nginx-upload-progress-module/ngx_http_uploadprogress_mod...

/*
 * Copyright (C) 2007 Brice Figureau
 */

#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>

typedef struct ngx_http_uploadprogress_node_s ngx_http_uploadprogress_node_t;

struct ngx_http_uploadprogress_node_s {
		ngx_rbtree_node_t   node;
 		ngx_http_request_t *r;
		ngx_uint_t					err_status;
		time_t							timeout;
    struct ngx_http_uploadprogress_node_s  *prev;
    struct ngx_http_uploadprogress_node_s  *next;
    u_char              len;
    u_char              data[1];
};

typedef struct {
    ngx_shm_zone_t     *shm_zone;
    ngx_rbtree_node_t  *node;
} ngx_http_uploadprogress_cleanup_t;

typedef struct {
    ngx_rbtree_t       *rbtree;
    ngx_http_uploadprogress_node_t   list_head;
    ngx_http_uploadprogress_node_t   list_tail;
} ngx_http_uploadprogress_ctx_t;

typedef struct {
    ngx_shm_zone_t     *shm_zone;
		u_char							track;
		ngx_event_t					cleanup;
} ngx_http_uploadprogress_conf_t;

static ngx_int_t ngx_http_reportuploads_handler(ngx_http_request_t *r);
static void ngx_http_uploadprogress_cleanup(void *data);
static char *ngx_http_report_uploads(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
static ngx_int_t ngx_http_uploadprogress_init_zone(ngx_shm_zone_t *shm_zone, void *data);
static ngx_int_t ngx_http_uploadprogress_init(ngx_conf_t *cf);
static void *ngx_http_uploadprogress_create_loc_conf(ngx_conf_t *cf);
static char *ngx_http_uploadprogress_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child);
static char *ngx_http_track_uploads(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
static char *ngx_http_report_uploads(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
static char *ngx_http_upload_progress(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
static void ngx_clean_old_connections(ngx_event_t *ev);

static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;

static ngx_command_t  ngx_http_uploadprogress_commands[] = {

  { ngx_string("upload_progress"),
    NGX_HTTP_MAIN_CONF|NGX_CONF_TAKE2,
    ngx_http_upload_progress,
    0,
    0,
    NULL },

  { ngx_string("track_uploads"),
	  NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
	  ngx_http_track_uploads,
	  NGX_HTTP_LOC_CONF_OFFSET,
    0,
    NULL },

  { ngx_string("report_uploads"),
    NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
    ngx_http_report_uploads,
    NGX_HTTP_LOC_CONF_OFFSET,
    0,
    NULL },

		ngx_null_command
};


static ngx_http_module_t  ngx_http_uploadprogress_module_ctx = {
    NULL,                          /* preconfiguration */
    ngx_http_uploadprogress_init,  /* postconfiguration */

    NULL,  /* create main configuration */
    NULL,    /* init main configuration */

    NULL,                          /* create server configuration */
    NULL,                          /* merge server configuration */

    ngx_http_uploadprogress_create_loc_conf,          /* create location configuration */
    ngx_http_uploadprogress_merge_loc_conf            /* merge location configuration */
};


ngx_module_t  ngx_http_uploadprogress_module = {
    NGX_MODULE_V1,
    &ngx_http_uploadprogress_module_ctx,      /* module context */
    ngx_http_uploadprogress_commands,         /* module directives */
    NGX_HTTP_MODULE,               /* module type */
    NULL,                          /* init master */
    NULL,                          /* init module */
    NULL,                          /* init process */
    NULL,                          /* init thread */
    NULL,                          /* exit thread */
    NULL,                          /* exit process */
    NULL,                          /* exit master */
    NGX_MODULE_V1_PADDING
};

static ngx_str_t x_progress_id = ngx_string("X-Progress-ID");

static ngx_str_t*
get_tracking_id(ngx_http_request_t *r)
{
	u_char										 *p,*start_p;
	ngx_uint_t i;
  ngx_list_part_t              *part;
  ngx_table_elt_t              *header;
	ngx_str_t										 *ret;

  part = &r->headers_in.headers.part;
  header = part->elts;

  for (i = 0; /* void */; i++) {

      if (i >= part->nelts) {
          if (part->next == NULL) {
              break;
          }

          part = part->next;
          header = part->elts;
          i = 0;
      }

			if (header[i].key.len == x_progress_id.len && ngx_strncmp(header[i].key.data, x_progress_id.data,header[i].key.len) == 0)
			{
				ret = ngx_pcalloc(r->pool, sizeof(ngx_str_t));
				ret->data = header[i].value.data;
				ret->len = header[i].value.len;
				return ret;
			}
  }

