Questions tagged [cache]

A location or process for storing of transitory or temporary data in order to improve application or system performance.

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Client-side caching when using CSP with nonces in nginx - how do you use weak caching validators/etags?

I'm using nginx's expires directive; its etag directive as well as the Last-Modified header (if I understand correctly) are on by default. In order to allow specific inline JavaScripts when using ...
Christian's user avatar
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4 votes
7 answers
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Scaling large file downloads?

We currently deliver large (1GB+) files via a single Apache server, but our Apache server is extremely disk-IO-bound and we need to scale. My first idea was to simply duplicate this Apache server, ...
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4 votes
1 answer
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Two separate PHP-FPM sites seem to be using the same code?

I have two websites with two codebases, yet when I change one codebase, I see the change in both. I have two checkouts of the same website. They are set up to use PHP-FPM through Apache2 with FastCGI....
Sander Marechal's user avatar
4 votes
2 answers
26k views

Linux cached memory: Over 85% of cached memory and using swap

I read about Linux and cachd memory at linuxatemyram but there is something that doesn't make sense to me, if the server have even a low load, instead of freeing some cached memory it starts using ...
Kuf's user avatar
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3 answers
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Ignoring GET parameters in Varnish VCL

Okay: I've got a site set up which has some APIs we expose to developers, which are in the format /api/item.xml?type_ids=34,35,37&region_ids=1000002,1000003&key=SOMERANDOMALPHANUM In this ...
JamesHarrison's user avatar
4 votes
5 answers
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SSDs as Linux swap for large virtual mem applications?

This question topically touched on this, but running on 64-bit Linux, I have a set of data caching JVMs as well as wanting a large web cache. Each cache today is configured to in gross fit in system ...
Jé Queue's user avatar
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4 votes
2 answers
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NGINX proxy default cache time with Cache-Control and no expiration

I have caching enabled on an NGINX proxy. As I understand it, as long as I'm not ignoring the Cache-Control header in my proxy configuration (proxy_ignore_headers), the cache time before expiration ...
dlrust's user avatar
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How to configure Varnish not to cache a particular folder?

I would like to set up Varnish as reverse proxy cache for Apache. How can I setup Varnish so that it does not cache content from a particular folder (and its subfolders), let's say /public_html/shop/...
OC2PS's user avatar
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4 votes
3 answers
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Chrome caching 302 redirects

I have a php script with is used to rotate banner images on a site. Under Firefox/IE page refreshes will make another request and a different image will be returned. Under Chrome, the request seems ...
Thermionix's user avatar
4 votes
2 answers
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Wrong DNS answer with CNAME and A Record at the same time

We had a customer which has set a CNAME Record for his domain. Somehow he managed it to set an A Record too, which should be not possible and is forbidden by DNS. But the result was: $ dig @ns1.your-...
Janning's user avatar
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Statically mirroring a heavy trafficked site, CloudFlare as DNS

I run a fairly heavy trafficked website and due to some unfortunate incidents the machines that are in my cloud at Linode went down. And I have only a single Load Balancer machine exposed to the ...
Quintin Par's user avatar
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3 answers
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Nginx -- disable aggressive caching for Wordpress admin areas

I have a fully Nginx install now, with PHP-FPM. Coming from a world of Apache with Nginx proxying in front. It seems Nginx has its own moody caching, very aggressive. There are a few layers of ...
PKHunter's user avatar
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4 votes
2 answers
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How to whitelist Authorization header in CloudFront custom Origin Request Policy?

I have created the following CloudFront Origin Request Policy: I need Authorization header (without Authorization header the AntiForgeryToken header is not forwarded) but I do not understand why ...
Hooman Bahreini's user avatar
4 votes
2 answers
6k views

LVM cache in writeback mode is equivalent to external ext4 journal?

I am running ext4 filesystems on LVM. The two big speedup options I'm looking at are, LVM cache and the external ext4 journal. It sounds like if I'm using a single SSD for this, LVM cache in ...
RobC's user avatar
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2 answers
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Why is Varnish not caching?

I am troubleshooting the setup of Varnish 3.x on my Ubuntu server. I'm running Drupal 7 on two sites set up on the box, via named-based vhosts. Before trying to get Varnish to play nice with Drupal I'...
Justin's user avatar
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3 answers
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File change on a LAMP development server not taken into account

I set up a small LAMP virtual machine for PHP development. It works fine, excepted that when an image which has already been served is modified on disk, then requested again, the "old" image is still ...
oparisy's user avatar
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3 answers
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What's a good resource for learning about scaling PHP applications?

