Last night, I stayed up until three in the morning again, just because the high defense CDN we used suddenly jerked off. Background monitoring is all red alarm, user complaints like snowflakes flying in. These days, even the CDN, which claims 99.99% availability, can give you a show of “evaporation”, which really prevents hackers from preventing teammates.
To be honest, high defense CDN node instability this thing, I have stepped on the pit than some people have written the code are more. Some service providers blowing sky-high, really encountered traffic over, the node collapsed faster than the paper mache. Last year, I used a CDN07, usually as stable as the old dog, a CC attack directly lying flat, the response time from 200ms soared to 20 seconds, the customer phone call almost hit our landline.
Don't be in a hurry to scold the service provider first, the reasons for node instability may be more complicated than you think. I summarize the main situations: network backbone fluctuations (especially cross-continental nodes), local ISP pumping, DDoS traffic exceeds the node cleaning capacity, SSL certificate configuration error, and may even be the server room air conditioning is broken - I really encountered a vendor because of the air conditioning failure led to node overheating downgrade.
Last week to help friends troubleshoot a particularly typical case: with the well-known vendor CDN5, suddenly found that the East Asia node latency skyrocketed. MTR check, found that the node itself is not a problem, is an intermediate routing jump point bombed. At this time you scold the CDN vendor is useless, people can not control the operator routing.
The first thing to do is to determine the scope of the problem. Don't wait foolishly for the service provider to respond, use the tools to troubleshoot it yourself first:
If you find that users in a particular area are accessing the site abnormally, it is likely that there is a problem with the local POP point. Don't trust the monitoring panel at this point - some vendors“ status pages will always say ”all is well", which is less reliable than a weather forecast.
I had a loss last year with 08Host. Their status page was all green, but in fact the South China node had been down for half an hour. Then I got smart and used UptimeRobot to set up more than 20 monitoring points, which is more sensitive than the service provider's own monitoring.
The golden procedure after discovering a node abnormality: immediately enable the backup node! A reliable CDN should support multi-node load balancing. Our practice is that the usual traffic goes to the main node, and automatically switches to the standby node when anomalies are detected. Let me show you a real configuration:
Watch out for that BACKUP parameter - it's the last line of defense. When all the CDN nodes hang, the traffic will be sourced back to your own server. It may not be able to carry the heavy traffic, but at least it ensures that the business is not completely paralyzed.
Switching nodes is only an emergency solution, the fundamental problem is still to find the service provider. But how to communicate with a good idea. Don't just say “your node hangs”, engineers are most annoyed with this vague description. Prepare a failure report template, every time directly thrown over:
I've tested it and found that if you take the data to customer service, the processing speed can be more than three times faster. CDN07 case last week, from the report to solve only 18 minutes - because their engineers take a look at the data to directly locate the Shanghai Mobile peering link problem.
Long-term solutions have to start from the beginning of the selection to avoid risk. Now choose CDN I must look at three indicators: node redundancy (at least two available nodes in each region), the number of BGP links (to determine the route optimization capabilities), cleaning capacity (do not believe in the theoretical value, to see the performance of the actual attack).
08Host has done a good job in this area, deploying 3+ nodes in each region, and using different server room providers for different nodes. Even if one server room has a problem, the other nodes can still be covered. Although the price is a little more expensive, but much more cost-effective than the loss of business downtime.
Here's another tip: Do regular failure drills. Every month, choose a low peak period, manually simulate node failure, to see if the switching process is smooth. Don't wait until something really happens to realize that the standby node is configured with the wrong SSL certificate - I've seen this kind of low-level error more than once.
Finally, a solid fact: there is no 100% stable CDN. strong as Cloudflare also have downtime. The key is to have a complete disaster recovery system. We are now deploying a three-tier architecture: CDN5 for front-end acceleration and DDoS prevention, CDN07 for global load balancing in the middle, and finally 08Host for backup solutions. Although the cost is a little higher, but in the past two years, we have never caused business interruption due to CDN problems.
Remember, a high defense CDN isn't just about buying a service and calling it a day. You have to continuously monitor, regularly test, and establish contingency plans. Those who say “buy a high defense to rest easy”, either stupid or bad. Network security is supposed to be a war of attack and defense, today's stable nodes may collapse tomorrow, remain vigilant than anything else.
The next time you encounter a node pumping, first take a deep breath, and then follow this process: monitoring and positioning → switching nodes → data collection → contact vendors. Do not be in a hurry to blindly change the configuration, once my colleague slipped and cut all the traffic to the standby node, the results of that node is not configured to protect the rules, directly brushed 500G flow ...... that is a real disaster.
Go check your CDN configuration now. Is there any auto-switching set up? Have the backup nodes been tested? Service provider SLA terms read and understood? These homework usually do not do, the accident can only kneel and beg.
