Rewrite pages asynchronously (branch jefftk-async-rewrite, pull request 11).

config

@@ -57,6 +57,7 @@ if [ $ngx_found = yes ]; then
   ngx_addon_name=ngx_pagespeed
   NGX_ADDON_SRCS="$NGX_ADDON_SRCS $ps_src/ngx_pagespeed.cc"
   NGX_ADDON_SRCS="$NGX_ADDON_SRCS $ps_src/ngx_rewrite_driver_factory.cc"
+  NGX_ADDON_SRCS="$NGX_ADDON_SRCS $ps_src/ngx_base_fetch.cc"
   HTTP_AUX_FILTER_MODULES="$HTTP_AUX_FILTER_MODULES $ngx_addon_name"
   CORE_LIBS="$CORE_LIBS $pagespeed_libs"
   CORE_INCS="$CORE_INCS $pagespeed_include"

src/ngx_base_fetch.cc

@@ -0,0 +1,165 @@
+/*
+ * Copyright 2012 Google Inc.
+ *
+ * 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.
+ */
+
+// Author: jefftk@google.com (Jeff Kaufman)
+
+#include "ngx_base_fetch.h"
+#include "ngx_pagespeed.h"
+#include "net/instaweb/util/public/google_message_handler.h"
+#include "net/instaweb/util/public/message_handler.h"
+
+namespace net_instaweb {
+
+NgxBaseFetch::NgxBaseFetch(ngx_http_request_t* r, int pipe_fd)
+    : request_(r), done_called_(false), pipe_fd_(pipe_fd) {
+}
+
+NgxBaseFetch::~NgxBaseFetch() { }
+
+void NgxBaseFetch::PopulateHeaders() {
+  // http_version is the version number of protocol; 1.1 = 1001. See
+  // NGX_HTTP_VERSION_* in ngx_http_request.h 
+  response_headers()->set_major_version(request_->http_version / 1000);
+  response_headers()->set_minor_version(request_->http_version % 1000);
+
+  // Standard nginx idiom for iterating over a list.  See ngx_list.h
+  ngx_uint_t i;
+  ngx_list_part_t* part = &request_->headers_out.headers.part;
+  ngx_table_elt_t* header = static_cast<ngx_table_elt_t*>(part->elts);
+
+  for (i = 0 ; /* void */; i++) {
+    if (i >= part->nelts) {
+      if (part->next == NULL) {
+        break;
+      }
+
+      part = part->next;
+      header = static_cast<ngx_table_elt_t*>(part->elts);
+      i = 0;
+    }
+
+    StringPiece key = ngx_http_pagespeed_str_to_string_piece(&header[i].key);
+    StringPiece value = ngx_http_pagespeed_str_to_string_piece(
+        &header[i].value);
+
+    response_headers()->Add(key, value);
+  }
+
+  // For some reason content_type is not included in
+  // request_->headers_out.headers, which means I don't fully understand how
+  // headers_out works, but manually copying over content type works.
+  StringPiece content_type = ngx_http_pagespeed_str_to_string_piece(
+      &request_->headers_out.content_type);
+  response_headers()->Add(HttpAttributes::kContentType, content_type);
+}
+
+bool NgxBaseFetch::HandleWrite(const StringPiece& sp,
+                               MessageHandler* handler) {
+  // TODO(jefftk): acquire lock on buffer_ here.
+  buffer_.append(sp.data(), sp.size());
+  // TODO(jefftk): release lock here.
+  return true;
+}
+
+// TODO(jefftk): this is vulnerable to race conditions.  Memory inconsistencies
+// between threads can mean that chain links get dropped, which is of course
+// very bad.  To fix this we should protect buffer_ with a lock that gets
+// acquired both here and in HandleWrite so that we make sure they both have a
+// consistent view of memory.
+//
+// There may also be a race condition if this is called between the last Write()
+// and Done() such that we're sending an empty buffer with last_buf set, which I
+// think nginx will reject.
+ngx_int_t NgxBaseFetch::CollectAccumulatedWrites(ngx_chain_t** link_ptr) {
+  // TODO(jefftk): acquire lock on buffer_ here.
+
+  if (!done_called_ && buffer_.length() == 0) {
+    // Nothing to send.  But if done_called_ then we can't short circuit because
+    // we need to set last_buf.
+    *link_ptr = NULL;
+    return NGX_OK;
+  }
+
+  // Prepare a new nginx buffer to put our buffered writes into.
+  ngx_buf_t* b = static_cast<ngx_buf_t*>(ngx_calloc_buf(request_->pool));
+  if (b == NULL) {
+    return NGX_ERROR;
+  }
+  b->start = b->pos = static_cast<u_char*>(
+      ngx_palloc(request_->pool, buffer_.length()));
+  if (b->pos == NULL) {
+    return NGX_ERROR;
+  }
+
+  // Copy our writes over.
+  buffer_.copy(reinterpret_cast<char*>(b->pos), buffer_.length());
+  b->last = b->end = b->pos + buffer_.length();
+
+  if (buffer_.length()) {
+    b->temporary = 1;
+  } else {
+    b->sync = 1;
+  }
+
+  // Done with buffer contents now.
+  buffer_.clear();
+
+  // TODO(jefftk): release lock here.
+
+  b->last_buf = b->last_in_chain = done_called_;
+  
+  // Prepare a chain link for our new buffer.
+  *link_ptr = static_cast<ngx_chain_t*>(
+      ngx_alloc_chain_link(request_->pool));
+  if (*link_ptr == NULL) {
+    return NGX_ERROR;
+  }
+
+  (*link_ptr)->buf = b;
+  (*link_ptr)->next = NULL;
+  return NGX_OK;
+}
+
+void NgxBaseFetch::RequestCollection() {
+  int rc;
+  char c = 'A';  // What byte we write is arbitrary.
+  while (true) {
+    rc = write(pipe_fd_, &c, 1);
+    if (rc == 1) {
+      break;
+    } else if (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK) {
+      // TODO(jefftk): is this rare enough that spinning isn't a problem?  Could
+      // we get into a case where the pipe fills up and we spin forever?
+      
+    } else {
+      perror("NgxBaseFetch::RequestCollection");
+      break;
+    }
+  }
+}
+
+bool NgxBaseFetch::HandleFlush(MessageHandler* handler) {
+  RequestCollection();  // data available.
+  return true;
+}
+
+void NgxBaseFetch::HandleDone(bool success) {
+  done_called_ = true;
+  close(pipe_fd_);  // Indicates to nginx that we're done with the rewrite.
+  pipe_fd_ = -1;
+}
+
+}  // namespace net_instaweb

