin of blitz 2.0 fcs - no installer yet.
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17 could have been carried out without the appropriate Allocator instances |
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18 being sync'd to disk. Thus, the allocator simply ensures that all it's |
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19 oid generators are incremented by the value of the SyncBarrier and sync'd |
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20 back to disk. This guarentees that there will be no oid overlap and |
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Initial checkin of blitz 2.0 fcs - no installer yet.
Dan Creswell <dan.creswell@gmail.com>
parents:
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21 means that "user code" need not be involved in the recovery process.</p> |
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Initial checkin of blitz 2.0 fcs - no installer yet.
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22 */ |
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23 public interface Allocator { |
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24 public OID getNextId() throws IOException; |
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25 |
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26 /** |
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27 @return the maximum number of zone id's this Allocator instance |
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28 is allowed to use. |
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29 */ |
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30 public int getMaxZoneId(); |
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31 } |