Connection pool and File handles

Question

We use Retrofit/OkHttp3 for all network traffic from our Android application. So far everything seems to run quite smoothly.

However, we have now occasionally had ou

Answer 1

I am answering my own question here to document this issue we had. It took us a while to figure this out and I think others might encounter this too and might be glad for this answer.

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Our problem was that we created one OkHttpClient per request, as we used it's builder/interceptor API to configure some per-request parameters like HTTP headers or timeouts.

By default each OkHttpClient comes with its own connection pool, which of course blows up the number of connections/threads/file handles and prevents proper reuse in the pool.

Our solution

We solved the problem by manually creating a global ConnectionPool in a singleton, and then passing that to the OkHttpClient.Builder object which build the actual OkHttpClient.

• This still allows for per-request configuration using the OkHttpClient.Builder
• Makes sure all OkHttpClient instances are still using a common connection pool.

We were the able to properly size the global connection pool.