I know PHP fairly well. But one aspect of PHP which I am fairly green in is caching, loading balancing etc. A lot of companies hiring PHP developers are looking for these high-use background, which I'...
qodeninja's user avatar
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4 votes
2 answers
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DL380p G8 SSD cache

I have HP DL380p G8 with smart array P421i. I would like to use SSD cache for my HDDs RAID 10 volume. I got know I have to buy a SmartCache license for the array and I found some weird info about the ...
Garen's user avatar
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4 votes
2 answers
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How does Windows write cache work with mounted VHDs?

Suppose I have a VHD residing on Disk A mounted on a Windows Server 2016. If I turn write caching on for Disk A and the VHD, do I have double write caching? If yes, is this recommended? If it is ...
RJ-'s user avatar
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4 votes
2 answers
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Force browser to empty DNS cache

So I migrated a mediawiki site to a new Server. The old one is still up but the database is locked and I merge the new Content with rsync and mysqldump every 15 min. So we can read the content from ...
Finn's user avatar
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4 votes
1 answer
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NGINX cache error: conflicts with already declared size 0 in /etc/nginx/nginx.conf

My current nginx for drupal config gives following error. Somehow, I am not able to enable nginx cache. Tried different config but overtime i get the same error. Can anyone help please? nginx: [emerg]...
Tapash's user avatar
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4 votes
2 answers
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Is this a case of a stale ISP DNS cache or did I fudge something up?

I am currently in the process of transferring a legacy website (from a legacy hosting service provider) to a modern solution. Due to my context-specific requirements (which include financial ...
dvijayak's user avatar
4 votes
1 answer
7k views

What is the maximum file size that will be cached by a browser? [closed]

What is the maximum file size that will be cached by a browser? Note that I don't mean the maximum size of the browser cache. I mean, what is the maximum individual file that will be cached. If ...
paleozogt's user avatar
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4 votes
1 answer
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Data syncing behavior for filesystems in Windows

In Linux mounting supports commit option, which is described in mount(8) man page as: commit=nrsec Sync all data and metadata every nrsec seconds. The default value is 5 seconds. Zero ...
przemoc's user avatar
  • 141
4 votes
1 answer
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Caching large amounts of data

We need to cache all psd/zip files from our amazone S3 storage. The amount of the cache between 150-200 Gb (we need to store files at least 2 month). Now we use transparent proxy squid without any ...
ALex_hha's user avatar
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4 votes
2 answers
2k views

Can varnish cache files without specific extension or residing in specific directory

I have a varnish installation to cache (MANY) images that my service serves. It is about 200 images of around 4k per second and varnish happily serves them according to the following rule: if (req....
pataroulis's user avatar
4 votes
2 answers
5k views

Howto prevent snmpd cache results from extend script

On my freebsd box i have snmpd daemon from net-snmp-5.5_4 packet. In snmpd.conf file i have: extend .1.3.6.1.4.1.2021.2 inpt /usr/bin/perl /usr/local/etc/snmp/mpdinput.pl where mpdinput.pl my ...
Korjavin Ivan's user avatar
4 votes
2 answers
3k views

Apache web server intermittently serves 403: "Directory index forbidden by Options directive" and 304

We have configured a web site with SSI for .html files on Apache/2.2.19 on CentOS 5.5 Linux. Works OK, but occasionally get 403 for the root page (index.html served as a directory index). No file ...
Duncan Harris's user avatar
4 votes
1 answer
3k views

Varnish doesn't seem to be caching

I've setup a Varnish cache mirror to sit in front of a file server, but it seems to be endlessly re-downloading data from my file server. There's about 100GB of data in total, but so far Varnish has ...
anonymous coward's user avatar
4 votes
1 answer
2k views

How do Proxies handle ETags?

I use ETags to improve performance. I decided to use an Etag that is valid on Server, Client and Proxy. But how is this handled if the proxy has saved the ETag? Does the Proxy still ask the website ...
user avatar
4 votes
1 answer
368 views

Does the SOA serial have importance when it comes to ISP caching nameservers?

Lets say I forget to update the SOA serial when updating the zonefile. Of course, this means any slaves will not sync to the master because it thinks no change has been done. The question I have, is, ...
sebastian nielsen's user avatar
4 votes
1 answer
2k views

Growing OS cache in RAM causing high system CPU usage

I'm having a weird issue with a server that I've never seen before. On a machine with ~30G of RAM with an application that takes ~10G (spread across hundreds of processes). Over time the OS starts to ...
mpeters's user avatar
  • 233
4 votes
1 answer
786 views

What is the difference between a web cache and a hierarchial cache server?

I'm trying to make sense of how to set up the simplest possible thing that could actually work at my office where we host events and have lots of people coming, potentially everyone downloading the ...
Henrik's user avatar
  • 386
4 votes
2 answers
4k views

File Specific cache http header for IIS 6

Is there a way to set cache related header for a specific file type in II6? We want to turn off cache on all our *.js and *.css file here, but IIS6 is forcing us to do a all or nothing approach.
user avatar
4 votes
1 answer
3k views

How to create a CSP nonce and yet continue website caching?

