CODEWITHSUNDEEP
okhttp
imb
imb

Reputation: 71

How to close response body without reading the response body in okhttp3

Environment

The environment I'm working on is quite sensitive with the network bandwidth.
Sometimes, I don't need to read all the response body. A part of the response body could be enough to decide a result.

I want to close the response(=response body) without reading the body.

What do I want to do is like below

try (Response response = client.newCall(request).execute()) {
    assertThat(response.code(), is(200))
    // do nothing with the response body
}

But, when the connection is established with HTTP1, the ResponseBody::close invokes Http1ExchangeCodec.FixedLengthSource::close in the end.

Http1ExchangeCodec.FixedLengthSource::close

override fun close() {
    if (closed) return

    if (bytesRemaining != 0L &&
        !discard(ExchangeCodec.DISCARD_STREAM_TIMEOUT_MILLIS, MILLISECONDS)) {
    connection.noNewExchanges() // Unread bytes remain on the stream.
    responseBodyComplete()
    }

    closed = true
}

Then, the discard method reads all the response body source as below.

Util.kt

fun Source.discard(timeout: Int, timeUnit: TimeUnit): Boolean = try {
    this.skipAll(timeout, timeUnit)
} catch (_: IOException) {
    false
}

@Throws(IOException::class)
fun Source.skipAll(duration: Int, timeUnit: TimeUnit): Boolean {
    val nowNs = System.nanoTime()
    val originalDurationNs = if (timeout().hasDeadline()) {
        timeout().deadlineNanoTime() - nowNs
    } else {
        Long.MAX_VALUE
    }
    timeout().deadlineNanoTime(nowNs + minOf(originalDurationNs, timeUnit.toNanos(duration.toLong())))
    return try {
        val skipBuffer = Buffer()
        while (read(skipBuffer, 8192) != -1L) {
            skipBuffer.clear()
        }
        true // Success! The source has been exhausted.
    } catch (_: InterruptedIOException) {
        false // We ran out of time before exhausting the source.
    } finally {
        if (originalDurationNs == Long.MAX_VALUE) {
            timeout().clearDeadline()
        } else {
            timeout().deadlineNanoTime(nowNs + originalDurationNs)
        }
    }
}

It reads all the body and clears buffer. In my case, it's a waste of the CPU time and the network bandwidth.

Is there any way to just close it literally?

Upvotes: 2

Views: 2497

Answers (2)

imb
imb

Reputation: 71

Workaround

Even though I couldn't reuse the connection, I wanted to close connection without reading all the buffer to save network bandwidth and CPU.

To skip the reading all, I tried to change Http1ExchangeCodec.FixedLengthSource's bytesRemaining field to 0. bytesRemaining is set by "Content-Length" response header value.
But, there's no way to change bytesRemaining even if changing the response header with custom interceptor. Because, "Content-Length" is check whne the CallServerInterceptor(the last interceptor of interceptor chains) proceed the request so, bytesRemaining is set by the original response header.

Finally, I found that I can use the timeout deadline of Source. Source.skipAll() can be interrupted belong to timeout deadline. Set the timeout deadline to 0 to ensure timeout always occurs. This makes the connection close literally without reading remaining bytes.

try (Response response = client.newCall(request).execute()) {
    assertThat(response.code(), is(200))
    
    response.body()
        .source()
        .timeout()
        .deadlineNanoTime(0);
    // close without reading remaining bytes
}

Upvotes: 2

Jesse Wilson
Jesse Wilson

Reputation: 40613

No, there's no way to immediately close the response body. If you never issue another HTTP request on that connection it is a waste of bandwidth and CPU. But it is necessary for the connection to be pooled.

Consider using a HEAD method or adding a range header if you're not interested in the response body. That way you're also saving the server’s CPU and bandwidth.

Upvotes: 4

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