cloud performance optimizations

Performance Optimizations in a CloudCentric World Andy Still Performance Optimizations in a Cloud-Centric World by Andy Still Copyright © 2015 O’Reilly Media, Inc All rights reserved Printed in the United States of America Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472 O’Reilly books may be purchased for educational, business, or sales promotional use Online editions are also available for most titles ( http://safaribooksonline.com ) For more information, contact our corporate/institutional sales department: 800-998-9938 or corporate@oreilly.com Editor: Brian Anderson Copyeditor: Holly Bauer Proofreader: Nicole Shelby Cover Designer: Randy Comer July 2015: First Edition Revision History for the First Edition 2015-07-19: First Release 2015-09-02: Second Release The O’Reilly logo is a registered trademark of O’Reilly Media, Inc Performance Optimizations in a Cloud-Centric World, the cover image, and related trade dress are trademarks of O’Reilly Media, Inc While the publisher and the author have used good faith efforts to ensure that the information and instructions contained in this work are accurate, the publisher and the author disclaim all responsibility for errors or omissions, including without limitation responsibility for damages resulting from the use of or reliance on this work Use of the information and instructions contained in this work is at your own risk If any code samples or other technology this work contains or describes is subject to open source licenses or the intellectual property rights of others, it is your responsibility to ensure that your use thereof complies with such licenses and/or rights Cover image courtesy of Vera & Jean-Christophe, from flickr The original image (“Heavy Traffic”) was in color 978-1-491-93137-0 [LSI] For Candance For Candance, who insists that all poor performance on the Internet is my fault Introduction Back in the day, it was simple Content was served from your server, over your network, and then to client machines that you controlled Even when that moved out from a LAN to a WAN, the connectivity came from a single provider—it was all under your control Then came the Internet… Now content was being served across the public Internet to end-user machines—you lost control of the location, type of machine, and type of connectivity Then came the cloud… The cloud brought with it a new way of thinking about web system hosting Hosting shifted from being a hand-crafted service to a commodity service providing throwaway systems You moved from being a hardware owner to being a service consumer With this change came the increasing loss of control over your system Nowadays your application is often the only element that you control directly, and even that can be dependent on consuming thirdparty services This is not a bad thing, but you need to be aware of the issues that can arise as a result of this shift to the cloud Whether you’ve already moved systems to the cloud or are thinking of doing so, this book will point out some of the risks to your site’s performance created by this loss of control and puts forth some methods to identify and then mitigate those risks In no way, though, does this book set out to deter you from moving into the cloud This author has long been a cloud advocate and works almost exclusively on cloud-based systems Terminology For simplicity, I’ve used the term “website” throughout to refer to any system that distributes data across the Internet, including browser-based applications, mobile apps, etc Chapter Losing Control So, here we are in the world of the cloud, with ever-expanding elements of our websites being placed in the hands of others Advantages to Giving Up Control There are many positive aspects to making this move (after all, why else would so many people be doing it?), so before going into the negatives, let’s remind ourselves of some of the advantages of cloud-based systems: Quick and easy access to enterprise-level solutions For example, building your own geographically available SQL server cluster with real-time failover would take lots of hardware, high-quality connectivity between data centers, a high degree of expertise in databases and networking, and a reasonable amount of time and ongoing maintenance Services such as Amazon RDS make this achievable within an hour, and at a reasonable hourly rate Flexibility and the ability to experiment and evolve systems easily The ability to create and throw away systems means that you can make mistakes and learn from experience what’s the best setup for your system Rather than spending time and effort doing capacity estimates to determine the hardware needed, you can just try different sizes, find the best size, and then change the setup if you reach capacity, or even at different times of day Access to data you could never create yourself Third-party data sources create risks, but they also enhance the attractiveness of your system by providing data that you otherwise wouldn’t be able to provide but that your users rely upon— either because that data is about a third-party system (e.g., Twitter feeds), or because it would not be economical (e.g., mapping data) They improve performance and resilience While they are out of your control, most cloud-based systems have higher levels of resilience built in than you would build into an equivalent system Likewise, though, there are potential issues created by how CDNs route traffic; CDNs will usually offer performance improvements over systems that not use them Cloud-based systems are also built for high performance and throughput and designed to scale out