Adding upstream version 2.4.38.upstream/2.4.38upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1282 insertions, 0 deletions

diff --git a/modules/http2/h2_mplx.c b/modules/http2/h2_mplx.c
new file mode 100644
index 0000000..0fae117
--- /dev/null
+++ b/modules/http2/h2_mplx.c
@@ -0,0 +1,1282 @@
+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+ 
+#include <assert.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+#include <apr_atomic.h>
+#include <apr_thread_mutex.h>
+#include <apr_thread_cond.h>
+#include <apr_strings.h>
+#include <apr_time.h>
+
+#include <httpd.h>
+#include <http_core.h>
+#include <http_log.h>
+
+#include <mpm_common.h>
+
+#include "mod_http2.h"
+
+#include "h2.h"
+#include "h2_private.h"
+#include "h2_bucket_beam.h"
+#include "h2_config.h"
+#include "h2_conn.h"
+#include "h2_ctx.h"
+#include "h2_h2.h"
+#include "h2_mplx.h"
+#include "h2_ngn_shed.h"
+#include "h2_request.h"
+#include "h2_stream.h"
+#include "h2_session.h"
+#include "h2_task.h"
+#include "h2_workers.h"
+#include "h2_util.h"
+
+
+/* utility for iterating over ihash stream sets */
+typedef struct {
+    h2_mplx *m;
+    h2_stream *stream;
+    apr_time_t now;
+} stream_iter_ctx;
+
+apr_status_t h2_mplx_child_init(apr_pool_t *pool, server_rec *s)
+{
+    return APR_SUCCESS;
+}
+
+#define H2_MPLX_ENTER(m)    \
+    do { apr_status_t rv; if ((rv = apr_thread_mutex_lock(m->lock)) != APR_SUCCESS) {\
+        return rv;\
+    } } while(0)
+
+#define H2_MPLX_LEAVE(m)    \
+    apr_thread_mutex_unlock(m->lock)
+ 
+#define H2_MPLX_ENTER_ALWAYS(m)    \
+    apr_thread_mutex_lock(m->lock)
+
+#define H2_MPLX_ENTER_MAYBE(m, lock)    \
+    if (lock) apr_thread_mutex_lock(m->lock)
+
+#define H2_MPLX_LEAVE_MAYBE(m, lock)    \
+    if (lock) apr_thread_mutex_unlock(m->lock)
+
+static void check_data_for(h2_mplx *m, h2_stream *stream, int lock);
+
+static void stream_output_consumed(void *ctx, 
+                                   h2_bucket_beam *beam, apr_off_t length)
+{
+    h2_stream *stream = ctx;
+    h2_task *task = stream->task;
+    
+    if (length > 0 && task && task->assigned) {
+        h2_req_engine_out_consumed(task->assigned, task->c, length); 
+    }
+}
+
+static void stream_input_ev(void *ctx, h2_bucket_beam *beam)
+{
+    h2_stream *stream = ctx;
+    h2_mplx *m = stream->session->mplx;
+    apr_atomic_set32(&m->event_pending, 1); 
+}
+
+static void stream_input_consumed(void *ctx, h2_bucket_beam *beam, apr_off_t length)
+{
+    h2_stream_in_consumed(ctx, length);
+}
+
+static void stream_joined(h2_mplx *m, h2_stream *stream)
+{
+    ap_assert(!stream->task || stream->task->worker_done);
+    
+    h2_ihash_remove(m->shold, stream->id);
+    h2_ihash_add(m->spurge, stream);
+}
+
+static void stream_cleanup(h2_mplx *m, h2_stream *stream)
+{
+    ap_assert(stream->state == H2_SS_CLEANUP);
+
+    if (stream->input) {
+        h2_beam_on_consumed(stream->input, NULL, NULL, NULL);
+        h2_beam_abort(stream->input);
+    }
+    if (stream->output) {
+        h2_beam_on_produced(stream->output, NULL, NULL);
+        h2_beam_leave(stream->output);
+    }
+    
+    h2_stream_cleanup(stream);
+
+    h2_ihash_remove(m->streams, stream->id);
+    h2_iq_remove(m->q, stream->id);
+    h2_ififo_remove(m->readyq, stream->id);
+    h2_ihash_add(m->shold, stream);
+    
+    if (!stream->task || stream->task->worker_done) {
+        stream_joined(m, stream);
+    }
+    else if (stream->task) {
+        stream->task->c->aborted = 1;
+        apr_thread_cond_broadcast(m->task_thawed);
+    }
+}
+
+/**
+ * A h2_mplx needs to be thread-safe *and* if will be called by
+ * the h2_session thread *and* the h2_worker threads. Therefore:
+ * - calls are protected by a mutex lock, m->lock
+ * - the pool needs its own allocator, since apr_allocator_t are 
+ *   not re-entrant. The separate allocator works without a 
+ *   separate lock since we already protect h2_mplx itself.
+ *   Since HTTP/2 connections can be expected to live longer than
+ *   their HTTP/1 cousins, the separate allocator seems to work better
+ *   than protecting a shared h2_session one with an own lock.
+ */
+h2_mplx *h2_mplx_create(conn_rec *c, apr_pool_t *parent, 
+                        const h2_config *conf, 
+                        h2_workers *workers)
+{
+    apr_status_t status = APR_SUCCESS;
+    apr_allocator_t *allocator;
+    apr_thread_mutex_t *mutex;
+    h2_mplx *m;
+    h2_ctx *ctx = h2_ctx_get(c, 0);
+    ap_assert(conf);
+    
+    m = apr_pcalloc(parent, sizeof(h2_mplx));
+    if (m) {
+        m->id = c->id;
+        m->c = c;
+        m->s = (ctx? h2_ctx_server_get(ctx) : NULL);
+        if (!m->s) {
+            m->s = c->base_server;
+        }
+        
+        /* We create a pool with its own allocator to be used for
+         * processing slave connections. This is the only way to have the
+         * processing independant of its parent pool in the sense that it
+         * can work in another thread. Also, the new allocator needs its own
+         * mutex to synchronize sub-pools.
