redis实现异步任务队列

redis实现异步任务队列

先说思路：

将任务对象序列为JSON字符串，然后推入REDIS缓存，这叫入队。

通过独立的工作线程从REDIS拉出一个任务，这叫出队，工作线程将JSON字符串还原为任务对象，然后对这个任务对象进行处理，并取得执行结果。

整个过程是全异步执行的，所以叫异步任务队列。

下面附上演示代码。

1）任务对象定义

type
  TJob = class
  private
    FReplyTo: String;
    procedure SetReplyTo(const Value: String);
  public
    property ReplyTo: String read FReplyTo write SetReplyTo;
  end;

  TEvalJob = class(TJob)
  private
    FExpression: String;
    procedure SetExpression(const Value: String);
  public
    property Expression: String read FExpression write SetExpression;
  end;

  TDatabaseJob = class(TJob)
  private
    FProcedureName: String;
    procedure SetProcedureName(const Value: String);
  public
    property ProcedureName: String read FProcedureName
      write SetProcedureName;
  end;

　　2）入队

procedure TMainForm.Button1Click(Sender: TObject);
var
  lRedis: IRedisClient;
  lJob: TEvalJob;
  lJobString: string;
begin
  lRedis := NewRedisClient(REDIS_HOSTNAME);

  lJob := TEvalJob.Create;
  try
    lJob.ReplyTo := 'replies:' + FUserName;
    lJob.Expression := Edit1.Text;
    lJobString := TJson.ObjectToJsonString(lJob);
    lRedis.LPUSH('jobs', lJobString);
  finally
    lJob.free;
  end;
end;

　　3）出队并执行

procedure TMainForm.Timer1Timer(Sender: TObject);
var
  lJobj: TJSONObject;
  lExpression, lRes: string;
  lResponse: string;
begin
  if FRedis.RPOP('replies:' + FUserName, lResponse) then
  begin
    lJobj := TJSONObject.ParseJSONValue(lResponse) as TJSONObject;
    try
      lExpression := lJobj.GetValue<TJSONString>('expression').Value;
      lRes := lJobj.GetValue<TJSONString>('result').Value;
      Memo1.Lines.Add(Format('Response: %s = %s', [lExpression, lRes]));
    finally
      lJobj.free;
    end;
  end;
end;