OkHttp Interceptors are a fun & powerful way to implement cross-cutting behavior in your app. You can use ’em for authentication, performance, monitoring, and more. There’s even open source interceptors for OAuth signing and curl logging!
Suppose we want to write an interceptor that tracks which activities use the network the most. For each HTTP call we’ll measure how big it is, how long it took, and which activity triggered it:
public final class CallMeasurement {
long requestSize;
long responseSize;
long requestDurationMillis;
long responseDurationMillis;
String activityName;
}
Our interceptor watches all calls & measures them:
public final class MeasuringInterceptor implements Interceptor {
final List<CallMeasurement> measurements = new ArrayList<>();
@Override public Response intercept(Chain chain) {
...
}
}
We have a problem: there’s no obvious way for the interceptor to find out which activity triggered the call. We could cheat by doing pattern matching on the URLs, or by looking at which activity is in the foreground, but both are clumsy and could be unreliable.
It turns out that we can sneak data into an interceptor with a request header! When initiating each request, include a header that contains the data of interest:
Request request = new Request.Builder()
.url("...")
.header(
How your brain works. 
In Terminator, Skynet just launches the nukes. In Daemon, the AI is much better: it uses coercion! 
Feedback loops and failure. 
“I'm gonna have to science the shit out of this.”
