How To Consume Stream HTTP Response In Java? - docker

Question

I'm having trouble trying to consume the Response of an HTTP Endpoint which Streams real-time events continously. It's actually one of Docker's endpoints: https://docs.docker.com/engine/api/v1.40/#operation/SystemEvents
I am using Apache HTTP Client 4.5.5 and it just halts indefinitely when I try to consume the content InputStream:
HttpEntity entity = resp.getEntity();
EntityUtils.consume(entity);//it just hangs here.
//Even if I don't call this method, Apache calls it automatically
//after running all my ResponseHandlers
Apparently, it can be done by using JDK's raw URL: Stream a HTTP response in Java
But I cannot do that since local Docker communicates over a Unix Socket which I only managed to configure in Apache's HTTP Client with a 3rd party library for Unix Sockets in Java.
If there is a smarter HTTP Client library which I could switch to, that would also be an option.
Any ideas would be greatly appreciated. Thank you!

Answer 1

I managed to solve this issue by generating an infinite java.util.stream.Stream of JsonObject from the response InputStream (I know the json reading part is not the most elegant solution but there is no better way with that API and also, Docker doesn't send any separator between the jsons).
final InputStream content = response.getEntity().getContent();
final Stream<JsonObject> stream = Stream.generate(
() -> {
JsonObject read = null;
try {
final byte[] tmp = new byte[4096];
while (content.read(tmp) != -1) {
try {
final JsonReader reader = Json.createReader(
new ByteArrayInputStream(tmp)
);
read = reader.readObject();
break;
} catch (final Exception exception) {
//Couldn't parse byte[] to Json,
//try to read more bytes.
}
}
} catch (final IOException ex) {
throw new IllegalStateException(
"IOException when reading streamed JsonObjects!"
);
}
return read;
}
).onClose(
() -> {
try {
((CloseableHttpResponse) response).close();
} catch (final IOException ex) {
//There is a bug in Apache HTTPClient, when closing
//an infinite InputStream: IOException is thrown
//because the client still tries to read the remainder
// of the closed Stream. We should ignore this case.
}
}
);
return stream;