fastcci_server.cc

#include <time.h>
#include "fastcci.h"
#include <sys/stat.h>

// thread management objects
pthread_mutex_t handlerMutex = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t condition = PTHREAD_COND_INITIALIZER;

// category data and traversal information
const int maxdepth = 500;
int maxcat;
tree_type *cat, *tree, *parent;

// modification time of the tree database file
time_t treetime;

// new result data structure
struct resultList
{
  int max, num;
  result_type * buf;
  unsigned char *mask, *tags;
  resultList(int initialSize = 1024 * 1024) : max(initialSize), num(0), tags(NULL)
  {
    buf = (result_type *)malloc(max * sizeof *buf);
    mask = (unsigned char *)malloc(maxcat * sizeof *mask);
    printf("mask size = %d\n", maxcat);

    if (buf == NULL || mask == NULL)
    {
      perror("resultList()");
      exit(1);
    }
  }

  // pointer to element after the last result
  result_type * tail() const { return &(buf[num]); }

  // grow buffer to hold at least len more items
  void grow(int len)
  {
    if (num + len > max)
    {
      while (num + len > max)
        max *= 2;
      if ((buf = (result_type *)realloc(buf, max * sizeof *buf)) == NULL)
      {
        perror("resultList->grow()");
        exit(1);
      }
    }
  }

  // attempt to shrink large buffers to half their size
  void shrink()
  {
    if (num < max / 2 && max > (1024 * 1024))
    {
      max /= 2;
      if ((buf = (result_type *)realloc(buf, max * sizeof *buf)) == NULL)
      {
        perror("resultList->shrink()");
        exit(1);
      }
    }
  }

  // clear mask
  void clear() { memset(mask, 0, maxcat * sizeof *mask); }

  // tags list for special union groups (to identify FP/QI/VI for example)
  void addTags()
  {
    if ((tags = (unsigned char *)calloc(maxcat, sizeof(*tags))) == NULL)
    {
      perror("resultList->addTags()");
      exit(1);
    }
  }

  // sort result list (unused for output)
  void sort() { qsort(buf, num, sizeof *buf, compare); }
};

resultList *result[2], *goodImages;

// breadth first search ringbuffer
struct ringBuffer rb;

// work item queue
int aItem = 0, bItem = 0;
const int maxItem = 1000;
struct workItem queue[maxItem];

// check if an ID is a valid category
inline bool
isCategory(int i)
{
  return (i >= 0 && i < maxcat && cat[i] >= 0);
}

// check if an ID is a valid file
inline bool
isFile(int i)
{
  return (i >= 0 && i < maxcat && cat[i] < 0);
}

// buffering of up to 50 search results (the amount we can safely API query)
const int resmaxqueue = 50, resmaxbuf = 64 * resmaxqueue;
char rescombuf[resmaxbuf];
int resnumqueue = 0, residx = 0;
ssize_t
resultPrintf(int i, const char * fmt, ...)
{
  int ret;
  char buf[4096];
  va_list myargs;

  va_start(myargs, fmt);
  ret = vsnprintf(buf, 4096, fmt, myargs);
  va_end(myargs);

  onion_response * res = queue[i].res;
  onion_websocket * ws = queue[i].ws;

  // TODO: use onion_*_write here?
  if (res)
  {
    // regular text response
    if (queue[i].connection == WC_XHR)
      return onion_response_printf(res, "%s\n", buf);
    // wrap response in a callback call (first data item)
    else if (queue[i].connection == WC_JS)
      return onion_response_printf(res, " '%s',", buf);
  }

  if (ws)
    return onion_websocket_write(ws, buf, strnlen(buf, 4096));

  return 0;
}
void
resultDone(int i)
{
  queue[i].status = WS_DONE;
  onion_response * res = queue[i].res;
  onion_websocket * ws = queue[i].ws;

