目录
前言
云服务器用起来感觉最难受的就是带宽了，国内的云服务器普遍带宽都很小，但买国外或者香港的话延迟大还容易被封IP。一般网站/app最占带宽的是图片和音视频等文件的上传下载，下面我们要聊的cos和cdn就是解决这个问题来的。
简介
对象存储COS
- 对象存储不同于我们平时操作系统里的文件存储，它就像一个map，存储的所有文件都有一个唯一的名称作为key，文件内容作为value。而没有目录的概念。
- 这样做的意义在于，当文件很多，目录结构深时，文件存储需要根据那颗目录树一步一步找到文件，显然是比对象存储直接按文件名一步到位得到要来得慢。
- 但目前很多云服务厂商都有在对象存储上提供目录功能，这大多是模拟出来的。比如腾讯云是将文件名中的 / 识别为目录模拟得到的。
- 比如：放进两个文件：
- aaa.txt
- wow/abc.cpp
- 由于 "wow/abc.cpp" 的文件名带有 / ，则可以模拟解析为是放在wow目录下，存在一个文件叫abc.cpp。
- 我们使用云服务提供的COS来替换我们的服务器实现文件的上传和下载。一般云服务COS不限制下载速度，且用户上传也免费。但用户的下载流量、存储空间占用、请求次数是要收钱的。
- 注意这不是三选一的问题，是三个方面都要收钱的！
- 比如：在一个月的时间里，我们向COS上传了 100 MB 文件，发送过 1 w 次读写请求，且用户外网下载文件使用过 10G 的流量。
- 那么结算时，需要支付：A + B + C
- A：100M/1个月 的存储空间占用费用
- B：1w次读取请求费用
- C：外网下载 10 G 流量费用
- 显然，外网下载流量很容易被人攻击，盗刷流量，然后疯狂扣流量包扣费，容易出现一觉醒来，没了一套海景房的刺激。后面我们用CDN来防止一部分攻击，因为COS的流量费比CDN贵非常多，而且CDN能设置更多的访问限制，降低被攻击的损失，所以可以用CDN抗在前面。
CDN
- cdn的用途很广泛，由于用户在地域上分布全国甚至全球各地，而我们的服务器一般是只在一个或几个地方而已，cdn在地域上可以分散多个节点，作为一个中间人，缓存用户访问服务器上的文件，并在用户下一次请求这个文件时，cdn就可以直接提供给用户，而不需要大老远来请求服务器，提高用户的访问速度。
- 这里我们可以利用这个特性，且其价格低，来帮助COS降低被攻击的损失。
使用问题
盗刷COS流量
- 前面我们已经提到，COS的外网下载流量是比较贵的，而且速度快，容易被攻击刷流量。
- 解决办法：
- 把COS访问权限设置为 私有读私有写
- 当用户需要上传文件时，使用云厂商提供的SDK，服务端预签名上传文件的URL，并将签名后的链接发送给用户，客户端只能按照签名链接指定参数、请求头、请求类型的上传文件到COS，上传不需要使用CDN。
- 当用户需要下载时，使用SDK获取COS上对应文件名的文件链接，并将链接的域名替换为CDN的域名，然后返回替换后的链接给用户下载文件，并在CDN设置限制IP访问速度、下载速度等限制即可。
防盗链/限速
- 由于浏览器不允许伪造请求头中的Referer、Host、Origin，因此可以在CDN/COS都配置防盗链，限制请求的Referer。这个可以阻止别人的网站直接把你的资源链接放到他的网站使用的情况，减少一些被偷资源流量的问题，但他直接下载你的资源然后上传到他的服务器还是可以的。
- 注意网页是可以指定浏览器不携带Referer的，即请求是空Referer。而在浏览器直接敲网址进入网页时的请求也是空Referer，你需要考虑是否需要允许空Referer的请求。防盗链挡不住客户端请求，因为客户端是可以随意伪造请求中的任意值的。如APP、nodejs、命令行、服务端程序等，只要是非标准浏览器环境就可以随意伪造。
- 在CDN中，可以限制下载速度、IP访问速度等。
https网站中使用http资源
- 由于CDN的Https目前很多云厂商是收费的，虽然不贵，但也是钱。
- 如果你CDN访问使用了http，但网站是https协议时，直接在https网站里获取http资源（图片、音视频等）会被浏览器认为是不安全的，并在浏览器的开发者工具中打印警告，但也是能用的。但默认不会带上Referer，因此如果你设置了防盗链不允许空Referer的话，就有问题了，这个时候可以在网页的<head></head>中添加配置：<meta content="always" name="referrer" >，这样浏览器在获取Http资源时也会带上Referer了
- https网站中发起http请求是不允许的！
上传文件大小/数量限制
- 用户向我们的服务端申请用于上传文件的预签名URL时，需要携带参数：文件大小、文件MD5，然后我们可以指定该链接发送时必须携带：
- Content-Length=500
- x-cos-meta-md5: {文件md5值}
- 由此就可以防止用户拿到预签名URL后，上传了其他文件的问题
- 文件大小限制，就是在我们服务端给预签名URL时进行检查。
- 文件数量限制，可以将用户、IP获取上传链接时写入数据库记录，根据这个记录来设计用户上传文件的数量和总大小等。
腾讯云COS的SDK/c++
- 整了老半天，终于写好了cmakelist能编译运行release，但debug版一直找不到链接符号。
- 看了大概是因为他是SDK源码里有一个文件夹three-party存放了已经编译好的第三方依赖库，但这些库是release的，因此需要我们编译debug的依赖库。但我的项目里也依赖openssl，改来改去才能release，最终debug版放弃了。
- 后来开始用上go了，学1天然后上手引入他的sdk和框架开发完cos相关的接口。有c基础还是很快上手的。
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vibration analysis
The Importance of Vibration Management Apparatus in Machinery
Across manufacturing environments, devices and rotating devices are the foundation of manufacturing. However, an of the highly widespread concerns that may hinder the efficiency as well as lifetime remains vibrations. Oscillation can result in a variety of complications, ranging from minimized precision along with effectiveness to elevated wear and tear, eventually causing pricey downtime along with repairs. Such a situation is why vibration control equipment becomes necessary.
