Initial OpenECOMP Demo commit

Change-Id: Ibf8696196a7ac2c84ac8aa7cde1982c9c89fb64d
Signed-off-by: platania <platania@research.att.com>

1 files changed, 1053 insertions, 0 deletions

diff --git a/vnfs/VES/code/evel_library/evel_event_mgr.c b/vnfs/VES/code/evel_library/evel_event_mgr.c
new file mode 100644
index 00000000..0cc049f5
--- /dev/null
+++ b/vnfs/VES/code/evel_library/evel_event_mgr.c
@@ -0,0 +1,1053 @@
+/**************************************************************************//**
+ * @file
+ * Event Manager
+ *
+ * Simple event manager that is responsible for taking events (Heartbeats,
+ * Faults and Measurements) from the ring-buffer and posting them to the API.
+ *
+ * License
+ * -------
+ *
+ * Copyright(c) <2016>, AT&T Intellectual Property.  All other rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:  This product includes
+ *    software developed by the AT&T.
+ * 4. Neither the name of AT&T nor the names of its contributors may be used to
+ *    endorse or promote products derived from this software without specific
+ *    prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY AT&T INTELLECTUAL PROPERTY ''AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL AT&T INTELLECTUAL PROPERTY BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*****************************************************************************/
+
+#include <string.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <pthread.h>
+
+#include <curl/curl.h>
+
+#include "evel.h"
+#include "evel_internal.h"
+#include "ring_buffer.h"
+#include "evel_throttle.h"
+
+/**************************************************************************//**
+ * How long we're prepared to wait for the API service to respond in
+ * seconds.
+ *****************************************************************************/
+static const int EVEL_API_TIMEOUT = 5;
+
+/*****************************************************************************/
+/* Prototypes of locally scoped functions.                                   */
+/*****************************************************************************/
+static size_t read_callback(void *ptr, size_t size, size_t nmemb, void *userp);
+static void * event_handler(void *arg);
+static bool evel_handle_response_tokens(const MEMORY_CHUNK * const chunk,
+                                        const jsmntok_t * const json_tokens,
+                                        const int num_tokens,
+                                        MEMORY_CHUNK * const post);
+static bool evel_tokens_match_command_list(const MEMORY_CHUNK * const chunk,
+                                           const jsmntok_t * const json_token,
+                                           const int num_tokens);
+static bool evel_token_equals_string(const MEMORY_CHUNK * const chunk,
+                                     const jsmntok_t * const json_token,
+                                     const char * check_string);
+
+/**************************************************************************//**
+ * Buffers for error strings from libcurl.
+ *****************************************************************************/
+static char curl_err_string[CURL_ERROR_SIZE] = "<NULL>";
+
+/**************************************************************************//**
+ * Handle for the API into libcurl.
+ *****************************************************************************/
+static CURL * curl_handle = NULL;
+
+/**************************************************************************//**
+ * Special headers that we send.
+ *****************************************************************************/
+static struct curl_slist * hdr_chunk = NULL;
+
+/**************************************************************************//**
+ * Message queue for sending events to the API.
+ *****************************************************************************/
+static ring_buffer event_buffer;
+
+/**************************************************************************//**
+ * Single pending priority post, which can be generated as a result of a
+ * response to an event.  Currently only used to respond to a commandList.
+ *****************************************************************************/
+static MEMORY_CHUNK priority_post;
+
+/**************************************************************************//**
+ * The thread which is responsible for handling events off of the ring-buffer
+ * and posting them to the Event Handler API.
+ *****************************************************************************/
+static pthread_t evt_handler_thread;
+
+/**************************************************************************//**
+ * Variable to convey to the event handler thread what the foreground wants it
+ * to do.
+ *****************************************************************************/
+static EVT_HANDLER_STATE evt_handler_state = EVT_HANDLER_UNINITIALIZED;
+
+/**************************************************************************//**
+ * The configured API URL for event and throttling.
+ *****************************************************************************/
+static char * evel_event_api_url;
+static char * evel_throt_api_url;
+
+/**************************************************************************//**
+ * Initialize the event handler.