  // TODO: use onion_*_write here?
  if (res)
  {
    // regular text response
    if (queue[i].connection == WC_XHR)
      onion_response_printf(res, "DONE\n");
    else
      onion_response_printf(res, " 'DONE'] );\n");
  }
  if (ws)
    onion_websocket_printf(ws, "DONE");
}
void
resultStart(int i)
{
  onion_response * res = queue[i].res;
  onion_websocket * ws = queue[i].ws;

  if (res && queue[i].connection == WC_JS)
    onion_response_printf(res, "fastcciCallback( [");
  if (queue[i].ws)
    onion_websocket_printf(queue[i].ws, "COMPUTE_START");
}
void
resultFlush(int i)
{
  // nothing to flush
  if (residx == 0)
    return;

  //
  onion_response * res = queue[i].res;
  onion_websocket * ws = queue[i].ws;

  // zero terminate buffer
  rescombuf[residx - 1] = 0;

  // send buffer and reset inices
  resultPrintf(i, "RESULT %s", rescombuf);
  resnumqueue = 0;
  residx = 0;
}

void
resultQueue(int i, result_type item, unsigned char tag)
{
  // TODO check for truncation (but what then?!)
  residx += snprintf(&(rescombuf[residx]),
                     resmaxbuf - residx,
                     "%d,%d,%d|",
                     int(item & cat_mask),
                     int((item & depth_mask) >> depth_shift),
                     tag);

  // queued enough values?
  if (++resnumqueue == resmaxqueue)
    resultFlush(i);
}

//
// Fetch all files in and below category 'id'
// in a breadth first search up to depth 'depth'
// if 'depth' is negative treat it as infinity
//
void
fetchFiles(tree_type id, int depth, resultList * r1)
{
  // clear ring buffer
  rbClear(rb);

  // push root node (depth 0)
  rbPush(rb, id);

  result_type r, d, e, i;
  unsigned char f;
  int c, len;
  while (!rbEmpty(rb))
  {
    r = rbPop(rb);
    d = (r & depth_mask) >> depth_shift;
    i = r & cat_mask;
    if (i >= maxcat) continue;

    // tag current category as visited
    r1->mask[i] = 1;

    int c = cat[i], cend = tree[c], cfile = tree[c + 1];
    c += 2;

    // push all subcats to queue
    if (d < depth || depth < 0)
    {
      e = (d + 1) << depth_shift;
      while (c < cend)
      {
        // push unvisited categories (that are not empty, cat[id]==0) into the queue
        if (tree[c] < maxcat && r1->mask[tree[c]] == 0 && cat[tree[c]] > 0)
          rbPush(rb, tree[c] | e);
        c++;
      }
    }

    // copy and add the depth on top
    int len = cfile - c;
    r1->grow(len);
    result_type *dst = r1->tail(), *old = dst;
    tree_type * src = &(tree[c]);
    f = d < 254 ? (d + 1) : 255;
    d = d << depth_shift;
    while (len--)
    {
      r = (*src++);
      if ((r & cat_mask) < maxcat && r1->mask[r & cat_mask] == 0)
      {
        *dst++ = (r | d);
        r1->mask[r & cat_mask] = f;
      }
    }
    r1->num += dst - old;
  }
}

//
// iteratively do a breadth first path search
//
result_type history[maxdepth];
void
tagCat(tree_type sid, int qi, int maxDepth, resultList * r1)
{
  // clear ring buffer
  rbClear(rb);

  bool foundPath = false, c2isFile = (cat[queue[qi].c2] < 0);
  int depth = -1;
  result_type id = sid, did = queue[qi].c2;

  // push root node (depth 0)
  rbPush(rb, sid);

  result_type r, d, e, ld = -1;
  int c, len;
  while (!rbEmpty(rb) && !foundPath)
  {
    r = rbPop(rb);
    d = (r & depth_mask) >> depth_shift;
    id = r & cat_mask;

    // next layer?
    if (d != ld)
    {
      depth++;
      ld = d;
    }

    // head category header
    int c = cat[id], cend = tree[c], cend2 = tree[c + 1];
    c += 2;