The Reason Vibrations Mitigation remains Crucial
Resonance within machinery can bring about numerous harmful consequences:
Decreased Operational Productivity: Excessive resonance can result in misalignments as well as unbalance, lowering total efficiency of the equipment. This can bring about delayed output times and elevated power consumption.
Elevated Erosion: Ongoing vibration accelerates the erosion of equipment components, bringing about more regular repairs and the chance of unforeseen malfunctions. This not only elevates operating costs but also decreases the lifetime for the existing systems.
Protection Hazards: Uncontrolled oscillation may pose substantial safety concerns to both the equipment and the machines as well as the operators. In, severe cases, these could result in cataclysmic system collapse, threatening operators as well as causing widespread devastation to the environment.
Precision as well as Quality Issues: In industries that depend on exact measurements, for example manufacturing as well as aerospace, resonance might lead to discrepancies with the manufacturing process, causing faulty goods along with greater waste.
Economical Approaches for Vibration Control
Putting money in the resonance control tools is not merely essential but a sound investment for all businesses that any business that relies on mechanical systems. The offered state-of-the-art vibration control systems are designed to reduce vibrations in any machinery or spinning equipment, ensuring uninterrupted and productive processes.
What distinguishes our systems apart is its economic value. It is recognized that the necessity of affordability inside the modern competitive marketplace, which is why we have top-tier oscillation control tools at pricing that are reasonable.
Through selecting our systems, you’re not only preserving your machines along with enhancing its productivity but also investing into the long-term success of your business.
Conclusion
Resonance mitigation remains an essential component in preserving the operational performance, safety, and longevity of your machinery. With these reasonably priced vibration management tools, one can be certain your operations operate seamlessly, your products are of high quality, as well as your workers stay secure. Don’t let resonance undermine your company—invest in the correct apparatus today.
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The Value of Vibration Regulation Systems in Mechanical Systems
Within industrial environments, devices along with turning machinery serve as the core of manufacturing. However, one of the most frequent concerns which might impede its operation and longevity is oscillation. Resonance could lead to an series of issues, ranging from minimized exactness as well as effectiveness resulting in increased damage, ultimately bringing about high-cost delays as well as maintenance. This is where vibration regulation systems proves to be essential.
Why Vibrations Mitigation is Important
Vibration within industrial equipment can bring about multiple harmful consequences:
Minimized Production Performance: Excessive vibration may cause misalignment along with imbalance, reducing overall efficiency with the equipment. Such a scenario may lead to reduced production times and elevated energy use.
Heightened Deterioration: Constant vibrations accelerates total erosion in machine components, bringing about more frequent maintenance and an chance for unanticipated unexpected breakdowns. This doesn’t merely raises operational costs and reduces the longevity in the devices.
Protection Dangers: Uncontrolled resonance could introduce considerable security risks for both the equipment and the machines and the operators. In severe cases, extreme situations, it could result in disastrous system collapse, jeopardizing personnel along with leading to widespread harm in the facility.
Precision as well as Quality Issues: For industries where depend on high accuracy, for example manufacturing or space industry, oscillations may result in errors in the manufacturing process, producing defects along with more waste.
Economical Alternatives to Vibration Management
Investing in vibration control apparatus is not just necessary but a smart decision for any industry that uses mechanical systems. The offered modern vibration control systems are designed to remove vibrations from all mechanical systems as well as spinning equipment, ensuring seamless and effective performance.
One thing that sets our systems apart is its its affordability. We know the value of keeping costs low inside the current market, which is why our offerings include top-tier vibration management solutions at costs that are affordable.
Through selecting our offerings, you aren’t simply protecting your machines and enhancing its performance as well as investing in the long-term achievement of your company.