+ *
+ * Primarily responsible for getting CURL ready for use.
+ *
+ * @param[in] event_api_url
+ *                      The URL where the Vendor Event Listener API is expected
+ *                      to be.
+ * @param[in] throt_api_url
+ *                      The URL where the Throttling API is expected to be.
+ * @param[in] username  The username for the Basic Authentication of requests.
+ * @param[in] password  The password for the Basic Authentication of requests.
+ * @param     verbosity 0 for normal operation, positive values for chattier
+ *                        logs.
+ *****************************************************************************/
+EVEL_ERR_CODES event_handler_initialize(const char * const event_api_url,
+                                        const char * const throt_api_url,
+                                        const char * const username,
+                                        const char * const password,
+                                        int verbosity)
+{
+  int rc = EVEL_SUCCESS;
+  CURLcode curl_rc = CURLE_OK;
+
+  EVEL_ENTER();
+
+  /***************************************************************************/
+  /* Check assumptions.                                                      */
+  /***************************************************************************/
+  assert(event_api_url != NULL);
+  assert(throt_api_url != NULL);
+  assert(username != NULL);
+  assert(password != NULL);
+
+  /***************************************************************************/
+  /* Store the API URLs.                                                     */
+  /***************************************************************************/
+  evel_event_api_url = strdup(event_api_url);
+  assert(evel_event_api_url != NULL);
+  evel_throt_api_url = strdup(throt_api_url);
+  assert(evel_throt_api_url != NULL);
+
+  /***************************************************************************/
+  /* Start the CURL library. Note that this initialization is not threadsafe */
+  /* which imposes a constraint that the EVEL library is initialized before  */
+  /* any threads are started.                                                */
+  /***************************************************************************/
+  curl_rc = curl_global_init(CURL_GLOBAL_SSL);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL. Error code=%d", curl_rc);
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* Get a curl handle which we'll use for all of our output.                */
+  /***************************************************************************/
+  curl_handle = curl_easy_init();
+  if (curl_handle == NULL)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to get libCURL handle");
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* Prime the library to give friendly error codes.                         */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle,
+                             CURLOPT_ERRORBUFFER,
+                             curl_err_string);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL to provide friendly errors. "
+                    "Error code=%d", curl_rc);
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* If running in verbose mode generate more output.                        */
+  /***************************************************************************/
+  if (verbosity > 0)
+  {
+    curl_rc = curl_easy_setopt(curl_handle, CURLOPT_VERBOSE, 1L);
+    if (curl_rc != CURLE_OK)
+    {
+      rc = EVEL_CURL_LIBRARY_FAIL;
+      log_error_state("Failed to initialize libCURL to be verbose. "
+                      "Error code=%d", curl_rc);
+      goto exit_label;
+    }
+  }
+
+  /***************************************************************************/
+  /* Set the URL for the API.                                                */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle, CURLOPT_URL, event_api_url);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL with the API URL. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+  EVEL_INFO("Initializing CURL to send events to: %s", event_api_url);
+
+  /***************************************************************************/
+  /* send all data to this function.                                         */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle,
+                             CURLOPT_WRITEFUNCTION,
+                             evel_write_callback);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL with the write callback. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* some servers don't like requests that are made without a user-agent     */
+  /* field, so we provide one.                                               */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle,
+                             CURLOPT_USERAGENT,
+                             "libcurl-agent/1.0");
