Finding the length of a strength in an nginx.conf file
-
05-07-2019 - |
Question
I am having a problem with my $memcached_keys being too long in my .conf file for nginx. I am using the memcached module but some of my urls are too long. I am in the process of trying to user MD5 hashes of the urls instead but in the meantime I was just wondering if there was a way I could check on the length of a string stored in a variable.
so:
set $memcached_key "byp-$uri";
if ($args) {
set $memcached_key "byp-$uri?$args";
}
if (len($memcache_key) < 250) {
memcached_pass 127.0.0.1:11211;
error_page 404 = @cache_miss;
error_page 502 = @cache_miss;
}
else {
pass to @cache_miss;
}
Solution
I'm not positive, but I don't think it can be done within the nginx config language. I suspect it would be documented here if it existed, and I don't see anything.
OTHER TIPS
Old question but ....
To do this sort of thing, you need a scripting setup such as the Lua Module:
location / {
set_by_lua $memcached_key '
if not ngx.var.args then
return "byp-" .. ngx.var.uri
else
return "byp-" .. ngx.var.uri .. "?" .. ngx.var.args
end
';
content_by_lua '
local string = string;
if string.len($memcached_key) < 250 then
ngx.exec("/memcached");
else
ngx.exec("/cache_miss");
end
';
}
location /memcached {
internal;
memcached_pass 127.0.0.1:11211;
error_page 404 = /cache_miss;
error_page 502 = /cache_miss;
}
location /cache_miss {
internal;
...
}
Suggest "internal" locations instead of named locations due to a few quirks with the latter but named locations can be used as well.