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Worker key reference counting #3641

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Worker key reference counting #3641

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8edba46
Add worker key reference counting
jacobtomlinson Mar 26, 2020
53691d2
Add test
jacobtomlinson Mar 26, 2020
a799dd5
Cast keys to list as it sometimes is a tuple
jacobtomlinson Mar 26, 2020
3b4b779
Update test
jacobtomlinson Mar 26, 2020
6d6f44c
Fix test
jacobtomlinson Mar 27, 2020
05b6069
Check both workers for value
jacobtomlinson Mar 27, 2020
3eaa30f
Update test so that sum key is also the same both times
jacobtomlinson Mar 27, 2020
e249c8a
Merge branch 'master' of github.com:dask/distributed into worker-refe…
mrocklin Apr 25, 2020
6114d4b
Create futures at the beginning of scatter rather than the end
mrocklin Apr 25, 2020
e84ff97
Improve logging on lost data
mrocklin Apr 25, 2020
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2 changes: 1 addition & 1 deletion distributed/client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1985,6 +1985,7 @@ async def _scatter(
if w.scheduler.address == self.scheduler.address:
direct = True

out = {k: Future(k, self, inform=False) for k in data}
if local_worker: # running within task
local_worker.update_data(data=data, report=False)

Expand Down Expand Up @@ -2024,7 +2025,6 @@ async def _scatter(
timeout=timeout,
)

out = {k: Future(k, self, inform=False) for k in data}
for key, typ in types.items():
self.futures[key].finish(type=typ)

Expand Down
6 changes: 5 additions & 1 deletion distributed/scheduler.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1815,7 +1815,11 @@ def update_graph(
if any(
dep not in self.tasks and dep not in tasks for dep in deps
): # bad key
logger.info("User asked for computation on lost data, %s", k)
logger.info(
"User asked for computation %s lost data %s",
k,
[dep for dep in deps if dep not in self.tasks],
)
del tasks[k]
del dependencies[k]
if k in keys:
Expand Down
13 changes: 13 additions & 0 deletions distributed/tests/test_worker_client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -315,3 +315,16 @@ async def test_submit_different_names(s, a, b):
assert fut > 0
finally:
await c.close()


@gen_cluster(client=True)
async def test_task_unique_groups_scatter(c, s, a, b):
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Not sure why, but occasionally when I run I get a timeouterror:

E tornado.util.TimeoutError: Operation timed out after 20 seconds

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How occasionally? I'm not seeing this after 10 runs.

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I was seeing it after 3 runs on my machine

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I tried converting Corey's example into a test and now I see that timeouterror every time. I wonder if pytest is masking the CancelledError somehow.

@gen_cluster(client=True)
async def test_task_unique_groups_scatter_tree_reduce(c, s, a, b):
    from toolz import first

    def tree_reduce(objs):
        while len(objs) > 1:
            new_objs = []
            n_objs = len(objs)
            for i in range(0, n_objs, 2):
                inputs = objs[i : i + 2]
                obj = c.submit(sum, inputs)
                new_objs.append(obj)
            wait(new_objs)
            objs = new_objs

        return first(objs)

    for n_parts in [1, 2, 5, 10, 15]:
        a = await c.scatter(range(n_parts))
        b = tree_reduce(a)

        assert sum(range(n_parts)) == await b

        del a

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I've been seeing this timeout exception as well and what's very strange is that I've even increased the timeout to 50s and I get the exception long before 50s has passed. This is specifically true in the case of dask/dask#6037

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I'm getting it almost immediately. Within a second.

""" This test ensure that tasks are correctly deleted when using scatter/submit
"""
n = await c.scatter([0, 1], hash=True)
x = await c.submit(sum, n)
del n
del x
m = await c.scatter([0, 1], hash=True)
y = await c.submit(sum, m)
assert y in list(b.data.values()) or y in list(a.data.values())
17 changes: 16 additions & 1 deletion distributed/worker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -332,6 +332,7 @@ def __init__(
):
self.tasks = dict()
self.task_state = dict()
self.task_refs = dict()
self.dep_state = dict()
self.dependencies = dict()
self.dependents = dict()
Expand Down Expand Up @@ -1300,6 +1301,11 @@ def update_data(self, comm=None, data=None, report=True, serializers=None):
if key in self.dep_state:
self.transition_dep(key, "memory", value=value)

if key in self.task_refs:
self.task_refs[key] += 1
else:
self.task_refs[key] = 1

self.log.append((key, "receive-from-scatter"))

if report:
Expand All @@ -1308,8 +1314,17 @@ def update_data(self, comm=None, data=None, report=True, serializers=None):
return info

async def delete_data(self, comm=None, keys=None, report=True):
keys = list(keys)
if keys:
for key in list(keys):
for key in keys:
if key in self.task_refs:
self.task_refs[key] -= 1
if self.task_refs[key] > 0:
keys.remove(key)
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continue
else:
del self.task_refs[key]

self.log.append((key, "delete"))
if key in self.task_state:
self.release_key(key)
Expand Down