+         */
+        status = apr_allocator_create(&allocator);
+        if (status != APR_SUCCESS) {
+            return NULL;
+        }
+        apr_allocator_max_free_set(allocator, ap_max_mem_free);
+        apr_pool_create_ex(&m->pool, parent, NULL, allocator);
+        if (!m->pool) {
+            apr_allocator_destroy(allocator);
+            return NULL;
+        }
+        apr_pool_tag(m->pool, "h2_mplx");
+        apr_allocator_owner_set(allocator, m->pool);
+        status = apr_thread_mutex_create(&mutex, APR_THREAD_MUTEX_DEFAULT,
+                                         m->pool);
+        if (status != APR_SUCCESS) {
+            apr_pool_destroy(m->pool);
+            return NULL;
+        }
+        apr_allocator_mutex_set(allocator, mutex);
+
+        status = apr_thread_mutex_create(&m->lock, APR_THREAD_MUTEX_DEFAULT,
+                                         m->pool);
+        if (status != APR_SUCCESS) {
+            apr_pool_destroy(m->pool);
+            return NULL;
+        }
+        
+        status = apr_thread_cond_create(&m->task_thawed, m->pool);
+        if (status != APR_SUCCESS) {
+            apr_pool_destroy(m->pool);
+            return NULL;
+        }
+    
+        m->max_streams = h2_config_geti(conf, H2_CONF_MAX_STREAMS);
+        m->stream_max_mem = h2_config_geti(conf, H2_CONF_STREAM_MAX_MEM);
+
+        m->streams = h2_ihash_create(m->pool, offsetof(h2_stream,id));
+        m->sredo = h2_ihash_create(m->pool, offsetof(h2_stream,id));
+        m->shold = h2_ihash_create(m->pool, offsetof(h2_stream,id));
+        m->spurge = h2_ihash_create(m->pool, offsetof(h2_stream,id));
+        m->q = h2_iq_create(m->pool, m->max_streams);
+
+        status = h2_ififo_set_create(&m->readyq, m->pool, m->max_streams);
+        if (status != APR_SUCCESS) {
+            apr_pool_destroy(m->pool);
+            return NULL;
+        }
+
+        m->workers = workers;
+        m->max_active = workers->max_workers;
+        m->limit_active = 6; /* the original h1 max parallel connections */
+        m->last_limit_change = m->last_idle_block = apr_time_now();
+        m->limit_change_interval = apr_time_from_msec(100);
+        
+        m->spare_slaves = apr_array_make(m->pool, 10, sizeof(conn_rec*));
+        
+        m->ngn_shed = h2_ngn_shed_create(m->pool, m->c, m->max_streams, 
+                                         m->stream_max_mem);
+        h2_ngn_shed_set_ctx(m->ngn_shed , m);
+    }
+    return m;
+}
+
+int h2_mplx_shutdown(h2_mplx *m)
+{
+    int max_stream_started = 0;
+    
+    H2_MPLX_ENTER(m);
+
+    max_stream_started = m->max_stream_started;
+    /* Clear schedule queue, disabling existing streams from starting */ 
+    h2_iq_clear(m->q);
+
+    H2_MPLX_LEAVE(m);
+    return max_stream_started;
+}
+
+static int input_consumed_signal(h2_mplx *m, h2_stream *stream)
+{
+    if (stream->input) {
+        return h2_beam_report_consumption(stream->input);
+    }
+    return 0;
+}
+
+static int report_consumption_iter(void *ctx, void *val)
+{
+    h2_stream *stream = val;
+    h2_mplx *m = ctx;
+    
+    input_consumed_signal(m, stream);
+    if (stream->state == H2_SS_CLOSED_L
+        && (!stream->task || stream->task->worker_done)) {
+        ap_log_cerror(APLOG_MARK, APLOG_DEBUG, 0, m->c, 
+                      H2_STRM_LOG(APLOGNO(10026), stream, "remote close missing")); 
+        nghttp2_submit_rst_stream(stream->session->ngh2, NGHTTP2_FLAG_NONE, 
+                                  stream->id, NGHTTP2_NO_ERROR);
+    }
+    return 1;
+}
+
+static int output_consumed_signal(h2_mplx *m, h2_task *task)
+{
+    if (task->output.beam) {
+        return h2_beam_report_consumption(task->output.beam);
+    }
+    return 0;
+}
+
+static int stream_destroy_iter(void *ctx, void *val) 
+{   
+    h2_mplx *m = ctx;
+    h2_stream *stream = val;
+
+    h2_ihash_remove(m->spurge, stream->id);
+    ap_assert(stream->state == H2_SS_CLEANUP);
+    
+    if (stream->input) {
+        /* Process outstanding events before destruction */
+        input_consumed_signal(m, stream);    
+        h2_beam_log(stream->input, m->c, APLOG_TRACE2, "stream_destroy");
+        h2_beam_destroy(stream->input);
+        stream->input = NULL;
+    }
+
+    if (stream->task) {
+        h2_task *task = stream->task;
+        conn_rec *slave;
+        int reuse_slave = 0;
+        
+        stream->task = NULL;
+        slave = task->c;
+        if (slave) {
+            /* On non-serialized requests, the IO logging has not accounted for any
+             * meta data send over the network: response headers and h2 frame headers. we
+             * counted this on the stream and need to add this now.
