事务性增强

Author: Aph-CUG

设计文档.md

@@ -0,0 +1,239 @@
+## 事务日志——checklist
+
+使用checklist来执行事务日志的记录，checklist以类的形式保存，记录检查点，每执行完一个节点需要做对应的记录。
+
+checklist的结构如下：
+
+```java
+package org.apache.hugegraph.variables;
+
+import org.apache.hugegraph.config.HugeConfig;
+import org.apache.hugegraph.masterelection.GlobalMasterInfo;
+
+import java.io.Serializable;
+
+public class CheckList implements Serializable {
+
+    private String name;
+    private String configText;
+    
+    private HugeConfig config;
+
+    private boolean initBackended;
+
+    private boolean serverStarted;
+
+    private String stage;
+
+    private String configPath;
+
+    private GlobalMasterInfo nodeInfo;
+
+    boolean toCheck;
+    String context;
+    private boolean isBuild;
+
+    public void setBuild(boolean build) {
+        isBuild = build;
+    }
+
+    public CheckList(String name, String context) {
+        this.name = name;
+        this.context = context;
+    }
+
+    public HugeConfig getConfig() {
+        return config;
+    }
+
+    public void setConfig(HugeConfig config) {
+        this.config = config;
+    }
+
+    public boolean isInitBackended() {
+        return initBackended;
+    }
+
+    public void setInitBackended(boolean initBackended) {
+        this.initBackended = initBackended;
+    }
+
+    public boolean isServerStarted() {
+        return serverStarted;
+    }
+
+    public void setServerStarted(boolean serverStarted) {
+        this.serverStarted = serverStarted;
+    }
+
+    public String getStage() {
+        return stage;
+    }
+
+    public void setStage(String stage) {
+        this.stage = stage;
+    }
+
+    public String getConfigPath() {
+        return configPath;
+    }
+
+    public void setConfigPath(String configPath) {
+        this.configPath = configPath;
+    }
+
+    public GlobalMasterInfo getNodeInfo() {
+        return nodeInfo;
+    }
+
+    public void setNodeInfo(GlobalMasterInfo nodeInfo) {
+        this.nodeInfo = nodeInfo;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}
+
+```
+
+
+
+主要涉及到的函数有GraphsAPI类中的create、drop两个函数，以create为例，在原来的流程之上，在检查点处保存log信息：
+
+```java
+    public void create(String configPath, GlobalMasterInfo nodeInfo){
+        //CheckList checkList = new CheckList();
+        KResponse result = null;
+        try {
+            result = client.get(this.name);
+            String json = result.getValue();
+            CheckList checkList = JsonUtil.fromJson(json, CheckList.class);
+
+            this.initBackend();
+            checkList.setInitBackended(true);
+            checkList.setStage("initBackend");
+            client.put(name, JsonUtil.toJson(checkList));
+            this.serverStarted(nodeInfo);
+            checkList.setServerStarted(true);
+            checkList.setStage("setServerStarted");
+            client.put(name, JsonUtil.toJson(checkList));
+
+
+            // Write config to disk file
+            String confPath = ConfigUtil.writeToFile(configPath, this.name(),
+                                                     this.configuration());
+            this.configuration.file(confPath);
+        } 
+```
+
+
+
+除此之外，还有一些上下文信息需要保存，便于重新恢复：
+
+```java
+checkList.setConfig(config);
+```
+
+
+
+序列化与日志存放，分别借用了hugegraph中的Jsonutil与pd中的kvclient：
+
+```java
+private KvClient<WatchResponse> client;
+CheckList checkList = JsonUtil.fromJson(json, CheckList.class);
+client.put(name, JsonUtil.toJson(checkList));
+```
+
+
+
+恢复机制：在HugeGraphServer中，启动时添加对事务的扫描，扫描的机制为，使用KvClient的前缀扫描，遇到没有执行完的，进行恢复执行。
+
+```java
+package org.apache.hugegraph;
+
+import org.apache.hugegraph.config.HugeConfig;
+import org.apache.hugegraph.core.GraphManager;
+import org.apache.hugegraph.masterelection.GlobalMasterInfo;
+import org.apache.hugegraph.pd.client.KvClient;
+import org.apache.hugegraph.pd.common.PDException;
+import org.apache.hugegraph.pd.grpc.kv.ScanPrefixResponse;
+import org.apache.hugegraph.pd.grpc.kv.WatchResponse;
+import org.apache.hugegraph.util.ConfigUtil;
+import org.apache.hugegraph.util.Events;
+import org.apache.hugegraph.util.JsonUtil;
+import org.apache.hugegraph.variables.CheckList;
+import org.apache.tinkerpop.gremlin.structure.util.GraphFactory;
+
+
+
+public class TxScanner {
+    private final String prefix = "graph_creat_tx";
+
+    private KvClient<WatchResponse> client;
+
+    public TxScanner(KvClient<WatchResponse> client) {
+    }
+
+
+    public void scan() {
+        try {
+            ScanPrefixResponse response = this.client.scanPrefix(prefix);
+            for(String key : response.getKvsMap().keySet()) {
+                String value = response.getKvsMap().get(key);
+                CheckList checkList = JsonUtil.fromJson(value, CheckList.class);
+                switch (checkList.getStage()) {
+                    case "config": {
+                        configContinue(checkList);
+                    }
+                    case "initBackend" : {
+                        HugeConfig config = checkList.getConfig();
+                        HugeGraph graph = (HugeGraph) GraphFactory.open(config);
+                        GlobalMasterInfo globalMasterInfo = checkList.getNodeInfo();
+                        graph.serverStarted(globalMasterInfo);
+                        // Write config to disk file
+                        String confPath = ConfigUtil.writeToFile(checkList.getConfigPath(), graph.name(),
+                                                                 (HugeConfig)graph.configuration());
+                    }
+                    case "setServerStarted" : {
+                        HugeConfig config = checkList.getConfig();
+                        HugeGraph graph = (HugeGraph) GraphFactory.open(config);
+                        String confPath = ConfigUtil.writeToFile(checkList.getConfigPath(), graph.name(),
+                                                                 (HugeConfig)graph.configuration());
+                    }
+                    case "finish" : {
+                        client.delete(prefix + checkList.getName());
+                    }
+                }
+            }
+        } catch (PDException e) {
+            throw new RuntimeException(e);
+        }
+
+    }
+
+    private void configContinue(CheckList checkList) {
+        HugeConfig config = checkList.getConfig();
+        HugeGraph graph = (HugeGraph) GraphFactory.open(config);
+        try {
+            // Create graph instance
+            graph = (HugeGraph) GraphFactory.open(config);
+            String configPath = checkList.getConfigPath();
+            GlobalMasterInfo globalMasterInfo = checkList.getNodeInfo();
+            // Init graph and start it
+            graph.create(configPath, globalMasterInfo);
+        } catch (Throwable e) {
+            throw e;
+        }
+
+    }
+
+}
+```
+
+
+