    // push all subcat to queue
    if (depth < maxDepth || maxDepth < 0)
    {
      e = (d + 1) << depth_shift;

      while (c < cend)
      {
        // inspect if we are pushing the target cat to the queue
        if (tree[c] == did)
        {
          parent[did] = id;
          id = did;
          foundPath = true;
          break;
        }

        // push unvisited categories into the queue
        if (tree[c] < maxcat && r1->mask[tree[c]] == 0)
        {
          parent[tree[c]] = id;
          r1->mask[tree[c]] = 1;
          rbPush(rb, tree[c] | e);
        }
        c++;
      }
    }

    // check if a file in the category is a match
    if (c2isFile)
    {
      for (c = cend; c < cend2; ++c)
        if (tree[c] == did)
        {
          foundPath = true;
          break;
        }
    }
  }

  // found the target category
  if (foundPath)
  {
    // TODO backtrack through the parent category buffer
    int i = 0;
    while (true)
    {
      history[i++] = id;
      if (id == sid)
        break;
      id = parent[id];
    }
    int len = i;

    // output in reverse to get the forward chain
    while (i--)
      resultQueue(qi, history[i] + (result_type(len - i) << depth_shift), 0);

    resultFlush(qi);
  }
  else
    resultPrintf(qi, "NOPATH");
}

//
// all images in result
//
void
traverse(int qi, resultList * r1)
{
  int outstart = queue[qi].o;
  int outend = outstart + queue[qi].s;
  onion_response * res = queue[qi].res;
  onion_websocket * ws = queue[qi].ws;

  // output selected subset
  queue[qi].status = WS_STREAMING;
  if (outend > r1->num)
    outend = r1->num;

  result_type r;
  for (int i = outstart; i < outend; ++i)
  {
    r = r1->buf[i] & cat_mask;
    resultQueue(qi, r1->buf[i], r1->tags == NULL ? goodImages->tags[r] : r1->tags[r]);
  }
  resultFlush(qi);

  // send the (exact) size of the complete result set
  resultPrintf(qi, "OUTOF %d", r1->num);
}

//
// all images in result that are not flagged in the mask
//
void
notin(int qi, resultList * r1, resultList * r2)
{
  int n = 0; // number of current output item

  int outstart = queue[qi].o;
  int outend = outstart + queue[qi].s;
  onion_response * res = queue[qi].res;
  onion_websocket * ws = queue[qi].ws;

  // No sorting, show least depth first, use mask for NOT test
  fprintf(stderr, "using mask strategy.\n");

  // perform subtraction
  queue[qi].status = WS_STREAMING;
  result_type r;
  int i;
  for (i = 0; i < r1->num; ++i)
  {
    r = r1->buf[i] & cat_mask;

    if (r < maxcat && r2->mask[r] == 0)
    {
      n++;
      // are we still below the offset?
      if (n <= outstart)
        continue;
      // output file
      resultQueue(qi, r1->buf[i], r1->tags == NULL ? goodImages->tags[r] : r1->tags[r]);
      // are we at the end of the output window?
      if (n >= outend)
        break;
    }
  }

  resultFlush(qi);

  // did we make it all the way to the end of the result set?
  if (i == r1->num)
    resultPrintf(qi, "OUTOF %d", n - outstart);
  // otherwise make a crude guess based on the progress within result r1
  else if (i > 0)
    resultPrintf(qi, "OUTOF %d", (outend * r1->num) / i);
}

//
// all images in both c1 and c2 output is sorted by depth in c1
//
void
intersect(int qi, resultList * r1, resultList * r2)
{
  int n = 0; // number of current output item

  int outstart = queue[qi].o;
  int outend = outstart + queue[qi].s;
  onion_response * res = queue[qi].res;
  onion_websocket * ws = queue[qi].ws;

  // was one of the results empty?
  if (r2->num == 0)
  {
    resultPrintf(qi, "OUTOF %d", 0);
    return;
  }