+             * This is supposed to happen before the EOR bucket triggers the
+             * logging of the transaction. *fingers crossed* */
+            if (task->request && !task->request->serialize && h2_task_logio_add_bytes_out) {
+                apr_off_t unaccounted = stream->out_frame_octets - stream->out_data_octets;
+                if (unaccounted > 0) {
+                    h2_task_logio_add_bytes_out(slave, unaccounted);
+                }
+            }
+        
+            if (m->s->keep_alive_max == 0 || slave->keepalives < m->s->keep_alive_max) {
+                reuse_slave = ((m->spare_slaves->nelts < (m->limit_active * 3 / 2))
+                               && !task->rst_error);
+            }
+            
+            if (reuse_slave && slave->keepalive == AP_CONN_KEEPALIVE) {
+                h2_beam_log(task->output.beam, m->c, APLOG_DEBUG, 
+                            APLOGNO(03385) "h2_task_destroy, reuse slave");    
+                h2_task_destroy(task);
+                APR_ARRAY_PUSH(m->spare_slaves, conn_rec*) = slave;
+            }
+            else {
+                h2_beam_log(task->output.beam, m->c, APLOG_TRACE1, 
+                            "h2_task_destroy, destroy slave");    
+                h2_slave_destroy(slave);
+            }
+        }
+    }
+    h2_stream_destroy(stream);
+    return 0;
+}
+
+static void purge_streams(h2_mplx *m, int lock)
+{
+    if (!h2_ihash_empty(m->spurge)) {
+        H2_MPLX_ENTER_MAYBE(m, lock);
+        while (!h2_ihash_iter(m->spurge, stream_destroy_iter, m)) {
+            /* repeat until empty */
+        }
+        H2_MPLX_LEAVE_MAYBE(m, lock);
+    }
+}
+
+typedef struct {
+    h2_mplx_stream_cb *cb;
+    void *ctx;
+} stream_iter_ctx_t;
+
+static int stream_iter_wrap(void *ctx, void *stream)
+{
+    stream_iter_ctx_t *x = ctx;
+    return x->cb(stream, x->ctx);
+}
+
+apr_status_t h2_mplx_stream_do(h2_mplx *m, h2_mplx_stream_cb *cb, void *ctx)
+{
+    stream_iter_ctx_t x;
+    
+    H2_MPLX_ENTER(m);
+
+    x.cb = cb;
+    x.ctx = ctx;
+    h2_ihash_iter(m->streams, stream_iter_wrap, &x);
+        
+    H2_MPLX_LEAVE(m);
+    return APR_SUCCESS;
+}
+
+static int report_stream_iter(void *ctx, void *val) {
+    h2_mplx *m = ctx;
+    h2_stream *stream = val;
+    h2_task *task = stream->task;
+    if (APLOGctrace1(m->c)) {
+        ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                      H2_STRM_MSG(stream, "started=%d, scheduled=%d, ready=%d, out_buffer=%ld"), 
+                      !!stream->task, stream->scheduled, h2_stream_is_ready(stream),
+                      (long)h2_beam_get_buffered(stream->output));
+    }
+    if (task) {
+        ap_log_cerror(APLOG_MARK, APLOG_DEBUG, 0, m->c, /* NO APLOGNO */
+                      H2_STRM_MSG(stream, "->03198: %s %s %s"
+                      "[started=%d/done=%d/frozen=%d]"), 
+                      task->request->method, task->request->authority, 
+                      task->request->path, task->worker_started, 
+                      task->worker_done, task->frozen);
+    }
+    else {
+        ap_log_cerror(APLOG_MARK, APLOG_DEBUG, 0, m->c, /* NO APLOGNO */
+                      H2_STRM_MSG(stream, "->03198: no task"));
+    }
+    return 1;
+}
+
+static int unexpected_stream_iter(void *ctx, void *val) {
+    h2_mplx *m = ctx;
+    h2_stream *stream = val;
+    ap_log_cerror(APLOG_MARK, APLOG_WARNING, 0, m->c, /* NO APLOGNO */
+                  H2_STRM_MSG(stream, "unexpected, started=%d, scheduled=%d, ready=%d"), 
+                  !!stream->task, stream->scheduled, h2_stream_is_ready(stream));
+    return 1;
+}
+
+static int stream_cancel_iter(void *ctx, void *val) {
+    h2_mplx *m = ctx;
+    h2_stream *stream = val;
+
+    /* disabled input consumed reporting */
+    if (stream->input) {
+        h2_beam_on_consumed(stream->input, NULL, NULL, NULL);
+    }
+    /* take over event monitoring */
+    h2_stream_set_monitor(stream, NULL);
+    /* Reset, should transit to CLOSED state */
+    h2_stream_rst(stream, H2_ERR_NO_ERROR);
+    /* All connection data has been sent, simulate cleanup */
+    h2_stream_dispatch(stream, H2_SEV_EOS_SENT);
+    stream_cleanup(m, stream);  
+    return 0;
+}
+
+void h2_mplx_release_and_join(h2_mplx *m, apr_thread_cond_t *wait)
+{
+    apr_status_t status;
+    int i, wait_secs = 60;
+
+    /* How to shut down a h2 connection:
+     * 0. abort and tell the workers that no more tasks will come from us */
+    m->aborted = 1;
+    h2_workers_unregister(m->workers, m);
+    
+    H2_MPLX_ENTER_ALWAYS(m);
+
+    /* How to shut down a h2 connection:
+     * 1. cancel all streams still active */
+    while (!h2_ihash_iter(m->streams, stream_cancel_iter, m)) {
+        /* until empty */
+    }
+    
+    /* 2. terminate ngn_shed, no more streams
+     * should be scheduled or in the active set */
+    h2_ngn_shed_abort(m->ngn_shed);
+    ap_assert(h2_ihash_empty(m->streams));
+    ap_assert(h2_iq_empty(m->q));
+    
+    /* 3. while workers are busy on this connection, meaning they
+     *    are processing tasks from this connection, wait on them finishing
+     *    in order to wake us and let us check again. 
