Difference between revisions of "Varnish"

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(Benchmarks)
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*Apache 2.2 is being used behind Varnish on the same server.
 
*Apache 2.2 is being used behind Varnish on the same server.
 
*Varnish 3.0 using the following settings: VARNISH_STORAGE="malloc,256MB"
 
*Varnish 3.0 using the following settings: VARNISH_STORAGE="malloc,256MB"
*This is on a 1GB Storm instance
+
*This is on a 1GB instance
  
 
Test files:
 
Test files:

Revision as of 17:59, 13 June 2013

Overview

Varnish Cache is a web application accelerator also known as a caching HTTP reverse proxy. You install it in front of any server that speaks HTTP and configure it to cache the contents. Varnish Cache is really, really fast. It typically speeds up delivery with a factor of 300 - 1000x, depending on your architecture. A high level overview of what Varnish does can be seen in the video attached to this web page.

Configuration Files

  • Used for parameters and command line arguments. When you change this, you need to run service varnish restart for the changes to take effect.

Debian based

/etc/default/varnish 

Redhat / CentOS

/etc/sysconfig/varnish


  • This contains your VCL and backend-definitions. After changing this, you can run either service varnish reload, which will not restart Varnish, or you can run service varnish restart, which empties the cache.
/etc/varnish/default.vcl
backend default {
   .host = "localhost";
   .port = "8080";
}
  • A backend server is the server providing the content Varnish will accelerate.

.host = The host that varnish will talk to get content. If this is installed on the same server that Apache is using, this would be localhost or 127.0.0.1. If the Apache server is on another server, you would put in the IP of that server, private network is preferable, but a public IP will work as well.

.port = The port that Varnish will connect to to get content to cache. If Apache is listening on port 80, then you would configure this to listen on port 80. If Apache is listening on port 8080, then you would set this to port 8080.

Main Configuration Options

# # Default address and port to bind to
# # Blank address means all IPv4 and IPv6 interfaces, otherwise specify
# # a host name, an IPv4 dotted quad, or an IPv6 address in brackets.
VARNISH_LISTEN_ADDRESS=
VARNISH_LISTEN_PORT=80

#### I've added this to explain these options a bit more thoroughly. 

VARNISH_LISTEN_ADDRESS= Leaving this blank means that Varnish will listen on all interfaces. You can specify whether or not to listen on a public IP, or private, 
if this is the front end server then you will want this to listen on the public IP.

VARNISH_LISTEN_PORT= The port that Varnish will listen on, you will more than likely want to set this to port 80.

Storage Backends

malloc Varnish will request the entire size of the cache with a malloc call. The OS divides the cache between memory and disk by swapping out what it can't fit into memory.

  • Choose malloc if your cache can fit entirely into RAM.


file Varnish creates a file on the filesystem to contain the entire cache. It then tells the OS via mmap() to map the entire file into memory if possible. This method does not retain data when you stop or start Varnish.

  • Choose file if you have a large cache that will not fit entirely into RAM.

Shared memory log -- Not much needs to be done with this besides making sure the log is stored in RAM (/dev/shm)

Configuration

To configure Varnish using the file backend, do nothing, it's the default. However, you can change the size of RAM to use by changing the "1GB" value to whatever is appropriate.

vim /etc/sysconfig/varnish

# # Cache file location
VARNISH_STORAGE_FILE=/var/lib/varnish/varnish_storage.bin
#
# # Cache file size: in bytes, optionally using k / M / G / T suffix,
# # or in percentage of available disk space using the % suffix.
VARNISH_STORAGE_SIZE=1GB
#
# # Backend storage specification
VARNISH_STORAGE="file,${VARNISH_STORAGE_FILE},${VARNISH_STORAGE_SIZE}"

To configure Varnish to use the malloc backend, you will need to comment out the original VARNISH_STORAGE setting, create a new one, specify "malloc,$size_of_cache"

# # Backend storage specification
#VARNISH_STORAGE="file,${VARNISH_STORAGE_FILE},${VARNISH_STORAGE_SIZE}"
VARNISH_STORAGE="malloc,256MB"

Commands and Arguments

Restart Varnish and clear it's cache

service varnish restart

Reloads the vcl file, the cache is not affected

service varnish reload

Shows the cache status and hit ratio

varnishstat

Command line options.