of the box Many services will scale automatically and invisibly to you as the consumer, and others will scale at the click of a button or an API call Access to systems run by specialists in the area—not generalists In house or using a general data center, you may have a small team dedicated to a task—or more likely, a team of generalists who have a degree of expertise across a range of areas Bringing in a range of specialist cloud providers allows to you work with entire companies that are dedicated to expertise in specific areas, such as security, DNS, or geolocation Performance Risks Despite these advantages, it’s important to be aware of the inherent performance risks, especially in this era where good website performance is key to user satisfaction The next sections cover important considerations for performance and outline key performance risks, following the journey that a user must travel in order to take advantage of your website The Last Mile Before any user can access your website, they need to connect from their device to your servers The first stage of this connection, between the user’s device and the Internet backbone, is known as the last mile For a desktop user, this is usually the connection to their ISP, whether that be by DSL, cable, or even dial-up For a mobile user, it’s the connection via their mobile network This section of the connection between user and server is the most inefficient and variable, and it will add latency onto any connection To illustrate this, in 2013 the FCC released research that showed that a top-speed fiber connection would add 18ms latency—and that was the best-case scenario—a DSL connection would add 44ms, and dial-up was considerably slower For mobile users, the story was even worse: a 4G connection had a latency overhead of 600ms on new connections, a 3G connection had a latency of over 2s on new connections, and even existing open connection had a latency as high as 500ms T HE “LAST M ILE” OR T HE “FIRST M ILE”? Although the last mile is the traditional name of the first stage of the connection between a user and the server, it may be more appropriate to think of it as the first mile or the on ramp, as the delay is often in establishing the connection in the first instance, particularly in mobile networks Mobile connections have to communicate with the network to validate that a connection is allowed and to define the speed at which they can connect before anything can be opened For 4G networks, this exchange happens with the local cell tower, but for 3G networks, the exchange takes place with the core network; therefore, 3G networks have much higher latency on newly opened connections This is a high-impact area of the delivery of any website, and it’s the one area where there is genuinely little to be done about the issue Nevertheless, it’s important to be aware of the variations that are possible and actually being experienced, and to ensure that your website’s functionality is not affected by them Performance Risks Unreliable delivery of content The variability in connection speed of the last mile means that it’s hard to determine how fast content will be delivered to users This presents many of the same challenges that we’ll explore in the next section—they’re often amplified by the challenges of the last mile Backbone Connectivity Traditionally, this is seen as the path that the data from your website takes after it leaves your data center until it arrives at the end user’s machine However, in the Internet age, backbone connectivity can be seen more as the means by which a user reaches your data—you have little control over how or from where the user is coming to you to request it Users are now accessing data from an expanding range of devices, via many different means of connectivity, and from an ever-widening range of locations To understand the performance challenges caused by unknown means of connectivity, you need to look at three key factors: Bandwidth Bandwidth is the amount of traffic that can physically pass through the hardware en route to the end destination Bandwidth can usually be increased on demand from your ISP Contention Contention is the amount of other traffic that is sharing your connectivity This will often vary greatly depending on the time of day Like bandwidth, contention is something that can be minimized on demand from your ISP Latency Latency is based on the distance that the data has to travel to get from end to end and any other associated delays involved in establishing and maintaining a connection Which Is the Biggest Challenge to Performance? Bandwidth is often discussed as a limiting factor, but in many cases, latency is the killer—bandwidth can be scaled up, but latency is not as easy to address There is a theoretical minimum latency that will exist based on the physical distance between two places Optimally configured fiber connections can travel at approximately 1.5× the time taken to travel at the speed of light The speed of light is very fast, but there is still a measurable delay when transmitting over long distances For example, the theoretical fastest speed for sending data from New York to London is 56ms; to Sydney, it’s 160ms This means that to serve data to a user in Sydney from your servers in New York, 160ms will pass to establish a connection, and another 160ms will pass before the first byte of data is returned That services Complete failure or performance degradation Like with third-party SaaS tools, if a cloud system you rely on goes down, so will your system Likewise, if that cloud system starts to run slowly, so will your system This could be caused by