+     *    Eventually, this has to succeed. */    
+    m->join_wait = wait;
+    for (i = 0; h2_ihash_count(m->shold) > 0; ++i) {        
+        status = apr_thread_cond_timedwait(wait, m->lock, apr_time_from_sec(wait_secs));
+        
+        if (APR_STATUS_IS_TIMEUP(status)) {
+            /* This can happen if we have very long running requests
+             * that do not time out on IO. */
+            ap_log_cerror(APLOG_MARK, APLOG_DEBUG, 0, m->c, APLOGNO(03198)
+                          "h2_mplx(%ld): waited %d sec for %d tasks", 
+                          m->id, i*wait_secs, (int)h2_ihash_count(m->shold));
+            h2_ihash_iter(m->shold, report_stream_iter, m);
+        }
+    }
+    ap_assert(m->tasks_active == 0);
+    m->join_wait = NULL;
+    
+    /* 4. close the h2_req_enginge shed */
+    h2_ngn_shed_destroy(m->ngn_shed);
+    m->ngn_shed = NULL;
+    
+    /* 4. With all workers done, all streams should be in spurge */
+    if (!h2_ihash_empty(m->shold)) {
+        ap_log_cerror(APLOG_MARK, APLOG_WARNING, 0, m->c, APLOGNO(03516)
+                      "h2_mplx(%ld): unexpected %d streams in hold", 
+                      m->id, (int)h2_ihash_count(m->shold));
+        h2_ihash_iter(m->shold, unexpected_stream_iter, m);
+    }
+    
+    H2_MPLX_LEAVE(m);
+
+    ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                  "h2_mplx(%ld): released", m->id);
+}
+
+apr_status_t h2_mplx_stream_cleanup(h2_mplx *m, h2_stream *stream)
+{
+    H2_MPLX_ENTER(m);
+    
+    ap_log_cerror(APLOG_MARK, APLOG_TRACE2, 0, m->c, 
+                  H2_STRM_MSG(stream, "cleanup"));
+    stream_cleanup(m, stream);        
+    
+    H2_MPLX_LEAVE(m);
+    return APR_SUCCESS;
+}
+
+h2_stream *h2_mplx_stream_get(h2_mplx *m, int id)
+{
+    h2_stream *s = NULL;
+    
+    H2_MPLX_ENTER_ALWAYS(m);
+
+    s = h2_ihash_get(m->streams, id);
+
+    H2_MPLX_LEAVE(m);
+    return s;
+}
+
+static void output_produced(void *ctx, h2_bucket_beam *beam, apr_off_t bytes)
+{
+    h2_stream *stream = ctx;
+    h2_mplx *m = stream->session->mplx;
+    
+    check_data_for(m, stream, 1);
+}
+
+static apr_status_t out_open(h2_mplx *m, int stream_id, h2_bucket_beam *beam)
+{
+    apr_status_t status = APR_SUCCESS;
+    h2_stream *stream = h2_ihash_get(m->streams, stream_id);
+    
+    if (!stream || !stream->task || m->aborted) {
+        return APR_ECONNABORTED;
+    }
+    
+    ap_assert(stream->output == NULL);
+    stream->output = beam;
+    
+    if (APLOGctrace2(m->c)) {
+        h2_beam_log(beam, m->c, APLOG_TRACE2, "out_open");
+    }
+    else {
+        ap_log_cerror(APLOG_MARK, APLOG_TRACE1, status, m->c,
+                      "h2_mplx(%s): out open", stream->task->id);
+    }
+    
+    h2_beam_on_consumed(stream->output, NULL, stream_output_consumed, stream);
+    h2_beam_on_produced(stream->output, output_produced, stream);
+    if (stream->task->output.copy_files) {
+        h2_beam_on_file_beam(stream->output, h2_beam_no_files, NULL);
+    }
+    
+    /* we might see some file buckets in the output, see
+     * if we have enough handles reserved. */
+    check_data_for(m, stream, 0);
+    return status;
+}
+
+apr_status_t h2_mplx_out_open(h2_mplx *m, int stream_id, h2_bucket_beam *beam)
+{
+    apr_status_t status;
+    
+    H2_MPLX_ENTER(m);
+
+    if (m->aborted) {
+        status = APR_ECONNABORTED;
+    }
+    else {
+        status = out_open(m, stream_id, beam);
+    }
+
+    H2_MPLX_LEAVE(m);
+    return status;
+}
+
+static apr_status_t out_close(h2_mplx *m, h2_task *task)
+{
+    apr_status_t status = APR_SUCCESS;
+    h2_stream *stream;
+    
+    if (!task) {
+        return APR_ECONNABORTED;
+    }
+    if (task->c) {
+        ++task->c->keepalives;
+    }
+    
+    stream = h2_ihash_get(m->streams, task->stream_id);
+    if (!stream) {
+        return APR_ECONNABORTED;
+    }
+
+    ap_log_cerror(APLOG_MARK, APLOG_TRACE2, status, m->c,
+                  "h2_mplx(%s): close", task->id);
+    status = h2_beam_close(task->output.beam);
+    h2_beam_log(task->output.beam, m->c, APLOG_TRACE2, "out_close");
+    output_consumed_signal(m, task);
+    check_data_for(m, stream, 0);
+    return status;
+}
+
+apr_status_t h2_mplx_out_trywait(h2_mplx *m, apr_interval_time_t timeout,
+                                 apr_thread_cond_t *iowait)
+{
+    apr_status_t status;
+    
+    H2_MPLX_ENTER(m);
+
+    if (m->aborted) {
+        status = APR_ECONNABORTED;
+    }
+    else if (h2_mplx_has_master_events(m)) {
+        status = APR_SUCCESS;
+    }
+    else {
+        purge_streams(m, 0);
+        h2_ihash_iter(m->streams, report_consumption_iter, m);
+        m->added_output = iowait;
+        status = apr_thread_cond_timedwait(m->added_output, m->lock, timeout);
+        if (APLOGctrace2(m->c)) {
+            ap_log_cerror(APLOG_MARK, APLOG_TRACE2, 0, m->c,
+                          "h2_mplx(%ld): trywait on data for %f ms)",
+                          m->id, timeout/1000.0);
+        }
+        m->added_output = NULL;
+    }
+
+    H2_MPLX_LEAVE(m);
+    return status;
+}
+
+static void check_data_for(h2_mplx *m, h2_stream *stream, int lock)
+{
+    if (h2_ififo_push(m->readyq, stream->id) == APR_SUCCESS) {
+        apr_atomic_set32(&m->event_pending, 1);
+        H2_MPLX_ENTER_MAYBE(m, lock);
+        if (m->added_output) {
+            apr_thread_cond_signal(m->added_output);
+        }
+        H2_MPLX_LEAVE_MAYBE(m, lock);
+    }
+}
+
+apr_status_t h2_mplx_reprioritize(h2_mplx *m, h2_stream_pri_cmp *cmp, void *ctx)
+{
+    apr_status_t status;
+    
+    H2_MPLX_ENTER(m);
+
+    if (m->aborted) {
+        status = APR_ECONNABORTED;
+    }
+    else {
+        h2_iq_sort(m->q, cmp, ctx);
+        ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                      "h2_mplx(%ld): reprioritize tasks", m->id);
