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/*
* Copyright 2018 The gRPC Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.grpc.servlet;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static io.grpc.internal.GrpcUtil.TIMEOUT_KEY;
import static java.util.logging.Level.FINE;
import static java.util.logging.Level.FINEST;
import com.google.common.io.BaseEncoding;
import io.grpc.Attributes;
import io.grpc.ExperimentalApi;
import io.grpc.Grpc;
import io.grpc.InternalLogId;
import io.grpc.InternalMetadata;
import io.grpc.Metadata;
import io.grpc.ServerStreamTracer;
import io.grpc.Status;
import io.grpc.internal.GrpcUtil;
import io.grpc.internal.ReadableBuffers;
import io.grpc.internal.ServerTransportListener;
import io.grpc.internal.StatsTraceContext;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.logging.Logger;
import javax.servlet.AsyncContext;
import javax.servlet.AsyncEvent;
import javax.servlet.AsyncListener;
import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* An adapter that transforms {@link HttpServletRequest} into gRPC request and lets a gRPC server
* process it, and transforms the gRPC response into {@link HttpServletResponse}. An adapter can be
* instantiated by {@link ServletServerBuilder#buildServletAdapter()}.
*
* In a servlet, calling {@link #doPost(HttpServletRequest, HttpServletResponse)} inside {@link
* javax.servlet.http.HttpServlet#doPost(HttpServletRequest, HttpServletResponse)} makes the servlet
* backed by the gRPC server associated with the adapter. The servlet must support Asynchronous
* Processing and must be deployed to a container that supports servlet 4.0 and enables HTTP/2.
*
*
The API is experimental. The authors would like to know more about the real usecases. Users
* are welcome to provide feedback by commenting on
* the tracking issue.
*/
@ExperimentalApi("https://github.com/grpc/grpc-java/issues/5066")
public final class ServletAdapter {
static final Logger logger = Logger.getLogger(ServletAdapter.class.getName());
private final ServerTransportListener transportListener;
private final List streamTracerFactories;
private final int maxInboundMessageSize;
private final Attributes attributes;
ServletAdapter(
ServerTransportListener transportListener,
List streamTracerFactories,
int maxInboundMessageSize) {
this.transportListener = transportListener;
this.streamTracerFactories = streamTracerFactories;
this.maxInboundMessageSize = maxInboundMessageSize;
attributes = transportListener.transportReady(Attributes.EMPTY);
}
/**
* Call this method inside {@link javax.servlet.http.HttpServlet#doGet(HttpServletRequest,
* HttpServletResponse)} to serve gRPC GET request.
*
*
This method is currently not implemented.
*
*
Note that in rare case gRPC client sends GET requests.
*
*
Do not modify {@code req} and {@code resp} before or after calling this method. However,
* calling {@code resp.setBufferSize()} before invocation is allowed.
*/
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
resp.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "GET method not supported");
}
/**
* Call this method inside {@link javax.servlet.http.HttpServlet#doPost(HttpServletRequest,
* HttpServletResponse)} to serve gRPC POST request.
*
*
Do not modify {@code req} and {@code resp} before or after calling this method. However,
* calling {@code resp.setBufferSize()} before invocation is allowed.
*/
public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
checkArgument(req.isAsyncSupported(), "servlet does not support asynchronous operation");
checkArgument(ServletAdapter.isGrpc(req), "the request is not a gRPC request");
InternalLogId logId = InternalLogId.allocate(ServletAdapter.class, null);
logger.log(FINE, "[{0}] RPC started", logId);
AsyncContext asyncCtx = req.startAsync(req, resp);
String method = req.getRequestURI().substring(1); // remove the leading "/"
Metadata headers = getHeaders(req);
if (logger.isLoggable(FINEST)) {
logger.log(FINEST, "[{0}] method: {1}", new Object[] {logId, method});
logger.log(FINEST, "[{0}] headers: {1}", new Object[] {logId, headers});
}
Long timeoutNanos = headers.get(TIMEOUT_KEY);
if (timeoutNanos == null) {
timeoutNanos = 0L;
}
asyncCtx.setTimeout(TimeUnit.NANOSECONDS.toMillis(timeoutNanos));
StatsTraceContext statsTraceCtx =
StatsTraceContext.newServerContext(streamTracerFactories, method, headers);
ServletServerStream stream = new ServletServerStream(
asyncCtx,
statsTraceCtx,
maxInboundMessageSize,
attributes.toBuilder()
.set(
Grpc.TRANSPORT_ATTR_REMOTE_ADDR,
new InetSocketAddress(req.getRemoteHost(), req.getRemotePort()))
.set(
Grpc.TRANSPORT_ATTR_LOCAL_ADDR,
new InetSocketAddress(req.getLocalAddr(), req.getLocalPort()))
.build(),
getAuthority(req),
logId);
transportListener.streamCreated(stream, method, headers);
stream.transportState().runOnTransportThread(stream.transportState()::onStreamAllocated);
asyncCtx.getRequest().getInputStream()
.setReadListener(new GrpcReadListener(stream, asyncCtx, logId));
asyncCtx.addListener(new GrpcAsyncListener(stream, logId));
}
// This method must use Enumeration and its members, since that is the only way to read headers
// from the servlet api.