	/* not found, check as a reaquest arg */
	if (r->args.len) {
		p = (u_char *) ngx_strstr(r->args.data, "X-Progress-ID=");

		if (p) {
			start_p = p += 14;
	    while (p < r->args.data + r->args.len) {
	        if (*p++ != '&') {
	            continue;
	        }
			}
			
			ret = ngx_pcalloc(r->pool, sizeof(ngx_str_t));
			ret->data = start_p;
			ret->len = p-start_p;
			return ret;
		}
	}

	return NULL;
}

static ngx_http_uploadprogress_node_t*
find_node(ngx_str_t *id, ngx_http_uploadprogress_ctx_t *ctx, ngx_log_t *log)
{
  uint32_t                        hash;
  ngx_rbtree_node_t              *node, *sentinel;
	ngx_int_t                       rc;
	ngx_http_uploadprogress_node_t *up;
	
  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, log, 0,
                 "upload-progress: find_node %V", id);	
	
	hash = ngx_crc32_short(id->data, id->len);
	
  node = ctx->rbtree->root;
  sentinel = ctx->rbtree->sentinel;

  while (node != sentinel) {

      if (hash < node->key) {
          node = node->left;
          continue;
      }

      if (hash > node->key) {
          node = node->right;
          continue;
      }

      /* hash == node->key */

      do {
          up = (ngx_http_uploadprogress_node_t *) node;

          rc = ngx_memn2cmp(id->data, up->data, id->len, (size_t) up->len);

          if (rc == 0) {
					  	ngx_log_debug0(NGX_LOG_DEBUG_HTTP, log, 0,
					                 "upload-progress: found node");	
              return up;
          }

          node = (rc < 0) ? node->left : node->right;

      } while (node != sentinel && hash == node->key);

      break;
  }
	ngx_log_debug0(NGX_LOG_DEBUG_HTTP, log, 0,
               "upload-progress: can't find node");	
	return NULL;
}

/* This generates the response for the report */
static ngx_int_t
ngx_http_reportuploads_handler(ngx_http_request_t *r)
{
	ngx_str_t		 *id;
  ngx_buf_t    *b;
  ngx_chain_t   out;
	ngx_http_request_t								 *orig;
	ngx_int_t                       rc, size; 
		ngx_uint_t										len, i;
  ngx_slab_pool_t                *shpool;
	ngx_http_uploadprogress_conf_t     *upcf;
  ngx_http_uploadprogress_ctx_t      *ctx;
  ngx_http_uploadprogress_node_t     *up;
  ngx_table_elt_t  *expires, *cc, **ccp;

  if (r->method != NGX_HTTP_GET && r->method != NGX_HTTP_HEAD) {
      return NGX_HTTP_NOT_ALLOWED;
  }

  rc = ngx_http_discard_request_body(r);

  if (rc != NGX_OK) {
      return rc;
  }

	/* get the tracking id if any */
	id = get_tracking_id(r);


	if ( id == NULL )
	{
	  ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
	                 "reportuploads handler cant find id");
    return NGX_DECLINED;
	}
	
  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                 "reportuploads handler found id: %V", id);

  upcf = ngx_http_get_module_loc_conf(r, ngx_http_uploadprogress_module);

  if (upcf->shm_zone == NULL) {
	  	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
	                 "reportuploads no shm_zone for id: %V", id);
      return NGX_DECLINED;
  }

	orig = NULL;
  ctx = upcf->shm_zone->data;

