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Global Varnish Cluster with GeoDNS
This document discusses improving website response times through a global Varnish cluster with GeoDNS. It describes setting up Varnish servers in edge locations like Tokyo, California, and Ireland, and using GeoDNS to direct visitors to the nearest cache. Load times dropped significantly, meeting targets of under 3.5 seconds for average 1.5 Mbps connections. CloudFront performed slightly better than Akamai in tests, so it was used for subsequent optimizations. The global Varnish cluster with GeoDNS effectively brought content closer to visitors to reduce network latency and improve site speeds.
Global Varnish Cluster with GeoDNS
- 1. Improving Site ResponseTime Part 2: Global Varnish Cluster with GeoDNS Kim Stefan Lindholm 1 18.2.2012
- 2. SETUP Same components asbefore with following additions/modifications: • Varnish Server: Amazon EC2 Micro Instance (613 MB) • Varnish Monitoring: New Relic, Munin, RevealCloud • Edge Locations: Tokyo, California, Ireland • GeoDNS: EdgeDirector DNS and newly added Google Analytics + New Relic code may slightly affect load times 2
- 3. Front-end optimization canspeed up a website but doesn’t tackle network latency. Content must be brought closer to visitors. 3
- 4. LOAD TIME, BEFORE Target Speed (1.5 Mbps connection) Average: <3.5s 18 s Worst Case: <5s 14 s Worst Case 9s Average 5s Los Angeles São Paulo Stockholm Shanghai Sydney ✘ ✘ ✘ ✘ ✘ 4
- 5. Solution: Set upremote Varnish caches and direct visitors to the nearest one with GeoDNS 5
- 6. Varnish serves filesthat it has previously cached (in its assigned geographic area) Varnish fetches uncached or expired content through Incapsula, never directly from website Incapsula fetches uncached content from origin server(s) If edge server is unresponsive, DNS failover redirects to Incapsula or another Varnish Website Varnish Varnish Varnish Incapsula 6
- 7. LOCAL VS. REMOTEVARNISH • Why would we place a Varnish box in the same region as the website? • Severalcloud application platforms (CloudControl, Heroku, etc.) have Varnish running locally but only default configuration is supported • Incapsula sets cookies but Varnish doesn't serve cached results to sessions with cookies ➔ limited benefits with default settings • We’dlike to see cache hit rates of up to 99.9 % so by manually configuring Varnish we ensure that it actually does its job 7
- 8. LOAD TIME, AFTER Target Speed (1.5 Mbps connection) Dotted line denotes load time before Average: <3.5s 18 s Worst Case: <5s 14 s Worst Case 9s Average 5s Los Angeles São Paulo Stockholm Shanghai Sydney ✔ ✔ ✔ ✔ ✔ 8
- 9. http://royal.pingdom.com/2010/11/12/real-connection-speeds-for-internet-users-across-the-world/ “The average connectionspeed for Internet users worldwide, not just among these 50 countries, but all countries, is an average of 1.8 Mbit/s” We’ll use 1.5 Mbit/s and 5.0 Mbit/s connections in tests that follow 9
- 10. TARGET SPEED, AVERAGE 1.5 Mbps <3.5s 5.0 Mbps <2.5s 10
- 11. 1.5 Mbps AVERAGE, BEFORE CloudFront 4.0 s 3.5 s 2.5 s 3.8 s 4.4 s 2.9 s 2.7 s 3.5 s 6.0 s 4.9 s 3.7 s 4.9 s 5.8 s <3.5s <3.5s <3.5s 5 measurements, >20 min intervals 11 DNS Provider: DNS Made Easy
- 12. 1.5 Mbps AVERAGE, BEFORE Akamai 3.6 s 3.3 s 2.1 s 4.5 s 5.0 s 3.1 s 2.7 s 3.7 s 6.2 s 4.8 s 4.9 s 4.0 s 4.8 s <3.5s <3.5s <3.5s 5 measurements, >20 min intervals 12 DNS Provider: DNS Made Easy
- 13. 1.5 Mbps CDN COMPARISON CloudFront Akamai - 0.4 s - 0.2 s - 0.4 s - 0.7 s - 0.6 s - 0.2 s 0.0 s - 0.2 s - 0.2 s - 0.1 s - 1.2 s - 0.9 s - 1.0 s We’ll be using CloudFront for subsequent tests 5 measurements, >20 min intervals 13 DNS Provider: DNS Made Easy
