RandomDisasterInterceptor.java

package com.smartthings.android.common.http;

import com.inkapplications.preferences.IntPreference;
import com.smartthings.android.di.annotation.HttpDisasterRate;
import com.squareup.okhttp.Interceptor;
import com.squareup.okhttp.Protocol;
import com.squareup.okhttp.MediaType;
import com.squareup.okhttp.Response;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.ResponseBody;

import javax.inject.Inject;
import javax.inject.Singleton;
import java.io.IOException;
import java.util.Random;

/**
 * Causes HTTP requests to fail with a 500 error randomly.
 *
 * This is an OkHTTP interceptor that will return fake 500 responses for http
 * requests based on a random chance constrained to a failure rate.
 * Ex. If the failure rate is set to 100% then ALL requests will fail. However,
 * if the rate is set to 20% then the requests will fail 20% of the time.
 *
 * This is intended to be enabled during debug builds in order to test how the
 * app responds to server outages.
 */
public class RandomDisasters implements Interceptor {
    private int failureRate;
    private Random random = new Random();

    public RandomDisasters(int failureRate) {
        this.failureRate = failureRate;
    }

    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        if (getRandomPercent() < failureRate) {
            chain.proceed(request); // throw this away.
            return this.createFailedRequest(request);
        }

        return chain.proceed(request);
    }

    /**
     * Create a fake "internal server error" response to return to the client.
     */
    private Response createFailedRequest(Request request) {
        Response.Builder responseBuilder = new Response.Builder();
        responseBuilder.code(500);
        responseBuilder.request(request);
        responseBuilder.protocol(Protocol.HTTP_1_1);
        responseBuilder.message("Fake failure for request " + request.urlString());
        responseBuilder.body(ResponseBody.create(MediaType.parse("text"), "Fake Failure"));

        return responseBuilder.build();
    }

    /**
     * Get a random number between 0 and 100 in order to determin if the request
     * should fail.
     */
    private int getRandomPercent() {
        int max = 100;
        int min = 0;
        return this.random.nextInt((max - min) + 1) + min;
    }
}