src/ngx_base_fetch.h

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2012 Google Inc.
+ *
+ * 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.
+ */
+
+// Author: jefftk@google.com (Jeff Kaufman)
+//
+// Collects output from pagespeed and buffers it until nginx asks for it.
+// Notifies nginx via pipe to call CollectAccumulatedWrites() on flush.
+//
+//  - nginx creates a base fetch and passes it to a new proxy fetch.
+//  - The proxy fetch manages rewriting and thread complexity, and through
+//    several chained steps passes rewritten html to HandleWrite().
+//  - Written data is buffered.
+//  - When Flush() is called the base fetch writes a byte to a pipe nginx is
+//    watching so nginx knows to call CollectAccumulatedWrites() to pick up the
+//    rewritten html.
+//  - When Done() is called the base fetch closes the pipe, which tells nginx to
+//    make a final call to CollectAccumulatedWrites().
+
+#ifndef NGX_BASE_FETCH_H_
+#define NGX_BASE_FETCH_H_
+
+extern "C" {
+#include <ngx_http.h>
+}
+
+#include "net/instaweb/http/public/async_fetch.h"
+#include "net/instaweb/util/public/string.h"
+
+namespace net_instaweb {
+
+class NgxBaseFetch : public AsyncFetch {
+ public:
+  NgxBaseFetch(ngx_http_request_t* r, int pipe_fd);
+  virtual ~NgxBaseFetch();
+
+  // Copies the response headers out of request_->headers_out->headers.
+  void PopulateHeaders();
+
+  // Puts a chain link in link_ptr if we have any output data buffered.  Returns
+  // NGX_OK on success, NGX_ERROR on errors.  If there's no data to send, sends
+  // data only if Done() has been called.  Indicates the end of output by
+  // setting last_buf on the chain link
+  //
+  // Always sets link_ptr to a single chain link, never a full chain.
+  //
+  // Called by nginx.
+  ngx_int_t CollectAccumulatedWrites(ngx_chain_t** link_ptr);
+
+ private:
+  ResponseHeaders response_headers_;
+  virtual bool HandleWrite(const StringPiece& sp, MessageHandler* handler);
+  virtual bool HandleFlush(MessageHandler* handler);
+  virtual void HandleHeadersComplete() {}
+  virtual void HandleDone(bool success);
+
+  // Indicate to nginx that we would like it to call
+  // CollectAccumulatedWrites().
+  void RequestCollection();
+
+  ngx_http_request_t* request_;
+  GoogleString buffer_;
+  bool done_called_;
+  int pipe_fd_;
+
+  DISALLOW_COPY_AND_ASSIGN(NgxBaseFetch);
+};
+
+} // namespace net_instaweb
+
+#endif  // NGX_BASE_FETCH_H_

src/ngx_pagespeed.cc

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+// Author: jefftk@google.com (Jeff Kaufman)
+
 /*
  * Usage:
  *   server {
@@ -21,43 +23,112 @@
  *   }
  */
 
+#include "ngx_pagespeed.h"
+
 extern "C" {
   #include <ngx_config.h>
   #include <ngx_core.h>
   #include <ngx_http.h>
 }
 
-#include "ngx_rewrite_driver_factory.h"
+#include <unistd.h>
 
+#include "ngx_rewrite_driver_factory.h"
+#include "ngx_base_fetch.h"
+
+#include "net/instaweb/automatic/public/proxy_fetch.h"
+#include "net/instaweb/rewriter/public/furious_matcher.h"
 #include "net/instaweb/rewriter/public/process_context.h"
 #include "net/instaweb/rewriter/public/rewrite_driver.h"
 #include "net/instaweb/public/version.h"
+#include "net/instaweb/util/public/google_url.h"
 #include "net/instaweb/util/public/string.h"
-#include "net/instaweb/util/public/string_util.h"
-#include "net/instaweb/util/public/string_writer.h"
-#include "net/instaweb/util/public/null_message_handler.h"
+#include "net/instaweb/util/public/google_message_handler.h"
 
 extern ngx_module_t ngx_pagespeed;
 
