1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
package com.orbekk.paxos;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import java.util.concurrent.atomic.AtomicInteger;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.google.protobuf.RpcCallback;
import com.orbekk.protobuf.Rpc;
import com.orbekk.same.ConnectionManager;
import com.orbekk.same.RpcFactory;
import com.orbekk.same.Services;
import com.orbekk.same.Services.ClientState;
import com.orbekk.same.Services.PaxosRequest;
import com.orbekk.same.Services.PaxosResponse;
public class MasterProposer extends Thread {
private final Logger logger = LoggerFactory.getLogger(getClass());
private final ClientState client;
private final List<String> paxosLocations;
private final ConnectionManager connections;
private final RpcFactory rpcf;
public MasterProposer(ClientState client, List<String> paxosLocations,
ConnectionManager connections, RpcFactory rpcf) {
this.client = client;
this.paxosLocations = paxosLocations;
this.connections = connections;
this.rpcf = rpcf;
}
private class ResponseHandler implements RpcCallback<PaxosResponse> {
final int proposalNumber;
final int numRequests;
AtomicInteger bestPromise = new AtomicInteger();
AtomicInteger numPromises = new AtomicInteger(0);
AtomicInteger numResponses = new AtomicInteger(0);
AtomicInteger result = new AtomicInteger();
CountDownLatch done = new CountDownLatch(1);
public ResponseHandler(int proposalNumber, int numRequests) {
this.proposalNumber = proposalNumber;
this.numRequests = numRequests;
bestPromise.set(-proposalNumber);
}
@Override public void run(PaxosResponse response) {
numResponses.incrementAndGet();
if (response != null) {
int result = response.getResult();
if (result == proposalNumber) {
numPromises.incrementAndGet();
}
while (true) {
int oldVal = bestPromise.get();
int update = Math.min(oldVal, result);
if (bestPromise.compareAndSet(oldVal, update)) {
break;
}
}
}
checkDone();
}
private void checkDone() {
if (done.getCount() > 0) {
if (numPromises.get() > numRequests / 2) {
result.set(proposalNumber);
done.countDown();
} else if (numResponses.get() >= numRequests) {
result.set(bestPromise.get());
done.countDown();
}
}
}
public int getResult() throws InterruptedException {
done.await();
return result.get();
}
}
private int internalPropose(int proposalNumber)
throws InterruptedException {
ResponseHandler handler = new ResponseHandler(proposalNumber,
paxosLocations.size());
for (String location : paxosLocations) {
Rpc rpc = rpcf.create();
Services.Paxos paxos = connections.getPaxos0(location);
if (paxos == null) {
handler.run(null);
continue;
}
PaxosRequest request = PaxosRequest.newBuilder()
.setClient(client)
.setProposalNumber(proposalNumber)
.build();
paxos.propose(rpc, request, handler);
}
return handler.getResult();
}
private int internalAcceptRequest(int proposalNumber)
throws InterruptedException {
ResponseHandler handler = new ResponseHandler(proposalNumber,
paxosLocations.size());
for (String location : paxosLocations) {
Rpc rpc = rpcf.create();
Services.Paxos paxos = connections.getPaxos0(location);
PaxosRequest request = PaxosRequest.newBuilder()
.setClient(client)
.setProposalNumber(proposalNumber)
.build();
paxos.acceptRequest(rpc, request, handler);
}
return handler.getResult();
}
boolean propose(int proposalNumber) throws InterruptedException {
int result = internalPropose(proposalNumber);
if (result == proposalNumber) {
result = internalAcceptRequest(proposalNumber);
}
if (result == proposalNumber) {
return true;
} else {
return false;
}
}
boolean proposeRetry(int proposalNumber) throws InterruptedException {
return proposeRetry(proposalNumber, null) != null;
}
Integer proposeRetry(int proposalNumber, Runnable retryAction)
throws InterruptedException {
assert proposalNumber > 0;
int nextProposal = proposalNumber;
int result = nextProposal - 1;
while (!Thread.currentThread().isInterrupted() && result != nextProposal) {
result = internalPropose(nextProposal);
if (result == nextProposal) {
result = internalAcceptRequest(nextProposal);
}
logger.info("Proposed value {}, result {}", nextProposal, result);
if (result < 0) {
nextProposal = -result + 1;
if (retryAction != null) {
retryAction.run();
}
}
}
if (Thread.interrupted()) {
throw new InterruptedException();
}
return result;
}
public Future<Integer> startProposalTask(final int proposalNumber,
final Runnable retryAction) {
Callable<Integer> proposalCallable = new Callable<Integer>() {
@Override public Integer call() throws Exception {
return proposeRetry(proposalNumber, retryAction);
}
};
FutureTask<Integer> task = new FutureTask<Integer>(proposalCallable);
new Thread(task).start();
return task;
}
}
|