	/* get the original connection of the upload */
  shpool = (ngx_slab_pool_t *) upcf->shm_zone->shm.addr;

	ngx_shmtx_lock(&shpool->mutex);

 	up = find_node(id, ctx, r->connection->log);
  if (up != NULL)
  {
	  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
	                 "reportuploads found node: %V", id);
		orig = up->r;
	}
	else
	{
	  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
	                 "reportuploads not found: %V", id);		
	}
	ngx_shmtx_unlock(&shpool->mutex);

	/* send the output */
  r->headers_out.content_type.len = sizeof("text/javascript") - 1;
  r->headers_out.content_type.data = (u_char *) "text/javascript";

	/* force no-cache */
  expires = r->headers_out.expires;

  if (expires == NULL) {

      expires = ngx_list_push(&r->headers_out.headers);
      if (expires == NULL) {
          return NGX_HTTP_INTERNAL_SERVER_ERROR;
      }

      r->headers_out.expires = expires;

      expires->hash = 1;
      expires->key.len = sizeof("Expires") - 1;
      expires->key.data = (u_char *) "Expires";
  }

  len = sizeof("Mon, 28 Sep 1970 06:00:00 GMT");
  expires->value.len = len - 1;

  ccp = r->headers_out.cache_control.elts;
  if (ccp == NULL) {

      if (ngx_array_init(&r->headers_out.cache_control, r->pool,
                         1, sizeof(ngx_table_elt_t *))
          != NGX_OK)
      {
          return NGX_HTTP_INTERNAL_SERVER_ERROR;
      }

      ccp = ngx_array_push(&r->headers_out.cache_control);
      if (ccp == NULL) {
          return NGX_HTTP_INTERNAL_SERVER_ERROR;
      }

      cc = ngx_list_push(&r->headers_out.headers);
      if (cc == NULL) {
          return NGX_HTTP_INTERNAL_SERVER_ERROR;
      }

      cc->hash = 1;
      cc->key.len = sizeof("Cache-Control") - 1;
      cc->key.data = (u_char *) "Cache-Control";

      *ccp = cc;

  } else {
      for (i = 1; i < r->headers_out.cache_control.nelts; i++) {
          ccp[i]->hash = 0;
      }

      cc = ccp[0];
  }

  expires->value.data = (u_char *) "Thu, 01 Jan 1970 00:00:01 GMT";

  cc->value.len = sizeof("no-cache") - 1;
  cc->value.data = (u_char *) "no-cache";


  if (r->method == NGX_HTTP_HEAD) {
      r->headers_out.status = NGX_HTTP_OK;

      rc = ngx_http_send_header(r);

      if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {
          return rc;
      }
  }

	if ( orig == NULL )
	{
		if (up != NULL && up->err_status != NGX_HTTP_REQUEST_ENTITY_TOO_LARGE )
		{
			size = sizeof("new Object({ 'state' : 'done' })\r\n");
  	}
		else if ( up != NULL && up->err_status == NGX_HTTP_REQUEST_ENTITY_TOO_LARGE )
		{
			size = sizeof("new Object({ 'state' : 'error', 'status' : 413 })\r\n");			
		}
		else
		{
			size = sizeof("new Object({ 'state' : 'starting' })\r\n");
  	}
	}
	else if ( orig->err_status == NGX_HTTP_REQUEST_ENTITY_TOO_LARGE )
	{
		size = sizeof("new Object({ 'state' : 'error', 'status' : 413 })\r\n");
	}
	else
	{
		size = sizeof("new Object({ 'state' : 'uploading', 'received' : ") + NGX_INT_T_LEN + sizeof(" })\r\n");
		size += sizeof(", 'size' : ") + NGX_INT_T_LEN;
	}

  b = ngx_create_temp_buf(r->pool, size);
  if (b == NULL) {
      return NGX_HTTP_INTERNAL_SERVER_ERROR;
  }

  out.buf = b;
  out.next = NULL;
	