 // Hacks for debugging.
 #define DBG(r, args...)                                       \
-  ngx_log_error(NGX_LOG_ALERT, (r)->connection->log, 0, args)
+  ngx_log_error(NGX_LOG_DEBUG, (r)->connection->log, 0, args)
+#define PDBG(ctx, args...)                                       \
+  ngx_log_error(NGX_LOG_DEBUG, (ctx)->pagespeed_connection->log, 0, args)
 #define CDBG(cf, args...)                                     \
-  ngx_conf_log_error(NGX_LOG_ALERT, cf, 0, args)
+  ngx_conf_log_error(NGX_LOG_DEBUG, cf, 0, args)
 
 typedef struct {
   ngx_flag_t active;
   ngx_str_t cache_dir;
   net_instaweb::NgxRewriteDriverFactory* driver_factory;
   net_instaweb::ServerContext* server_context;
+  net_instaweb::ProxyFetchFactory* proxy_fetch_factory;
+  net_instaweb::MessageHandler* handler;
 } ngx_http_pagespeed_srv_conf_t;
 
 typedef struct {
+  ngx_http_pagespeed_srv_conf_t* cfg;
   net_instaweb::RewriteDriver* driver;
-  scoped_ptr<GoogleString> output;
-  scoped_ptr<net_instaweb::StringWriter> writer;
+  net_instaweb::ProxyFetch* proxy_fetch;
+  net_instaweb::NgxBaseFetch* base_fetch;
+  bool data_received;
+  int pipe_fd;
+  ngx_connection_t* pagespeed_connection;
+  ngx_http_request_t* r;
+  const net_instaweb::ContentType* content_type;
 } ngx_http_pagespeed_request_ctx_t;
 
+static ngx_int_t
+ngx_http_pagespeed_body_filter(ngx_http_request_t* r, ngx_chain_t* in);
+
+static void*
+ngx_http_pagespeed_create_srv_conf(ngx_conf_t* cf);
+
+static char*
+ngx_http_pagespeed_merge_srv_conf(ngx_conf_t* cf, void* parent, void* child);
+
+static void
+ngx_http_pagespeed_release_request_context(void* data);
+
+static void
+ngx_http_pagespeed_set_buffered(ngx_http_request_t* r, bool on);
+
+static GoogleString
+ngx_http_pagespeed_determine_url(ngx_http_request_t* r);
+
+static ngx_http_pagespeed_request_ctx_t*
+ngx_http_pagespeed_get_request_context(ngx_http_request_t* r);
+
+static void
+ngx_http_pagespeed_initialize_server_context(
+    ngx_http_pagespeed_srv_conf_t* cfg);
+
+static ngx_int_t
+ngx_http_pagespeed_update(ngx_http_pagespeed_request_ctx_t* ctx,
+                          ngx_event_t* ev);
+
+static void
+ngx_http_pagespeed_connection_read_handler(ngx_event_t* ev);
+
+static ngx_int_t
+ngx_http_pagespeed_create_connection(ngx_http_pagespeed_request_ctx_t* ctx);
+
+static ngx_int_t
+ngx_http_pagespeed_create_request_context(ngx_http_request_t* r);
+
+static void
+ngx_http_pagespeed_send_to_pagespeed(
+    ngx_http_request_t* r,
+    ngx_http_pagespeed_request_ctx_t* ctx,
+    ngx_chain_t* in);
+
+static ngx_int_t
+ngx_http_pagespeed_body_filter(ngx_http_request_t* r, ngx_chain_t* in);
+
+static ngx_int_t
+ngx_http_pagespeed_header_filter(ngx_http_request_t* r);
+
+static ngx_int_t
+ngx_http_pagespeed_init(ngx_conf_t* cf);
+
 static ngx_command_t ngx_http_pagespeed_commands[] = {
   { ngx_string("pagespeed"),
     NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_TAKE1,
@@ -65,7 +136,6 @@ static ngx_command_t ngx_http_pagespeed_commands[] = {
     NGX_HTTP_SRV_CONF_OFFSET,
     offsetof(ngx_http_pagespeed_srv_conf_t, active),
     NULL },
-
   { ngx_string("pagespeed_cache"),
     NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_CONF_TAKE1,
     ngx_conf_set_str_slot,
@@ -76,14 +146,13 @@ static ngx_command_t ngx_http_pagespeed_commands[] = {
   ngx_null_command
 };
 
-static StringPiece
+StringPiece
 ngx_http_pagespeed_str_to_string_piece(ngx_str_t* s) {
   return StringPiece(reinterpret_cast<char*>(s->data), s->len);
 }
 
 static void*
-ngx_http_pagespeed_create_srv_conf(ngx_conf_t* cf)
-{
+ngx_http_pagespeed_create_srv_conf(ngx_conf_t* cf) {
   ngx_http_pagespeed_srv_conf_t* conf;
 
   conf = static_cast<ngx_http_pagespeed_srv_conf_t*>(
@@ -102,8 +171,7 @@ ngx_http_pagespeed_create_srv_conf(ngx_conf_t* cf)
 }
 
 static char*
-ngx_http_pagespeed_merge_srv_conf(ngx_conf_t* cf, void* parent, void* child)
-{
+ngx_http_pagespeed_merge_srv_conf(ngx_conf_t* cf, void* parent, void* child) {
   ngx_http_pagespeed_srv_conf_t* prev =
       static_cast<ngx_http_pagespeed_srv_conf_t*>(parent);
   ngx_http_pagespeed_srv_conf_t* conf =
@@ -118,78 +186,42 @@ ngx_http_pagespeed_merge_srv_conf(ngx_conf_t* cf, void* parent, void* child)
 static ngx_http_output_header_filter_pt ngx_http_next_header_filter;
 static ngx_http_output_body_filter_pt ngx_http_next_body_filter;
 
