在Apache BEAM管道中实现消息批处理和立即触发需要在PipelineOptions中设置GlobalWindow和TriggeringPolicy。下面是一个示例代码：

import apache_beam as beam
from apache_beam.options.pipeline_options import PipelineOptions
from apache_beam.transforms.trigger import AfterWatermark, Repeatedly, AfterCount

p = beam.Pipeline(options=PipelineOptions())

messages = [
    {"id": 1, "message": "hello"},
    {"id": 2, "message": "world"},
    {"id": 3, "message": "apache"},
    {"id": 4, "message": "beam"}
]

batched_messages = (
    p
    | "Create Messages" >> beam.Create(messages)
    | "Batch Messages" >> beam.WindowInto(beam.window.GlobalWindows())
    | "Trigger Immediately" >> beam.TriggeringPolicy(
        AfterCount(1),
        Repeatedly(AfterWatermark()),
    )
    | "Print Batched Messages" >> beam.Map(print)
)

result = p.run()
result.wait_until_finish()

此代码使用GlobalWindows()将所有消息分配给全局窗口，然后使用TriggeringPolicy设置立即触发，以在批处理包含一条消息时立即触发管道。