  // perform intersection
  queue[qi].status = WS_STREAMING;
  result_type r, m;

  int i;
  for (i = 0; i < r1->num; ++i)
  {
    r = r1->buf[i] & cat_mask;
    if (r >= maxcat) continue;

    m = r2->mask[r];
    if (m != 0)
    {
      n++;
      // are we still below the offset?
      if (n <= outstart)
        continue;

      // output file
      resultQueue(qi,
                  r1->buf[i] + ((m - 1) << depth_shift),
                  r2->tags == NULL ? goodImages->tags[r] : r2->tags[r]);

      // are we at the end of the output window?
      if (n >= outend)
        break;
    }
  }

  resultFlush(qi);

  // did we make it all the way to the end of the result set?
  if (i == r1->num)
    resultPrintf(qi, "OUTOF %d", n - outstart);
  // otherwise make a crude guess based on the progress within result r1
  else if (i > 0)
    resultPrintf(qi, "OUTOF %d", (outend * r1->num) / i);
}

//
// all FPs, FVs, QIs, VIs in c1 in that order
//
void
findFQV(int qi, resultList * r1)
{
  int n = 0; // number of current output item

  int outstart = queue[qi].o;
  int outend = outstart + queue[qi].s;
  onion_response * res = queue[qi].res;
  onion_websocket * ws = queue[qi].ws;

  // was one of the results empty?
  if (r1->num == 0)
  {
    resultPrintf(qi, "OUTOF %d", 0);
    return;
  }

  // perform intersection
  queue[qi].status = WS_STREAMING;
  result_type r, m;

  // loop over tags
  unsigned char k;
  int i;
  for (k = 1; k <= 4; ++k)
  {
    // loop over c1 images
    for (i = 0; i < r1->num; ++i)
    {
      r = r1->buf[i] & cat_mask;
      if (r >= maxcat) continue;

      m = goodImages->mask[r];
      if (m != 0 && k == goodImages->tags[r])
      {
        n++;
        // are we still below the offset?
        if (n <= outstart)
          continue;

        // output file
        resultQueue(qi, r1->buf[i] + ((m - 1) << depth_shift), goodImages->tags[r]);

        // are we at the end of the output window?
        if (n >= outend)
          break;
      }
    }
    if (n >= outend)
      break;
  }

  resultFlush(qi);

  // did we make it all the way to the end of the result set?
  if (k == 5)
    resultPrintf(qi, "OUTOF %d", n - outstart);
  // otherwise make a crude guess
  else if (((k - 1) * r1->num + i) > 0)
    resultPrintf(qi, "OUTOF %d", (outend * r1->num * 3) / ((k - 1) * r1->num + i));
}

onion_connection_status
handleStatus(void * d, onion_request * req, onion_response * res)
{
  onion_response_set_header(res, "Access-Control-Allow-Origin", "*");

  time_t now = time(NULL);
  double loadavg[3] = {0, 0, 0};
  getloadavg(loadavg, 3);

  pthread_mutex_lock(&mutex);
  onion_response_printf(res, "{\"queue\":%d,\"relsize\":%d,", bItem - aItem, maxcat);
  onion_response_printf(res,
                        "\"dbage\":%.f,\"load\":[%f,%f,%f]}",
                        difftime(now, treetime),
                        loadavg[0],
                        loadavg[1],
                        loadavg[2]);

  pthread_mutex_unlock(&mutex);
  return OCS_CLOSE_CONNECTION;
}

onion_connection_status
handleRequest(void * d, onion_request * req, onion_response * res)
{
  // parse parameters
  const char * c1 = onion_request_get_query(req, "c1");
  const char * c2 = onion_request_get_query(req, "c2");

  if (c1 == NULL)
  {
    // must supply c1 parameter!
    fprintf(stderr, "No c1 parameter.\n");
    return OCS_INTERNAL_ERROR;
  }