hardware or infrastructure issues, or issues associated with software releases (SaaS providers will usually release often and unannounced) They could also be caused by third-party malicious activities such as hacking or DoS attacks—SaaS systems can be high profile and therefore potential targets for such attacks Increased overhead All additional processing being done will add time to the overall processing time of a request When adding an additional system in front of your own system, you’re not only adding the time taken for that service to execute the functionality that it is providing, but you’re also adding to the number of network hops the data has to make to complete its journey Increased latency All services will add additional hops onto the route taken by the request Some services offer geolocation so that users will be routed to a locally based service, but others not It’s not uncommon to hear of systems where requests are routed back and forth across the Atlantic several times between the user and the server as they pass through cloud providers offering different functionality Third-Party Components Websites are increasingly dependent on being consumers of data or functionality provided by thirdparty systems Client Side Client-side systems will commonly display data from third parties as part of their core content This can include: Data from third-party advertising systems (e.g., Google AdWords) Social media content (e.g., Twitter feeds or Facebook “like” counts) News feeds provided by RSS feeds Location mapping and directions (e.g., Google Maps) Unseen third party calls, such as analytics, affiliate tracking tags, or monitoring tools Server Side Server-side content will often retrieve external data and combine it with your data to create a mashup of multiple data sources These can include freely available and commercial data sources; for example, combining your branch locations with mapping data to determine the nearest branch to the user’s location Performance Risks Dependence on these third-party components can create the following performance risks Complete failure or inconsistent performance If your system depends on third-party data and that third party becomes unavailable, your system could fail completely Likewise, poor performance by the third party can have a domino effect on your system’s performance Unexpected results Third parties can sometimes change the data they return or the way their data feeds work, resulting in errors when you make requests or when the requests return unexpected data Chapter If You Can’t Control It, Monitor It It’s vitally important for you to understand what’s going on with the elements of your website and infrastructure that you can’t control—particularly their impact on other areas of your website A good monitoring system is essential to enabling the performance optimizations that are recommended in Chapter In addition to monitoring, it’s important that you set up appropriate alerting to notify you when issues may be occurring A good monitoring solution needs to gather a full range of data about how your website is performing This needs to illustrate not only what is happening across the full end to end—from server to user— but also across the full range of users It not only needs to gauge the user experience, but also provide sufficient data to be able to determine the root cause if the experience is not at the level expected Reasonable end-to-end monitoring requires five types of monitoring RUM and EUM Ultimately, the most important data answers the question: what is the user seeing? This is the task of real user monitoring (RUM) and end user monitoring (EUM) RUM gathers data from all user activity and passes that data back to a central collection server, allowing analysis of your users’ exact experience This will flag any unexpected behavior and can help you drill down to identify the cause of the problem RUM is also useful for determining whether there is a pattern to the types of users who are experiencing a particular problem For example, is it related to a specific geographic area, type of connection, browser, or device? EUM is similar, but relies on synthetically generated, regularly repeated tests of specific functionality EUM will quickly show if tasks are varying over time and whether key functionality is still acting as expected EUM is valuable in that you can be proactively alerted when problems occur without having to depend on real users executing a specific function (and hopefully resolve issues before they are noticed) Also, because you control the way the test is executed, you can remove other variables and only run a known, repeatable test RUM is valuable because it executes any functionality within your system that users are doing without your having to specify what that functionality is This means that you see issues that are occurring in areas that you may not have expected A good monitoring solution includes elements of both RUM and EUM APM Application performance management (APM) is a monitoring technology that sits on your server and tracks all activity and reports to a central analysis server This will collect code-level metrics (e.g., method and SQL query execution times) and details of communications with external systems, in addition to hardware metrics (e.g., memory and CPU usage) APM systems are very useful for getting a detailed understanding of what your application is doing under the hood, and they’re a good starting point for root-cause analysis of issues with your system Some APM solutions will integrate with RUM and EUM tools to give a full end-to-end breakdown of a user’s