-// Add a buffer to the end of the buffer chain indicating that we were processed
-// through ngx_pagespeed.
-static ngx_int_t
-ngx_http_pagespeed_note_processed(ngx_http_request_t* r, ngx_chain_t* in) {
-  // Find the end of the buffer chain.
-  ngx_chain_t* chain_link;
-  int chain_contains_last_buffer = 0;
-  for (chain_link = in; chain_link != NULL; chain_link = chain_link->next) {
-    if (chain_link->buf->last_buf) {
-      chain_contains_last_buffer = 1;
-      if (chain_link->next != NULL) {
-        ngx_log_error(NGX_LOG_ERR, (r)->connection->log, 0,
-                      "Chain link thinks its last but has a child.");
-        return NGX_ERROR;
-      }
-      break;  // Chain link now is the last link in the chain.
-    }
-  }
-
-  if (!chain_contains_last_buffer) {
-    // None of the buffers had last_buf set, meaning we have an incomplete chain
-    // and are still waiting to get the final buffer.  Wait until we're called
-    // again with the last buffer.
-    return NGX_OK;
-  }
-
-  // Prepare a new buffer to put the note into.
-  ngx_buf_t* b = static_cast<ngx_buf_t*>(ngx_calloc_buf(r->pool));
-  if (b == NULL) {
-    return NGX_ERROR;
-  }
-
-  // Write to the new buffer.
-  const char note[] = "<!-- Processed through ngx_pagespeed using PSOL version "
-      MOD_PAGESPEED_VERSION_STRING " -->\n";
-  int note_len = strlen(note);
-  b->start = b->pos = static_cast<u_char*>(ngx_pnalloc(r->pool, note_len));
-  strncpy((char*)b->pos, note, note_len);
-  b->end = b->last = b->pos + note_len;
-  b->temporary = 1;
-
-  // Link the new buffer into the buffer chain.
-  ngx_chain_t* added_link = static_cast<ngx_chain_t*>(
-      ngx_alloc_chain_link(r->pool));
-  if (added_link == NULL) {
-    return NGX_ERROR;
-  }
-
-  added_link->buf = b;
-
-  // Add our new link to the buffer chain.
-  added_link->next = NULL;
-  chain_link->next = added_link;
-
-  // Mark our new link as the end of the chain.
-  chain_link->buf->last_buf = 0;
-  added_link->buf->last_buf = 1;
-  chain_link->buf->last_in_chain = 0;
-  added_link->buf->last_in_chain = 1;
-
-  return NGX_OK;
-}
-
 static void
-ngx_http_pagespeed_release_request_context(
-    ngx_http_request_t* r, ngx_http_pagespeed_request_ctx_t* ctx) {
+ngx_http_pagespeed_release_request_context(void* data) {
+  ngx_http_pagespeed_request_ctx_t* ctx =
+      static_cast<ngx_http_pagespeed_request_ctx_t*>(data);
+
+  // The proxy fetch deleted itself if we called Done(), but if an error
+  // happened before then we need to tell it to delete itself.
+  if (ctx->proxy_fetch != NULL) {
+    ctx->proxy_fetch->Done(false /* failure */);
+  }
+
+  // BaseFetch doesn't delete itself in HandleDone() because we still need to
+  // recieve notification via pipe and call CollectAccumulatedWrites.
+  // TODO(jefftk): If we close the proxy_fetch above and not in the normal flow,
+  // can this delete base_fetch while proxy_fetch still needs it? Is there a
+  // race condition here?
+  delete ctx->base_fetch;
+
+  // Don't close the pipe if it was never opened or already closed.
+  if (ctx->pipe_fd != -1) {
+    close(ctx->pipe_fd);
+  }
 
-    // release request context
-    ngx_http_set_ctx(r, NULL, ngx_pagespeed);
   delete ctx;
 }
 
+// Tell nginx whether we have network activity we're waiting for so that it sets
+// a write handler.  See src/http/ngx_http_request.c:2083.
+static void
+ngx_http_pagespeed_set_buffered(ngx_http_request_t* r, bool on) {
+  if (on) {
+    r->buffered |= NGX_HTTP_SSI_BUFFERED;
+  } else {
+    r->buffered &= ~NGX_HTTP_SSI_BUFFERED;
+  }
+}
 
 static GoogleString
 ngx_http_pagespeed_determine_url(ngx_http_request_t* r) {
@@ -263,179 +295,316 @@ ngx_http_pagespeed_initialize_server_context(
   // TODO(jefftk): We should call NgxRewriteDriverFactory::Terminate() when
   // we're done with it.
 
