Delete NGINX cached items with a PURGE with wildcard support

purge-multi.lua

-- Tit Petric, Monotek d.o.o., Tue 03 Jan 2017 06:54:56 PM CET
--
-- Delete nginx cached assets with a PURGE request against an endpoint
-- supports extended regular expression PURGE requests (/upload/.*)
--

function file_exists(name)
        local f = io.open(name, "r")
        if f~=nil then io.close(f) return true else return false end
end

function explode(d, p)
        local t, ll
        t={}
        ll=0
        if(#p == 1) then return {p} end
                while true do
                        l=string.find(p, d, ll, true) -- find the next d in the string
                        if l~=nil then -- if "not not" found then..
                                table.insert(t, string.sub(p, ll, l-1)) -- Save it in our array.
                                ll=l+1 -- save just after where we found it for searching next time.
                        else
                                table.insert(t, string.sub(p, ll)) -- Save what's left in our array.
                                break -- Break at end, as it should be, according to the lua manual.
                        end
                end
        return t
end

function purge(filename)
        if (file_exists(filename)) then
                os.remove(filename)
        end
end

function trim(s)
        return (string.gsub(s, "^%s*(.-)%s*$", "%1"))
end

function exec(cmd)
        local handle = io.popen(cmd)
        local result = handle:read("*all")
        handle:close()
        return trim(result)
end

function list_files(cache_path, purge_upstream, purge_pattern)
        local result = exec("/usr/bin/find " .. cache_path .. " -type f | /usr/bin/xargs --no-run-if-empty -n1000 /bin/grep -El -m 1 '^KEY: " .. purge_upstream .. purge_pattern .. "' 2>&1")
        if result == "" then
                return {}
        end
        return explode("\n", result)
end

if ngx ~= nil then
        -- list all cached items matching upstream+request_uri (extended regex)
        local files = list_files(ngx.var.lua_purge_path, ngx.var.lua_purge_upstream, ngx.var.request_uri)

        ngx.header["Content-type"] = "text/plain; charset=utf-8"
        ngx.header["X-Purged-Count"] = table.getn(files)
        for k, v in pairs(files) do
                purge(v)
        end
        ngx.say("OK")
        ngx.exit(ngx.OK)
end