Examples with ChunkResponder co.cask.http.ChunkResponder used on opensource projects

Example 1 with ChunkResponder

use of co.cask.http.ChunkResponder in project cdap by caskdata.

the class StreamFetchHandler method fetch.

/**
 * Handler for the HTTP API {@code /streams/[stream_name]/events?start=[start_ts]&end=[end_ts]&limit=[event_limit]}
 * <p>
 * Responds with:
 * <ul>
 * <li>404 if stream does not exist</li>
 * <li>204 if no event in the given start/end time range exists</li>
 * <li>200 if there is are one or more events</li>
 * </ul>
 * </p>
 * <p>
 * Response body is a JSON array of the StreamEvent object.
 * </p>
 *
 * @see StreamEventTypeAdapter StreamEventTypeAdapter for the format of the StreamEvent object
 */
@GET
@Path("/{stream}/events")
public void fetch(HttpRequest request, final HttpResponder responder, @PathParam("namespace-id") String namespaceId, @PathParam("stream") String stream, @QueryParam("start") @DefaultValue("0") String start, @QueryParam("end") @DefaultValue("9223372036854775807") String end, @QueryParam("limit") @DefaultValue("2147483647") final int limitEvents) throws Exception {
    long startTime = TimeMathParser.parseTime(start, TimeUnit.MILLISECONDS);
    long endTime = TimeMathParser.parseTime(end, TimeUnit.MILLISECONDS);
    StreamId streamId = new StreamId(namespaceId, stream);
    if (!verifyGetEventsRequest(streamId, startTime, endTime, limitEvents, responder)) {
        return;
    }
    // Make sure the user has READ permission on the stream since getConfig doesn't check for the same.
    authorizationEnforcer.enforce(streamId, authenticationContext.getPrincipal(), Action.READ);
    final StreamConfig streamConfig = streamAdmin.getConfig(streamId);
    long now = System.currentTimeMillis();
    startTime = Math.max(startTime, now - streamConfig.getTTL());
    endTime = Math.min(endTime, now);
    final long streamStartTime = startTime;
    final long streamEndTime = endTime;
    impersonator.doAs(streamId, new Callable<Void>() {

        @Override
        public Void call() throws Exception {
            int limit = limitEvents;
            // Create the stream event reader
            try (FileReader<StreamEventOffset, Iterable<StreamFileOffset>> reader = createReader(streamConfig, streamStartTime)) {
                TimeRangeReadFilter readFilter = new TimeRangeReadFilter(streamStartTime, streamEndTime);
                List<StreamEvent> events = Lists.newArrayListWithCapacity(100);
                // Reads the first batch of events from the stream.
                int eventsRead = readEvents(reader, events, limit, readFilter);
                // If empty already, return 204 no content
                if (eventsRead <= 0) {
                    responder.sendStatus(HttpResponseStatus.NO_CONTENT);
                    return null;
                }
                // Send with chunk response, as we don't want to buffer all events in memory to determine the content-length.
                ChunkResponder chunkResponder = responder.sendChunkStart(HttpResponseStatus.OK, new DefaultHttpHeaders().set(HttpHeaderNames.CONTENT_TYPE, "application/json; charset=utf-8"));
                ByteBuf buffer = Unpooled.buffer();
                JsonWriter jsonWriter = new JsonWriter(new OutputStreamWriter(new ByteBufOutputStream(buffer), StandardCharsets.UTF_8));
                // Response is an array of stream event
                jsonWriter.beginArray();
                while (limit > 0 && eventsRead > 0) {
                    limit -= eventsRead;
                    for (StreamEvent event : events) {
                        GSON.toJson(event, StreamEvent.class, jsonWriter);
                        jsonWriter.flush();
                        // If exceeded chunk size limit, send a new chunk.
                        if (buffer.readableBytes() >= CHUNK_SIZE) {
                            // If the connect is closed, sendChunk will throw IOException.
                            // No need to handle the exception as it will just propagated back to the netty-http library
                            // and it will handle it.
                            // Need to copy the buffer because the buffer will get reused and send chunk is an async operation
                            chunkResponder.sendChunk(buffer.copy());
                            buffer.clear();
                        }
                    }
                    events.clear();
                    if (limit > 0) {
                        eventsRead = readEvents(reader, events, limit, readFilter);
                    }
                }
                jsonWriter.endArray();
                jsonWriter.close();
                // Send the last chunk that still has data
                if (buffer.isReadable()) {
                    // No need to copy the last chunk, since the buffer will not be reused
                    chunkResponder.sendChunk(buffer);
                }
                Closeables.closeQuietly(chunkResponder);
            }
            return null;
        }
    });
}