JVM 内存大对象监控和优化实践

-Xms4096M -Xmx4096M -Xmn1024M -XX:MetaspaceSize=256M -Djava.security.egd=file:/dev/./urandom -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/data/{runuser}/logs/other

//org.apache.dubbo.remoting.exchange.codec.ExchangeCodec#encodeResponseprotected void encodeResponse(Channel channel, ChannelBuffer buffer, Response res) throws IOException {    //...省略部分代码    try {         //1、检查响应大小是否超过 payload，如果超过，则抛出ExceedPayloadLimitException异常        checkPayload(channel, len);      } catch (Throwable t) {                 //2、重置buffer        buffer.writerIndex(savedWriteIndex);         //3、捕获异常后，生成一个新的空响应        Response r = new Response(res.getId(), res.getVersion());        r.setStatus(Response.BAD_RESPONSE);                 //4、ExceedPayloadLimitException异常，将生成的空响应重新发送一遍        if (t instanceof ExceedPayloadLimitException) {            r.setErrorMessage(t.getMessage());            channel.send(r);            return;        }             }} //org.apache.dubbo.remoting.transport.AbstractCodec#checkPayloadprotected static void checkPayload(Channel channel, long size) throws IOException {    int payload = getPayload(channel);    boolean overPayload = isOverPayload(payload, size);    if (overPayload) {        ExceedPayloadLimitException e = new ExceedPayloadLimitException("Data length too large: " + size + ", max payload: " + payload + ", channel: " + channel);        logger.error(e);        throw e;    }}

/** * 自定义dubbo编码类 **/public class MusicDubboCountCodec implements Codec2 {     /**     * 异常响应池：缓存超过payload大小的responseId     */    private static Cache<Long, String> EXCEED_PAYLOAD_LIMIT_CACHE = Caffeine.newBuilder()        // 缓存总条数        .maximumSize(100)        // 过期时间        .expireAfterWrite(300, TimeUnit.SECONDS)        // 将value设置为软引用，在OOM前直接淘汰        .softValues()        .build();      @Override    public void encode(Channel channel, ChannelBuffer buffer, Object message) throws IOException {        //1、记录数据编码前的buffer位置        int writeBefore = null == buffer ? 0 : buffer.writerIndex();         //2、调用原始的编码方法        dubboCountCodec.encode(channel, buffer, message);         //3、检查&记录超过payload的信息        checkOverPayload(message);         //4、计算对象长度        int writeAfter = null == buffer ? 0 : buffer.writerIndex();            int length = writeAfter - writeBefore;         //5、超过告警阈值，进行日志打印处理        warningLengthTooLong(length, message);    }     //校验response是否超过payload，超过了，缓存id    private void checkOverPayload(Object message){        if(!(message instanceof Response)){            return;        }        Response response = (Response) message;         //3.1、新的发送过程：通过状态码BAD_RESPONSE与错误信息识别出空响应，并记录响应id        if(Response.BAD_RESPONSE == response.getStatus() && StrUtil.contains(response.getErrorMessage(), OVER_PAYLOAD_ERROR_MESSAGE)){                      EXCEED_PAYLOAD_LIMIT_CACHE.put(response.getId(), response.getErrorMessage());            return;        }         //3.2、原先的发送过程：通过异常池识别出超过payload的响应，打印有用的信息        if(Response.OK == response.getStatus() &&  EXCEED_PAYLOAD_LIMIT_CACHE.getIfPresent(response.getId()) != null){                  String responseMessage = getResponseMessage(response);            log.warn("dubbo序列化对象大小超过payload,errorMsg is {},response is {}", EXCEED_PAYLOAD_LIMIT_CACHE.getIfPresent(response.getId()),responseMessage);        }    }     }