zachdaniel
6 years ago
committed by
Luke Imhoff
parent
e88fb5c999
commit
b02383a80b
@ -0,0 +1,106 @@ |
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defmodule Explorer.Counters.AverageBlockTime do |
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use GenServer |
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@moduledoc """ |
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Caches the number of token holders of a token. |
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""" |
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import Ecto.Query, only: [from: 2] |
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alias Explorer.Chain.Block |
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alias Explorer.Repo |
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alias Timex.Duration |
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@doc """ |
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Starts a process to periodically update the counter of the token holders. |
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""" |
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@spec start_link(term()) :: GenServer.on_start() |
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def start_link(_) do |
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GenServer.start_link(__MODULE__, :ok, name: __MODULE__) |
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end |
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def average_block_time(block \\ nil) do |
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enabled? = |
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:explorer |
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|> Application.fetch_env!(__MODULE__) |
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|> Keyword.fetch!(:enabled) |
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if enabled? do |
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block = if block, do: {block.number, DateTime.to_unix(block.timestamp)} |
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GenServer.call(__MODULE__, {:average_block_time, block}) |
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else |
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{:error, :disabled} |
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end |
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end |
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## Server |
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@impl true |
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def init(_) do |
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timestamps_query = |
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from(block in Block, |
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limit: 100, |
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offset: 1, |
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order_by: [desc: block.number], |
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select: {block.number, block.timestamp} |
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) |
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timestamps = |
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timestamps_query |
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|> Repo.all() |
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|> Enum.map(fn {number, timestamp} -> |
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{number, DateTime.to_unix(timestamp)} |
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end) |
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{:ok, %{timestamps: timestamps, average: average_distance(timestamps)}} |
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end |
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@impl true |
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def handle_call({:average_block_time, nil}, _from, %{average: average} = state), do: {:reply, average, state} |
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def handle_call({:average_block_time, block}, _from, state) do |
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state = add_block(state, block) |
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{:reply, state.average, state} |
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end |
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# This is pretty naive, but we'll only ever be sorting 100 dates so I don't think |
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# complex logic is really necessary here. |
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defp add_block(%{timestamps: timestamps} = state, block) do |
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timestamps = |
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[block | timestamps] |
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|> Enum.sort_by(fn {number, _} -> number end, &Kernel.>/2) |
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|> Enum.take(100) |
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%{state | timestamps: timestamps, average: average_distance(timestamps)} |
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end |
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defp average_distance([]), do: Duration.from_seconds(0) |
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defp average_distance([_]), do: Duration.from_seconds(0) |
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defp average_distance(timestamps) do |
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durations = durations(timestamps) |
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{sum, count} = |
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Enum.reduce(durations, {0, 0}, fn duration, {sum, count} -> |
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{sum + duration, count + 1} |
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end) |
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average = sum / count |
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average |
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|> round() |
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|> Duration.from_seconds() |
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end |
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defp durations(timestamps) do |
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timestamps |
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|> Enum.reduce({[], nil}, fn {_, timestamp}, {durations, last_timestamp} -> |
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if last_timestamp do |
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duration = last_timestamp - timestamp |
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{[duration | durations], timestamp} |
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else |
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{durations, timestamp} |
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end |
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end) |
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|> elem(0) |
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end |
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end |
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@ -0,0 +1,64 @@ |
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defmodule Explorer.Counters.AverageBlockTimeTest do |
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use Explorer.DataCase |
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alias Explorer.Counters.AverageBlockTime |
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defp block(number, last, duration), do: %{number: number, timestamp: Timex.shift(last, seconds: duration)} |
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setup do |
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start_supervised!(AverageBlockTime) |
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Application.put_env(:explorer, AverageBlockTime, enabled: true) |
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on_exit(fn -> |
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Application.put_env(:explorer, AverageBlockTime, enabled: false) |
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end) |
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end |
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describe "average_block_time/1" do |
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test "when disabled, it returns an error" do |
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Application.put_env(:explorer, AverageBlockTime, enabled: false) |
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assert AverageBlockTime.average_block_time() == {:error, :disabled} |
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end |
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test "without blocks duration is 0" do |
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assert AverageBlockTime.average_block_time() == Timex.Duration.parse!("PT0S") |
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end |
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test "with only one block, the duration is 0" do |
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now = Timex.now() |
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block = block(0, now, 0) |
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assert AverageBlockTime.average_block_time(block) == Timex.Duration.parse!("PT0S") |
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end |
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test "once there are two blocks, the duration is the average distance between them all" do |
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now = Timex.now() |
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block0 = block(0, now, 0) |
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block1 = block(1, now, 2) |
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block2 = block(2, now, 6) |
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AverageBlockTime.average_block_time(block0) |
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assert AverageBlockTime.average_block_time(block1) == Timex.Duration.parse!("PT2S") |
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assert AverageBlockTime.average_block_time(block2) == Timex.Duration.parse!("PT3S") |
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end |
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test "only the last 100 blocks are considered" do |
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now = Timex.now() |
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block0 = block(0, now, 0) |
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block1 = block(1, now, 2000) |
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AverageBlockTime.average_block_time(block0) |
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AverageBlockTime.average_block_time(block1) |
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for i <- 1..100 do |
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block = block(i + 1, now, 2000 + i) |
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AverageBlockTime.average_block_time(block) |
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end |
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assert AverageBlockTime.average_block_time() == Timex.Duration.parse!("PT1S") |
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end |
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end |
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end |
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