How to speed up view rendering on rails 5?

Question

I have a Rails 5 app with a model called Sensor Registry.

It currently has about 160,000 records, but I am experiencing extremely low loading times when trying to display this data.

The application is running on a dual core Intel(R) Xeon(R) CPU E5-2670 v3 @ 2.30GHz and 2GB of RAM.

The server logs show the following:

Started GET "/sensor_registries" for 187.220.30.180 at 2017-01-10 23:43:41 +0000

Cannot render console from 187.220.30.180! Allowed networks: 127.0.0.1, ::1, 127.0.0.0/127.255.255.255

ActiveRecord::SchemaMigration Load (1.2ms) SELECT "schema_migrations".* FROM "schema_migrations"

Processing by SensorRegistriesController#index as HTML Rendering sensor_registries/index.html.erb within layouts/application

SensorRegistry Load (604.0ms) SELECT "sensor_registries".* FROM "sensor_registries"

Sensor Load (0.6ms) SELECT "sensors".* FROM "sensors" WHERE "sensors"."id" IN (49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 65, 61, 63, 64, 62)

Rendered sensor_registries/index.html.erb within layouts/application (54663.9ms) Completed 200 OK in 55468ms (Views: 54827.7ms | ActiveRecord: 611.5ms)

I got rid of the N+1 problem, but I'm wondering if there is something more I can do about the database queries.

Anyway the problem seems to be at the moment of rendering the page, it takes about 54 seconds to process it.

Is there a way to optimize CPU usage?

What would be the best solution for speeding up the process and showing the data to the user fast enough?

This is a difficult one to answer without specific knowledge of the application. However, you'll want to profile your action and see where you can improve the slow parts. Tools like NewRelic and RequestProfiler/KCachegrind are useful for this sort of thing. — Chris Heald
i was just wondering why there is a need to show 160k records and how user can view all those records on a page with a huge scroll. — Milind
Usually, this is a code related problem, you should check for n+1 querys being called on view, or repetition of code that could be avoided — ErvalhouS

Glyoko Glyoko · Accepted Answer · 2017-01-11T00:59:09

This certainly doesn't look like a hardware problem, but a problem with implementation. This is impossible to answer perfectly without knowing more about your data structure and architecture, but a few thoughts that may help you track down the problem:

1) How big is the rendered page? Is it possible that the sheer size of the data is what's causing slow rendering times? If this is the problem and the rendered page is just too big, think about paginating the results.

2) How much memory is the ruby process using at any time? When you say, it "has about 160,000 records", I assume you're talking about the sensor_registries table, and I assume the subsequent sensors query with the sensors.id in (...) bit is constructed with some data from the sensor_registries table. If this entire table is loaded up in memory before any further work is done, is it possible that the ruby process is just out of memory?

3) Also, does the entire table really need to be loaded up all at once? You might want to take a look at http://apidock.com/rails/ActiveRecord/Batches/find_in_batches. That method is great for breaking up work that needs to be done on a large table.

4) Even better–and there's really not a better way to put this–rethink your architecture. Loading up a whole table in memory as part of a synchronous request (even a small one) is almost always a no-no. Can you come up with a sql query to get all your needed records without loading the whole table?

5) If you absolutely need the whole table, what about caching the result after a single load? If you expect the result of a query to be the same across requests with identical parameters, could you construct a cache key out of the params, and use that to store the result? At least that way, all requests after the first one will be fast(er).

How to speed up view rendering on rails 5?

3 Answers