What's the best way to configure LRU cache using open-resty lua scripts in nginx proxy?

erickmgriffin · 2018-07-06T03:58:52+00:00

Actually worked! Thanks. I guess I should've included the paths to libmaxminddb when running openresty ./configure script before, I had to do that to mak...

What's the best way to configure LRU cache using open-resty lua scripts in nginx proxy?

erickmgriffin

I have the stack overflow issue (https://stackoverflow.com/questions/51049811/whats-the-best-way-to-configure-lru-cache-using-open-resty-lua-scripts-in-nginx) open and am wondering how to use this cache. Apparently it can only be used within the context of the single path, which to me is not very useful, though in our particular case this would seem to fix. However, when I try to set the cache up, I see that it get's created on every time the path is called. When I try to isolate the initialization of the cache to an init_by_lua script any variable I try to use to access it loses scope. For those who do not have access to stack overflow I append the question here:

I have one main proxy.template that defines 3 locations, but want to use only one LRU cache for multiple process initialization calls (since they take so long and nothing else, that is why I am using a script). I want to define a variable that can be passed into each location, but am pretty sure I am not doing this correctly. I have:

      #init_by_lua_file $lru_cache /etc/scripts/lua/process_cache.lua;

      location /process {
          access_by_lua_file /etc/scripts/lua/process_access.lua;

          proxy_set_header Content-Type "application/json";
          proxy_set_header Accept "application/json";

          proxy_ssl_server_name      on;

          proxy_pass $target;
      }

      location /process/init {
          set_by_lua_file $lru_cache /etc/scripts/lua/process_cache.lua;

          add_header Access-Control-Expose-Headers set-cookie;
          add_header Access-Control-Allow-Headers set-cookie;

          access_by_lua_file /etc/scripts/lua/process_init.lua;
      }

The process_cache creates the cache (one per proxy startup) and I would like it to be referenced by the process_init.lua and process_access.lua which do different things. For example, process_init is only called once for a UI initialization and establishes the specific cache entries, process_access checks to make sure the entry hasn't expired and if not uses it, otherwise creates a new entry, so that a long call to another server is not needed.

The above would require the lru_cache variable to be passed amongst the two locations. My latest attempts were in the area of trying to place process_cache.lua within the /process/init path, but then it just gets initialized each time, so starting with an empty cache each /process/init call is useless. Thoughts?

jonathan

I typically handle stuff like this with a multi-tier cache--

1. I use a large shared nginx dict cache, which might be populated by being: primed/write-through/read-through, or all of the above.

2. Each worker implements a rather small LRU cache, which utilizes a failover into the shared dict if the entry isn't there.

2b. if the entry isn't in the main dict, there might be a read-through component which populates both the worker and shared caches.

bruce

Hi Erick,

Maybe you can have a look at https://github.com/thibaultcha/lua-resty-mlcache for some idea (or even use it as part of your solution)

HTH

Cheers,

Bruce

On Fri, Jul 6, 2018 at 5:58 AM, Erick Griffin <erickm...@gmail.com> wrote:

I have the stack overflow issue (https://stackoverflow.com/questions/51049811/whats-the-best-way-to-configure-lru-cache-using-open-resty-lua-scripts-in-nginx) open and am wondering how to use this cache. Apparently it can only be used within the context of the single path, which to me is not very useful, though in our particular case this would seem to fix. However, when I try to set the cache up, I see that it get's created on every time the path is called. When I try to isolate the initialization of the cache to an init_by_lua script any variable I try to use to access it loses scope. For those who do not have access to stack overflow I append the question here:

I have one main proxy.template that defines 3 locations, but want to use only one LRU cache for multiple process initialization calls (since they take so long and nothing else, that is why I am using a script). I want to define a variable that can be passed into each location, but am pretty sure I am not doing this correctly. I have:

      #init_by_lua_file $lru_cache /etc/scripts/lua/process_cache.lua;

      location /process {
          access_by_lua_file /etc/scripts/lua/process_access.lua;

          proxy_set_header Content-Type "application/json";
          proxy_set_header Accept "application/json";

          proxy_ssl_server_name      on;

          proxy_pass $target;
      }

      location /process/init {
          set_by_lua_file $lru_cache /etc/scripts/lua/process_cache.lua;

          add_header Access-Control-Expose-Headers set-cookie;
          add_header Access-Control-Allow-Headers set-cookie;

          access_by_lua_file /etc/scripts/lua/process_init.lua;
      }

The process_cache creates the cache (one per proxy startup) and I would like it to be referenced by the process_init.lua and process_access.lua which do different things. For example, process_init is only called once for a UI initialization and establishes the specific cache entries, process_access checks to make sure the entry hasn't expired and if not uses it, otherwise creates a new entry, so that a long call to another server is not needed.

The above would require the lru_cache variable to be passed amongst the two locations. My latest attempts were in the area of trying to place process_cache.lua within the /process/init path, but then it just gets initialized each time, so starting with an empty cache each /process/init call is useless. Thoughts?

.

peter_booth

I have found openresty to be a superb Swiss Army knife for solving gnarly web app issues. I also learned that if I’m trying to solve a problem with openresty feature X and it’s proving to be difficult then I’m probably approaching the problem the wrong way, and I should take a step back and ask “what’s the real requirement?”

