我是否正确释放了我的 SQL 连接？

Question

我有一个应用程序执行许多 API 调用，但我像这样释放每个连接？

app.put("/interview/create/questions/:lastEmployeeId", function (req, res) {
  console.log("It is getting to the route");
  const employee_id = req.body.lastEmployeeId;
  const tableName = req.body.table;
  connection.getConnection(function (err, connection) {
    connection.query(
      `INSERT INTO ${tableName} (employee_id)
            VALUES (?)`,
      [employee_id],
      function (error, results, fields) {
        if (error) throw error;
        res.json(results);
        console.log(`Interview has been created`);
      }
    );
    connection.release();
  });
});

这是正确的方法吗，因为我收到了很多不一致的 502 和 503 错误。在我看来，它可能正在耗尽资源。路径是正确的，因为有时它们有效，有时则无效。这是随机的，所以我不知道该怎么做。

connection.release() 不会释放资源吗？我目前将最大连接数设置为 50，这应该比我需要的要多，因为一次只有一个人会使用它，并且有一种方法可以进行 8 次调用。我不介意一些帮助重构它，但我仍然需要这么多调用，因为我需要它在 8 个不同的表中创建行。下面这个长方法只是取一个表中输入的值，并将其作为参考输入到其他 8 个表中。

createQuestions() {
    fetch(
      API_URL + `/interview/create/questions/${this.state.lastEmployeeId}`,
      {
        method: "PUT",
        body: JSON.stringify({
          lastEmployeeId: this.state.lastEmployeeId,
          table: "audit_general",
        }),
        headers: { "Content-Type": "application/json" },
      }
    )
      .then((res) => {
        if (!res.ok) {
          throw new Error();
        }
        return res.json();
      })
      .then((data) => console.log(data))
      .catch((err) => console.log(err))
      .then(
        fetch(
          API_URL + `/interview/create/questions/${this.state.lastEmployeeId}`,
          {
            method: "PUT",
            body: JSON.stringify({
              lastEmployeeId: this.state.lastEmployeeId,
              table: "audit_culture",
            }),
            headers: { "Content-Type": "application/json" },
          }
        )
          .then((res) => {
            if (!res.ok) {
              throw new Error();
            }
            return res.json();
          })
          .then((data) => console.log(data))
          .catch((err) => console.log(err))
      )
      .then(
        fetch(
          API_URL + `/interview/create/questions/${this.state.lastEmployeeId}`,
          {
            method: "PUT",
            body: JSON.stringify({
              lastEmployeeId: this.state.lastEmployeeId,
              table: "audit_performance",
            }),
            headers: { "Content-Type": "application/json" },
          }
        )
          .then((res) => {
            if (!res.ok) {
              throw new Error();
            }
            return res.json();
          })
          .then((data) => console.log(data))
          .catch((err) => console.log(err))
      )
      .then(
        fetch(
          API_URL + `/interview/create/questions/${this.state.lastEmployeeId}`,
          {
            method: "PUT",
            body: JSON.stringify({
              lastEmployeeId: this.state.lastEmployeeId,
              table: "audit_policies",
            }),
            headers: { "Content-Type": "application/json" },
          }
        )
          .then((res) => {
            if (!res.ok) {
              throw new Error();
            }
            return res.json();
          })
          .then((data) => console.log(data))
          .catch((err) => console.log(err))
      )
      .then(
        fetch(
          API_URL + `/interview/create/questions/${this.state.lastEmployeeId}`,
          {
            method: "PUT",
            body: JSON.stringify({
              lastEmployeeId: this.state.lastEmployeeId,
              table: "audit_risk",
            }),
            headers: { "Content-Type": "application/json" },
          }
        )
          .then((res) => {
            if (!res.ok) {
              throw new Error();
            }
            return res.json();
          })
          .then((data) => console.log(data))
          .catch((err) => console.log(err))
      )
      .then(
        fetch(
          API_URL + `/interview/create/questions/${this.state.lastEmployeeId}`,
          {
            method: "PUT",
            body: JSON.stringify({
              lastEmployeeId: this.state.lastEmployeeId,
              table: "audit_strategy",
            }),
            headers: { "Content-Type": "application/json" },
          }
        )
          .then((res) => {
            if (!res.ok) {
              throw new Error();
            }
            return res.json();
          })
          .then((data) => console.log(data))
          .catch((err) => console.log(err))
      )
      .then(
        fetch(
          API_URL + `/interview/create/questions/${this.state.lastEmployeeId}`,
          {
            method: "PUT",
            body: JSON.stringify({
              lastEmployeeId: this.state.lastEmployeeId,
              table: "audit_rewards",
            }),
            headers: { "Content-Type": "application/json" },
          }
        )
          .then((res) => {
            if (!res.ok) {
              throw new Error();
            }
            return res.json();
          })
          .then((data) => console.log(data))
          .catch((err) => console.log(err))
      )
      .then(
        fetch(
          API_URL + `/interview/create/questions/${this.state.lastEmployeeId}`,
          {
            method: "PUT",
            body: JSON.stringify({
              lastEmployeeId: this.state.lastEmployeeId,
              table: "audit_workforce",
            }),
            headers: { "Content-Type": "application/json" },
          }
        )
          .then((res) => {
            if (!res.ok) {
              throw new Error();
            }
            return res.json();
          })
          .then((data) => console.log(data))
          .catch((err) => console.log(err))
      );
  }

Answer 1

您将在查询完成之前释放连接。这需要解决：

app.put("/interview/create/questions/:lastEmployeeId", function (req, res) {
  console.log("It is getting to the route");
  const employee_id = req.body.lastEmployeeId;
  const tableName = req.body.table;

  connection.getConnection(function (err, connection) {
    if (err) {
      res.statusCode = 500;
      res.send('DB connection could not be acquired.');
      return;
    }

    connection.query(
      `INSERT INTO ${tableName} (employee_id)
            VALUES (?)`,
      [ employee_id ],
      function (error, results, fields) {
        // throw here does nothing useful, it's inside a callback and
        // the calling function may have terminated ages ago. You need
        // to handle this error here and now.
        if (error) {
          res.statusCode = 500;
          res.send('Nope!');
          return;
        }

        res.json(results);
        console.log(`Interview has been created`);

        // Now you can release the handle
        connection.release();
      }
    );
    
    // Code here runs before the query can complete.
  });
});

这样想你的异步程序流程：

connection.getConnection(..., cbGC) executes and returns

** Long time passes

cbGC executes -> connection.query(..., cbQ) executes and returns

** Tiny eternity elapses

cbQ executes!

调用带有回调的函数与实际执行的回调之间的时间间隔可能很长，秒或更长，这意味着调用函数不仅已死，而且是古老的历史，可能是垃圾回收。

您需要围绕嵌套任何内容这一原则来组织代码，这取决于该排序。