gistfile1.txt

function get_part(file_hash, part_number, quality, timeout)
    -- Trying to select the requested fragment
    local t = v.fragments_space.index.main:select(file_hash, part_number, quality)

    -- If it exists — returning immediately
    if t ~= nil then
        return t
    end

    -- Creating a key to identify the requested fragment, and an ipc channel, then writing it
    -- in a table in order to receive a “task completed” notification later
    local table_key = msgpack.encode{file_hash, part_number, quality}
    local ch = fiber.channel(1)
    v.ctable[table_key] = ch
 
    -- Creating a record about the fragment with the status “want to be converted”
    v.fragments_space:insert(file_hash, part_number, quality, STATUS_QUEUED)
 
    -- If we have idle workers, let’s notify them about the new task
    if s.waitch:has_readers() then
        s.waitch:put(true, 0)
    end
 
    -- Waiting for task completion for no more than “timeout” seconds
    local body = ch:get(timeout)

    if body ~= nil then
        if body == false then
            -- Couldn’t complete the task — return error
            return box.tuple.new{RET_ERROR}
        else
            -- Task completed, selecting and returning the result
            return v.fragments_space.index.main:select{file_hash, part_number, quality}
        end
    else
        -- Timeout error is returned
        return box.tuple.new{RET_ERROR}
    end
end
 
local table_key = msgpack.encode{file_hash, part_number, quality}
v.ctable[table_key]:put(true, 0)