Chances are there will be multiple ways to solve the real requirement at multiple levels perhaps with a design that coordinates multiple layers that collectively behave the right way.

Sent from my iPhone

On Jul 5, 2018, at 8:15 PM, Bruce Wang <br...@brucewang.net> wrote:

Hi Erick,

Maybe you can have a look at https://github.com/thibaultcha/lua-resty-mlcache for some idea (or even use it as part of your solution)

HTH

Cheers,
Bruce

On Fri, Jul 6, 2018 at 5:58 AM, Erick Griffin <erickm...@gmail.com> wrote:
I have the stack overflow issue (https://stackoverflow.com/questions/51049811/whats-the-best-way-to-configure-lru-cache-using-open-resty-lua-scripts-in-nginx) open and am wondering how to use this cache. Apparently it can only be used within the context of the single path, which to me is not very useful, though in our particular case this would seem to fix. However, when I try to set the cache up, I see that it get's created on every time the path is called. When I try to isolate the initialization of the cache to an init_by_lua script any variable I try to use to access it loses scope. For those who do not have access to stack overflow I append the question here:

I have one main proxy.template that defines 3 locations, but want to use only one LRU cache for multiple process initialization calls (since they take so long and nothing else, that is why I am using a script). I want to define a variable that can be passed into each location, but am pretty sure I am not doing this correctly. I have:

      #init_by_lua_file $lru_cache /etc/scripts/lua/process_cache.lua;

      location /process {
          access_by_lua_file /etc/scripts/lua/process_access.lua;

          proxy_set_header Content-Type "application/json";
          proxy_set_header Accept "application/json";

          proxy_ssl_server_name      on;

          proxy_pass $target;
      }

      location /process/init {
          set_by_lua_file $lru_cache /etc/scripts/lua/process_cache.lua;

          add_header Access-Control-Expose-Headers set-cookie;
          add_header Access-Control-Allow-Headers set-cookie;

          access_by_lua_file /etc/scripts/lua/process_init.lua;
      }

The process_cache creates the cache (one per proxy startup) and I would like it to be referenced by the process_init.lua and process_access.lua which do different things. For example, process_init is only called once for a UI initialization and establishes the specific cache entries, process_access checks to make sure the entry hasn't expired and if not uses it, otherwise creates a new entry, so that a long call to another server is not needed.

The above would require the lru_cache variable to be passed amongst the two locations. My latest attempts were in the area of trying to place process_cache.lua within the /process/init path, but then it just gets initialized each time, so starting with an empty cache each /process/init call is useless. Thoughts?

.

erickmgriffin

Hi Bruce,

I will take a look at it this morning and let you know, seems promising.

Erick

Am Donnerstag, 5. Juli 2018 20:15:59 UTC-4 schrieb Bruce Wang:

Hi Erick,

Maybe you can have a look at https://github.com/thibaultcha/lua-resty-mlcache for some idea (or even use it as part of your solution)

HTH

Cheers,
Bruce

On Fri, Jul 6, 2018 at 5:58 AM, Erick Griffin <erickm...@gmail.com> wrote:
I have the stack overflow issue (https://stackoverflow.com/questions/51049811/whats-the-best-way-to-configure-lru-cache-using-open-resty-lua-scripts-in-nginx) open and am wondering how to use this cache. Apparently it can only be used within the context of the single path, which to me is not very useful, though in our particular case this would seem to fix. However, when I try to set the cache up, I see that it get's created on every time the path is called. When I try to isolate the initialization of the cache to an init_by_lua script any variable I try to use to access it loses scope. For those who do not have access to stack overflow I append the question here:

I have one main proxy.template that defines 3 locations, but want to use only one LRU cache for multiple process initialization calls (since they take so long and nothing else, that is why I am using a script). I want to define a variable that can be passed into each location, but am pretty sure I am not doing this correctly. I have:

      #init_by_lua_file $lru_cache /etc/scripts/lua/process_cache.lua;

      location /process {
          access_by_lua_file /etc/scripts/lua/process_access.lua;

          proxy_set_header Content-Type "application/json";
          proxy_set_header Accept "application/json";

          proxy_ssl_server_name      on;

          proxy_pass $target;
      }

      location /process/init {
          set_by_lua_file $lru_cache /etc/scripts/lua/process_cache.lua;

          add_header Access-Control-Expose-Headers set-cookie;
          add_header Access-Control-Allow-Headers set-cookie;

          access_by_lua_file /etc/scripts/lua/process_init.lua;
      }

The process_cache creates the cache (one per proxy startup) and I would like it to be referenced by the process_init.lua and process_access.lua which do different things. For example, process_init is only called once for a UI initialization and establishes the specific cache entries, process_access checks to make sure the entry hasn't expired and if not uses it, otherwise creates a new entry, so that a long call to another server is not needed.

The above would require the lru_cache variable to be passed amongst the two locations. My latest attempts were in the area of trying to place process_cache.lua within the /process/init path, but then it just gets initialized each time, so starting with an empty cache each /process/init call is useless. Thoughts?

.