Non Blocking I/O for Everyone with RxJava
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The document discusses the complexities and challenges of writing non-blocking code in comparison to traditional blocking code, emphasizing the performance and efficiency advantages of non-blocking I/O in programming. It covers various programming techniques and frameworks, such as RxJava, and contrasts them with blocking methods, while supporting its points with code examples. Additionally, it addresses issues like back pressure, error handling, and the future inevitability of adopting non-blocking approaches in software development.
![A Blocking Echo Servlet 32
public class BlockingServlet extends HttpServlet {
private static final int BUFFER_SIZE = 1024;
protected void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
byte[] buffer = new byte[BUFFER_SIZE];
while (true) {
int read = request.getInputStream().read(buffer, 0, BUFFER_SIZE);
if (read < 0)
break;
response.getOutputStream().write(buffer, 0, read);
}
}
}](https://image.slidesharecdn.com/nonblockingforeveryone-170303121254/85/Non-Blocking-I-O-for-Everyone-with-RxJava-32-320.jpg)
![A Non Blocking Echo Servlet 33
public class NonBlockingServlet extends HttpServlet {
private static final int BUFFER_SIZE = 1024;
@Override
protected void service(HttpServletRequest request, HttpServletResponse
response) throws ServletException, IOException
{
AsyncContext asyncContext = request.startAsync(request, response);
asyncContext.setTimeout(0);
Echoer echoer = new Echoer(asyncContext);
request.getInputStream().setReadListener(echoer);
response.getOutputStream().setWriteListener(echoer);
}
private class Echoer implements ReadListener, WriteListener
{
private final byte[] buffer = new byte[BUFFER_SIZE];
private final AsyncContext asyncContext;
private final ServletInputStream input;
private final ServletOutputStream output;
private boolean complete;
private Echoer(AsyncContext asyncContext) throws IOException
{
this.asyncContext = asyncContext;
this.input = asyncContext.getRequest().getInputStream();
this.output = asyncContext.getResponse().getOutputStream();
}
@Override
public void onDataAvailable() throws IOException
{
while (input.isReady())
{
int read = input.read(buffer);
output.write(buffer, 0, read);
if (!output.isReady())
return;
}
if (input.isFinished())
{
complete = true;
asyncContext.complete();
}
}
@Override
public void onAllDataRead() throws IOException {}
@Override
public void onWritePossible() throws IOException
{
if (input.isFinished())
{
if (!complete)
asyncContext.complete();
}
else
{
onDataAvailable();
}
}
@Override
public void onError(Throwable failure)
{
failure.printStackTrace();
}
}
}](https://image.slidesharecdn.com/nonblockingforeveryone-170303121254/85/Non-Blocking-I-O-for-Everyone-with-RxJava-33-320.jpg)
![Maybe something simpler 34
protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
AsyncContext asyncContext = request.startAsync(request, response);
final ServletOutputStream out = resp.getOutputStream();
final byte[] buf = new byte[1024];
final FileInputStream file = …;
out.setWriteListener(new WriteListener() {
@Override
public void onWritePossible() throws IOException {
while(out.isReady()) {
int len = file.read(buf);
if(len<0) {
return;
}
out.write(buf, 0, len);
}
}
});
}](https://image.slidesharecdn.com/nonblockingforeveryone-170303121254/85/Non-Blocking-I-O-for-Everyone-with-RxJava-34-320.jpg)
![static Observable<byte[]> createSourceObservable(HttpServletRequest req);
static Subscriber<byte[]> createSink(HttpServletResponse resp);
protected void doPost(HttpServletRequest req, final HttpServletResponse resp) {
createSourceObservable(req)
.subscribe(createSink(resp));
}
RxJava Quick Intro](https://image.slidesharecdn.com/nonblockingforeveryone-170303121254/85/Non-Blocking-I-O-for-Everyone-with-RxJava-48-320.jpg)
![A Blocking Echo Servlet 60
public class BlockingServlet extends HttpServlet {
private static final int BUFFER_SIZE = 1024;
protected void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
byte[] buffer = new byte[BUFFER_SIZE];
while (true) {
int read = request.getInputStream().read(buffer, 0, BUFFER_SIZE);
if (read < 0)
break;
response.getOutputStream().write(buffer, 0, read);
}
}
}](https://image.slidesharecdn.com/nonblockingforeveryone-170303121254/85/Non-Blocking-I-O-for-Everyone-with-RxJava-60-320.jpg)
Non Blocking I/O for Everyone with RxJava
- 6. 8 - 24 minute delay
- 7. ± 30 min. round trip
- 8. Web • DNS • Redirect • Download HTML • Download CSS + JS + Images • Download more CSS + JS + Images • ….
