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 * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package jdk.internal.net.http;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.net.ConnectException;
import java.net.InetSocketAddress;
import java.net.URI;
import java.util.Base64;
import java.util.Collections;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CompletableFuture;
import jdk.internal.net.http.common.Log;
import jdk.internal.net.http.common.Logger;
import jdk.internal.net.http.common.MinimalFuture;
import jdk.internal.net.http.common.Utils;
import jdk.internal.net.http.frame.SettingsFrame;
import static jdk.internal.net.http.frame.SettingsFrame.INITIAL_WINDOW_SIZE;
import static jdk.internal.net.http.frame.SettingsFrame.ENABLE_PUSH;
import static jdk.internal.net.http.frame.SettingsFrame.HEADER_TABLE_SIZE;
import static jdk.internal.net.http.frame.SettingsFrame.MAX_CONCURRENT_STREAMS;
import static jdk.internal.net.http.frame.SettingsFrame.MAX_FRAME_SIZE;

 Http2 specific aspects of HttpClientImpl
/**
 *  Http2 specific aspects of HttpClientImpl
 */
class Http2ClientImpl {

    final static Logger debug =
            Utils.getDebugLogger("Http2ClientImpl"::toString, Utils.DEBUG);

    private final HttpClientImpl client;

    Http2ClientImpl(HttpClientImpl client) {
        this.client = client;
    }

    /* Map key is "scheme:host:port" */
    private final Map<String,Http2Connection> connections = new ConcurrentHashMap<>();

    private final Set<String> failures = Collections.synchronizedSet(new HashSet<>());

    
When HTTP/2 requested only. The following describes the aggregate behavior including the
calling code. In all cases, the HTTP2 connection cache
is checked first for a suitable connection and that is returned if available.
If not, a new connection is opened, except in https case when a previous negotiate failed.
In that case, we want to continue using http/1.1. When a connection is to be opened and
if multiple requests are sent in parallel then each will open a new connection.
If negotiation/upgrade succeeds then
one connection will be put in the cache and the others will be closed
after the initial request completes (not strictly necessary for h2, only for h2c)
If negotiate/upgrade fails, then any opened connections remain open (as http/1.1)
and will be used and cached in the http/1 cache. Note, this method handles the
https failure case only (by completing the CF with an ALPN exception, handled externally)
The h2c upgrade is handled externally also.
Specific CF behavior of this method.
1. completes with ALPN exception: h2 negotiate failed for first time. failure recorded.
2. completes with other exception: failure not recorded. Caller must handle
3. completes normally with null: no connection in cache for h2c or h2 failed previously
4. completes normally with connection: h2 or h2c connection in cache. Use it.
/**
     * When HTTP/2 requested only. The following describes the aggregate behavior including the
     * calling code. In all cases, the HTTP2 connection cache
     * is checked first for a suitable connection and that is returned if available.
     * If not, a new connection is opened, except in https case when a previous negotiate failed.
     * In that case, we want to continue using http/1.1. When a connection is to be opened and
     * if multiple requests are sent in parallel then each will open a new connection.
     *
     * If negotiation/upgrade succeeds then
     * one connection will be put in the cache and the others will be closed
     * after the initial request completes (not strictly necessary for h2, only for h2c)
     *
     * If negotiate/upgrade fails, then any opened connections remain open (as http/1.1)
     * and will be used and cached in the http/1 cache. Note, this method handles the
     * https failure case only (by completing the CF with an ALPN exception, handled externally)
     * The h2c upgrade is handled externally also.
     *
     * Specific CF behavior of this method.
     * 1. completes with ALPN exception: h2 negotiate failed for first time. failure recorded.
     * 2. completes with other exception: failure not recorded. Caller must handle
     * 3. completes normally with null: no connection in cache for h2c or h2 failed previously
     * 4. completes normally with connection: h2 or h2c connection in cache. Use it.
     */
    CompletableFuture<Http2Connection> getConnectionFor(HttpRequestImpl req,
                                                        Exchange<?> exchange) {
        URI uri = req.uri();
        InetSocketAddress proxy = req.proxy();
        String key = Http2Connection.keyFor(uri, proxy);

        synchronized (this) {
            Http2Connection connection = connections.get(key);
            if (connection != null) {
                try {
                    if (connection.closed || !connection.reserveStream(true)) {
                        if (debug.on())
                            debug.log("removing found closed or closing connection: %s", connection);
                        deleteConnection(connection);
                    } else {
                        // fast path if connection already exists
                        if (debug.on())
                            debug.log("found connection in the pool: %s", connection);
                        return MinimalFuture.completedFuture(connection);
                    }
                } catch (IOException e) {
                    // thrown by connection.reserveStream()
                    return MinimalFuture.failedFuture(e);
                }
            }

            if (!req.secure() || failures.contains(key)) {
                // secure: negotiate failed before. Use http/1.1
                // !secure: no connection available in cache. Attempt upgrade
                if (debug.on()) debug.log("not found in connection pool");
                return MinimalFuture.completedFuture(null);
            }
        }
        return Http2Connection
                .createAsync(req, this, exchange)
                .whenComplete((conn, t) -> {
                    synchronized (Http2ClientImpl.this) {
                        if (conn != null) {
                            try {
                                conn.reserveStream(true);
                            } catch (IOException e) {
                                throw new UncheckedIOException(e); // shouldn't happen
                            }
                            offerConnection(conn);
                        } else {
                            Throwable cause = Utils.getCompletionCause(t);
                            if (cause instanceof Http2Connection.ALPNException)
                                failures.add(key);
                        }
                    }
                });
    }