Final Thoughts
Resonance mitigation is a critical aspect in preserving the efficiency, safety, and durability of your industrial equipment. Through our economical vibration management tools, you can ensure your operations run smoothly, your products maintain top quality, and your employees are protected. Never let oscillation affect your business—invest in the correct apparatus now.
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Если вы искали где отремонтировать сломаную технику, обратите внимание – ремонт бытовой техники
Если вы искали где отремонтировать сломаную технику, обратите внимание – ремонт бытовой техники
vibration analysis
The Cruciality of Vibrations Regulation Apparatus in Machines
In manufacturing sites, equipment along with turning devices act as the foundation of production. Nonetheless, an of the highly prevalent issues that might hinder their operation as well as durability is vibration. Vibrations could result in an series of issues, from minimized perfection and productivity resulting in heightened erosion, finally causing pricey downtime along with repairs. This is when vibration management apparatus becomes essential.
Why Vibration Management remains Necessary
Vibration within machinery can lead to various harmful impacts:
Lowered Operational Performance: Exaggerated vibration could result in misalignment along with imbalance, minimizing the effectiveness in such systems. This might bring about reduced production times as well as elevated energy use.
Heightened Wear and Tear: Persistent vibrations speeds up the erosion of equipment components, leading to additional upkeep and the potential for unexpected breakdowns. This not only elevates operational costs as well as shortens the longevity of the equipment.
Security Concerns: Excessive resonance may bring considerable security risks to both the machinery along with the operators. In, severe cases, it can bring about devastating system collapse, jeopardizing employees and causing considerable devastation in the environment.
Precision along with Production Quality Challenges: Within businesses which demand high accuracy, for example manufacturing as well as aerospace, oscillations could cause inaccuracies with the manufacturing process, resulting in defective products as well as increased waste.
Economical Approaches for Vibration Management
Investing into vibration control tools remains not just a necessity and also a wise choice for any business any organization involved with equipment. Our cutting-edge vibration management systems are engineered to remove oscillation in various machine as well as rotating machinery, guaranteeing uninterrupted and effective performance.
Something that distinguishes our apparatus apart is its its economic value. We understand the significance of cost-effectiveness within the competitive market of today, thus we provide premium vibration management solutions at pricing that are reasonable.
By selecting our systems, you are not just securing your machinery as well as boosting its efficiency you’re also investing in the sustained success of your operations.
In Conclusion
Resonance mitigation is a necessary component in ensuring the efficiency, protection, and longevity of your equipment. With these reasonably priced oscillation control systems, you can ensure your operations function efficiently, your products are of high quality, and your workers remain safe. Never allow oscillation affect your machinery—put money in the proper tools today.
Если вы искали где отремонтировать сломаную технику, обратите внимание – ремонт бытовой техники в барнаул
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Если вы искали где отремонтировать сломаную технику, обратите внимание – ремонт бытовой техники
The Importance of Resonance Mitigation Systems in Machines
In industrial contexts, machines and spinning devices constitute the core of manufacturing. However, a of the most common challenges that might hinder their efficiency and lifespan exists as vibration. Vibrations may lead to a series of problems, ranging from reduced precision and performance resulting in heightened damage, ultimately bringing about pricey downtime and maintenance. This scenario is where vibration management tools becomes vital.
The Reason Vibrations Mitigation is Critical
Vibration inside machinery may bring about several negative effects:
Minimized Operational Performance: Excessive vibrations might bring about discrepancies and unbalance, minimizing the productivity in the machinery. This might bring about delayed output times and greater power consumption.
Heightened Deterioration: Continuous vibrations increases the damage of equipment components, leading to additional upkeep and an potential for unexpected failures. Such a scenario doesn’t merely raises maintenance expenses but also shortens the durability of the devices.
Security Concerns: Unmanaged vibration could bring considerable security risks to both the machines and the workers. In severe cases, extreme situations, these may result in cataclysmic equipment breakdown, threatening workers and resulting in considerable destruction in the facility.
Accuracy along with Production Quality Issues: Within industries that demand exact measurements, such as industrial sectors and aerospace, vibrations may result in discrepancies in production, producing defects and more waste.
Economical Alternatives for Vibration Control
Putting money in vibration control apparatus proves not just a necessity but a wise choice for any industry dependent on machinery. The offered state-of-the-art vibration control systems are designed to mitigate oscillation from any equipment and spinning equipment, providing uninterrupted and efficient functioning.
What distinguishes our equipment from others is its reasonable pricing. We know the necessity of cost-effectiveness inside the current market, which is why we provide top-tier vibration control solutions at pricing that won’t break the bank.
By selecting our systems, you’re not only preserving your equipment as well as improving its productivity but also putting resources in the long-term success in your organization.
Conclusion
Vibration management is a critical component of maintaining the efficiency, security, along with longevity of your machines. With our cost-effective vibration management tools, you can make sure your production run smoothly, all goods are of high quality, along with your workers are protected. Never permit vibration affect your company—make an investment in the appropriate systems today.
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