ExGitEngine.
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Runs long jobs (packs, blame, ahead/behind counts, pushed pack indexing,
per-file patches) at most max_jobs at a time, outside the processes that
ask for them.
These jobs call dirty NIFs, and the VM has only as many dirty CPU schedulers
as cores, shared with every other NIF. Without a limit, a burst of blames on a
big repository would take all of them and stall every other diff. The default
max_jobs is one less than the dirty CPU schedulers, so one is always free.
Set it with config :ex_git_engine, max_jobs: n.
Waiting jobs are dropped when their caller has exited before they start, so a page the user left does not still cost a blame.
Like a busy port, the limiter turns work away when its queue reaches
high_water (default 10 * max_jobs): callers get {:error, :busy} at once
instead of waiting until they time out. It accepts work again once the queue
has drained to low_water (default high_water / 2). Both can be set with
config :ex_git_engine, high_water: n, low_water: n.
Started by ExGitEngine.Application. GitAgent sends its long operations
here; run/3 is the same for any other function:
ExGitEngine.JobLimiter.run(fn -> expensive() end)Summary
Functions
Returns a specification to start this module under a supervisor.
Returns the number of jobs waiting for a slot.
Runs fun once a slot is free and returns its result. A job that raises
returns {:error, exception}, one that throws or exits {:error, {kind, reason}};
{:error, :busy} means the queue is full.
Returns the number of jobs running.
Starts a limiter. Options: :name (default ExGitEngine.JobLimiter, nil
for none), :max_jobs, :high_water and :low_water.
Like run/3, but answers from (a GenServer.from() received by another
server) instead of the caller, so that server can return {:noreply, ...}.
Types
@type server() :: GenServer.server()
Functions
Returns a specification to start this module under a supervisor.
See Supervisor.
@spec queued(server()) :: non_neg_integer()
Returns the number of jobs waiting for a slot.
@spec run(server(), (-> result), timeout()) :: result | {:error, :busy | term()} when result: term()
Runs fun once a slot is free and returns its result. A job that raises
returns {:error, exception}, one that throws or exits {:error, {kind, reason}};
{:error, :busy} means the queue is full.
@spec running(server()) :: non_neg_integer()
Returns the number of jobs running.
@spec start_link(keyword()) :: GenServer.on_start()
Starts a limiter. Options: :name (default ExGitEngine.JobLimiter, nil
for none), :max_jobs, :high_water and :low_water.
@spec submit(server(), GenServer.from(), (-> term())) :: :ok
Like run/3, but answers from (a GenServer.from() received by another
server) instead of the caller, so that server can return {:noreply, ...}.