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simplify event pulling #1801

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merged 5 commits into from
Dec 11, 2020
Merged

simplify event pulling #1801

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f0bd187
simplify event pulling
Dec 10, 2020
8fbc8fe
Update core_test.exs
Dec 10, 2020
2e5fe02
Update ethereum_event_listener.ex
Dec 10, 2020
f21fe8c
Update core.ex
Dec 10, 2020
19dbc39
Merge branch 'master' into inomurko/simplify_event_pulling
Dec 11, 2020
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31 changes: 16 additions & 15 deletions apps/omg/lib/omg/ethereum_event_listener.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -146,7 +146,7 @@ defmodule OMG.EthereumEventListener do

case RootChainCoordinator.get_sync_info() do
:nosync ->
:ok = RootChainCoordinator.check_in(Core.get_height_to_check_in(state), state.service_name)
:ok = RootChainCoordinator.check_in(state.synced_height, state.service_name)
{:ok, _} = schedule_get_events(state.ethereum_events_check_interval_ms)
{:noreply, {state, callbacks}}

Expand All @@ -158,31 +158,32 @@ defmodule OMG.EthereumEventListener do
end

# see `handle_info/2`, clause for `:sync`
@decorate span(service: :ethereum_event_listener, type: :backend, name: "sync_height/2")
@decorate span(service: :ethereum_event_listener, type: :backend, name: "sync_height/3")
defp sync_height(state, callbacks, sync_guide) do
{:ok, events, db_updates, height_to_check_in, new_state} =
Core.get_events_range_for_download(state, sync_guide)
|> maybe_update_event_cache(callbacks.get_ethereum_events_callback)
|> Core.get_events(sync_guide.sync_height)
{events, new_state} =
state
|> Core.calc_events_range_set_height(sync_guide)
|> get_events(callbacks.get_ethereum_events_callback)

:ok = :telemetry.execute([:process, __MODULE__], %{events: events}, state)
db_update = [{:put, new_state.synced_height_update_key, new_state.synced_height}]
:ok = :telemetry.execute([:process, __MODULE__], %{events: events}, new_state)

{:ok, db_updates_from_callback} = callbacks.process_events_callback.(events)
:ok = publish_events(events)
:ok = OMG.DB.multi_update(db_updates ++ db_updates_from_callback)
:ok = RootChainCoordinator.check_in(height_to_check_in, state.service_name)
:ok = OMG.DB.multi_update(db_update ++ db_updates_from_callback)
:ok = RootChainCoordinator.check_in(new_state.synced_height, new_state.service_name)

new_state
end

@decorate span(service: :ethereum_event_listener, type: :backend, name: "maybe_update_event_cache/2")
defp maybe_update_event_cache({:get_events, {from, to}, %Core{} = state}, get_ethereum_events_callback) do
{:ok, new_events} = get_ethereum_events_callback.(from, to)
Core.add_new_events(state, new_events)
defp get_events({{from, to}, state}, get_events_callback) do
{:ok, new_events} = get_events_callback.(from, to)
{new_events, state}
end

@decorate span(service: :ethereum_event_listener, type: :backend, name: "maybe_update_event_cache/2")
defp maybe_update_event_cache({:dont_fetch_events, %Core{} = state}, _callback), do: state
defp get_events({:dont_fetch_events, state}, _callback) do
{[], state}
end

defp schedule_get_events(ethereum_events_check_interval_ms) do
:timer.send_after(ethereum_events_check_interval_ms, self(), :sync)
Expand Down
121 changes: 32 additions & 89 deletions apps/omg/lib/omg/ethereum_event_listener/core.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -28,29 +28,22 @@ defmodule OMG.EthereumEventListener.Core do

use Spandex.Decorators

# synced_height is what's being exchanged with `RootChainCoordinator`.
# The point in root chain until where it processed
defstruct synced_height_update_key: nil,
service_name: nil,
# what's being exchanged with `RootChainCoordinator` - the point in root chain until where it processed
synced_height: 0,
ethereum_events_check_interval_ms: nil,
cached: %{
data: [],
request_max_size: 1000,
# until which height the events have been pulled and cached
events_upper_bound: 0
}
request_max_size: 1000

@type event :: %{eth_height: non_neg_integer()}

@type t() :: %__MODULE__{
synced_height_update_key: atom(),
service_name: atom(),
cached: %{
data: list(event),
request_max_size: pos_integer(),
events_upper_bound: non_neg_integer()
},
ethereum_events_check_interval_ms: non_neg_integer()
synced_height: integer(),
ethereum_events_check_interval_ms: non_neg_integer(),
request_max_size: pos_integer()
}