+        status = APR_SUCCESS;
+    }
+
+    H2_MPLX_LEAVE(m);
+    return status;
+}
+
+static void register_if_needed(h2_mplx *m) 
+{
+    if (!m->aborted && !m->is_registered && !h2_iq_empty(m->q)) {
+        apr_status_t status = h2_workers_register(m->workers, m); 
+        if (status == APR_SUCCESS) {
+            m->is_registered = 1;
+        }
+        else {
+            ap_log_cerror(APLOG_MARK, APLOG_ERR, status, m->c, APLOGNO(10021)
+                          "h2_mplx(%ld): register at workers", m->id);
+        }
+    }
+}
+
+apr_status_t h2_mplx_process(h2_mplx *m, struct h2_stream *stream, 
+                             h2_stream_pri_cmp *cmp, void *ctx)
+{
+    apr_status_t status;
+    
+    H2_MPLX_ENTER(m);
+
+    if (m->aborted) {
+        status = APR_ECONNABORTED;
+    }
+    else {
+        status = APR_SUCCESS;
+        h2_ihash_add(m->streams, stream);
+        if (h2_stream_is_ready(stream)) {
+            /* already have a response */
+            check_data_for(m, stream, 0);
+            ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                          H2_STRM_MSG(stream, "process, add to readyq")); 
+        }
+        else {
+            h2_iq_add(m->q, stream->id, cmp, ctx);
+            register_if_needed(m);                
+            ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                          H2_STRM_MSG(stream, "process, added to q")); 
+        }
+    }
+
+    H2_MPLX_LEAVE(m);
+    return status;
+}
+
+static h2_task *next_stream_task(h2_mplx *m)
+{
+    h2_stream *stream;
+    int sid;
+    while (!m->aborted && (m->tasks_active < m->limit_active)
+           && (sid = h2_iq_shift(m->q)) > 0) {
+        
+        stream = h2_ihash_get(m->streams, sid);
+        if (stream) {
+            conn_rec *slave, **pslave;
+
+            pslave = (conn_rec **)apr_array_pop(m->spare_slaves);
+            if (pslave) {
+                slave = *pslave;
+                slave->aborted = 0;
+            }
+            else {
+                slave = h2_slave_create(m->c, stream->id, m->pool);
+            }
+            
+            if (!stream->task) {
+
+                if (sid > m->max_stream_started) {
+                    m->max_stream_started = sid;
+                }
+                if (stream->input) {
+                    h2_beam_on_consumed(stream->input, stream_input_ev, 
+                                        stream_input_consumed, stream);
+                }
+                
+                stream->task = h2_task_create(slave, stream->id, 
+                                              stream->request, m, stream->input, 
+                                              stream->session->s->timeout,
+                                              m->stream_max_mem);
+                if (!stream->task) {
+                    ap_log_cerror(APLOG_MARK, APLOG_ERR, APR_ENOMEM, slave,
+                                  H2_STRM_LOG(APLOGNO(02941), stream, 
+                                  "create task"));
+                    return NULL;
+                }
+                
+            }
+            
+            ++m->tasks_active;
+            return stream->task;
+        }
+    }
+    return NULL;
+}
+
+apr_status_t h2_mplx_pop_task(h2_mplx *m, h2_task **ptask)
+{
+    apr_status_t rv = APR_EOF;
+    
+    *ptask = NULL;
+    ap_assert(m);
+    ap_assert(m->lock);
+    
+    if (APR_SUCCESS != (rv = apr_thread_mutex_lock(m->lock))) {
+        return rv;
+    }
+    
+    if (m->aborted) {
+        rv = APR_EOF;
+    }
+    else {
+        *ptask = next_stream_task(m);
+        rv = (*ptask != NULL && !h2_iq_empty(m->q))? APR_EAGAIN : APR_SUCCESS;
+    }
+    if (APR_EAGAIN != rv) {
+        m->is_registered = 0; /* h2_workers will discard this mplx */
+    }
+    H2_MPLX_LEAVE(m);
+    return rv;
+}
+
+static void task_done(h2_mplx *m, h2_task *task, h2_req_engine *ngn)
+{
+    h2_stream *stream;
+    
+    if (task->frozen) {
+        /* this task was handed over to an engine for processing 
+         * and the original worker has finished. That means the 
+         * engine may start processing now. */
+        h2_task_thaw(task);
+        apr_thread_cond_broadcast(m->task_thawed);
+        return;
+    }
+        
+    ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                  "h2_mplx(%ld): task(%s) done", m->id, task->id);
+    out_close(m, task);
+    
+    if (ngn) {
+        apr_off_t bytes = 0;
+        h2_beam_send(task->output.beam, NULL, APR_NONBLOCK_READ);
+        bytes += h2_beam_get_buffered(task->output.beam);
+        if (bytes > 0) {
+            /* we need to report consumed and current buffered output
+             * to the engine. The request will be streamed out or cancelled,
+             * no more data is coming from it and the engine should update
+             * its calculations before we destroy this information. */
+            h2_req_engine_out_consumed(ngn, task->c, bytes);
+        }
+    }
+    
+    if (task->engine) {
+        if (!m->aborted && !task->c->aborted 
+            && !h2_req_engine_is_shutdown(task->engine)) {
+            ap_log_cerror(APLOG_MARK, APLOG_DEBUG, 0, m->c, APLOGNO(10022)
+                          "h2_mplx(%ld): task(%s) has not-shutdown "
+                          "engine(%s)", m->id, task->id, 
+                          h2_req_engine_get_id(task->engine));
+        }
+        h2_ngn_shed_done_ngn(m->ngn_shed, task->engine);
+    }
+    
+    task->worker_done = 1;
+    task->done_at = apr_time_now();
+    ap_log_cerror(APLOG_MARK, APLOG_TRACE2, 0, m->c,
+                  "h2_mplx(%s): request done, %f ms elapsed", task->id, 
+                  (task->done_at - task->started_at) / 1000.0);
+    
+    if (task->started_at > m->last_idle_block) {
+        /* this task finished without causing an 'idle block', e.g.
