Upstream keepalive, Lua resty library keepalive, and Rest api

fc28222 · 2014-05-11T14:17:41+00:00

Hello! On Thu, May 8, 2014 at 8:07 AM, rvsw wrote: > I have been trying to understand the replace_filter code. It seems to follow > the general outlin...

Upstream keepalive, Lua resty library keepalive, and Rest api

fc28222

I am trying to connect to an upstream database which use the http rest api. I am having some confusions concerning keepalive.

I can specify keepalive in upstream like

upstream db {

server 123.0.1.2:8300;

keepalive 36;

}

or in lua resty library like lua-resty-redis and https://github.com/pintsized/lua-resty-http, there is option for keepalive for a connection.

What difference does it make? Should I specified keepalive in both case? Does the upstream database need to support "keepalive" or is it just something enforced on the nginx side?

agentzh

Hello!

On Sat, May 10, 2014 at 11:17 PM, arthurx wrote:
> I am trying to connect to an upstream database which use the http rest api.
> I am having some confusions concerning keepalive.
> I can specify keepalive in upstream like
>
> upstream db {
>   server 123.0.1.2:8300;
>   keepalive 36;
> }
>

I wonder what nginx C module are you using to make use of this named
upstream entity (that is, your "upstream db")? Is it ngx_drizzle, or
ngx_postgres, or ngx_proxy, or ngx_fastcgi?

> or in lua resty library like lua-resty-redis and
> https://github.com/pintsized/lua-resty-http, there is option for keepalive
> for a connection.
>

These lua-resty-* libraries are based on ngx_lua module's cosocket API
(https://github.com/openresty/lua-nginx-module#ngxsockettcp ) and
ngx_lua's cosocket implementation does not make use of nginx core's
ngx_http_upstream facility but does the thing all by itself. So these
two lua-resty-* libraries do not honor any upstream {} configurations
in nginx.conf.

I wonder how you connect lua-resty-* with your "upstream db", will you
provide the core part of your nginx.conf to demonstrate the idea?

> What difference does it make? Should I specified keepalive in both case?
> Does the upstream database need to support "keepalive" or is it just
> something enforced on the  nginx side?
>

I think you have to be more specific here :) Like what kind of
database and how you configure in your nginx.conf. There are just so
many ways of doing things in the nginx world, just like Perl :)

Regards,
-agentzh

lazy.dogtown

hi agentzh,

regarding db-connection, arthurx said:

> upstream database which use the http rest api


so i think this acts like a simple upstream-connections
(/me thinx)


regards,


mex

fc28222

Hello agentzh, Thanks for taking time to answer this even on a Sunday :)

I am actually trying to connect to Elasticsearch, which has endpoint like this

curl -XPOST "http://localhost:9200/sports/athlete/_search"

-d '{ "query":{ "match_all":{} } }'

The upstream blocks I mentioned is just the upstream declaraton in nginx conf

upstream backenddb {
123.0.1.2:9200;
keepalive 36;
}

And in order to access this endpoint in lua, I try to do ngx.location.capture on a location block that use this upstream.

Actually I am trying to debug some occasional lags I am experiencing. There are some lua-resty-http library that has the keep alive options, that's why I am trying to understand if keepalive in both context are relevant or not.

Also I wonder if the backend need to support the keepalive function, maybe some databses or backend servers do not support persistent connection natively?

agentzh於 2014年5月12日星期一UTC+8上午3時12分01秒寫道：

Hello!

On Sat, May 10, 2014 at 11:17 PM, arthurx wrote:
> I am trying to connect to an upstream database which use the http rest api.
> I am having some confusions concerning keepalive.
> I can specify keepalive in upstream like
>
> upstream db {
> server 123.0.1.2:8300;
> keepalive 36;
> }
>

I wonder what nginx C module are you using to make use of this named
upstream entity (that is, your "upstream db")? Is it ngx_drizzle, or
ngx_postgres, or ngx_proxy, or ngx_fastcgi?

> or in lua resty library like lua-resty-redis and
> https://github.com/pintsized/lua-resty-http, there is option for keepalive
> for a connection.
>

These lua-resty-* libraries are based on ngx_lua module's cosocket API
(https://github.com/openresty/lua-nginx-module#ngxsockettcp ) and
ngx_lua's cosocket implementation does not make use of nginx core's
ngx_http_upstream facility but does the thing all by itself. So these
two lua-resty-* libraries do not honor any upstream {} configurations
in nginx.conf.

I wonder how you connect lua-resty-* with your "upstream db", will you
provide the core part of your nginx.conf to demonstrate the idea?

> What difference does it make? Should I specified keepalive in both case?
> Does the upstream database need to support "keepalive" or is it just
> something enforced on the nginx side?
>

I think you have to be more specific here :) Like what kind of
database and how you configure in your nginx.conf. There are just so
many ways of doing things in the nginx world, just like Perl :)

Regards,
-agentzh

agentzh

Hello!

On Mon, May 12, 2014 at 11:07 AM, arthurx wrote:
> I am actually trying to connect to Elasticsearch, which has endpoint like
> this
>
> curl -XPOST "http://localhost:9200/sports/athlete/_search";
> -d '{ "query":{ "match_all":{} } }'
>
> The upstream blocks I mentioned is just the upstream declaraton in nginx
> conf
> upstream backenddb {
>    123.0.1.2:9200;
>     keepalive 36;
> }
>
> And in order to access this endpoint in lua, I try to do
> ngx.location.capture on a location block that use this upstream.

Okay, then you don't need to use lua-resty-http at the same time :)

> Actually I am trying to debug some occasional lags I am experiencing. There
> are some lua-resty-http library that has the keep alive options, that's why
> I am trying to understand if keepalive in both context are relevant or not.
>

Both your nginx upstream module and lua-resty-http library are "TCP
clients". So they offer you the choice to use keepalive connections or
not. It is that simple :)

> Also I wonder if the backend need to support the keepalive function, maybe
> some databses or backend servers do not support persistent connection
> natively?
>

Yes, the backend server may not support (or be configured to support)
TCP connection reuse (that is, keepalive connections). For example,
some http servers are particularly configured to disable HTTP
keep-alive to save server-side resources.

Best regards,
-agentzh