interaction with your system Network Monitoring (NPM) While RUM and EUM give you a good understanding of what the end user is experiencing and APM illustrates what’s going on on your server, network monitoring looks at the areas in between In traditional data centers, this would involve operational management tools such as Nagios, or NPM (network performance monitoring) tools such as Zabbix or SolarWinds to see details of how your network infrastructure is behaving (It’s worth noting that these two types of tools are increasingly overlapping.) However, the network infrastructure is largely hidden from you in cloud environments INT ERNET PERFORM ANCE M ONIT ORING In addition to NPM, it’s good practice instead to use IPM (Internet performance monitoring) tools to see how data is behaving when traveling over the Internet between your servers and your end users The depth of information offered by these tools allows you to understand the efficiency of the routing used by your cloud provider/third-party provider and to determine whether it is efficient in general or for your specific audience This is a good way to determine which is the best cloud provider in terms of reliable network performance Proprietary System Monitors Most cloud providers will offer their own tools for monitoring the performance of their systems, like Amazon’s CloudWatch for AWS services The depth of information and functionality provided by these systems varies greatly, but they should all should a first port of call for identifying issues with a system Data Aggregators/Dashboard Creation It can be difficult to stay on top of all of the monitoring tools that are necessary to understand the diverse elements in your system Data aggregators and dashboarding systems provide the ability to gather all these data sources into one central location and display them side by side There are many examples of these types of tools, from open source (e.g., Tableau) or cloud-based (e.g., DataDog) to enterprise-level (e.g., Soasta DOC) The more advanced of these systems will also allow you to correlate multiple datasets onto a single graph Chapter Minimizing Performance Risks The performance risks described previously can be minimized using the following five strategies: Use a best-of-breed DNS provider Cache content as close to the user as possible Understand the nature of cloud services Apply the same good practice to the cloud as you would to any other system Ensure you can handle any failure Use a Best-of-Breed DNS Provider DNS is your first point of contact with an end user; without it, your user will never access your site So it is essential that it is reliable, performant, and flexible Providers, such as cloud providers or CDNs, often prefer (or require) that they also manage your DNS, but this can create a single point of failure (SPOF); if a provider experiences problems with its own system, it may also have issues with its DNS provision, making it difficult to use DNS as a defense against that failure Having an independent DNS provider allows you to have policies that favor different cloud providers/CDNs in different circumstances, such as location, speed, SLAs, etc This allows you to optimize your systems based on the output from the monitoring solutions Therefore, it’s good practice to use a managed DNS solution that is provider-independent and to ensure that it offers the services described in the following sections A Low-Latency Network It is essential that the DNS provider you select operates a low-latency network, allowing fast resolution of DNS records wherever your users are situated As all users will need to resolve your DNS record before accessing your system, a slow resolution time will add delay onto the first request to your site for all users If you’re using domain sharding (i.e., serving your content from many subdomains to improve performance), then this delay is applicable for each of subdomains you are using (The actual impact of the overall delay will be dependent on how well constructed your page is; a well-constructed page will ensure that as many requests as possible are made concurrently.) Support for DNS-Based Failover If your provider has a complete outage, then your DNS provider should allow a switch to point traffic to another location Alternatively, if one of the cloud providers you’re sitting behind has an outage, then you need to be able to quickly reroute traffic to bypass that service T T L AND DNS TTL, or time to live, is the element of a DNS record that tells the requester how long the record is valid for In other words, if the TTL for your DNS record is set to 24 hours, once a browser has resolved that DNS record, it will continue to use that same value for the next 24 hours regardless of whether you’ve updated the details If the TTL is set too high, then DNS cannot be used as a failover method, as the change will take too long to take effect with any existing users Setting a very low TTL, however, adds extra overhead, as DNS lookups have to happen much more regularly, which adds to the page-load time for a user and increases the stress on the DNS servers Most DNS providers will allow you to access an interface to make these changes reactively If you’re planning to use DNS to provide this functionality, it is essential that you set the TTL for your domain name to a suitable value (The default value for most providers is 24 or 48 hours.) Some DNS providers not allow changes to TTL records or have minimum values More feature-rich managed DNS providers provide automated failover functionality that will constantly monitor the availability of systems and update DNS records to