	if (orig == NULL)
	{
		if (up == NULL )
		{
			b->last = ngx_cpymem(b->last, "new Object({ 'state' : 'starting' })\r\n",
		                       sizeof("new Object({ 'state' : 'starting' })\r\n") - 1);
			ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
											               "reportuploads returning starting");
		}
		else if ( up != NULL && up->err_status == NGX_HTTP_REQUEST_ENTITY_TOO_LARGE )
		{
			b->last = ngx_cpymem(b->last, "new Object({ 'state' : 'error', 'status' : 413 })\r\n",
		                       sizeof("new Object({ 'state' : 'error', 'status' : 413 })\r\n") - 1);
			ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
		               "reportuploads returning error 413");			
		}
		else 
		{
			b->last = ngx_cpymem(b->last, "new Object({ 'state' : 'done' })\r\n",
		                       sizeof("new Object({ 'state' : 'done' })\r\n") - 1);
			ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
		               "reportuploads returning done");
		}
	}
	else if ( orig->err_status == NGX_HTTP_REQUEST_ENTITY_TOO_LARGE)
	{
		b->last = ngx_cpymem(b->last, "new Object({ 'state' : 'error', 'status' : 413 })\r\n",
	                       sizeof("new Object({ 'state' : 'error', 'status' : 413 })\r\n") - 1);
		ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
	               "reportuploads returning error 413");
	}
	else
	{
		b->last = ngx_cpymem(b->last,"new Object({ 'state' : 'uploading', 'received' : ", 
			sizeof("new Object({ 'state' : 'uploading', 'received' : ")-1 );
			
		b->last = ngx_sprintf(b->last, "%uO, 'size' : %uO })\r\n", (orig->headers_in.content_length_n - orig->request_body->rest), orig->headers_in.content_length_n);

		ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
	               "reportuploads returning %uO / %uO", (orig->headers_in.content_length_n - orig->request_body->rest), orig->headers_in.content_length_n);

	}

	r->headers_out.status = NGX_HTTP_OK;
	r->headers_out.content_length_n = b->last - b->pos;

	b->last_buf = 1;
	rc = ngx_http_send_header(r);

	if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {
	    return rc;
	}

	return ngx_http_output_filter(r, &out);;
}

/* 
Let's register the upload connection in our connections rb-tree
*/
static ngx_int_t
ngx_http_uploadprogress_handler(ngx_http_request_t *r)
{
  size_t                          n;
	ngx_str_t 												 *id;
  uint32_t                        hash;
  ngx_slab_pool_t                *shpool;
  ngx_rbtree_node_t              *node;
	ngx_http_uploadprogress_conf_t     *upcf;
  ngx_http_uploadprogress_ctx_t      *ctx;
  ngx_http_uploadprogress_node_t     *up;
	ngx_http_uploadprogress_cleanup_t	 *upcln;
  ngx_pool_cleanup_t             *cln;

	/* Is it a POST connection */
	if (r->method != NGX_HTTP_POST) {
		return NGX_DECLINED;
	}

	id = get_tracking_id(r);
	if ( id == NULL )
	{
		ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
             "trackuploads no id found in POST upload req");
		return NGX_DECLINED;
	}
	
	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
           "trackuploads id found: %V", id);

  upcf = ngx_http_get_module_loc_conf(r, ngx_http_uploadprogress_module);

  if (!upcf->track) {
	  	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
	                 "trackuploads not tracking in this location for id: %V", id);
      return NGX_DECLINED;
  }

  if (upcf->shm_zone == NULL) {
  	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                 "trackuploads no shm_zone for id: %V", id);
      return NGX_DECLINED;
  }

  ctx = upcf->shm_zone->data;
	
  hash = ngx_crc32_short(id->data, id->len);

	ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
               "trackuploads hash %08XD for id: %V",hash, id);

  shpool = (ngx_slab_pool_t *) upcf->shm_zone->shm.addr;

  ngx_shmtx_lock(&shpool->mutex);

	if ( find_node(id, ctx, r->connection->log) != NULL )
	{
  	ngx_shmtx_unlock(&shpool->mutex);
		/* already found a node with matching progress ID */
		ngx_log_error(NGX_LOG_INFO, r->connection->log, 0,
                  "upload_progress: tracking already registered id: %V", id);
    
		return NGX_HTTP_INTERNAL_SERVER_ERROR;
	}

  cln = ngx_pool_cleanup_add(r->pool, sizeof(ngx_http_uploadprogress_cleanup_t));
  if (cln == NULL) {
    	ngx_shmtx_unlock(&shpool->mutex);
      return NGX_HTTP_INTERNAL_SERVER_ERROR;
  }

  n = sizeof(ngx_http_uploadprogress_node_t)
      + id->len;

  node = ngx_slab_alloc_locked(shpool, n);
  if (node == NULL) {
      ngx_shmtx_unlock(&shpool->mutex);
      return NGX_HTTP_SERVICE_UNAVAILABLE;
  }

  up = (ngx_http_uploadprogress_node_t *)node;

  node->key = hash;
  up->len = (u_char) id->len;
	up->r = r;
	up->err_status = r->err_status;
	
  up->next = ctx->list_head.next;
	up->next->prev = up;
  up->prev = &ctx->list_head;
  ctx->list_head.next = up;
		
  ngx_memcpy(up->data, id->data, id->len);

  ngx_rbtree_insert(ctx->rbtree, node);
  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                 "trackuploads: %08XD inserted in rbtree", node->key);

  ngx_shmtx_unlock(&shpool->mutex);

  cln->handler = ngx_http_uploadprogress_cleanup;
  upcln = cln->data;

  upcln->shm_zone = upcf->shm_zone;
  upcln->node = node;

	/* start the timer if needed */
	if ( !upcf->cleanup.timer_set)
	{
		upcf->cleanup.data = upcf->shm_zone;
		upcf->cleanup.handler = ngx_clean_old_connections;
		upcf->cleanup.log = r->connection->log;
		ngx_add_timer(&upcf->cleanup, 60 * 1000);
	}

  return NGX_DECLINED;
}

static void
ngx_http_uploadprogress_rbtree_insert_value(ngx_rbtree_node_t *temp,
    ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel)
{
    ngx_http_uploadprogress_node_t  *upn, *upnt;

    for ( ;; ) {

        if (node->key < temp->key) {

            if (temp->left == sentinel) {
                temp->left = node;
                break;
            }

            temp = temp->left;

        } else if (node->key > temp->key) {

            if (temp->right == sentinel) {
                temp->right = node;
                break;
            }

            temp = temp->right;

        } else { /* node->key == temp->key */

            upn = (ngx_http_uploadprogress_node_t *) node;
            upnt = (ngx_http_uploadprogress_node_t *) temp;

            if (ngx_memn2cmp(upn->data, upnt->data, upn->len, upnt->len) < 0) {

                if (temp->left == sentinel) {
                    temp->left = node;
                    break;
                }

                temp = temp->left;

            } else {

                if (temp->right == sentinel) {
                    temp->right = node;
                    break;
                }

                temp = temp->right;
            }
        }
    }

    node->parent = temp;
    node->left = sentinel;
    node->right = sentinel;
    ngx_rbt_red(node);
}


static void
ngx_clean_old_connections(ngx_event_t *ev)
{
  ngx_shm_zone_t             *shm_zone;
  ngx_http_uploadprogress_ctx_t  *ctx;
  ngx_slab_pool_t                *shpool;
  ngx_rbtree_node_t              *node;
	ngx_http_uploadprogress_node_t	*up;
	time_t	now = ngx_time();

	
	/* scan the rbtree */
	shm_zone = ev->data; 
	ctx = shm_zone->data;
  shpool = (ngx_slab_pool_t *) shm_zone->shm.addr;