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL to upload. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* Specify that we are going to POST data.                                 */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle, CURLOPT_POST, 1L);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL to upload. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* we want to use our own read function.                                   */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle, CURLOPT_READFUNCTION, read_callback);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL to upload using read "
+                    "function. Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* All of our events are JSON encoded.  We also suppress the               */
+  /* Expect: 100-continue   header that we would otherwise get since it      */
+  /* confuses some servers.                                                  */
+  /*                                                                         */
+  /* @TODO: do AT&T want this behavior?                                      */
+  /***************************************************************************/
+  hdr_chunk = curl_slist_append(hdr_chunk, "Content-type: application/json");
+  hdr_chunk = curl_slist_append(hdr_chunk, "Expect:");
+
+  /***************************************************************************/
+  /* set our custom set of headers.                                         */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle, CURLOPT_HTTPHEADER, hdr_chunk);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL to use custom headers. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* Set the timeout for the operation.                                      */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle,
+                             CURLOPT_TIMEOUT,
+                             EVEL_API_TIMEOUT);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL for API timeout. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* Set that we want Basic authentication with username:password Base-64    */
+  /* encoded for the operation.                                              */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL for Basic Authentication. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+  curl_rc = curl_easy_setopt(curl_handle, CURLOPT_USERNAME, username);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL with username. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+  curl_rc = curl_easy_setopt(curl_handle, CURLOPT_PASSWORD, password);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL with password. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* Initialize a message ring-buffer to be used between the foreground and  */
+  /* the thread which sends the messages.  This can't fail.                  */
+  /***************************************************************************/
+  ring_buffer_initialize(&event_buffer, EVEL_EVENT_BUFFER_DEPTH);
+
+  /***************************************************************************/
+  /* Initialize the priority post buffer to empty.                           */
+  /***************************************************************************/
+  priority_post.memory = NULL;
+
+exit_label:
+  EVEL_EXIT();
+
+  return(rc);
+}
+
+/**************************************************************************//**
+ * Run the event handler.
+ *
+ * Spawns the thread responsible for handling events and sending them to the
+ * API.
+ *
+ *  @return Status code.
+ *  @retval ::EVEL_SUCCESS if everything OK.
+ *  @retval One of ::EVEL_ERR_CODES if there was a problem.
+ *****************************************************************************/
+EVEL_ERR_CODES event_handler_run()
+{
+  EVEL_ERR_CODES rc = EVEL_SUCCESS;
+  int pthread_rc = 0;
+
+  EVEL_ENTER();
+
+  /***************************************************************************/
+  /* Start the event handler thread.                                         */
+  /***************************************************************************/
+  evt_handler_state = EVT_HANDLER_INACTIVE;
+  pthread_rc = pthread_create(&evt_handler_thread, NULL, event_handler, NULL);
+  if (pthread_rc != 0)
+  {
+    rc = EVEL_PTHREAD_LIBRARY_FAIL;
+    log_error_state("Failed to start event handler thread. "
+                    "Error code=%d", pthread_rc);
+  }
+
+  EVEL_EXIT()
+  return rc;
+}
+
+/**************************************************************************//**
+ * Terminate the event handler.
+ *
+ * Shuts down the event handler thread in as clean a way as possible. Sets the
+ * global exit flag and then signals the thread to interrupt it since it's
+ * most likely waiting on the ring-buffer.
+ *
+ * Having achieved an orderly shutdown of the event handler thread, clean up
+ * the cURL library's resources cleanly.
+ *
+ *  @return Status code.
+ *  @retval ::EVEL_SUCCESS if everything OK.
+ *  @retval One of ::EVEL_ERR_CODES if there was a problem.
