benchmark: add a benchmark for working with multiple consumers

Related to #105
Follows up #85

t/benchmark/multi_consumer_work.lua

@@ -0,0 +1,90 @@
+#!/usr/bin/env tarantool
+
+local clock = require('clock')
+local os = require('os')
+local fiber = require('fiber')
+local queue = require('queue')
+
+-- Set the number of consumers.
+local consumers_count = 100
+-- Set the number of tasks processed by one consumer per iteration.
+local batch_size = 100
+
+local barrier = fiber.cond()
+local wait_count = 0
+
+box.cfg()
+
+local test_queue = queue.create_tube('test_queue', 'fifo', {temporary = true})
+
+local function prepare_consumers()
+    local consumers = {}
+
+    for i = 1, consumers_count do
+        consumers[i] = fiber.new(function()
+            wait_count = wait_count + 1
+            -- Wait for all consumers to start.
+            barrier:wait()
+
+            -- Create test tasks.
+            for j = 1, batch_size do
+                test_queue:put('test, cons: ' .. i)
+            end
+
+            wait_count = wait_count + 1
+            -- Wait for all consumers to create tasks.
+            barrier:wait()
+
+            -- Ack the tasks.
+            for j = 1, batch_size do
+                local task = test_queue:take()
+                test_queue:ack(task[1])
+            end
+
+            wait_count = wait_count + 1
+        end)
+    end
+
+    return consumers
+end
+
+local function multi_consumer_bench()
+    --- Wait for all consumer fibers.
+    local wait_all = function()
+        while (wait_count ~= consumers_count) do
+            fiber.yield()
+        end
+        wait_count = 0
+    end
+
+    -- Wait for all consumers to start.
+    local consumers = prepare_consumers()
+    wait_all()
+
+    -- Start timing creation of tasks.
+    local start_put_time = clock.proc64()
+    barrier:broadcast()
+    -- Wait for all consumers to create tasks.
+    wait_all()
+    -- Complete timing creation of tasks.
+    local start_ack_time = clock.proc64()
+    barrier:broadcast()
+    -- Wait for all tasks to be acked.
+    wait_all()
+    -- Complete the timing of task confirmation.
+    local complete_time = clock.proc64()
+
+    --Print the result in microseconds
+    print("Time it takes to fill the queue: " ..
+        tostring((start_ack_time - start_put_time) / 10^3))
+    print("Time it takes to confirm the tasks: " ..
+        tostring((complete_time - start_ack_time) / 10^3))
+end
+
+-- Start benchmark.
+multi_consumer_bench()
+
+-- Cleanup.
+test_queue:drop()
+
+os.exit(0)