+  cfg->handler = new net_instaweb::GoogleMessageHandler();
+
   cfg->driver_factory = new net_instaweb::NgxRewriteDriverFactory();
   cfg->driver_factory->set_filename_prefix(
       ngx_http_pagespeed_str_to_string_piece(&cfg->cache_dir));
   cfg->server_context = cfg->driver_factory->CreateServerContext();
-
-  // In real use, with filters coming from the user, this would be some other
-  // kind of message handler that actually sent errors back to the user.
-  net_instaweb::NullMessageHandler handler;
+  cfg->proxy_fetch_factory =
+      new net_instaweb::ProxyFetchFactory(cfg->server_context);
 
   // Turn on some filters so we can see if this is working.  These filters are
-  // specifically chosen as ones that don't make requests for subresources or do
-  // work that needs to complete asynchronously.  They should be fast enough to
-  // run in the line of the request.
+  // chosen to make sub-resource fetches but not create any *.pagespeed.*
+  // resource urls because we don't yet have a handler in place for them.
   net_instaweb::RewriteOptions* global_options =
       cfg->server_context->global_options();
   global_options->SetRewriteLevel(net_instaweb::RewriteOptions::kPassThrough);
   global_options->EnableFiltersByCommaSeparatedList(
-      "collapse_whitespace,remove_comments,remove_quotes", &handler);
+      "collapse_whitespace,remove_comments,remove_quotes,"
+      "inline_css,inline_javascript,rewrite_css", cfg->handler);
 }
 
-
-// Set us up for processing a request.  When the request finishes, call
-// ngx_http_pagespeed_release_request_context.
+// Returns:
+//   NGX_OK: pagespeed is done, request complete
+//   NGX_AGAIN: pagespeed still working, needs to be called again later
+//   NGX_ERROR: error
 static ngx_int_t
-ngx_http_pagespeed_create_request_context(ngx_http_request_t* r) {
-  ngx_http_pagespeed_srv_conf_t* cfg =
-      static_cast<ngx_http_pagespeed_srv_conf_t*>(
-          ngx_http_get_module_srv_conf(r, ngx_pagespeed));
+ngx_http_pagespeed_update(ngx_http_pagespeed_request_ctx_t* ctx,
+                          ngx_event_t* ev) {
+  bool done;
+  int rc;
+  char chr;
+  do {
+    rc = read(ctx->pipe_fd, &chr, 1);
+  } while (rc == -1 && errno == EINTR);  // Retry on EINTR.
 
-  if (cfg->driver_factory == NULL) {
-    // This is the first request handled by this server block.
-    ngx_http_pagespeed_initialize_server_context(cfg);
-  }
+  // read() should only ever return 0 (closed), 1 (data), or -1 (error).
+  CHECK(rc == -1 || rc == 0 || rc == 1);
 
-  // Pull the server context out of the per-server config.
-  net_instaweb::ServerContext* server_context =
-      static_cast<ngx_http_pagespeed_srv_conf_t*>(
-          ngx_http_get_module_srv_conf(r, ngx_pagespeed))->server_context;
-
-  if (server_context == NULL) {
-    ngx_log_error(NGX_LOG_ERR, (r)->connection->log, 0,
-                  "ServerContext should have been initialized.");
+  if (rc == -1) {
+    if (errno == EAGAIN || errno == EWOULDBLOCK) {
+      PDBG(ctx, "no data to read from pagespeed yet");
+      return NGX_AGAIN;
+    } else {
+      perror("ngx_http_pagespeed_connection_read_handler");
       return NGX_ERROR;
     }
+  } else {
+    // We're done iff we read 0 bytes because that means the pipe was closed.
+    done = (rc == 0);
+  }
 
-  GoogleString url = ngx_http_pagespeed_determine_url(r);
+  // Get output from pagespeed.
+  ngx_chain_t* cl;
+  rc = ctx->base_fetch->CollectAccumulatedWrites(&cl);
+  if (rc != NGX_OK) {
+    PDBG(ctx, "problem with CollectAccumulatedWrites");
+    return rc;
+  }
+
+  rc = ngx_http_next_body_filter(ctx->r, cl);
+  if (rc != NGX_OK) {
+    return rc;
+  }
+  
+  return done ? NGX_OK : NGX_AGAIN;
+}
+
+static void
+ngx_http_pagespeed_connection_read_handler(ngx_event_t* ev) {
+  CHECK(ev != NULL);
+
+  ngx_connection_t* c = static_cast<ngx_connection_t*>(ev->data);
+  CHECK(c != NULL);
 
   ngx_http_pagespeed_request_ctx_t* ctx =
-      new ngx_http_pagespeed_request_ctx_t();
+      static_cast<ngx_http_pagespeed_request_ctx_t*>(c->data);
+  CHECK(ctx != NULL);
 
-  ctx->driver = server_context->NewRewriteDriver();
+  int rc = ngx_http_pagespeed_update(ctx, ev);
+  CHECK(rc == NGX_OK || rc == NGX_ERROR || rc == NGX_AGAIN);
+  if (rc == NGX_AGAIN) {
+    // request needs more work by pagespeed
+    rc = ngx_handle_read_event(ev, 0);    
+    CHECK(rc == NGX_OK);
+  } else {
+    ngx_del_event(ev, NGX_READ_EVENT, 0);
+    ngx_http_pagespeed_set_buffered(ctx->r, false);
+    ngx_http_finalize_request(ctx->r, rc == NGX_OK ? NGX_DONE : NGX_ERROR);
+  }
+}
 
-  // TODO(jefftk): replace this with a writer that generates proper nginx
-  // buffers and puts them in the chain.  Or avoids the double
-  // copy some other way.
-  ctx->output.reset(new GoogleString());
-  ctx->writer.reset(new net_instaweb::StringWriter(ctx->output.get()));
-  ctx->driver->SetWriter(ctx->writer.get());
-
-  // For testing we always want to perform any optimizations we can, so we
-  // wait until everything is done rather than using a deadline, the way we
-  // want to eventually.
-  ctx->driver->set_fully_rewrite_on_flush(true);
-
-  ngx_http_set_ctx(r, ctx, ngx_pagespeed);
-  bool ok = ctx->driver->StartParse(url);
-  if (!ok) {
-    ngx_log_error(NGX_LOG_ERR, (r)->connection->log, 0,
-                  "Failed to StartParse on url %*s",
-                  url.size(), url.data());
+static ngx_int_t
+ngx_http_pagespeed_create_connection(ngx_http_pagespeed_request_ctx_t* ctx) {
+  ngx_connection_t* c = ngx_get_connection(
+      ctx->pipe_fd, ctx->r->connection->log);
+  if (c == NULL) {
     return NGX_ERROR;
   }
 