alternative systems in the event that failure is identified Support for Geolocation A simple way to mitigate the impact of latency is to serve content from as close to users as possible This can be achieved by caching content close to user (see “CDNs”); however, it can also be achieved by hosting multiple systems at different locations around the world ANYCAST Anycast is an addressing methodology that allows a “one-to-nearest” transmission of traffic to a target node, usually using BGP to simultaneously advertise the same IP address at multiple locations In practice, this means that traffic to a single IP address can be routed to multiple locations based on the location of the request Managed DNS providers use anycast networks to allow resolution of DNS records of the most geographically relevant system This has some interesting potential solutions that can be employed to increase your control over your systems The obvious implementation of this is to host multiple versions of your system within different regions DNS resolution will then route the user to the one that is nearest to them Many cloud providers will provide this functionality as part of their service However, using a managed DNS service, rather than a cloud provider, to manage geolocation allows you to have more granular control over the situation under which you will use a cloud provider For example, if your chosen cloud provider is weak in one area, then you can use a secondary provider in that region Likewise, if your IPM data indicates that your cloud provider is routing traffic from certain locations via inefficient routes, you can elect to use a different provider in that region Cache Content as Close to the User as Possible It’s an old statement, but it’s still as true as ever: the fastest request is the one you don’t make, so it is best to cache content as close to the user as possible Make sure all your static resources have appropriate expires headers on them so the browser will cache as you expect If you’re using any client-side data retrieval from APIs, then try to store what you can locally— JavaScript has access to local storage on the client now, so data can be stored across sessions Future W3C standards such as service workers are designed to give more control to developers about what is cached on the client beyond the standard browser cache SERVICE WORKERS Service workers are a technology that allows you to install a JavaScript module that is executed as part of any future requests to your domain What this means in practice is that you can intercept that request and intelligently decide how to handle it, including returning content direct from your JavaScript module rather than passing the request onto the server Service workers are a published W3C standard but are currently only supported in Chrome CDNs If you can’t cache on the client, then try to cache as close as possible This leads us on to CDNs, which we discussed previously in “CDNs” CDNs are designed as globally distributed caching and delivery systems Modern CDNs offer much wider functionality than this, but this is the core of their function The advantages of CDNs are obvious: most of the time, users should be served content from destinations close to them CDNs are also typically set up for high-traffic usage, so a good CDN will address issues of both bandwidth and latency Using CDNs for dynamic content The caching capability of CDNs is only really useful for static content—dynamic content is by its nature less cacheable—though modern CDNs are doing their best to change that with technology such as Edge Side Includes (ESI) Despite this, though, there are still advantages to serving dynamic content via a CDN: it reduces the impact of HTTP slow-start The negative impact of slow-start increases as the latency of the connection increases CDNs maintain open HTTP connections to your server, meaning that only rarely they have to go through the slow-start process Using a CDN, therefore, means that even for dynamic content, the slow-start element is only completed for a short round trip between client and CDN, and the communication between CDN and server is carried out using an existing open connection T CP SLOW-START Slow-start is a core part of the TCP standard; it’s there to minimize network congestion and ensure that transmissions are made at a speed appropriate for the available bandwidth However, a side effect is that newly established connections have much higher latency than they theoretically need to Slow-start, as its name suggests, starts a transfer slowly and then builds up speed as it becomes apparent that the network can handle it After the initial connection is made and a handshake completed, the server sends a small number of packets, the client receives and acknowledges receipt, and the server can then send two packets for every packet successfully acknowledged This allows for exponential growth until the capacity of the network is determined This means that an initial request to a server will involve more round trips to the server than are actually necessary For example, a 20k request that could easily be served in one round trip will take four round trips on an initial connection to a server Choose the best CDN Not all CDNs are created equal, and this is where knowledge of your audience and some of the topology of the Internet comes in useful Most CDN providers publish maps of the locations of their POPs; the amount and distribution of them will vary from CDN to CDN Looking at a selection, you will soon see that there are areas that are well supported and others that are not A good understanding of the location