nacos中DistroFilter的作用是什么

本篇文章为大家展示了nacos中DistroFilter的作用是什么，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。

CanDistro

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/web/CanDistro.java

@Retention(RetentionPolicy.RUNTIME)public @interface CanDistro {}

• CanDistro用于标识一个方法需要判断是否应该根据distro被重定向

DistroFilter

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/web/DistroFilter.java

public class DistroFilter implements Filter {    private static final int PROXY_CONNECT_TIMEOUT = 2000;    private static final int PROXY_READ_TIMEOUT = 2000;    @Autowired    private DistroMapper distroMapper;    @Autowired    private SwitchDomain switchDomain;    @Autowired    private FilterBase filterBase;    @Override    public void init(FilterConfig filterConfig) throws ServletException {    }    @Override    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {        HttpServletRequest req = (HttpServletRequest) servletRequest;        HttpServletResponse resp = (HttpServletResponse) servletResponse;        String urlString = req.getRequestURI();        if (StringUtils.isNotBlank(req.getQueryString())) {            urlString += "?" + req.getQueryString();        }        try {            String path = new URI(req.getRequestURI()).getPath();            String serviceName = req.getParameter(CommonParams.SERVICE_NAME);            // For client under 0.8.0:            if (StringUtils.isBlank(serviceName)) {                serviceName = req.getParameter("dom");            }            Method method = filterBase.getMethod(req.getMethod(), path);            if (method == null) {                throw new NoSuchMethodException(req.getMethod() + " " + path);            }            String groupName = req.getParameter(CommonParams.GROUP_NAME);            if (StringUtils.isBlank(groupName)) {                groupName = Constants.DEFAULT_GROUP;            }            // use groupName@@serviceName as new service name:            String groupedServiceName = serviceName;            if (StringUtils.isNotBlank(serviceName) && !serviceName.contains(Constants.SERVICE_INFO_SPLITER)) {                groupedServiceName = groupName + Constants.SERVICE_INFO_SPLITER + serviceName;            }            // proxy request to other server if necessary:            if (method.isAnnotationPresent(CanDistro.class) && !distroMapper.responsible(groupedServiceName)) {                String userAgent = req.getHeader("User-Agent");                if (StringUtils.isNotBlank(userAgent) && userAgent.contains(UtilsAndCommons.NACOS_SERVER_HEADER)) {                    // This request is sent from peer server, should not be redirected again:                    Loggers.SRV_LOG.error("receive invalid redirect request from peer {}", req.getRemoteAddr());                    resp.sendError(HttpServletResponse.SC_BAD_REQUEST,                        "receive invalid redirect request from peer " + req.getRemoteAddr());                    return;                }                List headerList = new ArrayList<>(16);                Enumeration headers = req.getHeaderNames();                while (headers.hasMoreElements()) {                    String headerName = headers.nextElement();                    headerList.add(headerName);                    headerList.add(req.getHeader(headerName));                }                HttpClient.HttpResult result =                    HttpClient.request("http://" + distroMapper.mapSrv(groupedServiceName) + urlString, headerList,                        StringUtils.isBlank(req.getQueryString()) ? HttpClient.translateParameterMap(req.getParameterMap()) : new HashMap<>(2)                        , PROXY_CONNECT_TIMEOUT, PROXY_READ_TIMEOUT, "UTF-8", req.getMethod());                try {                    resp.setCharacterEncoding("UTF-8");                    resp.getWriter().write(result.content);                    resp.setStatus(result.code);                } catch (Exception ignore) {                    Loggers.SRV_LOG.warn("[DISTRO-FILTER] request failed: " + distroMapper.mapSrv(groupedServiceName) + urlString);                }                return;            }            OverrideParameterRequestWrapper requestWrapper = OverrideParameterRequestWrapper.buildRequest(req);            requestWrapper.addParameter(CommonParams.SERVICE_NAME, groupedServiceName);            filterChain.doFilter(requestWrapper, resp);        } catch (AccessControlException e) {            resp.sendError(HttpServletResponse.SC_FORBIDDEN, "access denied: " + UtilsAndCommons.getAllExceptionMsg(e));            return;        } catch (NoSuchMethodException e) {            resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, "no such api: " + e.getMessage());            return;        } catch (Exception e) {            resp.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,                "Server failed," + UtilsAndCommons.getAllExceptionMsg(e));            return;        }    }    @Override    public void destroy() {    }}

• DistroFilter实现了servlet的Filter接口；其doFilter方法会从servletRequest中读取serviceName、method、groupName等，然后判断method是否标注CanDistro，如果是而且distroMapper不负责该service则构建http请求然后将结果写回Filter；如果不需要重定向则继续filterChain.doFilter

HttpClient.request

nacos-1.1.3/naming/src/main/java/com/alibaba/nacos/naming/misc/HttpClient.java

public class HttpClient {    private static final int TIME_OUT_MILLIS = 10000;    private static final int CON_TIME_OUT_MILLIS = 5000;    private static AsyncHttpClient asyncHttpClient;    private static CloseableHttpClient postClient;    //......    public static HttpResult request(String url, List headers, Map paramValues, int connectTimeout, int readTimeout, String encoding, String method) {        HttpURLConnection conn = null;        try {            String encodedContent = encodingParams(paramValues, encoding);            url += (null == encodedContent) ? "" : ("?" + encodedContent);            conn = (HttpURLConnection) new URL(url).openConnection();            conn.setConnectTimeout(connectTimeout);            conn.setReadTimeout(readTimeout);            conn.setRequestMethod(method);            conn.addRequestProperty("Client-Version", UtilsAndCommons.SERVER_VERSION);            conn.addRequestProperty("User-Agent", UtilsAndCommons.SERVER_VERSION);            setHeaders(conn, headers, encoding);            conn.connect();            return getResult(conn);        } catch (Exception e) {            Loggers.SRV_LOG.warn("Exception while request: {}, caused: {}", url, e);            return new HttpResult(500, e.toString(), Collections.emptyMap());        } finally {            if (conn != null) {                conn.disconnect();            }        }    }    private static HttpResult getResult(HttpURLConnection conn) throws IOException {        int respCode = conn.getResponseCode();        InputStream inputStream;        if (HttpURLConnection.HTTP_OK == respCode) {            inputStream = conn.getInputStream();        } else {            inputStream = conn.getErrorStream();        }        Map respHeaders = new HashMap(conn.getHeaderFields().size());        for (Map.Entry> entry : conn.getHeaderFields().entrySet()) {            respHeaders.put(entry.getKey(), entry.getValue().get(0));        }        String gzipEncoding = "gzip";        if (gzipEncoding.equals(respHeaders.get(HttpHeaders.CONTENT_ENCODING))) {            inputStream = new GZIPInputStream(inputStream);        }        HttpResult result = new HttpResult(respCode, IOUtils.toString(inputStream, getCharset(conn)), respHeaders);        inputStream.close();        return result;    }    public static class HttpResult {        final public int code;        final public String content;        final private Map respHeaders;        public HttpResult(int code, String content, Map respHeaders) {            this.code = code;            this.content = content;            this.respHeaders = respHeaders;        }        public String getHeader(String name) {            return respHeaders.get(name);        }    }    //......}

• HttpClient的request方法直接使用jdk的HttpURLConnection进行请求，返回结果封装为HttpResult，其content即为响应的body

小结

DistroFilter实现了servlet的Filter接口；其doFilter方法会从servletRequest中读取serviceName、method、groupName等，然后判断method是否标注CanDistro，如果是而且distroMapper不负责该service则构建http请求然后将结果写回Filter；如果不需要重定向则继续filterChain.doFilter

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