  // still room on the queue?
  pthread_mutex_lock(&mutex);
  if (bItem - aItem + 1 >= maxItem)
  {
    // too many requests. reject
    fprintf(stderr, "Queue full.\n");
    pthread_mutex_unlock(&mutex);
    return OCS_INTERNAL_ERROR;
  }
  // new queue item
  int i = bItem % maxItem;
  pthread_mutex_unlock(&mutex);

  queue[i].c1 = atoi(c1);
  queue[i].c2 = c2 ? atoi(c2) : queue[i].c1;

  const char * d1 = onion_request_get_query(req, "d1");
  const char * d2 = onion_request_get_query(req, "d2");

  const char * oparam = onion_request_get_query(req, "o");
  const char * sparam = onion_request_get_query(req, "s");

  queue[i].d1 = d1 ? atoi(d1) : -1;
  queue[i].d2 = d2 ? atoi(d2) : -1;

  queue[i].o = oparam ? atoi(oparam) : 0;
  queue[i].s = sparam ? atoi(sparam) : 100;

  queue[i].status = WS_WAITING;

  const char * aparam = onion_request_get_query(req, "a");

  queue[i].type = WT_INTERSECT;
  if (aparam != NULL)
  {
    if (strcmp(aparam, "and") == 0)
      queue[i].type = WT_INTERSECT;
    else if (strcmp(aparam, "not") == 0)
      queue[i].type = WT_NOTIN;
    else if (strcmp(aparam, "fqv") == 0)
      queue[i].type = WT_FQV;
    else if (strcmp(aparam, "list") == 0)
      queue[i].type = WT_TRAVERSE;
    else if (strcmp(aparam, "path") == 0)
    {
      queue[i].type = WT_PATH;
      if (queue[i].c1 == queue[i].c2)
        return OCS_INTERNAL_ERROR;
    }
    else
      return OCS_INTERNAL_ERROR;
  }

  // check if invalid ids were specified
  if (queue[i].c1 >= maxcat || queue[i].c2 >= maxcat || queue[i].c1 < 0 || queue[i].c2 < 0)
    return OCS_INTERNAL_ERROR;

  // check if both c params are categories unless it is a path request
  if (isFile(queue[i].c1) || (isFile(queue[i].c2) && queue[i].type != WT_PATH))
    return OCS_INTERNAL_ERROR;

  // log request
  if (aparam == NULL)
    aparam = "and";
  fprintf(stderr,
          "Request [%ld %d]: a=%s c1=%d(%d) c2=%d(%d)\n",
          time(NULL),
          bItem - aItem,
          aparam,
          queue[i].c1,
          queue[i].d1,
          queue[i].c2,
          queue[i].d2);

  // attempt to open a websocket connection
  onion_websocket * ws = onion_websocket_new(req, res);
  if (!ws)
  {
    //
    // HTTP connection (fallback)
    //

    // send keep-alive response
    onion_response_set_header(res, "Access-Control-Allow-Origin", "*");

    // shuld we send a javascript callback for older browsers?
    const char * tparam = onion_request_get_query(req, "t");
    if (tparam != NULL && strcmp(tparam, "js") == 0)
    {
      queue[i].connection = WC_JS;
      onion_response_set_header(res, "Content-Type", "application/javascript; charset=utf8");
    }
    else
    {
      queue[i].connection = WC_XHR;
      onion_response_set_header(res, "Content-Type", "text/plain; charset=utf8");
    }

    queue[i].res = res;
    queue[i].ws = NULL;

    // append to the queue and signal worker thread
    pthread_mutex_lock(&mutex);
    bItem++;
    pthread_cond_signal(&condition);
    pthread_mutex_unlock(&mutex);

    // wait for signal from worker thread
    wiStatus status;
    do
    {
      pthread_mutex_lock(&(queue[i].mutex));
      pthread_cond_wait(&(queue[i].cond), &(queue[i].mutex));
      status = queue[i].status;
      pthread_mutex_unlock(&(queue[i].mutex));
    } while (status != WS_DONE);
  }
  else
  {
    //
    // Websocket connection
    //

    queue[i].connection = WC_SOCKET;
    queue[i].ws = ws;
    queue[i].res = NULL;

    onion_websocket_printf(ws, "QUEUED %d", i - aItem);