+         * a block by flow control.
+         */
+        if (task->done_at- m->last_limit_change >= m->limit_change_interval
+            && m->limit_active < m->max_active) {
+            /* Well behaving stream, allow it more workers */
+            m->limit_active = H2MIN(m->limit_active * 2, 
+                                     m->max_active);
+            m->last_limit_change = task->done_at;
+            ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                          "h2_mplx(%ld): increase worker limit to %d",
+                          m->id, m->limit_active);
+        }
+    }
+    
+    stream = h2_ihash_get(m->streams, task->stream_id);
+    if (stream) {
+        /* stream not done yet. */
+        if (!m->aborted && h2_ihash_get(m->sredo, stream->id)) {
+            /* reset and schedule again */
+            h2_task_redo(task);
+            h2_ihash_remove(m->sredo, stream->id);
+            h2_iq_add(m->q, stream->id, NULL, NULL);
+        }
+        else {
+            /* stream not cleaned up, stay around */
+            ap_log_cerror(APLOG_MARK, APLOG_TRACE2, 0, m->c,
+                          H2_STRM_MSG(stream, "task_done, stream open")); 
+            if (stream->input) {
+                h2_beam_leave(stream->input);
+            }
+
+            /* more data will not arrive, resume the stream */
+            check_data_for(m, stream, 0);            
+        }
+    }
+    else if ((stream = h2_ihash_get(m->shold, task->stream_id)) != NULL) {
+        /* stream is done, was just waiting for this. */
+        ap_log_cerror(APLOG_MARK, APLOG_TRACE2, 0, m->c,
+                      H2_STRM_MSG(stream, "task_done, in hold"));
+        if (stream->input) {
+            h2_beam_leave(stream->input);
+        }
+        stream_joined(m, stream);
+    }
+    else if ((stream = h2_ihash_get(m->spurge, task->stream_id)) != NULL) {
+        ap_log_cerror(APLOG_MARK, APLOG_WARNING, 0, m->c,   
+                      H2_STRM_LOG(APLOGNO(03517), stream, "already in spurge"));
+        ap_assert("stream should not be in spurge" == NULL);
+    }
+    else {
+        ap_log_cerror(APLOG_MARK, APLOG_WARNING, 0, m->c, APLOGNO(03518)
+                      "h2_mplx(%s): task_done, stream not found", 
+                      task->id);
+        ap_assert("stream should still be available" == NULL);
+    }
+}
+
+void h2_mplx_task_done(h2_mplx *m, h2_task *task, h2_task **ptask)
+{
+    H2_MPLX_ENTER_ALWAYS(m);
+
+    task_done(m, task, NULL);
+    --m->tasks_active;
+    
+    if (m->join_wait) {
+        apr_thread_cond_signal(m->join_wait);
+    }
+    if (ptask) {
+        /* caller wants another task */
+        *ptask = next_stream_task(m);
+    }
+    register_if_needed(m);
+
+    H2_MPLX_LEAVE(m);
+}
+
+/*******************************************************************************
+ * h2_mplx DoS protection
+ ******************************************************************************/
+
+static int latest_repeatable_unsubmitted_iter(void *data, void *val)
+{
+    stream_iter_ctx *ctx = data;
+    h2_stream *stream = val;
+    
+    if (stream->task && !stream->task->worker_done 
+        && h2_task_can_redo(stream->task) 
+        && !h2_ihash_get(ctx->m->sredo, stream->id)) {
+        if (!h2_stream_is_ready(stream)) {
+            /* this task occupies a worker, the response has not been submitted 
+             * yet, not been cancelled and it is a repeatable request
+             * -> it can be re-scheduled later */
+            if (!ctx->stream 
+                || (ctx->stream->task->started_at < stream->task->started_at)) {
+                /* we did not have one or this one was started later */
+                ctx->stream = stream;
+            }
+        }
+    }
+    return 1;
+}
+
+static h2_stream *get_latest_repeatable_unsubmitted_stream(h2_mplx *m) 
+{
+    stream_iter_ctx ctx;
+    ctx.m = m;
+    ctx.stream = NULL;
+    h2_ihash_iter(m->streams, latest_repeatable_unsubmitted_iter, &ctx);
+    return ctx.stream;
+}
+
+static int timed_out_busy_iter(void *data, void *val)
+{
+    stream_iter_ctx *ctx = data;
+    h2_stream *stream = val;
+    if (stream->task && !stream->task->worker_done
+        && (ctx->now - stream->task->started_at) > stream->task->timeout) {
+        /* timed out stream occupying a worker, found */
+        ctx->stream = stream;
+        return 0;
+    }
+    return 1;
+}
+
+static h2_stream *get_timed_out_busy_stream(h2_mplx *m) 
+{
+    stream_iter_ctx ctx;
+    ctx.m = m;
+    ctx.stream = NULL;
+    ctx.now = apr_time_now();
+    h2_ihash_iter(m->streams, timed_out_busy_iter, &ctx);
+    return ctx.stream;
+}
+
+static apr_status_t unschedule_slow_tasks(h2_mplx *m) 
+{
+    h2_stream *stream;
+    int n;
+    
+    /* Try to get rid of streams that occupy workers. Look for safe requests
+     * that are repeatable. If none found, fail the connection.