@SuppressWarnings("JdkObsolete")
private static Metadata getHeaders(HttpServletRequest req) {
Enumeration headerNames = req.getHeaderNames();
checkNotNull(
headerNames, "Servlet container does not allow HttpServletRequest.getHeaderNames()");
List byteArrays = new ArrayList<>();
while (headerNames.hasMoreElements()) {
String headerName = headerNames.nextElement();
Enumeration values = req.getHeaders(headerName);
if (values == null) {
continue;
}
while (values.hasMoreElements()) {
String value = values.nextElement();
if (headerName.endsWith(Metadata.BINARY_HEADER_SUFFIX)) {
byteArrays.add(headerName.getBytes(StandardCharsets.US_ASCII));
byteArrays.add(BaseEncoding.base64().decode(value));
} else {
byteArrays.add(headerName.getBytes(StandardCharsets.US_ASCII));
byteArrays.add(value.getBytes(StandardCharsets.US_ASCII));
}
}
}
return InternalMetadata.newMetadata(byteArrays.toArray(new byte[][]{}));
}
// This method must use HttpRequest#getRequestURL or HttpUtils#getRequestURL, both of which
// can only return StringBuffer instances
@SuppressWarnings("JdkObsolete")
private static String getAuthority(HttpServletRequest req) {
try {
return new URI(req.getRequestURL().toString()).getAuthority();
} catch (URISyntaxException e) {
logger.log(FINE, "Error getting authority from the request URL {0}", req.getRequestURL());
return req.getServerName() + ":" + req.getServerPort();
}
}
/**
* Call this method when the adapter is no longer needed. The gRPC server will be terminated.
*/
public void destroy() {
transportListener.transportTerminated();
}
private static final class GrpcAsyncListener implements AsyncListener {
final InternalLogId logId;
final ServletServerStream stream;
GrpcAsyncListener(ServletServerStream stream, InternalLogId logId) {
this.stream = stream;
this.logId = logId;
}
@Override
public void onComplete(AsyncEvent event) {}
@Override
public void onTimeout(AsyncEvent event) {
if (logger.isLoggable(FINE)) {
logger.log(FINE, String.format("[{%s}] Timeout: ", logId), event.getThrowable());
}
// If the resp is not committed, cancel() to avoid being redirected to an error page.
// Else, the container will send RST_STREAM in the end.
if (!event.getAsyncContext().getResponse().isCommitted()) {
stream.cancel(Status.DEADLINE_EXCEEDED);
} else {
stream.transportState().runOnTransportThread(
() -> stream.transportState().transportReportStatus(Status.DEADLINE_EXCEEDED));
}
}
@Override
public void onError(AsyncEvent event) {
if (logger.isLoggable(FINE)) {
logger.log(FINE, String.format("[{%s}] Error: ", logId), event.getThrowable());
}
// If the resp is not committed, cancel() to avoid being redirected to an error page.
// Else, the container will send RST_STREAM at the end.
if (!event.getAsyncContext().getResponse().isCommitted()) {
stream.cancel(Status.fromThrowable(event.getThrowable()));
} else {
stream.transportState().runOnTransportThread(
() -> stream.transportState().transportReportStatus(
Status.fromThrowable(event.getThrowable())));
}
}
@Override
public void onStartAsync(AsyncEvent event) {}
}
private static final class GrpcReadListener implements ReadListener {
final ServletServerStream stream;
final AsyncContext asyncCtx;
final ServletInputStream input;
final InternalLogId logId;
GrpcReadListener(
ServletServerStream stream,
AsyncContext asyncCtx,
InternalLogId logId) throws IOException {
this.stream = stream;
this.asyncCtx = asyncCtx;
input = asyncCtx.getRequest().getInputStream();
this.logId = logId;
}
final byte[] buffer = new byte[4 * 1024];
@Override
public void onDataAvailable() throws IOException {
logger.log(FINEST, "[{0}] onDataAvailable: ENTRY", logId);
while (input.isReady()) {
int length = input.read(buffer);
if (length == -1) {
logger.log(FINEST, "[{0}] inbound data: read end of stream", logId);
return;
} else {
if (logger.isLoggable(FINEST)) {
logger.log(
FINEST,
"[{0}] inbound data: length = {1}, bytes = {2}",
new Object[] {logId, length, ServletServerStream.toHexString(buffer, length)});
}
byte[] copy = Arrays.copyOf(buffer, length);
stream.transportState().runOnTransportThread(
() -> stream.transportState().inboundDataReceived(ReadableBuffers.wrap(copy), false));
}
}
logger.log(FINEST, "[{0}] onDataAvailable: EXIT", logId);
}
@Override
public void onAllDataRead() {
logger.log(FINE, "[{0}] onAllDataRead", logId);
stream.transportState().runOnTransportThread(() ->
stream.transportState().inboundDataReceived(ReadableBuffers.empty(), true));
}
@Override
public void onError(Throwable t) {
if (logger.isLoggable(FINE)) {
logger.log(FINE, String.format("[{%s}] Error: ", logId), t);
}
// If the resp is not committed, cancel() to avoid being redirected to an error page.
// Else, the container will send RST_STREAM at the end.
if (!asyncCtx.getResponse().isCommitted()) {
stream.cancel(Status.fromThrowable(t));
} else {
stream.transportState().runOnTransportThread(
() -> stream.transportState()
.transportReportStatus(Status.fromThrowable(t)));
}
}
}
/**
* Checks whether an incoming {@code HttpServletRequest} may come from a gRPC client.
*
* @return true if the request comes from a gRPC client
*/
public static boolean isGrpc(HttpServletRequest request) {
return request.getContentType() != null
&& request.getContentType().contains(GrpcUtil.CONTENT_TYPE_GRPC);
}
}