feat: 实现RCU升级后端服务初始版本

- 添加Kafka消费者组件用于消费升级事件数据
- 实现数据处理器进行数据验证和转换
- 添加数据库写入组件支持批量写入G5数据库
- 配置环境变量管理连接参数
- 添加日志记录和错误处理机制
- 实现优雅关闭和流控功能

bls-upgrade-backend/src/kafka/offsetTracker.js

@@ -0,0 +1,53 @@
+class OffsetTracker {
+  constructor() {
+    this.partitions = new Map();
+  }
+
+  add(topic, partition, offset) {
+    const key = `${topic}-${partition}`;
+    if (!this.partitions.has(key)) {
+      this.partitions.set(key, { nextCommitOffset: null, done: new Set() });
+    }
+
+    const state = this.partitions.get(key);
+    const numericOffset = Number(offset);
+    if (!Number.isFinite(numericOffset)) return;
+
+    if (state.nextCommitOffset === null) {
+      state.nextCommitOffset = numericOffset;
+    } else if (numericOffset < state.nextCommitOffset) {
+      state.nextCommitOffset = numericOffset;
+    }
+  }
+
+  markDone(topic, partition, offset) {
+    const key = `${topic}-${partition}`;
+    const state = this.partitions.get(key);
+    if (!state) return null;
+
+    const numericOffset = Number(offset);
+    if (!Number.isFinite(numericOffset)) return null;
+
+    state.done.add(numericOffset);
+
+    if (state.nextCommitOffset === null) {
+      state.nextCommitOffset = numericOffset;
+    }
+
+    let advanced = false;
+    while (state.nextCommitOffset !== null && state.done.has(state.nextCommitOffset)) {
+      state.done.delete(state.nextCommitOffset);
+      state.nextCommitOffset += 1;
+      advanced = true;
+    }
+
+    if (!advanced) return null;
+    return state.nextCommitOffset;
+  }
+
+  clear() {
+    this.partitions.clear();
+  }
+}
+
+export { OffsetTracker };