+  c->recv = ngx_recv;
+  c->send = ngx_send;
+  c->recv_chain = ngx_recv_chain;
+  c->send_chain = ngx_send_chain;
+
+  c->log_error = ctx->r->connection->log_error;
+
+  c->read->log = c->log;
+  c->write->log = c->log;
+
+  ctx->pagespeed_connection = c;
+
+  // Tell nginx to monitor this pipe and call us back when there's data.
+  c->data = ctx;
+  c->read->handler = ngx_http_pagespeed_connection_read_handler;
+  ngx_add_event(c->read, NGX_READ_EVENT, 0);
+
   return NGX_OK;
 }
 
-// Replace each buffer chain with a new one that's been optimized.
+// Set us up for processing a request.
 static ngx_int_t
-ngx_http_pagespeed_optimize_and_replace_buffer(ngx_http_request_t* r,
-                                               ngx_chain_t* in) {
+ngx_http_pagespeed_create_request_context(ngx_http_request_t* r) {
   ngx_http_pagespeed_request_ctx_t* ctx =
-      ngx_http_pagespeed_get_request_context(r);
-  if (ctx == NULL) {
+      new ngx_http_pagespeed_request_ctx_t();
+  ctx->pipe_fd = -1;
+  ctx->r = r;
+  ctx->cfg = static_cast<ngx_http_pagespeed_srv_conf_t*>(
+      ngx_http_get_module_srv_conf(r, ngx_pagespeed));
+
+  int file_descriptors[2];
+  int rc = pipe(file_descriptors);
+  if (rc != 0) {
+    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0, "pipe() failed");
+    ngx_http_pagespeed_release_request_context(ctx);
     return NGX_ERROR;
   }
 
+  if (ngx_nonblocking(file_descriptors[0]) == -1) {
+      ngx_log_error(NGX_LOG_EMERG, r->connection->log, ngx_socket_errno,
+                    ngx_nonblocking_n " pipe[0] failed");
+      ngx_http_pagespeed_release_request_context(ctx);
+      return NGX_ERROR;
+  }
+
+  if (ngx_nonblocking(file_descriptors[1]) == -1) {
+      ngx_log_error(NGX_LOG_EMERG, r->connection->log, ngx_socket_errno,
+                    ngx_nonblocking_n " pipe[1] failed");
+      ngx_http_pagespeed_release_request_context(ctx);
+      return NGX_ERROR;
+  }
+
+  ctx->pipe_fd = file_descriptors[0];
+  rc = ngx_http_pagespeed_create_connection(ctx);
+  if (rc != NGX_OK) {
+    close(file_descriptors[0]);
+    close(file_descriptors[1]);
+    ctx->pipe_fd = -1;
+
+    ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                  "ngx_http_pagespeed_create_request_context: "
+                  "no pagespeed connection.");
+    ngx_http_pagespeed_release_request_context(ctx);
+    return NGX_ERROR;
+  }
+
+  // Deletes itself when HandleDone is called, which happens when we call Done()
+  // on the proxy fetch below.
+  ctx->base_fetch = new net_instaweb::NgxBaseFetch(r, file_descriptors[1]);
+
+  if (ctx->cfg->driver_factory == NULL) {
+    // This is the first request handled by this server block.
+    ngx_http_pagespeed_initialize_server_context(ctx->cfg);
+  }
+
+  GoogleString url_string = ngx_http_pagespeed_determine_url(r);
+  net_instaweb::GoogleUrl request_url(url_string);
+
+  // This code is based off of ProxyInterface::ProxyRequestCallback and
+  // ProxyFetchFactory::StartNewProxyFetch
+
+  // If the global options say we're running furious (the experiment framework)
+  // then clone them into custom_options so we can manipulate custom options
+  // without affecting the global options.
+  net_instaweb::RewriteOptions* custom_options = NULL;
+  net_instaweb::RewriteOptions* global_options =
+      ctx->cfg->server_context->global_options();
+  if (global_options->running_furious()) {
+    custom_options = global_options->Clone();
+    custom_options->set_need_to_store_experiment_data(
+        ctx->cfg->server_context->furious_matcher()->ClassifyIntoExperiment(
+            *ctx->base_fetch->request_headers(), custom_options));
+  }
+
+  // TODO(jefftk): port ProxyInterface::InitiatePropertyCacheLookup so that we
+  // have the propery cache in nginx.
+
+  // If we don't have custom options we can use NewRewriteDriver which reuses
+  // rewrite drivers and so is faster because there's no wait to construct
+  // them.  Otherwise we have to build a new one every time.
+  if (custom_options == NULL) {
+    ctx->driver = ctx->cfg->server_context->NewRewriteDriver();
+  } else {
+    // NewCustomRewriteDriver takes ownership of custom_options.
+    ctx->driver = ctx->cfg->server_context->NewCustomRewriteDriver(
+        custom_options);
+  }
+  ctx->driver->set_log_record(ctx->base_fetch->log_record());
+
+  // TODO(jefftk): FlushEarlyFlow would go here.
+
+  ngx_http_set_ctx(r, ctx, ngx_pagespeed);
+
+  // Set up a cleanup handler on the request.
+  ngx_http_cleanup_t* cleanup = ngx_http_cleanup_add(r, 0);
+  if (cleanup == NULL) {
+    ngx_http_pagespeed_release_request_context(ctx);
+    return NGX_ERROR;
+  }
+  cleanup->handler = ngx_http_pagespeed_release_request_context;
+  cleanup->data = ctx;
+
+  // Will call StartParse etc.
+  ctx->proxy_fetch = ctx->cfg->proxy_fetch_factory->CreateNewProxyFetch(
+      url_string, ctx->base_fetch, ctx->driver,
+      NULL /* property_callback */,
+      NULL /* original_content_fetch */);
+
+  return NGX_OK;
+}
+
+// Send each buffer in the chain to the proxy_fetch for optimization.
+// Eventually it will make it's way, optimized, to base_fetch.
+static void
+ngx_http_pagespeed_send_to_pagespeed(
+    ngx_http_request_t* r,
+    ngx_http_pagespeed_request_ctx_t* ctx,
+    ngx_chain_t* in) {
+
   ngx_chain_t* cur;
   int last_buf = 0;
-  int last_in_chain = 0;
-  for (cur = in; cur != NULL;) {
+  for (cur = in; cur != NULL; cur = cur->next) {
     last_buf = cur->buf->last_buf;
-    last_in_chain = cur->buf->last_in_chain;
     
