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Shrink the Number of Tiers in a Multitier Architecture From 5 to 2

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Shrink the Number of Tiers in a Multitier Architecture From 5 to 2

I developed an upstream module for NGINX that helped me eliminate a thick bunch of tiers in a multitier architecture. It was so fun that I’ve decided to share my results here.

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I am a contributor to many open-source projects, but one day, I decided to make my life easier by writing some open-source software for a task I needed to personally accomplish. So, I developed an upstream module for NGINX that helped me eliminate a thick bunch of tiers in a multitier architecture. It was such a fun experience that I’ve decided to share my results and publish them here.

Introduction and Theory

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This is what the typical architecture of a microservice looks like. User requests come in through NGINX onto an application server. There is business logic running on the application server that the users interact with.

The application server does not hold any state, so you need to store states somewhere. You can use a database for that. Also, there is a cache to decrease latency and to ensure faster content delivery.

Let’s give definitions to the tiers that are commonly present in an individual microservice:

  1. Tier 1: NGINX

  2. Tier 2: Application server

  3. Tier 3: Cache

  4. Tier 4: Database proxy (you need a proxy in order to secure the fault tolerance of your database and to persist connections to it)

  5. Tier 5: Database server

So, as I mentioned, I was thinking about the five tiers and it occurred to me that I should eliminate some of them.

Why eliminate tiers? I prefer keeping things simple and not having to maintain many different systems in production. Also, fewer tiers mean fewer failure points.

So, I created my Tarantool NGINX upstream module, which helped me reduce the number of tiers down to two.

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Tier 1 is NGINX, and Tiers 2, 3, and 5 are now replaced by Tarantool. Tier 4, the database proxy, is inside NGINX now.

The trick is that Tarantool is a database, a cache, and an application server — all in one. My upstream module is the glue that sticks NGINX and Tarantool together and lets them work without the other three tiers.

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This is what our new microservice looks like. A user sends REST or JSON RPC requests to NGINX with the Tarantool upstream module. This module connects directly to Tarantool, or it can balance the workload among many Tarantool instances. I use a super efficient protocol between NGINX and Tarantool based on MessagePack. You can find more information in this article of mine.

Let’s pause for a minute so you can install everything. I would advise you to install via packages or to use a Docker image (docker pull tarantool/tarantool-nginx).

Docker Images

Sources

Documentation

How to Use the Technologies

Here is an example of an nginx.conf file. As you can see, it uses a regular NGINX upstream parameter. We add a tnt_pass directive telling NGINX that there is a Tarantool upstream in a specified location.

nginx-tnt.conf:

http {
 # upstream
 upstream tnt {
  server 127.0.0.1:3301;
  keepalive 1000;
 }
 server {
  listen 8081;
  # gateway 
  location /api/do {
   tnt_pass_http_request parse_args;
   tnt_pass tnt;
  }
 }
}

So we’ve connected NGINX with Tarantool. What’s the next step? We need to write a function and store it in a file. I’ll call the file app.lua.

-- Bootstrap Tarantool
box.cfg { listen='*:3301' }
-- Grants
box.once('grants', function()
 box.schema.user.grant('guest', 'read,write,execute', 'universe')
end)

-- Global variable
hello_str = 'Hello'
-- function
function api(http_request)
 local str = hello_str
 if http_request.method == 'GET' then
  str = 'Goodbye'
 end
 return 'first', 2, { str .. 'world!' }, http_request.args
end

Taking a closer look at the Lua code we can see:

  • box.cfg {}: This is telling Tarantool to start listening on port 3301 (it can also take other parameters).

  • box.once: This is telling Tarantool to execute a function provided that it has not been executed before.

  • function api(): This is our function, which I’m going to call soon. It is pretty simple, it takes an HTTP request as the first argument and it returns an array of values.

As mentioned, I store the code in a file named app.lua. I can execute it just by starting a Tarantool binary:

$ tarantool app.lua

Let’s call our function by using an HTTP GET request. I use wget for this. By default, wget puts the result into a file. So, I use cat to extract the contents of the file.

$ wget '0.0.0.0:8081/api/do?arg_1=1&arg_2=2'

$ cat do*

{ “id”:0, # — unique identifier of the request
“result”: [ # — is what our Tarantool function returns [“first”], [2], [{
“request”:{“arg_2”:”2",”arg_1":”1"}
“1”:”Goodbye world!”
}]
]}

Benchmarks

The following benchmarks are running with production data.

Input data for the benchmark is a large JSON object. Each object has an average size of 2 KB.

A single server with a 4-core CPU, 90GB RAM, and an OS of Ubuntu 14.04.1 LTS was used.

For this test, we used only one NGINX worker, a round-robin balancer. The worker is balancing the workload for two Tarantool instances and the instances are tied via sharding.

The following charts show us the number of reads per second. The top chart shows latencies (in ms).

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The next group of charts shows the number of writes per second. The top chart shows latencies (in ms).

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Impressive, right?

I hope that you will experiment with Tarantool and my module in order to simplify the architecture of your application. Please visit my module’s GitHub page or the Tarantool Google Group to share your experiences with it.

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Topics:
database ,nginx ,multitier architecture ,tarantool

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