+ *****************************************************************************/
+EVEL_ERR_CODES event_handler_terminate()
+{
+  EVEL_ERR_CODES rc = EVEL_SUCCESS;
+
+  EVEL_ENTER();
+  EVENT_INTERNAL *event = NULL;
+
+  /***************************************************************************/
+  /* Make sure that we were initialized before trying to terminate the       */
+  /* event handler thread.                                                   */
+  /***************************************************************************/
+  if (evt_handler_state != EVT_HANDLER_UNINITIALIZED)
+  {
+    /*************************************************************************/
+    /* Make sure that the event handler knows it's time to die.              */
+    /*************************************************************************/
+    event = evel_new_internal_event(EVT_CMD_TERMINATE);
+    if (event == NULL)
+    {
+      /***********************************************************************/
+      /* We failed to get an event, but we don't bail out - we will just     */
+      /* clean up what we can and continue on our way, since we're exiting   */
+      /* anyway.                                                             */
+      /***********************************************************************/
+      EVEL_ERROR("Failed to get internal event - perform dirty exit instead!");
+    }
+    else
+    {
+      /***********************************************************************/
+      /* Post the event then wait for the Event Handler to exit.  Set the    */
+      /* global command, too, in case the ring-buffer is full.               */
+      /***********************************************************************/
+      EVEL_DEBUG("Sending event to Event Hander to request it to exit.");
+      evt_handler_state = EVT_HANDLER_REQUEST_TERMINATE;
+      evel_post_event((EVENT_HEADER *) event);
+      pthread_join(evt_handler_thread, NULL);
+      EVEL_DEBUG("Event Handler thread has exited.");
+    }
+  }
+  else
+  {
+    EVEL_DEBUG("Event handler was not initialized, so no need to kill it");
+  }
+
+  /***************************************************************************/
+  /* Clean-up the cURL library.                                              */
+  /***************************************************************************/
+  if (curl_handle != NULL)
+  {
+    curl_easy_cleanup(curl_handle);
+    curl_handle = NULL;
+  }
+  if (hdr_chunk != NULL)
+  {
+    curl_slist_free_all(hdr_chunk);
+    hdr_chunk = NULL;
+  }
+
+  /***************************************************************************/
+  /* Free off the stored API URL strings.                                    */
+  /***************************************************************************/
+  if (evel_event_api_url != NULL)
+  {
+    free(evel_event_api_url);
+    evel_event_api_url = NULL;
+  }
+  if (evel_throt_api_url != NULL)
+  {
+    free(evel_throt_api_url);
+    evel_throt_api_url = NULL;
+  }
+
+  EVEL_EXIT();
+  return rc;
+}
+
+/**************************************************************************//**
+ * Post an event.
+ *
+ * @note  So far as the caller is concerned, successfully posting the event
+ * relinquishes all responsibility for the event - the library will take care
+ * of freeing the event in due course.
+
+ * @param event   The event to be posted.
+ *
+ * @returns Status code
+ * @retval  EVEL_SUCCESS On success
+ * @retval  "One of ::EVEL_ERR_CODES" On failure.
+ *****************************************************************************/
+EVEL_ERR_CODES evel_post_event(EVENT_HEADER * event)
+{
+  int rc = EVEL_SUCCESS;
+
+  EVEL_ENTER();
+
+  /***************************************************************************/
+  /* Check preconditions.                                                    */
+  /***************************************************************************/
+  assert(event != NULL);
+
+  /***************************************************************************/
+  /* We need to make sure that we are either initializing or running         */
+  /* normally before writing the event into the buffer so that we can        */
+  /* guarantee that the ring-buffer empties  properly on exit.               */
+  /***************************************************************************/
+  if ((evt_handler_state == EVT_HANDLER_ACTIVE) ||
+      (evt_handler_state == EVT_HANDLER_INACTIVE) ||
+      (evt_handler_state == EVT_HANDLER_REQUEST_TERMINATE))
+  {
+    if (ring_buffer_write(&event_buffer, event) == 0)
+    {
+      log_error_state("Failed to write event to buffer - event dropped!");
+      rc = EVEL_EVENT_BUFFER_FULL;
+      evel_free_event(event);
+    }
+  }
+  else
+  {
+    /*************************************************************************/
+    /* System is not in active operation, so reject the event.               */
+    /*************************************************************************/
+    log_error_state("Event Handler system not active - event dropped!");
+    rc = EVEL_EVENT_HANDLER_INACTIVE;
+    evel_free_event(event);
+  }
+
+  EVEL_EXIT();
+  return (rc);
+}
+
+/**************************************************************************//**
+ * Post an event to the Vendor Event Listener API.
+ *
+ * @returns Status code
+ * @retval  EVEL_SUCCESS On success
+ * @retval  "One of ::EVEL_ERR_CODES" On failure.