- 9. Ordering a pizza • Several hours per page • About 8 pages per order
- 18. • Connect TCP • Encryption handshake • Push request data through socket • … wait … • Pull data from the socket • Assemble and return the result
- 20. Blink of an eye 100ms
- 21. Time Network latency: milliseconds Application instruction: microseconds Hardware instructions: nanoseconds
- 23. =
- 24. #WRONG
- 26. Non Blocking For Everyone with RxJava @lyaruu Frank Lyaruu CTO Dexels
- 27. Non Blocking in Action 27 https://webtide.com/async-rest
- 28. So why are we still writing blocking code? ! It works pretty well in monoliths ! CPU and memory is cheap ! Networks are reliable and fast ! Writing non blocking code is hard 28
- 29. Writing non blocking code is rough 29
- 30. Servlet API 30
- 31. Non Blocking I/O Servlet API 3.1 31
- 32. A Blocking Echo Servlet 32 public class BlockingServlet extends HttpServlet { private static final int BUFFER_SIZE = 1024; protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { byte[] buffer = new byte[BUFFER_SIZE]; while (true) { int read = request.getInputStream().read(buffer, 0, BUFFER_SIZE); if (read < 0) break; response.getOutputStream().write(buffer, 0, read); } } }
- 33. A Non Blocking Echo Servlet 33 public class NonBlockingServlet extends HttpServlet { private static final int BUFFER_SIZE = 1024; @Override protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { AsyncContext asyncContext = request.startAsync(request, response); asyncContext.setTimeout(0); Echoer echoer = new Echoer(asyncContext); request.getInputStream().setReadListener(echoer); response.getOutputStream().setWriteListener(echoer); } private class Echoer implements ReadListener, WriteListener { private final byte[] buffer = new byte[BUFFER_SIZE]; private final AsyncContext asyncContext; private final ServletInputStream input; private final ServletOutputStream output; private boolean complete; private Echoer(AsyncContext asyncContext) throws IOException { this.asyncContext = asyncContext; this.input = asyncContext.getRequest().getInputStream(); this.output = asyncContext.getResponse().getOutputStream(); } @Override public void onDataAvailable() throws IOException { while (input.isReady()) { int read = input.read(buffer); output.write(buffer, 0, read); if (!output.isReady()) return; } if (input.isFinished()) { complete = true; asyncContext.complete(); } } @Override public void onAllDataRead() throws IOException {} @Override public void onWritePossible() throws IOException { if (input.isFinished()) { if (!complete) asyncContext.complete(); } else { onDataAvailable(); } } @Override public void onError(Throwable failure) { failure.printStackTrace(); } } }
- 34. Maybe something simpler 34 protected void doGet(HttpServletRequest req, HttpServletResponse resp) { AsyncContext asyncContext = request.startAsync(request, response); final ServletOutputStream out = resp.getOutputStream(); final byte[] buf = new byte[1024]; final FileInputStream file = …; out.setWriteListener(new WriteListener() { @Override public void onWritePossible() throws IOException { while(out.isReady()) { int len = file.read(buf); if(len<0) { return; } out.write(buf, 0, len); } } }); }
- 35. 35 Bob
- 36. 36 Developer
- 37. Node.js 37 var server = http.createServer(function (req, res) { req.pipe(res); });
- 38. Node.js 38 var server = http.createServer(function (req, res) { req.pipe(res); });
- 39. A pipe… 39
- 42. Observable<T> 42 Will push zero or more items of type T Followed by a ‘completed’ message (or an error…)
- 43. RxJava Quick Intro 43 Observable.<String>just("Ouagadougou","Dakar","Accra","Rabat") .subscribe(item->System.err.println(item)); Ouagadougou Dakar Accra Rabat
- 44. RxJava Quick Intro 44 Observable.range(0, 1000) .subscribe(item->System.err.println(item)); 0 1 2 3 4 5 6 … 998 999
- 45. RxJava Quick Intro 45 Observable.range(0, 1000) .skip(10) .take(10) .subscribe(item->System.err.println(item)); 10 11 12 13 14 15 16 17 18 19
- 46. RxJava Quick Intro 46 Bytes.fromFile("citiesafrica.xml") .lift(XML.parse()) .subscribe(item->System.err.println(item)); <cities> <africa> <city name="Lusaka"/> <city name="Harare"/> <city name="Kigali"/> </africa> </cities> START_DOCUMENT START_ELEMENT cities {} START_ELEMENT africa {} START_ELEMENT city {name=Lusaka} END_ELEMENT city START_ELEMENT city {name=Harare} END_ELEMENT city START_ELEMENT city {name=Kigali} END_ELEMENT city END_ELEMENT africa END_ELEMENT cities END_DOCUMENT
