Initial prototype of vmstats support, based on Dart VM Stats draft design doc.

runtime/bin/vmstats.cc

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file

[siva, 2013/02/09 01:00:57]

2013

[Tom Ball, 2013/02/14 23:45:16]

Done.

+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include "bin/vmstats.h"
+
+#include "bin/fdutils.h"
+#include "bin/file.h"
+#include "bin/platform.h"
+#include "bin/socket.h"
+#include "platform/json.h"
+#include "platform/thread.h"
+
+namespace dart {
+
+#define BUFSIZE 8192
+
+// Global static pointer used to ensure a single instance of the class.
+VmStats* VmStats::instance_ = NULL;
+
+
+void VmStats::Start(int port) {
+  if (instance_ != NULL) {
+    FATAL("VmStats already started.");
+  }
+  VmStats* vmstats = new VmStats;
+  Socket::Initialize();
+
+  // TODO(tball): replace $HOME with SDK-specific path to web server's
+  // root directory.
+  intptr_t num_vars;
+  char** env = Platform::Environment(&num_vars);

[siva, 2013/02/09 01:00:57]

Are you going to switch this to be a command line value so that people can
specify a root directory location?
If this is not specified then we pick the SDK-specific path to the root
directory.

[Tom Ball, 2013/02/14 23:45:16]

Done. I added a flag that optionally sets root directory, which only needs to be
used when working on the status UI code.

+  for (int i = 0; i < num_vars; i++) {
+    char* var = env[i];
+    if (strncmp(var, "HOME=", 5) == 0) {
+      char* home = var + 5;
+      ASSERT(strlen(home) > 0);
+      vmstats->root_directory_ = home;
+      vmstats->root_directory_.append("/vmstats");
+      break;
+    }
+  }
+  Platform::FreeEnvironment(env, num_vars);
+  ASSERT(vmstats->root_directory_.length() > 0);
+
+  const intptr_t BACKLOG = 128;  // Default value from HttpServer.dart
+  intptr_t bind_address =
+      ServerSocket::CreateBindListen("127.0.0.1", port, BACKLOG);

[siva, 2013/02/09 01:00:57]

fine for now but we may want to make 127.0.0.1 a parameter too. The command line
option could be specified as
--vmstats_port=8080 or
--vmstats_port=hostname:8080

[Tom Ball, 2013/02/14 23:45:16]

Sounds great -- any security issues with making this accessible from remote
sites I need to watch out for?

+  if (bind_address < 0) {
+    fprintf(stderr, "Failed binding VmStats socket: 127.0.0.1:%d\n", port);
+    return;
+  }
+  int errno = Thread::Start(WebServer, bind_address);
+  if (errno != 0) {
+    fprintf(stderr, "Failed starting VmStats thread: %d\n", errno);
+    return;
+  }
+  instance_ = vmstats;
+}
+
+
+void VmStats::Stop() {
+  if (instance_ != NULL) {
+    delete instance_;
+    instance_ = NULL;
+  }
+}
+
+
+
+void VmStats::AddIsolate(IsolateData* isolate_data,
+                                 Dart_Isolate isolate) {

[siva, 2013/02/09 01:00:57]

.... indentation.

[Tom Ball, 2013/02/14 23:45:16]

Done.

+  if (instance_ != NULL) {
+    instance_->isolate_table_[isolate_data] = isolate;

[siva, 2013/02/11 19:14:55]

This method needs to be thread safe right as we can potentially have multiple
isolates calling into it.

[Tom Ball, 2013/02/14 23:45:16]

Done.

+  }
+}
+
+
+void VmStats::RemoveIsolate(IsolateData* isolate_data) {

[siva, 2013/02/11 19:14:55]

Ditto comment about this method being thread safe.

[Tom Ball, 2013/02/14 23:45:16]

Done.

+  if (instance_ != NULL) {
+    instance_->isolate_table_.erase(isolate_data);
+  }
+}
+
+
+static bool endsWith(const std::string s, const char* ending) {
+  size_t ending_len = strlen(ending);
+  if (s.length() > ending_len) {
+    return s.compare(s.length() - ending_len, ending_len, ending) == 0;
+  } else {
+    return false;
+  }
+}
+
+
+static const char* ContentType(const char* url) {
+  // TODO(tball): replace with static map?
+  std::string path(url);
+  if (endsWith(path, ".html")) {
+    return "text/html; charset=UTF-8";
+  }
+  if (endsWith(path, ".dart")) {
+    return "application/dart; charset=UTF-8";
+  }
+  if (endsWith(path, ".js")) {
+    return "application/javascript; charset=UTF-8";
+  }
+  if (endsWith(path, ".css")) {
+    return "text/css; charset=UTF-8";
+  }
+  if (endsWith(path, ".gif")) {
+    return "image/gif";
+  }
+  if (endsWith(path, ".png")) {
+    return "image/png";
+  }
+  if (endsWith(path, ".jpg") || endsWith(path, ".jpeg")) {
+    return "image/jpeg";
+  }
+  return "text/plain";
+}
+
+
+void VmStats::WebServer(uword bind_address) {
+  while (true) {
+    intptr_t socket = ServerSocket::Accept(bind_address);
+    if (socket == ServerSocket::kTemporaryFailure) {
+      // Not a real failure, woke up but no connection available.
+      sleep(1);
+      continue;
+    }
+    if (socket < 0) {
+      FATAL("Accepting new web server connection failed.\n");
+    }
+    FDUtils::SetBlocking(socket);
+
+    // Read request.
+    static char buffer[BUFSIZE + 1];
+    int len = read(socket, buffer, BUFSIZE);

[siva, 2013/02/09 01:00:57]

How do you deal with partial reads here
(e.g: the read could have just read 5 bytes are returned)

The protocol states:
"The Request-Line begins with a method token, followed by the Request-URI and
the protocol version, and ending with CRLF. The elements are separated by SP
characters. No CR or LF is allowed except in the final CRLF sequence."