    // append to the queue and signal worker thread
    pthread_mutex_lock(&mutex);
    bItem++;
    pthread_cond_signal(&condition);
    pthread_mutex_unlock(&mutex);

    // wait for signal from worker thread (have a third thread periodically signal, only print
    // result when the calculation is done, otherwise print status)
    wiStatus status;
    do
    {
      pthread_mutex_lock(&(queue[i].mutex));
      pthread_cond_wait(&(queue[i].cond), &(queue[i].mutex));
      status = queue[i].status;
      pthread_mutex_unlock(&(queue[i].mutex));

      fprintf(stderr, "notify status %d\n", status);
      switch (status)
      {
        case WS_WAITING:
          // send number of jobs ahead of this one in queue
          if(!onion_websocket_printf(ws, "WAITING %d", i - aItem))
            status = WS_DONE;
          break;
        case WS_PREPROCESS:
        case WS_COMPUTING:
          // send intermediate result sizes
          onion_websocket_printf(ws, "WORKING %d %d", result[0]->num, result[1]->num);
          break;
      }
      // don't do anything if status is WS_STREAMING, the compute task is sending data
    } while (status != WS_DONE);
  }

  fprintf(stderr, "End of handle connection.\n");
  return OCS_CLOSE_CONNECTION;
}

void *
notifyThread(void * d)
{
  timespec updateInterval, t2;
  updateInterval.tv_sec = 0;
  updateInterval.tv_nsec = 1000 * 1000 * 200; // 200ms

  while (1)
  {
    nanosleep(&updateInterval, &t2);

    pthread_mutex_lock(&handlerMutex);
    pthread_mutex_lock(&mutex);

    // loop over all active queue items (actually lock &mutex as well!)
    for (int i = aItem; i < bItem; ++i)
      if (queue[i].connection == WC_SOCKET)
        pthread_cond_signal(&(queue[i].cond));

    pthread_mutex_unlock(&mutex);
    pthread_mutex_unlock(&handlerMutex);
  }
}

void *
computeThread(void * d)
{
  while (1)
  {
    // wait for pthread condition
    pthread_mutex_lock(&mutex);
    while (aItem == bItem)
      pthread_cond_wait(&condition, &mutex);
    pthread_mutex_unlock(&mutex);

    // process queue
    while (bItem > aItem)
    {
      // fetch next item
      int i = aItem % maxItem;

      // signal start of compute
      resultStart(i);

      int nr;
      if (queue[i].type == WT_PATH)
      {
        // path finding
        result[0]->clear();
        tagCat(queue[i].c1, i, queue[i].d1, result[0]);
      }
      else
      {
        // boolean operations (AND, LIST, NOTIN)
        result[0]->num = 0;
        result[1]->num = 0;
        queue[i].status = WS_PREPROCESS;

        // generate intermediate results
        int cid[2] = {queue[i].c1, queue[i].c2};
        int depth[2] = {queue[i].d1, queue[i].d2};
        // number of result lists needed
        nr = (queue[i].type == WT_TRAVERSE || queue[i].type == WT_FQV) ? 1 : 2;
        for (int j = 0; j < nr; ++j)
        {
          // clear visitation mask
          result[j]->clear();

          // fetch files through deep traversal
          fetchFiles(cid[j], depth[j], result[j]);
          fprintf(stderr, "fnum(%d) %d\n", cid[j], result[j]->num);
        }

        // compute result
        queue[i].status = WS_COMPUTING;

        switch (queue[i].type)
        {
          case WT_TRAVERSE:
            traverse(i, result[0]);
            break;
          case WT_FQV:
            findFQV(i, result[0]);
            break;

          case WT_NOTIN:
            notin(i, result[0], result[1]);
            break;
          case WT_INTERSECT:
            intersect(i, result[0], result[1]);
            break;
        }
      }

      // report database age
      time_t now = time(NULL);
      resultPrintf(i, "DBAGE %.f", difftime(now, treetime));

      // done with this request
      resultDone(i);

      // try to shrink result buffers uses in this request
      for (int j = 0; j < nr; ++j)
        result[0]->shrink();

