In this paper, we study the problem of task reallocation for load-balancing in distributed data processing models that tackle vast amount of data. We propose a strategy based on cooperative agents used to optimize the rescheduling of tasks in multiple jobs which must be executed as soon as possible. It allows agents to determine locally the next tasks to process, to delegate, possibly to swap according to their knowledge, their own belief base and their peer modelling. The novelty lies in the ability of agents to identify opportunities and bottleneck agents, and afterwards to reassign some bundles of tasks thanks to concurrent bilateral negotiations. The strategy adopted by the agents allows to warrant a continuous improvement of the flowtime. Our experimentation reveals that our strategy reaches a flowtime which is better than the one reached by a DCOP resolution, close to the one reached by the classical heuristic approach, and significantly reduces the rescheduling time.