    /*
     * Cache the given connection, if no connection to the same
     * destination exists. If one exists, then we let the initial stream
     * complete but allow it to close itself upon completion.
     * This situation should not arise with https because the request
     * has not been sent as part of the initial alpn negotiation
     */
    boolean offerConnection(Http2Connection c) {
        if (debug.on()) debug.log("offering to the connection pool: %s", c);
        if (c.closed || c.finalStream()) {
            if (debug.on())
                debug.log("skipping offered closed or closing connection: %s", c);
            return false;
        }

        String key = c.key();
        synchronized(this) {
            Http2Connection c1 = connections.putIfAbsent(key, c);
            if (c1 != null) {
                c.setFinalStream();
                if (debug.on())
                    debug.log("existing entry in connection pool for %s", key);
                return false;
            }
            if (debug.on())
                debug.log("put in the connection pool: %s", c);
            return true;
        }
    }

    void deleteConnection(Http2Connection c) {
        if (debug.on())
            debug.log("removing from the connection pool: %s", c);
        synchronized (this) {
            Http2Connection c1 = connections.get(c.key());
            if (c1 != null && c1.equals(c)) {
                connections.remove(c.key());
                if (debug.on())
                    debug.log("removed from the connection pool: %s", c);
            }
        }
    }

    void stop() {
        if (debug.on()) debug.log("stopping");
        connections.values().forEach(this::close);
        connections.clear();
    }

    private void close(Http2Connection h2c) {
        try { h2c.close(); } catch (Throwable t) {}
    }

    HttpClientImpl client() {
        return client;
    }

    
Returns the client settings as a base64 (url) encoded string /** Returns the client settings as a base64 (url) encoded string */
    String getSettingsString() {
        SettingsFrame sf = getClientSettings();
        byte[] settings = sf.toByteArray(); // without the header
        Base64.Encoder encoder = Base64.getUrlEncoder()
                                       .withoutPadding();
        return encoder.encodeToString(settings);
    }

    private static final int K = 1024;

    private static int getParameter(String property, int min, int max, int defaultValue) {
        int value =  Utils.getIntegerNetProperty(property, defaultValue);
        // use default value if misconfigured
        if (value < min || value > max) {
            Log.logError("Property value for {0}={1} not in [{2}..{3}]: " +
                    "using default={4}", property, value, min, max, defaultValue);
            value = defaultValue;
        }
        return value;
    }

    // used for the connection window, to have a connection window size
    // bigger than the initial stream window size.
    int getConnectionWindowSize(SettingsFrame clientSettings) {
        // Maximum size is 2^31-1. Don't allow window size to be less
        // than the stream window size. HTTP/2 specify a default of 64 * K -1,
        // but we use 2^26 by default for better performance.
        int streamWindow = clientSettings.getParameter(INITIAL_WINDOW_SIZE);

        // The default is the max between the stream window size
        // and the connection window size.
        int defaultValue = Math.min(Integer.MAX_VALUE,
                Math.max(streamWindow, K*K*32));

        return getParameter(
                "jdk.httpclient.connectionWindowSize",
                streamWindow, Integer.MAX_VALUE, defaultValue);
    }

    SettingsFrame getClientSettings() {
        SettingsFrame frame = new SettingsFrame();
        // default defined for HTTP/2 is 4 K, we use 16 K.
        frame.setParameter(HEADER_TABLE_SIZE, getParameter(
                "jdk.httpclient.hpack.maxheadertablesize",
                0, Integer.MAX_VALUE, 16 * K));
        // O: does not accept push streams. 1: accepts push streams.
        frame.setParameter(ENABLE_PUSH, getParameter(
                "jdk.httpclient.enablepush",
                0, 1, 1));
        // HTTP/2 recommends to set the number of concurrent streams
        // no lower than 100. We use 100. 0 means no stream would be
        // accepted. That would render the client to be non functional,
        // so we won't let 0 be configured for our Http2ClientImpl.
        frame.setParameter(MAX_CONCURRENT_STREAMS, getParameter(
                "jdk.httpclient.maxstreams",
                1, Integer.MAX_VALUE, 100));
        // Maximum size is 2^31-1. Don't allow window size to be less
        // than the minimum frame size as this is likely to be a
        // configuration error. HTTP/2 specify a default of 64 * K -1,
        // but we use 16 M  for better performance.
        frame.setParameter(INITIAL_WINDOW_SIZE, getParameter(
                "jdk.httpclient.windowsize",
                16 * K, Integer.MAX_VALUE, 16*K*K));
        // HTTP/2 specify a minimum size of 16 K, a maximum size of 2^24-1,
        // and a default of 16 K. We use 16 K as default.
        frame.setParameter(MAX_FRAME_SIZE, getParameter(
                "jdk.httpclient.maxframesize",
                16 * K, 16 * K * K -1, 16 * K));
        return frame;
    }
}