of your audience combined with a knowledge of Internet topology will allow you to identify a CDN provider that will sit beyond any bottlenecks that could affect your users Using multiple CDNs As discussed previously, it’s possible to use geolocation of DNS to manage multiple cloud providers This approach can also be used to take advantage of multiple CDNs For example, some CDNs specialize in specific areas (e.g., China), so if you have users in that area, it might be worth using that CDN Understand the Nature of Cloud Services Although there are risks inherent in taking advantage of cloud providers’ multitude of different services, they are generally built for high performance and high resiliency and are generally less risky than trying to create your own, especially when running that software on cloud-based infrastructure However, it’s essential to confirm that this is the case for you and that the cloud services are being used correctly Try Before You Buy Before using any service, you need to put it through its paces and ensure that it is behaving as expected and performing as advertised The nature of the cloud makes these kinds of proof-of-concept tests much more viable than non-cloud offerings They can be undertaken with minimal upfront costs and long-term commitment and can be thrown away if they fail While performing this testing, it’s good to get as many monitoring systems as possible going to ensure that you’re not just focusing on functional correctness; other metrics such as availability, reachability, and performance should be considered For example, the IPM data should be used to determine the network impact of using this service from different locations All tests should include a reasonable amount of load to understand the end-to-end performance of the system under normal and high traffic Optimize Your Systems for the Cloud It’s easy to use cloud services in a sub-optimal way, because they’re relatively new systems, have a high velocity of change, and because developers are usually self-taught Furthermore, developers often apply on-premise thinking and practices to the cloud, not realizing that cloud systems are built with a slightly different paradigm in mind For example, the cloud-based database as a service offerings are better suited for a few larger queries than many small queries, meaning that any systems that are very “chatty” with the database will likely perform considerably worse in the cloud than on premise with a direct database connection Monitoring data should be used to confirm that the performance of these services is as expected and required Understand the Configuration Options Cloud services are usually aimed at delivering complex pieces of functionality in a simple way through a GUI or API Therefore, you can usually get up and running with them fairly quickly However, the out-of-the-box configuration options may not be the most resilient or performant You should be proactive in understanding which options are available as well as being reactive to issues identified by monitoring and testing Understand the SLAs Most cloud providers will provide SLAs; however, it’s is important to understand the terms of the SLA that they provide and ensure that you have implemented your service correctly to take advantage of it For example, Microsoft Azure provides an uptime SLA for cloud services, but only if you’re running two or more instances Apply the Same Good Practice to the Cloud as You Would to Any Other System The same good practices that you would apply to on-premise solutions should be applied to cloudbased solutions A standard risk assessment process should be followed For example, the cloud-based database as a service systems provide multiple levels of resilience around data (multiple copies in multiple places) but still involve a SPOF if there’s a system failure that causes data corruption Good practice in this case would dictate that a separate backup be taken and stored remotely—in traditional terms, an “offsite backup.” This backup should ideally be stored with another cloud provider (or elsewhere) Ensure You Can Handle Any Failure When you’re dependent on services that are out of your control, you have to be conscious of two things: They may stop working at any point You will have no control whatsoever over when they will start working again Therefore, you have to architect your systems to handle this failure gracefully NOTE Failure is not just failure—it’s also poor performance You should be monitoring third-party services to ensure they’re responding in a timely manner Avoid “Death by Retry” Once a failure state is known, share that knowledge across any elements of your system that depend on that service and put in place a measured policy for attempting retries Do not create a death by retry situation where your system is brought down by constant attempts to connect to an unavailable system A good architectural practice is to route all requests through a central point of connection Have a Backup Plan If the functionality provided by the third-party system is key, then consider having a replacement system in place and automatically failover to it Another option is to capture all the details of the request for processing offline when the system returns This is valid for systems such those for payment processing or appointment bookings Provide Ability to Turn Functionality Off Your system should be built to provide the ability to remove elements of functionality by a simple configuration or application change—often referred to as feature toggles This allows you much more granular control over the impact of elements of your system