-    ctx->driver->ParseText(StringPiece(reinterpret_cast<char*>(cur->buf->pos),
-                                       cur->buf->last - cur->buf->pos));
+    // Buffers are not really the last buffer until they've been through
+    // pagespeed.
+    cur->buf->last_buf = 0;
 
-    // We're done with buffers as we pass them to the rewrite driver, so free
-    // them and their chain links as we go.  Don't free the first buffer (in)
-    // which we need below.
-    ngx_chain_t* next_link = cur->next;
-    if (cur != in) {
-      ngx_pfree(r->pool, cur->buf);
-      ngx_pfree(r->pool, cur);
+    ctx->proxy_fetch->Write(StringPiece(reinterpret_cast<char*>(cur->buf->pos),
+                                        cur->buf->last - cur->buf->pos),
+                            ctx->cfg->handler);
+
+    // We're done with buffers as we pass them through, so mark them as sent as
+    // we go.
+    cur->buf->pos = cur->buf->last;
   }
-    cur = next_link;
-  }
-  in->next = NULL;  // We freed all the later buffers.
-
-  // Prepare the new buffer.
-  ngx_buf_t* b = static_cast<ngx_buf_t*>(ngx_calloc_buf(r->pool));
-  if (b == NULL) {
-    ngx_log_error(NGX_LOG_ERR, (r)->connection->log, 0,
-                  "failed to allocate buffer");
-
-    return NGX_ERROR;
-  }
-
-  b->temporary = 1;
-  b->last_buf = last_buf;
-  b->last_in_chain = last_in_chain;
-  in->next = NULL;
-
-  // replace the first link's buffer with our new one.
-  ngx_pfree(r->pool, in->buf);
-  in->buf = b;
 
   if (last_buf) {
-    ctx->driver->FinishParse();
+    ctx->proxy_fetch->Done(true /* success */);
+    ctx->proxy_fetch = NULL;  // ProxyFetch deletes itself on Done().
   } else {
-    ctx->driver->Flush();
+    // TODO(jefftk): Decide whether Flush() is warranted here.
+    ctx->proxy_fetch->Flush(ctx->cfg->handler);
   }
-
-  // TODO(jefftk): need to store how much went out on previous flushes and only
-  // copy here the new stuff.  Keep the count in the request context.
-  b->pos = b->start = static_cast<u_char*>(
-      ngx_pnalloc(r->pool, ctx->output->length()));
-  if (b->pos == NULL) {
-    ngx_log_error(NGX_LOG_ERR, (r)->connection->log, 0,
-                  "failed to allocate %d bytes", ctx->output->length());
-    return NGX_ERROR;
-  }
-  ctx->output->copy(reinterpret_cast<char*>(b->pos), ctx->output->length());
-  b->last = b->end = b->pos + ctx->output->length();
-
-  if (last_buf) {
-    ngx_http_pagespeed_release_request_context(r, ctx);
-    ctx = NULL;
-  }
-
-  return NGX_OK;
 }
 
 static ngx_int_t
-ngx_http_pagespeed_body_filter(ngx_http_request_t* r, ngx_chain_t* in)
-{
-  ngx_int_t rc;
-
-  rc = ngx_http_pagespeed_optimize_and_replace_buffer(r, in);
-  if (rc != NGX_OK) {
-    return rc;
-  }
-
-  rc = ngx_http_pagespeed_note_processed(r, in);
-  if (rc != NGX_OK) {
-    return rc;
-  }
+ngx_http_pagespeed_body_filter(ngx_http_request_t* r, ngx_chain_t* in) {
+  ngx_http_pagespeed_request_ctx_t* ctx =
+      ngx_http_pagespeed_get_request_context(r);
 
+  if (ctx == NULL) {
+    // ctx is null iff we've decided to pass through this request unchanged.
     return ngx_http_next_body_filter(r, in);
   }
 
