Graham McIntire
d67186176f
Type spec fixes: - duct_usable_* return boolean→float (delegate to duct_usable_for_band) - sanitize/1 spec includes :unicode error tuples - match_delete/1 broadened from :ets.match_spec() - telemetry_event local type replaces :telemetry.event/0 - wgrib2 parse_lon_val_segment corrected to tuple spec - preloaded Ecto assoc types in get_mission/get_contact! specs Unmatched returns: - _ = prefix on Task.start, Oban.insert, Repo.query!, PubSub.subscribe, :ets.new, and if-expression returns across 18 files Pattern match fixes: - markdown: restructure acc!=[] guard as direct pattern match - path_compute/pskr/skewt_location_resolver: remove dead clauses - calibrate.aprs_144: remove unreachable format_float catch-all - unused.ex: suppress MapSet.union no_opaque Also: remove unused unicode_util_compat from mix.lock
117 lines
3.3 KiB
Elixir
117 lines
3.3 KiB
Elixir
defmodule Microwaveprop.Cache do
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@moduledoc """
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Tiny ETS-backed TTL cache for values that are expensive to compute but
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tolerate short staleness. Used for things like `Repo.aggregate` counts that
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would otherwise run on every page load.
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Not a replacement for `Microwaveprop.Propagation.ScoreCache` or
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`Microwaveprop.Weather.NexradCache` — those have bespoke invalidation logic
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driven by PubSub. This module is for generic time-boxed memoization.
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"""
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use GenServer
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@table :microwaveprop_cache
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@sweep_interval_ms to_timeout(minute: 1)
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@spec start_link(keyword()) :: GenServer.on_start()
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def start_link(opts) do
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GenServer.start_link(__MODULE__, opts, name: __MODULE__)
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end
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@doc """
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Return the cached value for `key` if it's still fresh, otherwise invoke
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`fun`, store the result with `ttl_ms` lifetime, and return it.
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"""
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@spec fetch_or_store(term(), non_neg_integer(), (-> value)) :: value when value: term()
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def fetch_or_store(key, ttl_ms, fun) when is_function(fun, 0) do
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now = System.monotonic_time(:millisecond)
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case :ets.lookup(@table, key) do
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[{_, value, expires_at}] when expires_at > now ->
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value
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_ ->
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value = fun.()
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:ets.insert(@table, {key, value, now + ttl_ms})
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value
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end
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end
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@doc "Insert `value` directly, overwriting any existing entry for `key`."
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@spec put(term(), term(), integer()) :: :ok
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def put(key, value, ttl_ms) do
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:ets.insert(@table, {key, value, System.monotonic_time(:millisecond) + ttl_ms})
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:ok
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end
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@doc "Remove `key` from the cache, forcing the next fetch to recompute."
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@spec invalidate(term()) :: :ok
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def invalidate(key) do
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:ets.delete(@table, key)
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:ok
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end
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@doc """
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Delete every entry matching a match pattern. The pattern follows
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`ets:match_delete/2` conventions — use `:"_"` for wildcards.
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Prefer `invalidate/1` for single-key deletions; use this when you
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need to bulk-delete a family of keys without clearing the entire table.
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"""
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@spec match_delete(atom() | tuple()) :: :ok
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def match_delete(pattern) do
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:ets.match_delete(@table, pattern)
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:ok
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end
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@spec clear() :: :ok
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def clear do
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:ets.delete_all_objects(@table)
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:ok
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end
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@doc """
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Delete every entry whose TTL has elapsed. Returns the number of rows
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removed.
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Because TTL enforcement in `fetch_or_store/3` is lazy, keys minted
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dynamically (e.g. per-URL HRRR idx entries) would otherwise accumulate
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forever. A supervised timer calls this on an interval; tests can call
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it directly to avoid waiting on the timer.
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Uses `:ets.select_delete/2` so the sweep happens in a single BIF call
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without blocking concurrent readers or writers.
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"""
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@spec sweep() :: non_neg_integer()
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def sweep do
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now = System.monotonic_time(:millisecond)
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match_spec = [{{:_, :_, :"$1"}, [{:"=<", :"$1", now}], [true]}]
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:ets.select_delete(@table, match_spec)
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end
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@impl true
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def init(_opts) do
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_ =
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:ets.new(@table, [
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:set,
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:named_table,
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:public,
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read_concurrency: true,
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write_concurrency: true
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])
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schedule_sweep()
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{:ok, %{}}
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end
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@impl true
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def handle_info(:sweep, state) do
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_ = sweep()
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schedule_sweep()
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{:noreply, state}
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end
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defp schedule_sweep do
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Process.send_after(self(), :sweep, @sweep_interval_ms)
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end
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end
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