@doc """
Expand All @@ -70,89 +63,39 @@ defmodule OMG.EthereumEventListener.Core do
synced_height_update_key: update_key,
synced_height: last_synced_ethereum_height,
service_name: service_name,
cached: %{
data: [],
request_max_size: request_max_size,
events_upper_bound: last_synced_ethereum_height
},
request_max_size: request_max_size,
ethereum_events_check_interval_ms: ethereum_events_check_interval_ms
}

{initial_state, get_height_to_check_in(initial_state)}
{initial_state, last_synced_ethereum_height}
end

@doc """
Provides a uniform way to get the height to check in.
Returns the events range -
- from (inclusive!),
- to (inclusive!)
that needs to be scraped and sets synced_height in the state.

Every call to RootChainCoordinator.check_in should use value taken from this, after all mutations to the state
"""
@spec get_height_to_check_in(t()) :: non_neg_integer()
def get_height_to_check_in(%__MODULE__{synced_height: synced_height}), do: synced_height

@doc """
Returns range Ethereum height to download
"""
@decorate span(service: :ethereum_event_listener, type: :backend, name: "get_events_range_for_download/2")
@spec get_events_range_for_download(t(), SyncGuide.t()) ::
{:dont_fetch_events, t()} | {:get_events, {non_neg_integer, non_neg_integer}, t()}
def get_events_range_for_download(%__MODULE__{cached: %{events_upper_bound: upper}} = state, %SyncGuide{
sync_height: sync_height
})
when sync_height <= upper,
do: {:dont_fetch_events, state}

@decorate span(service: :ethereum_event_listener, type: :backend, name: "get_events_range_for_download/2")
def get_events_range_for_download(
%__MODULE__{
cached: %{request_max_size: request_max_size, events_upper_bound: old_upper_bound} = cached_data
} = state,
%SyncGuide{root_chain_height: root_chain_height, sync_height: sync_height}
) do
# grab as much as allowed, but not higher than current root_chain_height and at least as much as needed to sync
# NOTE: both root_chain_height and sync_height are assumed to have any required finality margins applied by caller
next_upper_bound =
min(root_chain_height, old_upper_bound + request_max_size)
|> max(sync_height)

new_state = %__MODULE__{
state
| cached: %{cached_data | events_upper_bound: next_upper_bound}
}

{:get_events, {old_upper_bound + 1, next_upper_bound}, new_state}
end

@doc """
Stores the freshly fetched ethereum events into a memory-cache
"""
@decorate span(service: :ethereum_event_listener, type: :backend, name: "add_new_events/2")
@spec add_new_events(t(), list(event)) :: t()
def add_new_events(
%__MODULE__{cached: %{data: data} = cached_data} = state,
new_events
) do
%__MODULE__{state | cached: %{cached_data | data: data ++ new_events}}
end

@doc """
Pop some ethereum events stored in the memory-cache, up to a certain height
"""
@decorate span(service: :ethereum_event_listener, type: :backend, name: "get_events/2")
@spec get_events(t(), non_neg_integer) :: {:ok, list(event), list(), non_neg_integer, t()}
def get_events(
%__MODULE__{synced_height_update_key: update_key, cached: %{data: data}} = state,
new_sync_height
) do
{events, new_data} = Enum.split_while(data, fn %{eth_height: height} -> height <= new_sync_height end)

new_state =
state
|> Map.update!(:synced_height, &max(&1, new_sync_height))
|> Map.update!(:cached, &%{&1 | data: new_data})
|> struct!()

height_to_check_in = get_height_to_check_in(new_state)
db_update = [{:put, update_key, height_to_check_in}]
{:ok, events, db_update, height_to_check_in, new_state}
@decorate span(service: :ethereum_event_listener, type: :backend, name: "calc_events_range_set_height/2")
@spec calc_events_range_set_height(t(), SyncGuide.t()) ::
{:dont_fetch_events, t()} | {{non_neg_integer, non_neg_integer}, t()}
def calc_events_range_set_height(state, sync_guide) do
case sync_guide.sync_height <= state.synced_height do
true ->
{:dont_fetch_events, state}

_ ->
# if sync_guide.sync_height has applied margin (reorg protection)
# the only thing we need to be aware of is that we don't go pass that!
# but we want to move as fast as possible so we try to fetch as much as we can (request_max_size)
first_not_visited = state.synced_height + 1
# if first not visited = 1, and request max size is 10
# it means we can scrape AT MOST request_max_size events
max_height = state.request_max_size - 1
upper_bound = min(sync_guide.sync_height, first_not_visited + max_height)

{{first_not_visited, upper_bound}, %{state | synced_height: upper_bound}}
end
end
end
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