- 14. 1.5 Mbps AVERAGE, AFTER CloudFront 1.8 s 3.4 s 1.9 s 1.5 s 3.0 s 2.3 s 1.8 s 2.1 s 2.8 s 3.1 s 2.6 s 2.8 s 2.5 s <3.5s <3.5s <3.5s 5 measurements, >20 min intervals 14 DNS Provider: EdgeDirector
- 15. 5.0 Mbps AVERAGE, AFTER CloudFront 1.2 s 2.9 s 1.5 s 2.0 s 2.4 s 1.8 s 1.1 s 1.7 s 2.2 s 2.6 s 1.9 s 2.1 s 2.0 s <2.5s <2.5s <2.5s 5 measurements, >20 min intervals 15 DNS Provider: EdgeDirector
- 16. TARGET SPEED, WORSTCASE 1.5 Mbps <5.0s 5.0 Mbps <4.0s 16
- 17. 1.5 Mbps WORST CASE, BEFORE CloudFront 4.4 s 4.2 s 3.2 s 6.0 s 6.5 s 3.1 s 3.2 s 4.3 s 8.0 s 5.3 s 4.5 s 10.4 s 9.8 s <5.0s <5.0s <5.0s 5 measurements, >20 min intervals 17 DNS Provider: DNS Made Easy
- 18. 1.5 Mbps WORST CASE, AFTER CloudFront 1.9 s 4.0 s 2.2 s 1.6 s 4.6 s 2.3 s 2.1 s 2.7 s 3.6 s 3.6 s 3.2 s 3.9 s 2.8 s <5.0s <5.0s <5.0s 5 measurements, >20 min intervals 18 DNS Provider: EdgeDirector
- 19. 5.0 Mbps WORST CASE, AFTER CloudFront 1.4 s 3.0 s 1.7 s 3.9 s 3.2 s 1.9 s 1.2 s 2.2 s 2.8 s 2.9 s 2.2 s 2.2 s 2.2 s <4.0s <4.0s <4.0s 5 measurements, >20 min intervals 19 DNS Provider: EdgeDirector
- 20. CDN doesn’t guaranteeoptimal delivery locations. Where were assets actually served from? 20
- 21. AKAMAI LOCATIONS Files were loaded from 2 continents CloudFront seems to load all files from Seattle which is just a simple geo-IP lookup issue 21
- 22. How much doesa minimal Varnish cluster cost? 22
- 23. SERVERS VPS /Cloud Server Locations RAM Storage Price/month Linode 512 US, UK, Japan 512 MB 20 GB $19.95 Hetzner VQ 7 Germany 512 MB 20 GB €7.90 Zerigo Linux Denver, CO 512 MB 24 GB $19 Amazon EC2 micro US, EU, Asia, Brazil 613 MB 20 GB (EBS) $16.7 / $20.7 NB 1: Varnish should run on a 64-bit server NB 2: Amazon prices are for California and Tokyo, reserved, heavy utilization, 30 GB traffic 23
- 24. GEODNS Zerigo DNS DNS Made Easy DNS.com EdgeDirector Pro 4 Business + GTD Basic / Pro + Monitoring Monthly Queries 4 million 10 million 5 / 15 million Unlimited $1.5 / monitor + Monthly Price $20 $60 $34.95 $15 / M queries + DNS Failover X Included (3) X Included (1) + DNSSEC X X Included X + Vanity Name Included Included $44.95 X Servers NB: For a small website, EdgeDirector can cost less than $3/month 24
- 25. Without DNS Failover 2x Linode server + Zerigo DNS (1 M queries) = 720 USD (~550 EUR) per year With DNS Failover 2 x Linode server + EdgeDirector (1 M queries) = 690 USD (~530 EUR) per year 25 Rates in February 2012
- 26. LEARNINGS • Varnishmade areal improvement in response time (up to 7 sec) and as it now handles more than 99 % of requests, a website with few DB write operations performs fine even on shared cloud hosting • Varnish boxes don’t scale up automatically but as DNS failover bypasses failed edge servers, this doesn’t seem like a problem • GeoDNS isn’t always necessary for accelerating a website: even one Varnish serving all requests globally will significantly improve performance 26
- 27. LEARNINGS • Amazon micro instance isn’t suitable for production use due to high CPU steal • Setting up Varnish is pretty straightforward, see Part 3 for an example configuration on Amazon EC2 27
- 28. RESOURCES • Cloud & Virtual Private Servers (VPS) • Linode, http://www.linode.com/ • Hetzner, http://www.hetzner.de/hosting/produktmatrix_vserver/vserver-produktmatrix • Zerigo, http://www.zerigo.com/vps-servers • Amazon EC2, http://aws.amazon.com/ec2/ • GeoDNS / Global Server Load Balancing (GSLB) • http://www.zerigo.com/docs/managed-dns/setting_up_geodns • http://help.dnsmadeeasy.com/gtd/configure-gtd-with-dns-failover/ • http://dns.com/Help/#configure • http://edgedirector.com/how/both.htm 28