Listen address
-a <[hostname]:port>

Specifies the vcl file location
-f <filename>

Set the tunable parameters
-p <parameter=value>

Authentication secret for management
-S <secretfile>

Management interface
-T <hostname:port>

Where and how to store objects
-s <storagetype,options>

Troubleshooting

nf_conntrack

If you notice some odd issues with Varnish, check dmesg, if you see this you should raise the limit.

# dmesg
nf_conntrack: table full, dropping packet.
nf_conntrack: table full, dropping packet.
nf_conntrack: table full, dropping packet.

To raise the limit:

#See what the current limit is and note it:
cat /proc/sys/net/nf_conntrack_max

vim /etc/sysctl.conf

#Add the following
net.nf_conntrack_max = 100000

#Once that is added, run this to make the change permanent.
sysctl -p

Benchmarks

Setup

  • Running on CentOS 6
  • Apache 2.2 is being used behind Varnish on the same server.
  • Varnish 3.0 using the following settings: VARNISH_STORAGE="malloc,256MB"
  • This is on a 1GB instance

Test files:

http:///index.html (static, basic html page)
http:///index.php  (phpinfo page)
http:///perl.php   (grabs perl version)

Varnish

10,000 requests, 10 concurrency

ab -n 10000 -c 10 http:///index.html
Document Length:        169 bytes
Time taken for tests:   1.029 seconds
Requests per second:    9716.42 [#/sec] (mean)
Transfer rate:          4725.37 [Kbytes/sec] received

ab -n 10000 -c 10 http:///index.php
Document Length:        44303 bytes
Time taken for tests:   1.202 seconds
Requests per second:    8316.46 [#/sec] (mean)
Transfer rate:          362058.58 [Kbytes/sec] received

ab -n 10000 -c 10 http:///perl.php
Document Length:        237 bytes
Time taken for tests:   1.033 seconds
Requests per second:    9678.93 [#/sec] (mean)
Transfer rate:          4839.45 [Kbytes/sec] received

50,000 requests, 20 concurrency

ab -n 50000 -c 20 http:///index.html
Document Length:        169 bytes
Time taken for tests:   5.176 seconds
Requests per second:    9659.51 [#/sec] (mean)
Transfer rate:          4688.26 [Kbytes/sec] received

ab -n 50000 -c 20 http:///index.php
Document Length:        44303 bytes
Time taken for tests:   6.064 seconds
Requests per second:    8245.66 [#/sec] (mean)
Transfer rate:          358976.27 [Kbytes/sec] received

ab -n 50000 -c 20 http:///perl.php
Document Length:        237 bytes
Time taken for tests:   5.190 seconds
Requests per second:    9633.36 [#/sec] (mean)
Transfer rate:          4816.68 [Kbytes/sec] received

Apache

10,000 requests, 10 concurrency

ab -n 10000 -c 10 http:///index.html
Document Length:        169 bytes
Time taken for tests:   1.416 seconds
Requests per second:    7063.33 [#/sec] (mean)
Transfer rate:          3015.24 [Kbytes/sec] received

ab -n 10000 -c 10 http:///index.php
Document Length:        43540 bytes
Time taken for tests:   6.479 seconds
Requests per second:    1543.56 [#/sec] (mean)
Transfer rate:          65943.43 [Kbytes/sec] received

ab -n 10000 -c 10 http:///perl.php
Document Length:        237 bytes
Time taken for tests:   1.792 seconds
Requests per second:    5578.88 [#/sec] (mean)
Transfer rate:          2344.57 [Kbytes/sec] received

50,000 requests, 20 concurrency

ab -n 50000 -c 20 http:///index.html
Document Length:        169 bytes
Time taken for tests:   7.119 seconds
Requests per second:    7023.53 [#/sec] (mean)
Transfer rate:          2997.59 [Kbytes/sec] received

ab -n 50000 -c 20 http:///index.php
Document Length:        43540 bytes
Time taken for tests:   34.014 seconds
Requests per second:    1470.00 [#/sec] (mean)
Transfer rate:          62750.60 [Kbytes/sec] received

ab -n 50000 -c 20 http:///perl.php
Document Length:        237 bytes
Time taken for tests:   9.256 seconds
Requests per second:    5402.16 [#/sec] (mean)
Transfer rate:          2268.62 [Kbytes/sec] received