+ *****************************************************************************/
+static EVEL_ERR_CODES evel_post_api(char * msg, size_t size)
+{
+  int rc = EVEL_SUCCESS;
+  CURLcode curl_rc = CURLE_OK;
+  MEMORY_CHUNK rx_chunk;
+  MEMORY_CHUNK tx_chunk;
+  int http_response_code = 0;
+
+  EVEL_ENTER();
+
+  /***************************************************************************/
+  /* Create the memory chunk to be used for the response to the post.  The   */
+  /* will be realloced.                                                      */
+  /***************************************************************************/
+  rx_chunk.memory = malloc(1);
+  assert(rx_chunk.memory != NULL);
+  rx_chunk.size = 0;
+
+  /***************************************************************************/
+  /* Create the memory chunk to be sent as the body of the post.             */
+  /***************************************************************************/
+  tx_chunk.memory = msg;
+  tx_chunk.size = size;
+  EVEL_DEBUG("Sending chunk of size %d", tx_chunk.size);
+
+  /***************************************************************************/
+  /* Point to the data to be received.                                       */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, &rx_chunk);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to initialize libCURL to upload. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+  EVEL_DEBUG("Initialized data to receive");
+
+  /***************************************************************************/
+  /* Pointer to pass to our read function                                    */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle, CURLOPT_READDATA, &tx_chunk);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to set upload data for libCURL to upload. "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+  EVEL_DEBUG("Initialized data to send");
+
+  /***************************************************************************/
+  /* Size of the data to transmit.                                           */
+  /***************************************************************************/
+  curl_rc = curl_easy_setopt(curl_handle,
+                             CURLOPT_POSTFIELDSIZE,
+                             tx_chunk.size);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to set length of upload data for libCURL to "
+                    "upload.  Error code=%d (%s)", curl_rc, curl_err_string);
+    goto exit_label;
+  }
+  EVEL_DEBUG("Initialized length of data to send");
+
+  /***************************************************************************/
+  /* Now run off and do what you've been told!                               */
+  /***************************************************************************/
+  curl_rc = curl_easy_perform(curl_handle);
+  if (curl_rc != CURLE_OK)
+  {
+    rc = EVEL_CURL_LIBRARY_FAIL;
+    log_error_state("Failed to transfer an event to Vendor Event Listener! "
+                    "Error code=%d (%s)", curl_rc, curl_err_string);
+    EVEL_ERROR("Dropped event: %s", msg);
+    goto exit_label;
+  }
+
+  /***************************************************************************/
+  /* See what response we got - any 2XX response is good.                    */
+  /***************************************************************************/
+  curl_easy_getinfo(curl_handle, CURLINFO_RESPONSE_CODE, &http_response_code);
+  EVEL_DEBUG("HTTP response code: %d", http_response_code);
+  if ((http_response_code / 100) == 2)
+  {
+    /*************************************************************************/
+    /* If the server responded with data it may be interesting but not a     */
+    /* problem.                                                              */
+    /*************************************************************************/
+    if ((rx_chunk.size > 0) && (rx_chunk.memory != NULL))
+    {
+      EVEL_DEBUG("Server returned data = %d (%s)",
+                 rx_chunk.size,
+                 rx_chunk.memory);
+
+      /***********************************************************************/
+      /* If this is a response to priority post, then we're not interested.  */
+      /***********************************************************************/
+      if (priority_post.memory != NULL)
+      {
+        EVEL_ERROR("Ignoring priority post response");
+      }
+      else
+      {
+        evel_handle_event_response(&rx_chunk, &priority_post);
+      }
+    }
+  }
+  else
+  {
+    EVEL_ERROR("Unexpected HTTP response code: %d with data size %d (%s)",
+                http_response_code,
+                rx_chunk.size,
+                rx_chunk.size > 0 ? rx_chunk.memory : "NONE");
+    EVEL_ERROR("Potentially dropped event: %s", msg);
+  }
+
+exit_label:
+  free(rx_chunk.memory);
+  EVEL_EXIT();
+  return(rc);
+}
+
+/**************************************************************************//**
+ * Callback function to provide data to send.
