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add fix for thundering herd on initial connection pool setup #8 #9

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Merged
merged 3 commits into from
Mar 18, 2021
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add fix for thundering herd on initial connection pool setup #8 #9

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61b507f
add fix for thundering herd on initial connection pool setup #8
kevinlang Mar 18, 2021
0fdb559
rand_
kevinlang Mar 18, 2021
cecdc32
better match
kevinlang Mar 18, 2021
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18 changes: 14 additions & 4 deletions lib/ecto/adapters/sqlite3/connection.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -13,18 +13,28 @@ defmodule Ecto.Adapters.SQLite3.Connection do
import Ecto.Adapters.SQLite3.DataType

@parent_as __MODULE__
@connect_buffer 50
@idx_connect_buffer 5
@rand_connect_buffer 50

# db_connection eagerly obtains and holds the configured
# pool_size of connections, which can cause us to hit
# "SQLite Busy" issues. we solve this by making sure to wait
# a bit by hooking into the :configure callback opt and
# sleeping an amount of time which is a function of the pool_index
def handle_thundering_herd(opts) do
case Keyword.get(opts, :pool_index) do
idx when is_integer(idx) -> :timer.sleep(idx * @idx_connect_buffer)
nil -> :timer.sleep(:rand.uniform(@rand_connect_buffer))
end

def sleep(opts) do
:timer.sleep(:rand.uniform(@connect_buffer))
opts
end

defp default_opts(opts) do
# todo: we may want to consider wrapping any provided :configure
# with our custom connection buffering logic
opts
|> Keyword.put_new(:configure, {__MODULE__, :sleep, []})
|> Keyword.put_new(:configure, &handle_thundering_herd/1)
end

def start_link(opts) do
Expand Down