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local log = require "util.logger".init("util.async");
local new_id = require "util.id".short;
local function checkthread()
local thread, main = coroutine.running();
if not thread or main then
error("Not running in an async context, see https://prosody.im/doc/developers/util/async");
end
return thread;
end
local function runner_continue(thread)
-- ASSUMPTION: runner is in 'waiting' state (but we don't have the runner to know for sure)
if coroutine.status(thread) ~= "suspended" then -- This should suffice
log("warn", "unexpected async state: thread not suspended");
return false;
end
local ok, state, runner = coroutine.resume(thread);
if not ok then
-- Running the coroutine failed, which means we have to find the runner manually,
-- in order to inform the error handler
local level = 0;
while debug.getinfo(thread, level, "") do level = level + 1; end
ok, runner = debug.getlocal(thread, level-1, 1);
local error_handler = runner.watchers.error;
if error_handler then error_handler(runner, debug.traceback(thread, state)); end
elseif state == "ready" then
-- If state is 'ready', it is our responsibility to update runner.state from 'waiting'.
-- We also have to :run(), because the queue might have further items that will not be
-- processed otherwise. FIXME: It's probably best to do this in a nexttick (0 timer).
runner.state = "ready";
runner:run();
end
return true;
end
local function waiter(num)
local thread = checkthread();
num = num or 1;
local waiting;
return function ()
if num == 0 then return; end -- already done
waiting = true;
coroutine.yield("wait");
end, function ()
num = num - 1;
if num == 0 and waiting then
runner_continue(thread);
elseif num < 0 then
error("done() called too many times");
end
end;
end
local function guarder()
local guards = {};
return function (id, func)
local thread = checkthread();
local guard = guards[id];
if not guard then
guard = {};
guards[id] = guard;
log("debug", "New guard!");
else
table.insert(guard, thread);
log("debug", "Guarded. %d threads waiting.", #guard)
coroutine.yield("wait");
end
local function exit()
local next_waiting = table.remove(guard, 1);
if next_waiting then
log("debug", "guard: Executing next waiting thread (%d left)", #guard)
runner_continue(next_waiting);
else
log("debug", "Guard off duty.")
guards[id] = nil;
end
end
if func then
func();
exit();
return;
end
return exit;
end;
end
local runner_mt = {};
runner_mt.__index = runner_mt;
local function runner_create_thread(func, self)
local thread = coroutine.create(function (self) -- luacheck: ignore 432/self
while true do
func(coroutine.yield("ready", self));
end
end);
assert(coroutine.resume(thread, self)); -- Start it up, it will return instantly to wait for the first input
return thread;
end
local empty_watchers = {};
local function runner(func, watchers, data)
return setmetatable({ func = func, thread = false, state = "ready", notified_state = "ready",
queue = {}, watchers = watchers or empty_watchers, data = data, id = new_id() }
, runner_mt);
end
-- Add a task item for the runner to process
function runner_mt:run(input)
if input ~= nil then
self:log("debug", "queued new work item, %d items queued", #self.queue);
table.insert(self.queue, input);
end
if self.state ~= "ready" then
-- The runner is busy. Indicate that the task item has been
-- queued, and return information about the current runner state
return true, self.state, #self.queue;
end
local q, thread = self.queue, self.thread;
if not thread or coroutine.status(thread) == "dead" then
self:log("debug", "creating new coroutine");
-- Create a new coroutine for this runner
thread = runner_create_thread(self.func, self);
self.thread = thread;
end
-- Process task item(s) while the queue is not empty, and we're not blocked
local n, state, err = #q, self.state, nil;
self.state = "running";
self:log("debug", "running main loop");
while n > 0 and state == "ready" do
local consumed;
-- Loop through queue items, and attempt to run them
for i = 1,n do
local queued_input = q[i];
local ok, new_state = coroutine.resume(thread, queued_input);
if not ok then
-- There was an error running the coroutine, save the error, mark runner as ready to begin again
consumed, state, err = i, "ready", debug.traceback(thread, new_state);
self.thread = nil;
break;
elseif new_state == "wait" then
-- Runner is blocked on waiting for a task item to complete
consumed, state = i, "waiting";
break;
end
end
-- Loop ended - either queue empty because all tasks passed without blocking (consumed == nil)
-- or runner is blocked/errored, and consumed will contain the number of tasks processed so far
if not consumed then consumed = n; end
-- Remove consumed items from the queue array
if q[n+1] ~= nil then
n = #q;
end
for i = 1, n do
q[i] = q[consumed+i];
end
n = #q;
end
-- Runner processed all items it can, so save current runner state
self.state = state;
if err or state ~= self.notified_state then
self:log("debug", "changed state from %s to %s", self.notified_state, err and "error" or state);
if err then
state = "error"
else
self.notified_state = state;
end
local handler = self.watchers[state];
if handler then handler(self, err); end
end
return true, state, n;
end
-- Add a task item to the queue without invoking the runner, even if it is idle
function runner_mt:enqueue(input)
table.insert(self.queue, input);
end
function runner_mt:log(level, fmt, ...)
return log(level, "[runner %s] "..fmt, self.id, ...);
end
return { waiter = waiter, guarder = guarder, runner = runner };
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