+ *
+ * Copy data into the supplied buffer, read_callback::ptr, checking size
+ * limits.
+ *
+ * @returns   Number of bytes placed into read_callback::ptr. 0 for EOF.
+ *****************************************************************************/
+static size_t read_callback(void *ptr, size_t size, size_t nmemb, void *userp)
+{
+  size_t rtn = 0;
+  size_t bytes_to_write = 0;
+  MEMORY_CHUNK *tx_chunk = (MEMORY_CHUNK *)userp;
+
+  EVEL_ENTER();
+
+  bytes_to_write = min(size*nmemb, tx_chunk->size);
+
+  if (bytes_to_write > 0)
+  {
+    EVEL_DEBUG("Going to try to write %d bytes", bytes_to_write);
+    strncpy((char *)ptr, tx_chunk->memory, bytes_to_write);
+    tx_chunk->memory += bytes_to_write;
+    tx_chunk->size -= bytes_to_write;
+    rtn = bytes_to_write;
+  }
+  else
+  {
+    EVEL_DEBUG("Reached EOF");
+  }
+
+  EVEL_EXIT();
+  return rtn;
+}
+
+/**************************************************************************//**
+ * Callback function to provide returned data.
+ *
+ * Copy data into the supplied buffer, write_callback::ptr, checking size
+ * limits.
+ *
+ * @returns   Number of bytes placed into write_callback::ptr. 0 for EOF.
+ *****************************************************************************/
+size_t evel_write_callback(void *contents,
+                             size_t size,
+                             size_t nmemb,
+                             void *userp)
+{
+  size_t realsize = size * nmemb;
+  MEMORY_CHUNK * rx_chunk = (MEMORY_CHUNK *)userp;
+
+  EVEL_ENTER();
+
+  EVEL_DEBUG("Called with %d chunks of %d size = %d", nmemb, size, realsize);
+  EVEL_DEBUG("rx chunk size is %d", rx_chunk->size);
+
+  rx_chunk->memory = realloc(rx_chunk->memory, rx_chunk->size + realsize + 1);
+  if(rx_chunk->memory == NULL) {
+    /* out of memory! */
+    printf("not enough memory (realloc returned NULL)\n");
+    return 0;
+  }
+
+  memcpy(&(rx_chunk->memory[rx_chunk->size]), contents, realsize);
+  rx_chunk->size += realsize;
+  rx_chunk->memory[rx_chunk->size] = 0;
+
+  EVEL_DEBUG("Rx data: %s", rx_chunk->memory);
+  EVEL_DEBUG("Returning: %d", realsize);
+
+  EVEL_EXIT();
+  return realsize;
+}
+
+/**************************************************************************//**
+ * Event Handler.
+ *
+ * Watch for messages coming on the internal queue and send them to the
+ * listener.
+ *
+ * param[in]  arg  Argument - unused.
