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https://github.com/hamishforbes/lua-resty-dns-cache
Cache wrapper for lua-resty-dns
https://github.com/hamishforbes/lua-resty-dns-cache
Last synced: about 1 month ago
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Cache wrapper for lua-resty-dns
- Host: GitHub
- URL: https://github.com/hamishforbes/lua-resty-dns-cache
- Owner: hamishforbes
- License: mit
- Created: 2015-06-04T14:49:40.000Z (over 9 years ago)
- Default Branch: master
- Last Pushed: 2017-04-19T13:32:59.000Z (over 7 years ago)
- Last Synced: 2024-08-03T18:22:24.176Z (3 months ago)
- Language: Perl
- Size: 22.5 KB
- Stars: 10
- Watchers: 2
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE.txt
Awesome Lists containing this project
- awesome-nginx - lua-resty-dns-cache - Cache wrapper for lua-resty-dns. (Rust Modules / Lua Modules)
README
# lua-resty-dns-cache
A wrapper for [lua-resty-dns](https://github.com/openresty/lua-resty-dns) to cache responses based on record TTLs.
Uses [lua-resty-lrucache](https://github.com/openresty/lua-resty-lrucache) and [ngx.shared.DICT](https://github.com/openresty/lua-nginx-module#ngxshareddict) to provide a 2 level cache.
Can repopulate cache in the background while returning stale answers.
# Overview
```lua
lua_shared_dict dns_cache 1m;
init_by_lua '
require("resty.dns.cache").init_cache(200)
';
server {
listen 80;
server_name dns_cache;
location / {
content_by_lua '
local DNS_Cache = require("resty.dns.cache")
local dns = DNS_Cache.new({
dict = "dns_cache",
negative_ttl = 30,
max_stale = 300,
resolver = {
nameservers = {"123.123.123.123"}
}
})
local host = ngx.req.get_uri_args()["host"] or "www.google.com"
local answer, err, stale = dns:query(host)
if err then
if stale then
ngx.header["Warning"] = "110: Response is stale"
answer = stale
ngx.log(ngx.ERR, err)
else
ngx.status = 500
ngx.say(err)
return ngx.exit(ngx.status)
end
end
local cjson = require "cjson"
ngx.say(cjson.encode(answer))
';
}
}
```
# Methods
### init_cache
`syntax: ok, err = dns_cache.init_cache(max_items?)`
Creates a global lrucache object for caching responses.
Accepts an optional `max_items` argument, defaults to 200 entries.
Calling this repeatedly will reset the LRU cache
### initted
`syntax: ok = dns_cache.initted()`
Returns `true` if LRU Cache has been initialised
### new
`syntax: ok, err = dns_cache.new(opts)`
Returns a new DNS cache instance. Returns `nil` and a string on error
Accepts a table of options, if no shared dictionary is provided only lrucache is used.
* `dict` - Name of the [ngx.shared.DICT](https://github.com/openresty/lua-nginx-module#ngxshareddict) to use for cache.
* `resolver` - Table of options passed to [lua-resty-dns](https://github.com/openresty/lua-resty-dns#new). Defaults to using Google DNS.
* `normalise_ttl` - Boolean. Reduces TTL in cached answers to account for cached time. Defaults to `true`.
* `negative_ttl` - Time in seconds to cache negative / error responses. `nil` or `false` disables caching negative responses. Defaults to `false`
* `minimise_ttl` - Boolean. Set cache TTL based on the shortest DNS TTL in all responses rather than the first response. Defaults to `false`
* `max_stale` - Number of seconds past expiry to return stale content rather than querying. Stale hits will trigger a non-blocking background query to repopulate cache.
### query
`syntax: answers, err, stale = c:query(name, opts?)`
Passes through to lua-resty-dns' [query](https://github.com/openresty/lua-resty-dns#query) method.
Returns an extra `stale` variable containing stale data if a resolver cannot be contacted.
### tcp_query
`syntax: answers, err, stale = c:tcp_query(name, opts?)`
Passes through to lua-resty-dns' [tcp_query](https://github.com/openresty/lua-resty-dns#tcp_query) method.
Returns an extra `stale` variable containing stale data if a resolver cannot be contacted.
### set_timeout
`syntax: c:set_timeout(time)`
Passes through to lua-resty-dns' [set_timeout](https://github.com/openresty/lua-resty-dns#set_timeout) method.
## Constants
lua-resty-dns' [constants](https://github.com/openresty/lua-resty-dns#constants) are accessible on the `resty.dns.cache` object too.
## TODO
* Cap'n'proto serialisation