How to evaluate load balancing performance parameters ？

At present , In the demand environment dominated by cloud computing and big data , Load balancing and application delivery have been developed for large enterprise data centers “ Escort ” It's a must-have for you . however , Load balancing as a comparison “ novel ” The equipment , Although its main functions are well known to relevant demand persons , But its various performance indicators are “ The flowers are getting more and more attractive ”, Most people think for a long time, so .

that , From what aspects should the performance indicators of load balancing products be evaluated ？ The editor specially interviewed Mr. Yu Zhenbo, product director of Taiyi Xingchen, a domestic emerging application delivery enterprise . meanwhile , Not long ago, a batch of self-developed application delivery products passed the centralized purchase test of Unicom . As a top domestic operator , Unicom is very professional in testing the main functions and performance indicators of load balancing products . thus , Yu Zhenbo also made an in-depth interpretation of the performance parameters of load balancing in combination with Unicom's centralized purchase test .

Yu Zhenbo said , There are three main dimensions to evaluate the performance parameters of load balancing equipment , They are four / Layer 7 throughput 、 The rate of the maximum number of concurrent connections and the number of new connections in the fourth layer , The specific indicators of these three dimensions determine the performance effect of load balancing products .

One 、 Four / Layer 7 throughput , No more watching throughput, It depends on HTTPGoodput

1. What is throughput

Measuring the performance of load balancing products is the most common , The most basic indicator is “ throughput ”, This concept applies to routing devices 、 Firewall and other network equipment .

What is? “ throughput ”？ Simply speaking , We can think of the load equipment as a pipe , The maximum flow that can pass through the pipeline in unit time is the throughput . therefore , The larger the flow that can pass per unit time , It means that the processing capacity of the load balancing device is higher . The so-called “ Four / Seven layer throughput ”, That is, when you turn on the four layer function and the seven layer function , Processing capacity of the equipment .

2. Standard measurement method of throughput

There are standard test methods for throughput , Traditional router 、 Firewalls are tested in different sizes per unit time UDP Data package to measure product performance , That's what we usually say “throughput”. However, this indicator has been applied to load balancing products “ Out of style ” 了 .

In the Unicom test , Operators use a more “ Strictly ” To consider the performance of load balancing products ——“HTTP Effective throughput (HTTPGoodput)”. because UDP The transmission of is too simple , It is far from the actual processing capacity of the equipment , In the real network , Most of the application protocols are through TCP Transmission of ,TCP The agreement has a more complex negotiation process , As a load balancing device closely combined with Applications , Traditional firewall UDP Throughput is not critical , The real ability to deal with application layer protocols is to see “ Zhenzhang ” The place of .

In the actual test , Operators will use professional test instruments to simulate real customers to launch HTTP request , After passing the load equipment , The simulation server will respond , In the process , Continue to increase the number of simulation clients , Until the load equipment appears and cannot be handled in time 、 Connection failure or response timeout 、 The maximum that can be handled without failure recorded on the test instrument HTTP Until the transmission traffic statistics .

With the traditional UDP Compared with throughput ,HTTP Effective throughput is closer to the actual environment in measuring the performance of load devices , Also more strict .

Two 、 Maximum number of concurrent connections

if , The throughput index measures a pipeline , Then the maximum number of concurrent connections is equivalent to one “ A bottle of water ”, The so-called maximum concurrent connection refers to what this bottle can hold “ water ” The capacity of , That is, the maximum number of connections that the load equipment can maintain .

Testing for concurrent connections , The tester needs to simulate HTTP The client sends connection requests to the load device at a certain rate , And keep the connection uninterrupted . In this process, gradually increase the number of connections , Until the load device fails to process , Then count the maximum number of connections that the load equipment can carry .

Although this parameter is important , But it was not deliberately emphasized in the Unicom test . The reason is simple , This indicator only depends on the memory capacity of the device , To put it bluntly , The number of concurrent connections is determined by the size of memory , And now the number of memory devices can carry connections has already exceeded most practical scenarios .

3、 ... and 、 The number and rate of new connections on the fourth floor (L4 CPS)

In the Unicom test , The new connection rate per second of the fourth layer is highly valued , The concept of connection is also strictly defined ： There needs to be three complete handshakes (SYN,ACK/SYN,ACK), once HTTP The request and response of , as well as TCP Connection closed (FIN,ACK,FIN,ACK) The process —— This operation is to simulate the actual application as much as possible .

Four layer connection rate , It is to send connection requests to devices at the highest possible rate , After completing the connection data transmission , And quickly close the connection , To avoid the impact of packet size on the final result , The data transmitted by the connection is set to 64 byte , Unicom system fully tests the number of connections that the equipment can handle per second in this way . For operator users , This indicator is very important for application delivery products to cope with sudden large number of connections . It's a bit like the subway entrance around us , Although the subway transportation capacity is very strong , But if the entrance repair is too small , During rush hours, many passengers still can't walk in smoothly ！