Start implementing Paxos service.

2 files changed, 66 insertions, 0 deletions

diff --git a/same/src/main/java/com/orbekk/paxos/PaxosService.java b/same/src/main/java/com/orbekk/paxos/PaxosService.java
new file mode 100644
index 0000000..3398e81
--- /dev/null
+++ b/same/src/main/java/com/orbekk/paxos/PaxosService.java
@@ -0,0 +1,6 @@
+pakage com.orbekk.paxos;
+
+public interface PaxosService {
+    boolean propose(String clientUrl, int roundId, int proposalNumber);
+    boolean acceptRequest(String clientUrl, int roundId, int proposalNumber); 
+}
diff --git a/same/src/main/java/com/orbekk/paxos/PaxosServiceImpl.java b/same/src/main/java/com/orbekk/paxos/PaxosServiceImpl.java
new file mode 100644
index 0000000..a39abbe
--- /dev/null
+++ b/same/src/main/java/com/orbekk/paxos/PaxosServiceImpl.java
@@ -0,0 +1,60 @@
+package com.orbekk.paxos;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class PaxosServiceImpl implements PaxosService {
+    private Logger logger = LoggerFactory.getLogger(getClass());
+    private int roundId = 0;
+    private int highestPromise = 0;
+    private String tag = "";
+
+    @Override
+    public boolean propose(String clientUrl, int roundId, int proposalNumber) {
+        if (roundId > this.roundId) {
+            newRound(roundId);
+        }
+        if (roundId < this.roundId) {
+            logger.info(tag + "propose({}, {}, {}) = rejected " +
+                    "(current round: {})",
+                    new Object[]{clientUrl, roundId, proposalNumber,
+                            this.roundId});
+            return false;
+        }
+
+        if (proposalNumber > highestPromise) {
+            highestPromise = proposalNumber;
+            logger.info(tag + "propose({}, {}, {}) = accepted",
+                    new Object[]{clientUrl, roundId, proposalNumber);
+            return true;
+        } else {
+            logger.info(tag + "propose({}, {}, {}) = rejected " +
+                    "(promised: {})",
+                    new Object[]{clientUrl, roundId, proposalNumber,
+                            highestPromise});
+            return false;
+        }
+    }
+
+    @Override
+    public boolean acceptRequest(String clientUrl, int roundId,
+            int proposalNumber) {
+        if (roundId == this.roundId && proposalNumber == highestPromise) {
+            logger.info(tag + "acceptRequest({}, {}, {}) = accepted",
+                    new Object[]{clientUrl, roundId, proposalNumber});
+            return true;
+        } else {
+            logger.info(tag + "acceptRequest({}, {}, {}) = rejected " +
+                    "(roundId={}, promise={})",
+                    new Object[]{clientUrl, roundId, proposalNumber,
+                            this.roundId, highestPromise});
+            return false;
+        }
+    }
+
+    private void newRound(int roundId) {
+        logger.info(tag + "new round: {}", roundId);
+        this.roundId = roundId;
+        highestPromise = 0;
+    }
+}