	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, shm_zone->shm.log, 0,
           "uploadprogress clean old connections at %T", now);

  ngx_shmtx_lock(&shpool->mutex);
  node = (ngx_rbtree_node_t *)ctx->list_tail.prev;
  for ( ;; ) {


      if (node == &ctx->list_head.node) {
          break;
      }
			
			up = (ngx_http_uploadprogress_node_t *)node;

			ngx_log_debug3(NGX_LOG_DEBUG_HTTP, shm_zone->shm.log, 0,
		           "uploadprogress clean: scanning %08XD (req %p) timeout at %T", node->key, up->r, up->timeout);

			if ( up->r == NULL && up->timeout < now )
			{
	      up->next->prev = up->prev;
	      up->prev->next = up->next;

				ngx_log_debug3(NGX_LOG_DEBUG_HTTP, shm_zone->shm.log, 0,
			           "uploadprogress clean: removing %08XD (req %p) ", node->key, up->r, up->timeout);

				ngx_rbtree_delete(ctx->rbtree, node);
				ngx_slab_free_locked(shpool, node);
			}
			
			node = (ngx_rbtree_node_t *)up->prev;
		}
	  ngx_shmtx_unlock(&shpool->mutex);
		ngx_log_debug0(NGX_LOG_DEBUG_HTTP, shm_zone->shm.log, 0,
	           "uploadprogress clean old connections restarting timer");

	ngx_add_timer(ev, 60 * 1000); /* trigger again in 60s */
}



/*
removes the expired node from the upload rbtree
*/
static void
ngx_http_uploadprogress_cleanup(void *data)
{
    ngx_http_uploadprogress_cleanup_t  *upcln = data;
	  ngx_slab_pool_t             *shpool;
	  ngx_rbtree_node_t           *node;
    ngx_http_uploadprogress_ctx_t   *ctx;
    ngx_http_uploadprogress_node_t  *up;

		ngx_log_debug0(NGX_LOG_DEBUG_HTTP, upcln->shm_zone->shm.log, 0,
	           "uploadprogress cleanup called");

    ctx = upcln->shm_zone->data;
    shpool = (ngx_slab_pool_t *) upcln->shm_zone->shm.addr;
    node = upcln->node;
    up = (ngx_http_uploadprogress_node_t *) node;

		up->r = NULL; /* mark the original request as done */
		up->timeout = ngx_time() + 60; /* keep tracking for 60s */

		ngx_log_debug2(NGX_LOG_DEBUG_HTTP, upcln->shm_zone->shm.log, 0,
	           "uploadprogress cleanup: connection %08XD to be deleted at %T", node->key, up->timeout);
		
}

static ngx_int_t
ngx_http_uploadprogress_init_zone(ngx_shm_zone_t *shm_zone, void *data)
{
    ngx_http_uploadprogress_ctx_t  *octx = data;

    ngx_slab_pool_t            *shpool;
    ngx_rbtree_node_t          *sentinel;
    ngx_http_uploadprogress_ctx_t  *ctx;

    ctx = shm_zone->data;

    if (octx) {
        ctx->rbtree = octx->rbtree;
        return NGX_OK;
    }

    shpool = (ngx_slab_pool_t *) shm_zone->shm.addr;

    ctx->rbtree = ngx_slab_alloc(shpool, sizeof(ngx_rbtree_t));
    if (ctx->rbtree == NULL) {
        return NGX_ERROR;
    }

    sentinel = ngx_slab_alloc(shpool, sizeof(ngx_rbtree_node_t));
    if (sentinel == NULL) {
        return NGX_ERROR;
    }

    ngx_rbtree_sentinel_init(sentinel);

    ctx->rbtree->root = sentinel;
    ctx->rbtree->sentinel = sentinel;
    ctx->rbtree->insert = ngx_http_uploadprogress_rbtree_insert_value;

    return NGX_OK;
}

static ngx_int_t
ngx_http_uploadprogress_errortracker(ngx_http_request_t *r)
{
  	size_t                          n;
		ngx_str_t 										 *id;
  	ngx_slab_pool_t                *shpool;
  	ngx_rbtree_node_t              *node;
  	ngx_http_uploadprogress_ctx_t      *ctx;
  	ngx_http_uploadprogress_node_t     *up;
    ngx_http_uploadprogress_conf_t	  *upcf;
	  uint32_t                        hash;
		ngx_http_uploadprogress_cleanup_t	 *upcln;
	  ngx_pool_cleanup_t             *cln;

		ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
	           "uploadprogress error-tracker error: %D", r->err_status);
		if ( r->err_status == NGX_HTTP_REQUEST_ENTITY_TOO_LARGE )
		{

    	upcf = ngx_http_get_module_loc_conf(r, ngx_http_uploadprogress_module);

		  if (!upcf->track) {
			  	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
			                 "uploadprogress error-tracker not tracking in this location for id: %V", id);
		    goto finish;
		  }

			id = get_tracking_id(r);
			if ( id == NULL )
			{
				ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
		             "trackuploads error-tracker no id found in POST upload req");
				goto finish;
			}

			ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
		           "trackuploads error-tracker id found: %V", id);


		  if (upcf->shm_zone == NULL) {
		  	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
		                 "trackuploads no shm_zone for id: %V", id);
									goto finish;
		  }

		  ctx = upcf->shm_zone->data;

		  hash = ngx_crc32_short(id->data, id->len);

			ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
		               "trackuploads error-tracking hash %08XD for id: %V",hash, id);

		  shpool = (ngx_slab_pool_t *) upcf->shm_zone->shm.addr;

		  ngx_shmtx_lock(&shpool->mutex);

			if ( (up = find_node(id, ctx, r->connection->log)) != NULL )
			{
				ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
			               "trackuploads error-tracking found node for id: %V", id);
				up->r = NULL; /* don't really track it since it errors */
				up->err_status = r->err_status;
				goto finish;
			}

			/* no lz found for this tracking id */
		  n = sizeof(ngx_http_uploadprogress_node_t)
		      + id->len;

			  cln = ngx_pool_cleanup_add(r->pool, sizeof(ngx_http_uploadprogress_cleanup_t));
			  if (cln == NULL) {
					goto finish;
			  }


		  node = ngx_slab_alloc_locked(shpool, n);
		  if (node == NULL) {
		      ngx_shmtx_unlock(&shpool->mutex);
					goto finish;
		  }

		  up = (ngx_http_uploadprogress_node_t *) node;

		  node->key = hash;
		  up->len = (u_char) id->len;
			up->r = NULL; /* don't really track it since it errors */
			up->err_status = r->err_status;
		  ngx_memcpy(up->data, id->data, id->len);

		  up->next = ctx->list_head.next;
			up->next->prev = up;
		  up->prev = &ctx->list_head;
		  ctx->list_head.next = up;

		  ngx_rbtree_insert(ctx->rbtree, node);

		  ngx_shmtx_unlock(&shpool->mutex);

		  cln->handler = ngx_http_uploadprogress_cleanup;
		  upcln = cln->data;
		  upcln->shm_zone = upcf->shm_zone;
		  upcln->node = node;

		  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
		                 "trackuploads error-tracking adding: %08XD", node->key);

		}

finish:		
		/* call the filter chain as usual */ 
    return ngx_http_next_header_filter(r);
}


static ngx_int_t
ngx_http_uploadprogress_init(ngx_conf_t *cf)
{
    ngx_http_handler_pt        *h;
    ngx_http_core_main_conf_t  *cmcf;

    cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);

		/* install the tracking handler */
    h = ngx_array_push(&cmcf->phases[NGX_HTTP_REWRITE_PHASE].handlers);
    if (h == NULL) {
        return NGX_ERROR;
    }

    *h = ngx_http_uploadprogress_handler;

		/* 
			we also need to track HTTP 413 errors 
			unfortunately, the above handler is not called in case of 
			errors.
			we have to register a header output filter that will be
			called in any case to track those errors
		*/
	  ngx_http_next_header_filter = ngx_http_top_header_filter;
	  ngx_http_top_header_filter = ngx_http_uploadprogress_errortracker;
		
    return NGX_OK;
}

static void *
ngx_http_uploadprogress_create_loc_conf(ngx_conf_t *cf)
{
    ngx_http_uploadprogress_conf_t  *conf;

    conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_uploadprogress_conf_t));
    if (conf == NULL) {
        return NGX_CONF_ERROR;
    }
    return conf;
}


static char *
ngx_http_uploadprogress_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
{
  ngx_http_uploadprogress_conf_t *prev = parent;
  ngx_http_uploadprogress_conf_t *conf = child;

  if (conf->shm_zone == NULL) {
      *conf = *prev;
  }

  return NGX_CONF_OK;
}


static char *
ngx_http_upload_progress(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ssize_t                     n;
    ngx_str_t                  *value;
    ngx_shm_zone_t             *shm_zone;
    ngx_http_uploadprogress_ctx_t  *ctx;

    value = cf->args->elts;