You should probably read here in a loop till you get the entire request line or
have a ReadRequest method that ensures that you get a complete request.

+    if (len <= 0) {
+      // Invalid HTTP request, ignore.
+      continue;
+    }
+    buffer[len] = '\0';
+
+    // Verify it's a GET request.
+    if (strncmp("GET ", buffer, 4) != 0 && strncmp("get ", buffer, 4) != 0) {
+      fprintf(stderr, "Unsupported HTTP request type");
+      const char* response = "HTTP/1.1 403 Forbidden\n"
+          "Content-Length: 120\n"
+          "Connection: close\n"
+          "Content-Type: text/html\n\n"
+          "<html><head>\n<title>403 Forbidden</title>\n</head>"
+          "<body>\n<h1>Forbidden</h1>\nUnsupported HTTP request type\n</body>"
+          "</html>\n";
+      Socket::Write(socket, response, strlen(response));

[siva, 2013/02/09 01:00:57]

In all these writes I would assert that the returned value is equal to the
number of bytes requested to be written.

You could have helper methods WriteResponse, WriteErrorResponse(error_code (403,
404 etc.)) and move all the HTTP stuff in there. Would make this loop code less
verbose.

+      close(socket);
+      continue;
+    }
+
+    // Extract GET URL.
+    for (int i = 4; i < len; i++) {
+      if (buffer[i] == ' ') {
+        buffer[i] = '\0';
+        break;
+      }
+    }
+    char* url = &buffer[4];
+    printf("vmstats: %s requested\n", url);
+    // TODO(tball): parse URL to determine data requested.
+    if (strcmp(url, "/isolates") == 0) {
+      std::ostringstream stream;
+      stream << '{' << std::endl;
+      instance_->MemoryUsed(&stream);

[siva, 2013/02/09 01:00:57]

Instead of MemoryUsed you could probably call this
IsolateStatus or ToplevelIsolateStatus so that it can return
all the top level information available for the isolate which could potentially
include:
- script/library/class/method of the function used for spawning the isolate
- memory usage
- links to other information available for drilling down, this part was not
clear to me. How does a VM developer expose a new stat that he/she has added.

[Tom Ball, 2013/02/14 23:45:16]

Done.

+      // TODO(tball): add other metrics, separated by commas.
+      stream << std::endl << '}' << std::endl;
+      std::string content = stream.str();
+
+      len = snprintf(buffer, BUFSIZE-1,
+          "HTTP/1.1 200 OK\n:Content-Type: application/json; charset=UTF-8\n"
+          "Content-Length: %d\n\n", static_cast<int>(content.length()));
+      Socket::Write(socket, buffer, strlen(buffer));
+      Socket::Write(socket, content.c_str(), content.length());
+      Socket::Write(socket, "\n", 1);
+      Socket::Write(socket, buffer, strlen(buffer));
+    } else {

[siva, 2013/02/09 01:00:57]

I assume this else section is present for serving some static pages that are
present in the root directory. Could you add a comment.

[Tom Ball, 2013/02/14 23:45:16]

Done.

+      std::string path(instance_->root_directory_);
+      path.append(url);
+      bool success = false;
+      if (File::Exists(path.c_str())) {
+        File* f = File::Open(path.c_str(), File::kRead);
+        if (f != NULL) {
+          intptr_t len = f->Length();
+          char* text_buffer = reinterpret_cast<char*>(malloc(len));
+          if (f->ReadFully(text_buffer, len)) {
+            std::string content(text_buffer, len);
+            const char* content_type = ContentType(url);
+            len = snprintf(buffer, BUFSIZE-1,
+                "HTTP/1.1 200 OK\n:Content-Type: %s\n"
+                "Content-Length: %d\n\n",
+                content_type, static_cast<int>(content.length()));
+            Socket::Write(socket, buffer, strlen(buffer));
+            Socket::Write(socket, content.c_str(), content.length());
+            Socket::Write(socket, "\n", 1);
+            success = true;
+          }
+          free(text_buffer);
+          delete f;
+        }
+      }
+      if (!success) {
+        const char* response = "HTTP/1.1 404 Not Found\n\n";
+        Socket::Write(socket, response, strlen(response));
+      }
+    }
+    close(socket);
+  }
+}
+
+
+void VmStats::MemoryUsed(std::ostringstream* stream) {
+  *stream << "\"isolates\": [" << std::endl;
+  IsolateTable::iterator itr;
+  bool first = true;
+  for (itr = isolate_table_.begin(); itr != isolate_table_.end(); ++itr) {
+    if (!first) {
+      *stream << "," << std::endl;
+    }
+    first = false;
+
+    Dart_Isolate isolate = itr->second;
+    static char request[512];
+    snprintf(request, sizeof(request), "/isolate/0x%llx",
+             reinterpret_cast<int64_t>(isolate));
+    char* status = Dart_GetVmStatus(request);
+    *stream << status;
+    free(status);
+  }
+  *stream << std::endl << "]";
+}
+
+
+}  // namespace dart