Ryan Weald's Blog

Caching Responses From Remote APIs

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Dokbot, the project that I am currently working on, utilizes the mendeley API to add citations to posts. To achieve this the application allows users to click an add citation button which brings up a modal view where the user can enter a search term that will be sent off the the mendeley API. To provide the a positive user experience the search form must be highly responsive. This presented a problem because the mendeley API although resonably responsible was not quite snappy enought to provide the UX we were looking for.

To remidy this problem we decided to route the search request through our own application servers. Although at first glance this might appear to be a bad idea as it would increase latency, it turns out it actual decreased the average latency. The cause for this decrease in latency; caching. It turns out that most users enter the same search term almost every time they enter a citation. With this in mind we wrote some code in our application that caches the responses from mendeley API that way for any given search query we only have to make 1 request to the mendeley API. All subsequent requests for the search term will be returned from our application cache rather than a request to the API.

Caching was also a resonable solution for this particular problem because the mendeley search results change very infrequently.

You can see the code below that was used to cache the mendeley API response using whatever cache Rails is configured to use.

The Code

def self.search_mendeley(query=nil)
  raise "no query specified" unless query

  papers = Rails.cache.fetch(query) do |query|
    response = Mendeley::API::Documents.search(query)
    papers = response["documents"][0..5]

  return papers