+     */
+    n = (m->tasks_active - m->limit_active - (int)h2_ihash_count(m->sredo));
+    while (n > 0 && (stream = get_latest_repeatable_unsubmitted_stream(m))) {
+        h2_task_rst(stream->task, H2_ERR_CANCEL);
+        h2_ihash_add(m->sredo, stream);
+        --n;
+    }
+    
+    if ((m->tasks_active - h2_ihash_count(m->sredo)) > m->limit_active) {
+        h2_stream *stream = get_timed_out_busy_stream(m);
+        if (stream) {
+            /* Too many busy workers, unable to cancel enough streams
+             * and with a busy, timed out stream, we tell the client
+             * to go away... */
+            return APR_TIMEUP;
+        }
+    }
+    return APR_SUCCESS;
+}
+
+apr_status_t h2_mplx_idle(h2_mplx *m)
+{
+    apr_status_t status = APR_SUCCESS;
+    apr_time_t now;            
+    apr_size_t scount;
+    
+    H2_MPLX_ENTER(m);
+
+    scount = h2_ihash_count(m->streams);
+    if (scount > 0) {
+        if (m->tasks_active) {
+            /* If we have streams in connection state 'IDLE', meaning
+             * all streams are ready to sent data out, but lack
+             * WINDOW_UPDATEs. 
+             * 
+             * This is ok, unless we have streams that still occupy
+             * h2 workers. As worker threads are a scarce resource, 
+             * we need to take measures that we do not get DoSed.
+             * 
+             * This is what we call an 'idle block'. Limit the amount 
+             * of busy workers we allow for this connection until it
+             * well behaves.
+             */
+            now = apr_time_now();
+            m->last_idle_block = now;
+            if (m->limit_active > 2 
+                && now - m->last_limit_change >= m->limit_change_interval) {
+                if (m->limit_active > 16) {
+                    m->limit_active = 16;
+                }
+                else if (m->limit_active > 8) {
+                    m->limit_active = 8;
+                }
+                else if (m->limit_active > 4) {
+                    m->limit_active = 4;
+                }
+                else if (m->limit_active > 2) {
+                    m->limit_active = 2;
+                }
+                m->last_limit_change = now;
+                ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                              "h2_mplx(%ld): decrease worker limit to %d",
+                              m->id, m->limit_active);
+            }
+            
+            if (m->tasks_active > m->limit_active) {
+                status = unschedule_slow_tasks(m);
+            }
+        }
+        else if (!h2_iq_empty(m->q)) {
+            ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                          "h2_mplx(%ld): idle, but %d streams to process",
+                          m->id, (int)h2_iq_count(m->q));
+            status = APR_EAGAIN;
+        }
+        else {
+            /* idle, have streams, but no tasks active. what are we waiting for?
+             * WINDOW_UPDATEs from client? */
+            h2_stream *stream = NULL;
+            
+            ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                          "h2_mplx(%ld): idle, no tasks ongoing, %d streams",
+                          m->id, (int)h2_ihash_count(m->streams));
+            h2_ihash_shift(m->streams, (void**)&stream, 1);
+            if (stream) {
+                h2_ihash_add(m->streams, stream);
+                if (stream->output && !stream->out_checked) {
+                    /* FIXME: this looks like a race between the session thinking
+                     * it is idle and the EOF on a stream not being sent.
+                     * Signal to caller to leave IDLE state.