I am not getting any response to any way I try to phrase this question, so I keep trying. I feel I've got to be missing something, but I've searched and searched. Why isn't it obvious? Why is it so ...
jamminjames's user avatar
4 votes
1 answer
6k views

How to Cache SSL Data with Squid

What I want to do: My goal here is to cache data being transmitted over SSL with Squid - not just data transmitted over Http. Users should not be bothered with SSL certificate errors on every Https ...
Jaxian's user avatar
  • 169
4 votes
2 answers
4k views

LVM Raid 1 + SSD Caching

I have three disks: /dev/sda slow hdd /dev/sdb slow hdd /dev/sdc fast ssd /dev/vg0 volume group consisting /dev/sd{a,b,c} Each logical volume (lv) should be raid1 mirrored and ssd cached. With the ...
user1091344's user avatar
4 votes
1 answer
7k views

Nginx: using X-Accel-Expires with Cache-Control

I'm using Nginx as a caching proxy server. I have problems with caching responses using both X-Accel-Expires and Cache-Control headers. My upstream returns some request body with headers to nginx: [....
Tereska's user avatar
  • 143
4 votes
2 answers
393 views

Mirror/Cache Websites on a Mobile Server

I have been asked to determine the feasibility of mirroring or caching websites on a mobile server on a train. Unfortunately, this has been dropped on me at the last minute and I have to come up with ...
John Judd's user avatar
  • 173
4 votes
1 answer
903 views

Does fsfreeze flush FS caches?

If I run fsfreeze on a mounted filesystem, it will not be possible to perform new "write" operations on that FS until it is unfrozen, and "ongoing" writes should "complete". Now, will fsfreeze also ...
Bruno Reis's user avatar
4 votes
2 answers
5k views

How do I set nginx's cache files to file permissions 777?

I'm trying to write a process that invalidates the cache on nginx (and doesn't re-warm the cache). By default, nginx has 700 on its cache files. The closest setting that I could find was: ...
Homer6's user avatar
  • 221
4 votes
4 answers
3k views

Is it possible to cache subversion?

Is it possible to cache subversion at all? May be any commercial solution? Any help would by highly appreciated.
ALex_hha's user avatar
  • 7,303
4 votes
3 answers
5k views

nginx not returning 304 on cached content

I'm using nginx as a reverse proxy with an Apache back-end handling some PHP files. The files return the right expiry headers and proxy_cache does a good job of caching them, but I've noticed that ...
Don H's user avatar
  • 147
4 votes
2 answers
7k views

CloudFront with Custom Origin and ELB

We are using CloudFront for our static assets but also wanted to allow for Gzip. We set up a new distribution with a custom origin pointing back to our application servers which are behind a elastic ...
kmfk's user avatar
  • 161
4 votes
1 answer
431 views

Combining Heroku with custom external services (e. g. Varnish or Postgres on EC2)

I'm planning to set up a Django site on Heroku. It will run on Heroku's Cedar stack, which allows Python apps, but doesn't include or support HTTP upstream caching with Varnish like the other stacks ...
mkai's user avatar
  • 43
4 votes
2 answers
1k views

ratelimit POST requests

I'm running a large WordPress multiuser site. I have a varnish cache in front of the WordPress application server. As it makes no sense to cache POST requests, I am vulnerable to DDoS using lots of ...
Tonny Jørgensen's user avatar
4 votes
1 answer
2k views

How to utilize Varnish for A/B Testing and Feature Rollout?

Today we have our web layer exposed to the world. We would like to add Varnish in front of our web layer to accelerate the site and reduce calls to the backend. However, we have some concerns and i ...
Ken's user avatar
  • 181
4 votes
3 answers
7k views

Clear browser local cache by sending http headers?

I have modified js and css files in my website. But browser still fetch the contents from local cache because browser has stored it. I want to fetch the fresh content from the server without clearing ...
linux404's user avatar
  • 173
4 votes
1 answer
5k views

Problems on mounted NFS: 'No such file or directory' but files and directories exist

So we are having a medium-sized NFS4 storage server running CentOS 6.6 exporting an NFS share /storageDat (which is the NFS root, with two RAID volumes bound in there: ./dat1 and ./dat2); Export ...
Mone's user avatar
  • 41
4 votes
2 answers
2k views

Nginx Reverse Proxy : post_action if proxy cache hit - Possbile?

We have recently found out about nginxes post_action. We were wondering it there was a way to use this directive if a proxy cache hit is made? The flow we were hoping on is as follows: 1) User ...
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