请教一个建网站的笔试题 - 未名空间MITBBS历史存档

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请教一个建网站的笔试题

请教一个建网站的笔试题# Java - 爪哇娇娃

l*b2010-03-25 07:03

1 楼

我申请的是java职位，一个建网站的题问假设知道数据库平均处理的信用卡
transaction是40个每秒，请问如何估计同时在线打开信用卡支付网页的人数？大概
要从哪些因素考虑？有没有计算方程式？谢谢各位。

g*e2010-03-25 07:03

2 楼

主要石每个transaction的时间长度吧？如果每个transaction只有1/40秒，那么同时在
线的只有1
人。

【在 l*****b 的大作中提到】

: 我申请的是java职位，一个建网站的题问假设知道数据库平均处理的信用卡
: transaction是40个每秒，请问如何估计同时在线打开信用卡支付网页的人数？大概
: 要从哪些因素考虑？有没有计算方程式？谢谢各位。

g*g2010-03-25 07:03

3 楼

If you want to know how many people are opening that page, why
don't you just setup a counter? Before session expires and another
page requests, that's the accurate number you are looking for.
I don't quite understand when you can get accurate number with
some simple counter why you need that kind of estimation.

【在 l*****b 的大作中提到】

k*u2010-03-25 07:03

4 楼

If I understand your question correctly, you are asking the throughput of
the whole application, assuming DB layer is the bottle neck and its
throughput is 40 transactions/second.
This depends directly on how often a user session triggers a DB transaction.
Some simple examples, if a user session triggers a DB transaction every
second, you can have only 40 simultaneous user sessions; if a user session
triggers a DB transaction every 10 seconds, you can have 400 simultaneous
user sessions; and so

m*t2010-03-25 07:03

5 楼

This makes sense. I was thinking along some similar lines, e.g., estimate
how long does it typically take a user to input the credit card info and hit
the button. (It's of course much longer for me personally because I always
have trouble locating my wallet...)

transaction.

【在 k****u 的大作中提到】

: If I understand your question correctly, you are asking the throughput of
: the whole application, assuming DB layer is the bottle neck and its
: throughput is 40 transactions/second.
: This depends directly on how often a user session triggers a DB transaction.
: Some simple examples, if a user session triggers a DB transaction every
: second, you can have only 40 simultaneous user sessions; if a user session
: triggers a DB transaction every 10 seconds, you can have 400 simultaneous
: user sessions; and so

l*b2010-03-25 07:03

6 楼

Thanks for all your helps. I tried the following assumption. I assume the
average time user stay and fill in the payment form is between 3-5 mins. The
assumption is the system could handle about 12,000 (40X5X60) simultaneous
online users at the peak time. Does it make sense? Thanks.

q*u2010-03-25 07:03

7 楼

有意思的题目，
Speed = Amount / Time
Amount = Speed * Time = 40 (Transaction/Sec) * 300 (Sec) = 12, 000(
Transactions)
思路真重要，一看答案恍然大悟，但是一下子答不上来，给已经知道答案的
interviewer，岂不是被bs

Thanks for all your helps. I tried the following assumption. I assume the
average time user stay and fill in the payment form is between 3-5 mins. The
assumption is the system could handle about 12,000 (40X5X60) simultaneous
online users at the peak time. Does it make sense? Thanks.

【在 l*****b 的大作中提到】

: Thanks for all your helps. I tried the following assumption. I assume the
: average time user stay and fill in the payment form is between 3-5 mins. The
: assumption is the system could handle about 12,000 (40X5X60) simultaneous
: online users at the peak time. Does it make sense? Thanks.

h*02010-03-25 07:03

8 楼

这个关键是要有能力想到“每个人处理时间约为3到5分钟”

The

【在 q*********u 的大作中提到】

: 有意思的题目，
: Speed = Amount / Time
: Amount = Speed * Time = 40 (Transaction/Sec) * 300 (Sec) = 12, 000(
: Transactions)
: 思路真重要，一看答案恍然大悟，但是一下子答不上来，给已经知道答案的
: interviewer，岂不是被bs
:
: Thanks for all your helps. I tried the following assumption. I assume the
: average time user stay and fill in the payment form is between 3-5 mins. The
: assumption is the system could handle about 12,000 (40X5X60) simultaneous