- 47. RxJava Quick Intro 47 Bytes.fromFile("citiesafrica.xml") .lift(XML.parse()) .filter(e->e.getType()==XmlEventTypes.START_ELEMENT) .map(e->e.getAttributes().get("name")) .subscribe(item->System.err.println(item)); <cities> <africa> <city name="Lusaka"/> <city name="Harare"/> <city name="Kigali"/> </africa> </cities> Lusaka Harare Kigali
- 48. static Observable<byte[]> createSourceObservable(HttpServletRequest req); static Subscriber<byte[]> createSink(HttpServletResponse resp); protected void doPost(HttpServletRequest req, final HttpServletResponse resp) { createSourceObservable(req) .subscribe(createSink(resp)); } RxJava Quick Intro
- 50. A Blocking API public static Double temperatureInCity(String city) { return Double.parseDouble(HTTPClient .get("http://api.weather.org/weather?q="+city) .toXml() .getContent("temperature")); } For consumers: Double temperature = temperatureInCity("Tripoli");
- 51. Convert to Reactive public Observable<Double> temperatureInCity(String city) { return Observable.just( Double.parseDouble(HTTPClient .get("http://api.weather.org/weather?q="+city) .toXml() .getContent("temperature") )); }
- 53. Sort of… Double temp = temperatureInCity(“Cairo”).blockingFirst(); updateTemperatureUI(temp); This code is still just as blocking But now the consumer and producer have independent threading
- 54. Use a Non Blocking HTTP Client public static Observable<Double> temperatureInCity(String city) { return HTTP.get("http://api.weather.org/weather?q="+city) .subscribeOn(Schedulers.io()) .lift(XML.parse()) .filter(e->e.getType()==XmlEventTypes.START_ELEMENT) .filter(e->e.getText().equals("temperature")) .first() .map(xml->Double.parseDouble(xml.getAttributes().get("value"))); }
- 55. Add a Cache public Observable<Double> temperatureInCity(String city) { Double temperature = temperatureCache.get(city); if(temperature!=null) { return Observable.just(temperature); } return HTTP.get("http://api.weather.org/weather?q="+city) .subscribeOn(Schedulers.io()) .lift(XML.parse()) .filter(e->e.getType()==XmlEventTypes.START_ELEMENT) .filter(e->e.getText().equals("temperature")) .first() .map(xml->Double.parseDouble(xml.getAttributes().get("value"))) .doOnNext(temperature->temperatureCache.put(city,temperature)); }
- 56. Non Blocking Client Blocking: Double temp = temperatureInCity(“Cairo").toBlocking().first(); updateTemperatureUI(temp); Non blocking: temperatureInCity(“Nairobi”) .observeOn(UISchedulers.uiThread()) .subscribe(d->updateTemperatureUI(d));
- 57. Challenges 57
- 58. Back pressure 58
- 60. A Blocking Echo Servlet 60 public class BlockingServlet extends HttpServlet { private static final int BUFFER_SIZE = 1024; protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { byte[] buffer = new byte[BUFFER_SIZE]; while (true) { int read = request.getInputStream().read(buffer, 0, BUFFER_SIZE); if (read < 0) break; response.getOutputStream().write(buffer, 0, read); } } }
- 61. Back pressure 61 ! Observable: No back pressure ! Flowable: Back pressure
- 62. RxJava back pressure 62 Bytes.fromNetwork(“something_huge.xml”) .lift(XML.parse()) .filter(e->e.getType()==XmlEventTypes.START_ELEMENT) .map(e->e.getAttributes().get("name")) .subscribe(item->doSomethingComplicated(item));
- 65. Memory Consumption 65 ! Much better ! … or much worse
- 66. Error Handling 66 ! Some patterns don’t work any more ! Requires some thought
- 67. Error handling 67 Servlet.handlePost() .lift(XML.parse()) .subscribe(item->sendSomeWhere(item)); <cities> <africa> <city name="Lusaka"/> <city name="Harare"/> <city name="Kigali"/> </cities> START_DOCUMENT START_ELEMENT cities {} START_ELEMENT africa {} START_ELEMENT city {name=Lusaka} END_ELEMENT city START_ELEMENT city {name=Harare} END_ELEMENT city START_ELEMENT city {name=Kigali} END_ELEMENT city END_ELEMENT africa PARSE_ERROR
- 68. Non Blocking is not faster 68 ! It is about utilising threads better ! If thread utilisation is not an issue, it will perform similarly
- 69. Thoughts 69 ! RxJava is lightweight and easy to add to existing software ! Pleasant programming model ! Makes non blocking I/O bearable ! Can be used incrementally
- 70. Conclusions 70 ! Threads are expensive ! Everything keeps getting faster except the speed of light ! Micro services ! Blocking code misbehaves under pressure ! The price of blocking communication will keep going up I believe that, in time, some non blocking code is inevitable
- 71. Frank @Lyaruu dexels.com Dexels [email protected] Please rate!