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counters for cache stats #5127

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counters for cache stats #5127

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4943212
counters for cache stats
ruslandoga Feb 27, 2025
0e2d286
return license check
ruslandoga Feb 27, 2025
86905c5
Merge branch 'master' into counters
ruslandoga Mar 3, 2025
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6 changes: 4 additions & 2 deletions lib/plausible/application.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,6 @@ defmodule Plausible.Application do
children =
[
Plausible.Session.BalancerSupervisor,
Plausible.Cache.Stats,
Plausible.PromEx,
{Plausible.Auth.TOTP.Vault, key: totp_vault_key()},
Plausible.Repo,
Expand Down Expand Up @@ -126,7 +125,10 @@ defmodule Plausible.Application do
Plausible.Ingestion.Source.init()
Plausible.Geo.await_loader()

Supervisor.start_link(List.flatten(children), opts)
with {:ok, _pid} = ok <- Supervisor.start_link(List.flatten(children), opts) do
Plausible.Cache.Stats.attach()
ok
end
end

def config_change(changed, _new, removed) do
Expand Down
1 change: 1 addition & 0 deletions lib/plausible/cache/adapter.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ defmodule Plausible.Cache.Adapter do
cache_name = Keyword.get(opts, :cache_name, name)
child_id = Keyword.get(opts, :child_id, child_id)
ttl_check_interval = Keyword.get(opts, :ttl_check_interval, false)
Plausible.Cache.Stats.create_counters(cache_name)

opts =
opts
Expand Down
48 changes: 15 additions & 33 deletions lib/plausible/cache/stats.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -3,28 +3,13 @@ defmodule Plausible.Cache.Stats do
Keeps track of hit/miss ratio for various caches.
"""

use GenServer

@hit :hit
@miss :miss
@telemetry_hit ConCache.Operations.telemetry_hit()
@telemetry_miss ConCache.Operations.telemetry_miss()
@telemetry_events [@telemetry_hit, @telemetry_miss]

def start_link(_opts) do
GenServer.start_link(__MODULE__, nil)
end

def init(nil) do
__MODULE__ =
:ets.new(__MODULE__, [
:public,
:named_table,
:set,
read_concurrency: true,
write_concurrency: true
])

def attach do
:telemetry.attach_many(
"plausible-cache-stats",
@telemetry_events,
Expand All @@ -35,6 +20,16 @@ defmodule Plausible.Cache.Stats do
{:ok, nil}
end

def create_counters(cache_name) do
:persistent_term.put({__MODULE__, cache_name, @hit}, :counters.new(1, []))
:persistent_term.put({__MODULE__, cache_name, @miss}, :counters.new(1, []))
end

defp counter(cache_name, type) do
:persistent_term.get({__MODULE__, cache_name, type}, nil) ||
raise "counter not found for #{cache_name} #{type}"
end
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This is all very quick and dirty. The API can be improved if this works out.


def handle_telemetry_event(@telemetry_hit, _measurments, %{cache: %{name: cache_name}}, _) do
bump(cache_name, @hit)
end
Expand All @@ -54,12 +49,7 @@ defmodule Plausible.Cache.Stats do
defdelegate size(cache_name), to: Plausible.Cache.Adapter

def bump(cache_name, type) do
:ets.update_counter(
__MODULE__,
{cache_name, type},
1,
{{cache_name, type}, 0}
)
:counters.add(counter(cache_name, type), 1, 1)
end

def hit_rate(cache_name) do
Expand All @@ -68,23 +58,15 @@ defmodule Plausible.Cache.Stats do
|> Enum.reduce(
%{hit: 0, miss: 0, hit_miss: 0.0},
fn name, acc ->
hit =
acc.hit + :ets.lookup_element(__MODULE__, {name, @hit}, 2, 0)

miss =
acc.miss + :ets.lookup_element(__MODULE__, {name, @miss}, 2, 0)

hit = acc.hit + :counters.get(counter(name, @hit), 1)
miss = acc.miss + :counters.get(counter(name, @miss), 1)
hit_miss = hit + miss

hit_miss = if(hit_miss == 0, do: 0.0, else: hit / hit_miss * 100)

acc
|> Map.put(:hit, hit)
|> Map.put(:miss, miss)
|> Map.put(
:hit_miss,
hit_miss
)
|> Map.put(:hit_miss, hit_miss)
end
)
|> Map.fetch!(:hit_miss)
Expand Down
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