If they’re starting to cause issues, then remove then FEAT URE T OGGLES Feature toggles are a development methodology where software features are built into systems with the ability to turn them on and off without redeploying the application This approach is often used as a way of pushing new features into production ahead of the time that they need to be made active, allowing the wider business to activate the feature at an appropriate time with minimal assistance needed from the IT team More intelligent feature toggle systems will allow gradual roll-out of new features to subgroups of users This allows the company to validate aspects such as functional correctness, performance, and popularity of features before rolling them out completely Feature toggles are designed to be short term, then to be removed after the feature is fully rolled out into production, as there is overhead in running and maintaining them Longer-term feature toggles should only be considered for specific pieces of functionality that are part of a set plan to remove on demand Examples of this may be predictive search that is triggered on every key press If this uses a search system that’s out of your control, then when you start to see problems with that service, you can change the toggle to remove predictive search If the service starts to struggle even more, then you can change the toggle to remove search functionality completely Fail Gracefully If there’s no way to proactively handle the failure and prevent any impact on the user, then you need to ensure that your system will fail gracefully The user should see a properly designed and presented page with a helpful error message that explains what has happened If the failure happens within a data transaction, the user should be notified of the current state of the transaction (e.g., has their order been placed successfully?) Create a “Flight Manual” A “flight manual” should be created with mitigation plans associated with each type of failure This should include the nature of the change that can be made and the circumstances under which it is acceptable to make that change Having this sort of manual allows people on the ground to be empowered to make decisions and changes without having to go through a complex decision-making process with management Chapter Takeaways There are six important lessons to take from this book: Don’t fear loss of control—embrace the cloud Introducing cloud systems will lead to further loss of control over your website, but the advantages of using these systems outweigh the disadvantages For most people, the services offered by cloud providers will be faster and easier to implement and manage, as well as more resilient, technologically advanced, and cost effective to run than anything they could implement themselves Ensure you have sufficient monitoring in place You can’t control what’s going on, so make sure you’re gathering data and can determine what users are seeing (across the full range of your audience) and some root-cause analysis on any issues raised This should include the following types of monitors: RUM/EUM IPM APM Stay in control—maintain an independent DNS provider Keeping your DNS independent and flexible allows you to implement a “right tool for the right job” strategy, combining multiple cloud providers/CDNs for different sections of your audience based on the data returned from your monitoring Offload the load—use caching and a CDN Make sure you’re caching data as close to the user as possible Implement a CDN to optimize responses and minimize latency Use your monitoring to determine the best CDN or combination of CDNs to use Understand the difference between cloud and on-premise Cloud providers offer many advantages over on-premise systems, and it’s important to understand the differences between them Research, investigate, and try new systems to ensure that you’re taking advantage of their features and understanding their weaknesses Failure will happen—build systems and processes to handle it As good as they are, when it comes down to it, you have no control over the systems and services you’re using, so your website must be able to handle the failure or poor performance, and you must have a process to be able to handle it About the Author Andy Still has worked in the web industry since 1998, leading development on some of the highesttraffic sites in the UK He co-founded Intechnica, a vendor-independent IT performance consultancy, to focus on helping companies improve performance on their IT systems, particularly websites He is also the creator of TrafficDefender, a cloud-based traffic-management tool Andy is one of the organizers of the Web Performance Group North UK and Amazon Web Services NW UK User Group Acknowledgments As usual, I have to pay tribute to all my fellow Performance Architects at Intechnica for sharing their knowledge across the spectrum of performance issues Books like this wouldn’t be possible without them Thanks also to Samir Jafferali for taking the time out to review the content and provide feedback and invaluable comments ... Performance Optimizations in a CloudCentric World Andy Still Performance Optimizations in a Cloud- Centric World by Andy Still Copyright © 2015... inherent performance risks, especially in this era where good website performance is key to user satisfaction The next sections cover important considerations for performance and outline key performance. .. routed via multiple cloud- based services between the user and your server Performance Risks There are a number of performance risks associated with moving your website behind cloud- based services