+                     */
+                    ap_log_cerror(APLOG_MARK, APLOG_TRACE2, 0, m->c,
+                                  H2_STRM_MSG(stream, "output closed=%d, mplx idle"
+                                              ", out has %ld bytes buffered"),
+                                  h2_beam_is_closed(stream->output),
+                                  (long)h2_beam_get_buffered(stream->output));
+                    h2_ihash_add(m->streams, stream);
+                    check_data_for(m, stream, 0);
+                    stream->out_checked = 1;
+                    status = APR_EAGAIN;
+                }
+            }
+        }
+    }
+    register_if_needed(m);
+
+    H2_MPLX_LEAVE(m);
+    return status;
+}
+
+/*******************************************************************************
+ * HTTP/2 request engines
+ ******************************************************************************/
+
+typedef struct {
+    h2_mplx * m;
+    h2_req_engine *ngn;
+    int streams_updated;
+} ngn_update_ctx;
+
+static int ngn_update_window(void *ctx, void *val)
+{
+    ngn_update_ctx *uctx = ctx;
+    h2_stream *stream = val;
+    if (stream->task && stream->task->assigned == uctx->ngn
+        && output_consumed_signal(uctx->m, stream->task)) {
+        ++uctx->streams_updated;
+    }
+    return 1;
+}
+
+static apr_status_t ngn_out_update_windows(h2_mplx *m, h2_req_engine *ngn)
+{
+    ngn_update_ctx ctx;
+        
+    ctx.m = m;
+    ctx.ngn = ngn;
+    ctx.streams_updated = 0;
+    h2_ihash_iter(m->streams, ngn_update_window, &ctx);
+    
+    return ctx.streams_updated? APR_SUCCESS : APR_EAGAIN;
+}
+
+apr_status_t h2_mplx_req_engine_push(const char *ngn_type, 
+                                     request_rec *r,
+                                     http2_req_engine_init *einit)
+{
+    apr_status_t status;
+    h2_mplx *m;
+    h2_task *task;
+    h2_stream *stream;
+    
+    task = h2_ctx_rget_task(r);
+    if (!task) {
+        return APR_ECONNABORTED;
+    }
+    m = task->mplx;
+    
+    H2_MPLX_ENTER(m);
+
+    stream = h2_ihash_get(m->streams, task->stream_id);
+    if (stream) {
+        status = h2_ngn_shed_push_request(m->ngn_shed, ngn_type, r, einit);
+    }
+    else {
+        status = APR_ECONNABORTED;
+    }
+
+    H2_MPLX_LEAVE(m);
+    return status;
+}
+
+apr_status_t h2_mplx_req_engine_pull(h2_req_engine *ngn, 
+                                     apr_read_type_e block, 
+                                     int capacity, 
+                                     request_rec **pr)
+{   
+    h2_ngn_shed *shed = h2_ngn_shed_get_shed(ngn);
+    h2_mplx *m = h2_ngn_shed_get_ctx(shed);
+    apr_status_t status;
+    int want_shutdown;
+    
+    H2_MPLX_ENTER(m);
+
+    want_shutdown = (block == APR_BLOCK_READ);
+
+    /* Take this opportunity to update output consummation 
+     * for this engine */
+    ngn_out_update_windows(m, ngn);
+    
+    if (want_shutdown && !h2_iq_empty(m->q)) {
+        /* For a blocking read, check first if requests are to be
+         * had and, if not, wait a short while before doing the
+         * blocking, and if unsuccessful, terminating read.
+         */
+        status = h2_ngn_shed_pull_request(shed, ngn, capacity, 1, pr);
+        if (APR_STATUS_IS_EAGAIN(status)) {
+            ap_log_cerror(APLOG_MARK, APLOG_TRACE1, 0, m->c,
+                          "h2_mplx(%ld): start block engine pull", m->id);
+            apr_thread_cond_timedwait(m->task_thawed, m->lock, 
+                                      apr_time_from_msec(20));
+            status = h2_ngn_shed_pull_request(shed, ngn, capacity, 1, pr);
+        }
+    }
+    else {
+        status = h2_ngn_shed_pull_request(shed, ngn, capacity,
+                                          want_shutdown, pr);
+    }
+
+    H2_MPLX_LEAVE(m);
+    return status;
+}
+ 
+void h2_mplx_req_engine_done(h2_req_engine *ngn, conn_rec *r_conn,
+                             apr_status_t status)
+{
+    h2_task *task = h2_ctx_cget_task(r_conn);
+    
+    if (task) {
+        h2_mplx *m = task->mplx;
+        h2_stream *stream;
+
+        H2_MPLX_ENTER_ALWAYS(m);
+
+        stream = h2_ihash_get(m->streams, task->stream_id);
+        
+        ngn_out_update_windows(m, ngn);
+        h2_ngn_shed_done_task(m->ngn_shed, ngn, task);
+        
+        if (status != APR_SUCCESS && stream 
+            && h2_task_can_redo(task) 
+            && !h2_ihash_get(m->sredo, stream->id)) {
+            h2_ihash_add(m->sredo, stream);
+        }
+
+        if (task->engine) { 
+            /* cannot report that as done until engine returns */
+        }
+        else {
+            task_done(m, task, ngn);
+        }
+
+        H2_MPLX_LEAVE(m);
+    }
+}
+
+/*******************************************************************************
+ * mplx master events dispatching
+ ******************************************************************************/
+
+int h2_mplx_has_master_events(h2_mplx *m)
+{
+    return apr_atomic_read32(&m->event_pending) > 0;
+}
+
+apr_status_t h2_mplx_dispatch_master_events(h2_mplx *m, 
+                                            stream_ev_callback *on_resume, 
+                                            void *on_ctx)
+{
+    h2_stream *stream;
+    int n, id;
+    
+    ap_log_cerror(APLOG_MARK, APLOG_TRACE2, 0, m->c, 
+                  "h2_mplx(%ld): dispatch events", m->id);        
+    apr_atomic_set32(&m->event_pending, 0);
+
+    /* update input windows for streams */
+    h2_ihash_iter(m->streams, report_consumption_iter, m);    
+    purge_streams(m, 1);
+    
+    n = h2_ififo_count(m->readyq);
+    while (n > 0 
+           && (h2_ififo_try_pull(m->readyq, &id) == APR_SUCCESS)) {
+        --n;
+        stream = h2_ihash_get(m->streams, id);
+        if (stream) {
+            on_resume(on_ctx, stream);
+        }
+    }
+    
+    return APR_SUCCESS;
+}
+
+apr_status_t h2_mplx_keep_active(h2_mplx *m, h2_stream *stream)
+{
+    check_data_for(m, stream, 1);
+    return APR_SUCCESS;
+}
+
+int h2_mplx_awaits_data(h2_mplx *m)
+{
+    int waiting = 1;
+     
+    H2_MPLX_ENTER_ALWAYS(m);
+
+    if (h2_ihash_empty(m->streams)) {
+        waiting = 0;
+    }
+    else if (!m->tasks_active && !h2_ififo_count(m->readyq)
+             && h2_iq_empty(m->q)) {
+        waiting = 0;
+    }
+
+    H2_MPLX_LEAVE(m);
+    return waiting;
+}