aboutsummaryrefslogtreecommitdiffstats
path: root/util/async.lua
blob: a07226debd6d626e75b8ef683f204b1f8f703565 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
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
		local err = state;
		-- Running the coroutine failed, which means we have to find the runner manually,
		-- in order to inform the error handler
		local level = 0;
		-- Find the 'level' of the top-most function (0 == current level, 1 == caller, ...)
		while debug.getinfo(thread, level, "") do level = level + 1; end
		ok, runner = debug.getlocal(thread, level-1, 1);
		if ok ~= "self" or runner.thread ~= thread then
			log("warn", "unexpected async state: unable to locate runner during error handling, got %s", ok);
			return false;
		end
		local error_handler = runner.watchers.error;
		if error_handler then error_handler(runner, debug.traceback(thread, err)); end
		runner.state, runner.thread = "ready", nil;
		return runner:run();
	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
		table.insert(self.queue, input);
		self:log("debug", "queued new work item, %d items queued", #self.queue);
	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" and not err 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 ("..state..")") 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
	if n > 0 then
		return self:run();
	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);
	self:log("debug", "queued new work item, %d items queued", #self.queue);
end

function runner_mt:log(level, fmt, ...)
	return log(level, "[runner %s] "..fmt, self.id, ...);
end

return { waiter = waiter, guarder = guarder, runner = runner };