id,page,ref,title,content,breadcrumbs,references
internals:internals-tracer-trace-child-tasks,internals,internals-tracer-trace-child-tasks,Tracing child tasks,"If your code uses a mechanism such as  asyncio.gather()  to execute code in additional tasks you may find that some of the traces are missing from the display. 
                 You can use the  trace_child_tasks()  context manager to ensure these child tasks are correctly handled. 
                 from datasette import tracer

with tracer.trace_child_tasks():
    results = await asyncio.gather(
        # ... async tasks here
    ) 
                 This example uses the  register_routes()  plugin hook to add a page at  /parallel-queries  which executes two SQL queries in parallel using  asyncio.gather()  and returns their results. 
                 from datasette import hookimpl
from datasette import tracer


@hookimpl
def register_routes():
    async def parallel_queries(datasette):
        db = datasette.get_database()
        with tracer.trace_child_tasks():
            one, two = await asyncio.gather(
                db.execute(""select 1""),
                db.execute(""select 2""),
            )
        return Response.json(
            {
                ""one"": one.single_value(),
                ""two"": two.single_value(),
            }
        )

    return [
        (r""/parallel-queries$"", parallel_queries),
    ] 
                 Note that running parallel SQL queries in this way has  been known to cause problems in the past , so treat this example with caution. 
                 Adding  ?_trace=1  will show that the trace covers both of those child tasks.","[""Internals for plugins"", ""datasette.tracer""]","[{""href"": ""https://github.com/simonw/datasette/issues/2189"", ""label"": ""been known to cause problems in the past""}]"