defmodule Oban.Engines.Lite do
@moduledoc """
An engine for running Oban with SQLite3.
## Usage
Start an `Oban` instance using the `Lite` engine:
Oban.start_link(
engine: Oban.Engines.Lite,
queues: [default: 10],
repo: MyApp.Repo
)
"""
@behaviour Oban.Engine
import DateTime, only: [utc_now: 0]
import Ecto.Query
alias Ecto.Changeset
alias Oban.Engines.Basic
alias Oban.{Engine, Job, Repo}
@forever 60 * 60 * 24 * 365 * 99
# EctoSQLite3 doesn't implement `push` for updates, so a json_insert is required.
defmacrop json_push(column, value) do
quote do
fragment("json_insert(?, '$[#]', ?)", unquote(column), unquote(value))
end
end
defmacrop json_contains(column, object) do
quote do
fragment(
"""
SELECT 0 NOT IN (SELECT json_extract(?, '$.' || t.key) = t.value FROM json_each(?) t)
""",
unquote(column),
unquote(object)
)
end
end
@impl Engine
defdelegate init(conf, opts), to: Basic
@impl Engine
defdelegate put_meta(conf, meta, key, value), to: Basic
@impl Engine
defdelegate check_meta(conf, meta, running), to: Basic
@impl Engine
defdelegate refresh(conf, meta), to: Basic
@impl Engine
defdelegate shutdown(conf, meta), to: Basic
@impl Engine
def insert_job(conf, %Changeset{} = changeset, _opts) do
with {:ok, job} <- fetch_unique(conf, changeset),
{:ok, job} <- resolve_conflict(conf, job, changeset) do
{:ok, %Job{job | conflict?: true}}
else
:not_found ->
Repo.insert(conf, changeset)
error ->
error
end
end
@impl Engine
defdelegate insert_all_jobs(conf, changesets, opts), to: Basic
@impl Engine
def fetch_jobs(_conf, %{paused: true} = meta, _running) do
{:ok, {meta, []}}
end
def fetch_jobs(_conf, %{limit: limit} = meta, running) when map_size(running) >= limit do
{:ok, {meta, []}}
end
def fetch_jobs(conf, meta, running) do
demand = meta.limit - map_size(running)
subset =
Job
|> select([:id])
|> where([j], j.state == "available")
|> where([j], j.queue == ^meta.queue)
|> where([j], j.attempt < j.max_attempts)
|> order_by([j], asc: j.priority, asc: j.scheduled_at, asc: j.id)
|> limit(^demand)
updates = [
set: [state: "executing", attempted_at: utc_now(), attempted_by: [meta.node]],
inc: [attempt: 1]
]
query =
Job
|> where([j], j.id in subquery(subset))
|> select([j, _], j)
jobs =
case Repo.update_all(conf, query, updates) do
{0, nil} -> []
{_count, jobs} -> jobs
end
{:ok, {meta, jobs}}
end
@impl Engine
defdelegate complete_job(conf, job), to: Basic
@impl Engine
defdelegate snooze_job(conf, job, seconds), to: Basic
@impl Engine
def discard_job(conf, job) do
query =
Job
|> where(id: ^job.id)
|> update([j],
set: [
state: "discarded",
discarded_at: ^utc_now(),
errors: json_push(j.errors, ^encode_unsaved(job))
]
)
Repo.update_all(conf, query, [])
:ok
end
@impl Engine
def error_job(conf, job, seconds) do
query =
Job
|> where(id: ^job.id)
|> update([j],
set: [
state: "retryable",
scheduled_at: ^seconds_from_now(seconds),
errors: json_push(j.errors, ^encode_unsaved(job))
]
)
Repo.update_all(conf, query, [])
:ok
end
@impl Engine
def cancel_job(conf, job) do
query = where(Job, id: ^job.id)
query =
if is_map(job.unsaved_error) do
update(query, [j],
set: [
state: "cancelled",
cancelled_at: ^utc_now(),
errors: json_push(j.errors, ^encode_unsaved(job))
]
)
else
query
|> where([j], j.state not in ["cancelled", "completed", "discarded"])
|> update(set: [state: "cancelled", cancelled_at: ^utc_now()])
end
Repo.update_all(conf, query, [])
:ok
end
@impl Engine
def cancel_all_jobs(conf, queryable) do
base_query = where(queryable, [j], j.state not in ["cancelled", "completed", "discarded"])
# In SQLite3 an "UPDATE FROM" query returns the final value, not the original from a join. A
# separate query is needed to get the original state.
states_map =
base_query
|> select([j], {j.id, j.state})
|> then(&Repo.all(conf, &1))
|> Map.new()
query = select(base_query, [j], map(j, [:id, :queue, :state, :worker]))
jobs =
conf
|> Repo.update_all(query, set: [state: "cancelled", cancelled_at: utc_now()])
|> elem(1)
|> Enum.map(fn job -> %{job | state: Map.fetch!(states_map, job.id)} end)
{:ok, jobs}
end
@impl Engine
def retry_job(conf, %Job{id: id}) do
retry_all_jobs(conf, where(Job, [j], j.id == ^id))
:ok
end
@impl Engine
def retry_all_jobs(conf, queryable) do
subquery = where(queryable, [j], j.state not in ["available", "executing"])
query =
Job
|> join(:inner, [j], x in subquery(subquery), on: j.id == x.id)
|> select([_, x], map(x, [:id, :queue, :state, :worker]))
|> update([j],
set: [
state: "available",
max_attempts: fragment("MAX(?, ? + 1)", j.max_attempts, j.attempt),
scheduled_at: ^utc_now(),
completed_at: nil,
cancelled_at: nil,
discarded_at: nil
]
)
{_, jobs} = Repo.update_all(conf, query, [])
{:ok, jobs}
end
# Insertion
defp fetch_unique(conf, %{changes: %{unique: %{} = unique}} = changeset) do
%{fields: fields, keys: keys, period: period, states: states} = unique
keys = Enum.map(keys, &to_string/1)
states = Enum.map(states, &to_string/1)
since = seconds_from_now(min(period, @forever) * -1)
dynamic =
Enum.reduce(fields, true, fn
field, acc when field in [:args, :meta] ->
value =
changeset
|> Changeset.get_field(field)
|> map_values(keys)
if value == %{} do
dynamic([j], field(j, ^field) == ^value and ^acc)
else
dynamic([j], json_contains(field(j, ^field), ^Jason.encode!(value)) and ^acc)
end
field, acc ->
value = Changeset.get_field(changeset, field)
dynamic([j], field(j, ^field) == ^value and ^acc)
end)
query =
Job
|> where([j], j.state in ^states)
|> where([j], fragment("datetime(?) >= datetime(?)", j.inserted_at, ^since))
|> where(^dynamic)
|> limit(1)
case Repo.one(conf, query) do
nil -> :not_found
job -> {:ok, job}
end
end
defp fetch_unique(_conf, _changeset), do: :not_found
defp map_values(value, []), do: value
defp map_values(value, keys) do
for {key, val} <- value, str_key = to_string(key), str_key in keys, into: %{} do
{str_key, val}
end
end
defp resolve_conflict(conf, job, changeset) do
case Changeset.fetch_change(changeset, :replace) do
{:ok, replace} ->
keys = Keyword.get(replace, String.to_existing_atom(job.state), [])
Repo.update(conf, Changeset.change(job, Map.take(changeset.changes, keys)))
:error ->
{:ok, job}
end
end
defp seconds_from_now(seconds), do: DateTime.add(utc_now(), seconds, :second)
defp encode_unsaved(job) do
job
|> Job.format_attempt()
|> Jason.encode!()
end
end
