redis實現異步任務隊列

redis實現異步任務隊列

先說思路：

將任務對象序列爲JSON字符串，而後推入REDIS緩存，這叫入隊。

經過獨立的工做線程從REDIS拉出一個任務，這叫出隊，工做線程將JSON字符串還原爲任務對象，而後對這個任務對象進行處理，並取得執行結果。

整個過程是全異步執行的，因此叫異步任務隊列。

下面附上演示代碼。

1）任務對象定義

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）入隊

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）出隊並執行

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;