--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_log_ringbuffer/mod_log_ringbuffer.lua	Thu Oct 15 16:47:21 2020 +0100
@@ -0,0 +1,85 @@
+module:set_global();
+
+local loggingmanager = require "core.loggingmanager";
+local format = require "util.format".format;
+local pposix = require "util.pposix";
+local rb = require "util.ringbuffer";
+
+local default_timestamp = "%b %d %H:%M:%S ";
+local max_chunk_size = module:get_option_number("log_ringbuffer_chunk_size", 16384);
+
+local os_date = os.date;
+
+local default_filename_template = "ringbuffer-logs-{pid}-{count}.log";
+local render_filename = require "util.interpolation".new("%b{}", function (s) return s; end, {
+	yyyymmdd = function (t)
+		return os_date("%Y%m%d", t);
+	end;
+	hhmmss = function (t)
+		return os_date("%H%M%S", t);
+	end;
+});
+
+local dump_count = 0;
+
+local function dump_buffer(buffer, filename)
+	dump_count = dump_count + 1;
+	local f, err = io.open(filename, "a+");
+	if not f then
+		module:log("error", "Unable to open output file: %s", err);
+		return;
+	end
+	local bytes_remaining = buffer:length();
+	f:write(("-- Dumping %d bytes at %s --\n"):format(bytes_remaining, os_date(default_timestamp)));
+	while bytes_remaining > 0 do
+		local chunk_size = math.min(bytes_remaining, max_chunk_size);
+		local chunk = buffer:read(chunk_size);
+		if not chunk then
+			f:write("-- Dump aborted due to error --\n\n");
+			f:close();
+			return;
+		end
+		f:write(chunk);
+		bytes_remaining = bytes_remaining - chunk_size;
+	end
+	f:write("-- End of dump --\n\n");
+	f:close();
+end
+
+local function get_filename(filename_template)
+	filename_template = filename_template or default_filename_template;
+	return render_filename(filename_template, {
+		paths = prosody.paths;
+		pid = pposix.getpid();
+		count = dump_count;
+		time = os.time();
+	});
+end
+
+local function ringbuffer_log_sink_maker(sink_config)
+	local buffer = rb.new(sink_config.size or 100*1024);
+
+	local timestamps = sink_config.timestamps;
+
+	if timestamps == true or timestamps == nil then
+		timestamps = default_timestamp; -- Default format
+	elseif timestamps then
+		timestamps = timestamps .. " ";
+	end
+
+	local function dump()
+		dump_buffer(buffer, get_filename(sink_config.filename));
+	end
+
+	if sink_config.signal then
+		require "util.signal".signal(sink_config.signal, dump);
+	elseif sink_config.event then
+		module:hook_global(sink_config.global_event, dump);
+	end
+
+	return function (name, level, message, ...)
+		buffer:write(format("%s%s\t%s\t%s\n", timestamps and os_date(timestamps) or "", name, level, format(message, ...)));
+	end;
+end
+
+loggingmanager.register_sink_type("ringbuffer", ringbuffer_log_sink_maker);