Top ten questions for senior Performance Test Engineer

A former colleague came to me yesterday , Do you have any interview questions for performance testing positions , Just before that, I helped the business team to meet with candidates for performance testing positions for several times , I listed some questions I would ask during the interview and the points to be investigated , For your reference .

• Introduce the recent projects , background 、 Expected indicators 、 System architecture 、 Scene design and performance problems encountered , Positioning analysis and optimization ;

Inspection point ：

• Knowledge of the project ;

• Requirements analysis and scenario design ideas ;

• Problem analysis ideas and optimized verification methods ;

Refer to the answer ：

• I recently made a XXX project , The background is old service refactoring , The expected target is to improve the performance of the original system 3 times , Architecture design is XXX. For this project, I sorted out the core applications and interfaces, including XXX individual , The corresponding scenarios are XXX, My pressure testing strategy is XXX. During the test XXX problem , The problem is XXX, adopt XXX( journal 、 Tools ) The reason is that XXX, The final optimization strategy is XXX, The optimized result is XXX.

• At what stage is the project suitable for performance test intervention , What's the reason ？

Inspection point ：

• Do you know enough about business iterations ;

• Ability to control, evaluate and analyze project quality ;

Refer to the answer ：

• This problem should be analyzed according to the project type and specific situation , Take our company as an example , The daily iteration frequency is XXX, Usually I am XXX Stage intervention performance test , The reason is XXX, The advantage of this is XXX;

• If it is an independent project or an inverted project , Then I think it should be in XXX Stage intervention , The reason for this is XXX, The advantage is XXX;

• There are also teams that are not very good at building performance testing systems , I suggest starting with XXX Start , then XXX, Try to balance the quality and input cost ;

• What factors should be considered in the design of performance test scenarios ？

Refer to the answer ：

• business model , Traffic model , Data model , Call relation, etc ;

• For a newly developed application , Performance test is required before going online , What factors would you consider ？

Refer to the answer ：

• Online configuration of the application ( How many cores and how many G);

• The amount of traffic to be undertaken after the launch ;

• The business type of this application （ Read / write cache or DB）;

• Introduce the monitoring and analysis tools you have used in your work , What are the characteristics of each ？

Inspection point ：

• Knowledge and mastery of tools ;

Refer to the answer ：

• The monitoring tools I often use are zabbix/Prometheus/grafana/skywalking, Use them to view XXX indicators ;

• The analysis tools I often use are arthas,jvm Built in command analysis tool , Use them separately XXX analysis ;

• I also know and have studied with myself XXX Tools , I find its characteristics are very suitable for XXX Type of problem analysis and troubleshooting ;

• Have you known about full link voltage measurement ？ Explain your understanding or practical experience ;

Inspection point ：

• Do you know and practice the cutting-edge technologies in the industry ;

• How to check CPU More thread consuming methods ;

Inspection point ：

• The investigation is right Linux Command familiarity ;

Refer to the answer ：

• top command ： find CPU% Highest process PID;

• top -H -p pid： View the threads under the process , Find the thread with the highest resource consumption pid;

• shell command ：
  printf
   
  ”%x\n“
   
  pid（%x, Express
   
  Hexadecimal ,\n It's line breaking ）;

• jstack analysis ：jstack pid ( Hexadecimal ) 1> xxx.tmp;

• introduce JVM The structure of heap memory ,YGC,FGC What is the principle of ？

Inspection point ：

• Yes JVM Understanding of principles and common factors affecting performance ;

Refer to the answer ：

• JVM Heap memory is mainly divided into new generation
  (Young Gen)
  、 Old age (Tenured Gen)、 Lasting generation (Perm Gen);

• The Cenozoic era is divided into Eden district (Eden)、 Survival zone from District (Servivor from)、 Survival zone to District (To Servivor);

• The characteristic of the old age is that it takes up a lot of memory , Garbage collection operation frequency is low ;

• Persistent generation mainly stores class definitions 、 Information such as bytecodes and constants that rarely change ;

• YGC The principle is XXX,FGC The principle is XXX;

• commonly FGC stay XXX Performance will be affected in case of ;

• Online systems have emerged MQ Message backlog , What to do at this time ？

Inspection point ：

• Is there any experience in handling wired abnormal disaster tolerance ;

Refer to the answer ：

• First, quickly solve the problem of message backlog , For example, increase consumer Number , Consumption frequency ;

• If there are too many messages, evaluate whether to discard messages or restart MQ;

• Keep logs , After the online business stops bleeding, quickly check the causes of the problems , Is there any other similar scenario with the same problem ;

• Organization recheck , Evaluate the subsequent optimization plan , Timely follow up the progress and effect of landing optimization ;

• If you are responsible for the performance test of the team , In what way would you consider and carry out your work ？

Inspection point ：

• Whether there is a complete summary of performance test technical system ;

• According to the analysis of the actual situation and the implementation ability ;

• Whether to pay attention to team cooperation 、 Member training and quality control ability ;

These are some of the questions I often ask when interviewing candidates for performance testing positions , For your reference only .