      // pop item off queue
      pthread_mutex_lock(&mutex);
      aItem++;
      pthread_mutex_unlock(&mutex);

      // wake up thread to finish connection
      pthread_mutex_lock(&handlerMutex);
      pthread_cond_signal(&(queue[i].cond));
      pthread_mutex_unlock(&handlerMutex);
    }
  }
}

int
main(int argc, char * argv[])
{
  if (argc != 3)
  {
    printf("%s PORT DATADIR\n", argv[0]);
    return 1;
  }

  // ring buffer for breadth first
  rbInit(rb);

  const int buflen = 1000;
  char fname[buflen];

  snprintf(fname, buflen, "%s/fastcci.cat", argv[2]);
  unsigned int cat_file_len = readFile(fname, cat);
  maxcat = cat_file_len / sizeof(tree_type);

  // result structures (including visitation mask buffer)
  result[0] = new resultList(1024 * 1024);
  result[1] = new resultList(1024 * 1024);
  goodImages = new resultList(512);

  // parent category buffer for shortest path finding
  if ((parent = (tree_type *)malloc(maxcat * sizeof *parent)) == NULL)
  {
    perror("parent");
    exit(1);
  }

  // read tree file
  snprintf(fname, buflen, "%s/fastcci.tree", argv[2]);
  unsigned int tree_file_len = readFile(fname, tree);

  // get modification time of tree file
  struct stat statbuf;
  if (stat(fname, &statbuf) == -1)
  {
    perror(fname);
    exit(1);
  }
  treetime = statbuf.st_mtime;

  // thread properties
  pthread_attr_t attr;
  pthread_attr_init(&attr);
  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

  // setup compute thread
  pthread_t compute_thread;
  if (pthread_create(&compute_thread, &attr, computeThread, NULL))
    return 1;

  // setup compute thread
  pthread_t notify_thread;
  if (pthread_create(&notify_thread, &attr, notifyThread, NULL))
    return 1;

  // precompute a union of Commons FPs, Wikipedia FPs, Commons FVs, QIs, and VIs
  int goodCats[][3] = {
      {3943817, 0, 1}, // [[Category:Featured_pictures_on_Wikimedia_Commons]]     (depth 0)
      {5799448, 1, 1}, // [[Category:Featured_pictures_on_Wikipedia_by_language]] (depth 1)
      {91039287, 0, 2}, // [[Category:Featured_media]]                            (depth 0)
      {3618826, 0, 3}, // [[Category:Quality_images]]                             (depth 0)
      {4143367, 0, 4}  // [[Category:Valued_images_sorted_by_promotion_date]]     (depth 0)
  };
  goodImages->clear();
  goodImages->addTags();
  result_type r;
  for (int i = 5; i > 0; --i)
  {
    printf("goodImages[%d]\n", i);
    result[0]->clear();
    result[0]->num = 0;
    fetchFiles(goodCats[i - 1][0], goodCats[i - 1][1], result[0]);
    for (int j = 0; j < result[0]->num; j++)
    {
      r = result[0]->buf[j] & cat_mask;
      if (r < maxcat)
      {
        goodImages->mask[r] = result[0]->mask[r];
        goodImages->tags[r] = goodCats[i - 1][2];
      }
    }
  }
  goodImages->num = -1;

  // start webserver
  onion * o = onion_new(O_THREADED);

  onion_set_port(o, argv[1]);
  onion_set_hostname(o, "0.0.0.0");
  onion_set_timeout(o, 1000000000);

  // add handlers
  onion_url * url = onion_root_url(o);
  onion_url_add(url, "status", (void *)handleStatus);
  onion_url_add(url, "", (void *)handleRequest);

  fprintf(stderr, "Server ready. [%ld,%ld]\n", sizeof(tree_type), sizeof(result_type));
  int error = onion_listen(o);
  if (error)
    perror("Cant create the server");

  onion_free(o);

  munmap(cat, cat_file_len);
  munmap(tree, tree_file_len);
  return 0;
}