+  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+                 "http pagespeed filter \"%V\"", &r->uri);
+
+  if (ctx->content_type == NULL) {
+    // We don't know what type of resource this is, but we only want to send
+    // html through to pagespeed.  Check the content type header and find out.
+    ctx->content_type = net_instaweb::MimeTypeToContentType(
+        ngx_http_pagespeed_str_to_string_piece(
+            &r->headers_out.content_type));
+    if (ctx->content_type == NULL || !ctx->content_type->IsHtmlLike()) {
+      // Unknown or otherwise non-html content type: skip it.
+      ngx_http_set_ctx(r, NULL, ngx_pagespeed);
+      return ngx_http_next_body_filter(r, in);
+    }
+  }
+
+  if (!ctx->data_received) {
+    // This is the first set of buffers we've got for this request.
+    ctx->data_received = true;
+    // Call this here and not in the header filter because we want to see the
+    // headers after any other filters are finished modifying them.  At this
+    // point they are final.
+    ctx->base_fetch->PopulateHeaders();  // TODO(jefftk): is this thread safe?
+  }
+
+  if (in != NULL) {
+    // Send all input data to the proxy fetch.
+    ngx_http_pagespeed_send_to_pagespeed(r, ctx, in);
+  }  
+
+  ngx_http_pagespeed_set_buffered(r, true);
+  return NGX_AGAIN;
+}
+
 static ngx_int_t
-ngx_http_pagespeed_header_filter(ngx_http_request_t* r)
-{
+ngx_http_pagespeed_header_filter(ngx_http_request_t* r) {
   // We're modifying content below, so switch to 'Transfer-Encoding: chunked'
   // and calculate on the fly.
   ngx_http_clear_content_length(r);
@@ -444,6 +613,7 @@ ngx_http_pagespeed_header_filter(ngx_http_request_t* r)
 
   int rc = ngx_http_pagespeed_create_request_context(r);
   if (rc != NGX_OK) {
+    ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
     return rc;
   }
 
@@ -451,8 +621,7 @@ ngx_http_pagespeed_header_filter(ngx_http_request_t* r)
 }
 
 static ngx_int_t
-ngx_http_pagespeed_init(ngx_conf_t* cf)
-{
+ngx_http_pagespeed_init(ngx_conf_t* cf) {
   ngx_http_pagespeed_srv_conf_t* pagespeed_config;
   pagespeed_config = static_cast<ngx_http_pagespeed_srv_conf_t*>(
     ngx_http_conf_get_module_srv_conf(cf, ngx_pagespeed));

src/ngx_pagespeed.h

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2012 Google Inc.
+ *
+ * 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.
+ */
+
+// Author: jefftk@google.com (Jeff Kaufman)
+
+#ifndef NGX_PAGESPEED_H_
+#define NGX_PAGESPEED_H_
+
+extern "C" {
+  #include <ngx_core.h>
+}
+
+#include "net/instaweb/util/public/string_util.h"
+
+StringPiece ngx_http_pagespeed_str_to_string_piece(ngx_str_t* s);
+
+#endif  // NGX_PAGESPEED_H_

src/ngx_rewrite_driver_factory.cc

@@ -27,7 +27,6 @@
 #include "net/instaweb/rewriter/public/server_context.h"
 #include "net/instaweb/rewriter/public/rewrite_driver.h"
 #include "net/instaweb/rewriter/public/rewrite_driver_factory.h"
-#include "net/instaweb/rewriter/public/rewrite_gflags.h"
 #include "net/instaweb/util/public/google_message_handler.h"
 #include "net/instaweb/util/public/google_timer.h"
 #include "net/instaweb/util/public/lru_cache.h"
@@ -90,7 +89,8 @@ Timer* NgxRewriteDriverFactory::DefaultTimer() {
 }
 
 void NgxRewriteDriverFactory::SetupCaches(ServerContext* resource_manager) {
-  LRUCache* lru_cache = new LRUCache(gflags_.lru_cache_size_bytes());
+  // TODO(jefftk): make LRUCache size configurable.
+  LRUCache* lru_cache = new LRUCache(10 * 1000 * 1000);
   CacheInterface* cache = new ThreadsafeCache(
       lru_cache, thread_system()->NewMutex());
   HTTPCache* http_cache = new HTTPCache(cache, timer(), hasher(), statistics());

src/ngx_rewrite_driver_factory.h

@@ -20,7 +20,6 @@
 #define NGX_REWRITE_DRIVER_FACTORY_H_
 
 #include "net/instaweb/rewriter/public/rewrite_driver_factory.h"
-#include "net/instaweb/rewriter/public/rewrite_gflags.h"
 #include "net/instaweb/util/public/simple_stats.h"
 
 namespace net_instaweb {
@@ -41,7 +40,6 @@ class NgxRewriteDriverFactory : public RewriteDriverFactory {
 
  private:
   SimpleStats simple_stats_;
-  const RewriteGflags gflags_;
   Timer* timer_;
   
   DISALLOW_COPY_AND_ASSIGN(NgxRewriteDriverFactory);

test/www/script.js

@@ -0,0 +1 @@
+alert('run script');

test/www/style.css

@@ -0,0 +1 @@
+h2 { color: green }

test/www/test.html

@@ -16,6 +16,8 @@
       <!-- another comment -->
 
       <b>bold text</b>
+
+      <img src="Puzzle.jpg">
     </p>
   </body>
 </html>