	  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, cf->log, 0,
	                 "ngx_upload_progress name: %V", &value[1]);

    ctx = ngx_pcalloc(cf->pool, sizeof(ngx_http_uploadprogress_ctx_t));
    if (ctx == NULL) {
        return NGX_CONF_ERROR;
    }

    ctx->list_head.prev = NULL;
    ctx->list_head.next = &ctx->list_tail;

    ctx->list_tail.prev = &ctx->list_head;
    ctx->list_tail.next = NULL;

    n = ngx_parse_size(&value[2]);

    if (n == NGX_ERROR) {
        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "invalid size of track_uploads \"%V\"", &value[2]);
        return NGX_CONF_ERROR;
    }

    if (n < (ngx_int_t) (8 * ngx_pagesize)) {
        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "track_uploads \"%V\" is too small", &value[1]);
        return NGX_CONF_ERROR;
    }

    shm_zone = ngx_shared_memory_add(cf, &value[1], n,
                                     &ngx_http_uploadprogress_module);
    if (shm_zone == NULL) {
        return NGX_CONF_ERROR;
    }

	  ngx_log_debug2(NGX_LOG_DEBUG_HTTP, cf->log, 0,
	                 "ngx_upload_progress name: %V, szhm_zone: %p", &value[1], shm_zone);

    if (shm_zone->data) {
        ctx = shm_zone->data;

        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                        "track_uploads \"%V\" is already created",
                        &value[1]);
        return NGX_CONF_ERROR;
    }

    shm_zone->init = ngx_http_uploadprogress_init_zone;
    shm_zone->data = ctx;

    return NGX_CONF_OK;
}



static char *
ngx_http_track_uploads(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_http_uploadprogress_conf_t  *lzcf = conf;
    ngx_str_t  *value;

	  ngx_log_debug0(NGX_LOG_DEBUG_HTTP, cf->log, 0,
	                 "ngx_track_uploads in");

    value = cf->args->elts;

		ngx_log_debug1(NGX_LOG_DEBUG_HTTP, cf->log, 0,
		                 "ngx_track_uploads name: %V", &value[1]);

    lzcf->shm_zone = ngx_shared_memory_add(cf, &value[1], 0,
                                           &ngx_http_uploadprogress_module);
    if (lzcf->shm_zone == NULL) {
        return NGX_CONF_ERROR;
    }

		lzcf->track = (u_char)1;

	  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, cf->log, 0,
	                 "ngx_track_uploads name: %V,szhm_zone: %p", &value[1], lzcf->shm_zone);

    return NGX_CONF_OK;
}


static char *
ngx_http_report_uploads(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_http_uploadprogress_conf_t  *lzcf = conf;
    ngx_http_core_loc_conf_t  *clcf;
    ngx_str_t  *value;

	  ngx_log_debug0(NGX_LOG_DEBUG_HTTP, cf->log, 0,
	                 "ngx_report_uploads in");

    value = cf->args->elts;

	  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, cf->log, 0,
	                 "ngx_report_uploads name: %V", &value[1]);

    lzcf->shm_zone = ngx_shared_memory_add(cf, &value[1], 0,
                                           &ngx_http_uploadprogress_module);
    if (lzcf->shm_zone == NULL) {
        return NGX_CONF_ERROR;
    }

	  ngx_log_debug1(NGX_LOG_DEBUG_HTTP, cf->log, 0,
	                 "ngx_report_uploads name: %V, szhm_zone: %p", &value[1], lzcf->shm_zone);

		lzcf->track = (u_char)0;

		/* install our report handler */
    clcf = ngx_http_conf_get_module_loc_conf(cf, ngx_http_core_module);
    clcf->handler = ngx_http_reportuploads_handler;

    return NGX_CONF_OK;
}