+ *****************************************************************************/
+static void * event_handler(void * arg __attribute__ ((unused)))
+{
+  int old_type = 0;
+  EVENT_HEADER * msg = NULL;
+  EVENT_INTERNAL * internal_msg = NULL;
+  int json_size = 0;
+  char json_body[EVEL_MAX_JSON_BODY];
+  int rc = EVEL_SUCCESS;
+  CURLcode curl_rc;
+
+  EVEL_INFO("Event handler thread started");
+
+  /***************************************************************************/
+  /* Set this thread to be cancellable immediately.                          */
+  /***************************************************************************/
+  pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, &old_type);
+
+  /***************************************************************************/
+  /* Set the handler as active, defending against weird situations like      */
+  /* immediately shutting down after initializing the library so the         */
+  /* handler never gets started up properly.                                 */
+  /***************************************************************************/
+  if (evt_handler_state == EVT_HANDLER_INACTIVE)
+  {
+    evt_handler_state = EVT_HANDLER_ACTIVE;
+  }
+  else
+  {
+    EVEL_ERROR("Event Handler State was not INACTIVE at start-up - "
+               "Handler will exit immediately!");
+  }
+
+  while (evt_handler_state == EVT_HANDLER_ACTIVE)
+  {
+    /*************************************************************************/
+    /* Wait for a message to be received.                                    */
+    /*************************************************************************/
+    EVEL_DEBUG("Event handler getting any messages");
+    msg = ring_buffer_read(&event_buffer);
+
+    /*************************************************************************/
+    /* Internal events get special treatment while regular events get posted */
+    /* to the far side.                                                      */
+    /*************************************************************************/
+    if (msg->event_domain != EVEL_DOMAIN_INTERNAL)
+    {
+      EVEL_DEBUG("External event received");
+
+      /***********************************************************************/
+      /* Encode the event in JSON.                                           */
+      /***********************************************************************/
+      json_size = evel_json_encode_event(json_body, EVEL_MAX_JSON_BODY, msg);
+
+      /***********************************************************************/
+      /* Send the JSON across the API.                                       */
+      /***********************************************************************/
+      EVEL_DEBUG("Sending JSON of size %d is: %s", json_size, json_body);
+      rc = evel_post_api(json_body, json_size);
+      if (rc != EVEL_SUCCESS)
+      {
+        EVEL_ERROR("Failed to transfer the data. Error code=%d", rc);
+      }
+    }
+    else
+    {
+      EVEL_DEBUG("Internal event received");
+      internal_msg = (EVENT_INTERNAL *) msg;
+      assert(internal_msg->command == EVT_CMD_TERMINATE);
+      evt_handler_state = EVT_HANDLER_TERMINATING;
+    }
+
+    /*************************************************************************/
+    /* We are responsible for freeing the memory.                            */
+    /*************************************************************************/
+    evel_free_event(msg);
+    msg = NULL;
+
+    /*************************************************************************/
+    /* There may be a single priority post to be sent.                       */
+    /*************************************************************************/
+    if (priority_post.memory != NULL)
+    {
+      EVEL_DEBUG("Priority Post");
+
+      /***********************************************************************/
+      /* Set the URL for the throttling API.                                 */
+      /***********************************************************************/
+      curl_rc = curl_easy_setopt(curl_handle, CURLOPT_URL, evel_throt_api_url);
+      if (curl_rc != CURLE_OK)
+      {
+        /*********************************************************************/
+        /* This is only likely to happen with CURLE_OUT_OF_MEMORY, in which  */
+        /* case we carry on regardless.                                      */
+        /*********************************************************************/
+        EVEL_ERROR("Failed to set throttling URL. Error code=%d", rc);
+      }
+      else
+      {
+        rc = evel_post_api(priority_post.memory, priority_post.size);
+        if (rc != EVEL_SUCCESS)
+        {
+          EVEL_ERROR("Failed to transfer priority post. Error code=%d", rc);
+        }
+      }
+
+      /***********************************************************************/
+      /* Reinstate the URL for the event API.                                */
+      /***********************************************************************/
+      curl_rc = curl_easy_setopt(curl_handle, CURLOPT_URL, evel_event_api_url);
+      if (curl_rc != CURLE_OK)
+      {
+        /*********************************************************************/
+        /* This is only likely to happen with CURLE_OUT_OF_MEMORY, in which  */
+        /* case we carry on regardless.                                      */
+        /*********************************************************************/
+        EVEL_ERROR("Failed to reinstate events URL. Error code=%d", rc);
+      }
+
+      /***********************************************************************/
+      /* We are responsible for freeing the memory.                          */
+      /***********************************************************************/
+      free(priority_post.memory);
+      priority_post.memory = NULL;
+    }
+  }
+
+  /***************************************************************************/
+  /* The event handler is now exiting. The ring-buffer could contain events  */
+  /* which have not been processed, so deplete those.  Because we've been    */
+  /* asked to exit we can be confident that the foreground will have stopped */
+  /* sending events in so we know that this process will conclude!           */
+  /***************************************************************************/
+  evt_handler_state = EVT_HANDLER_TERMINATING;
+  while (!ring_buffer_is_empty(&event_buffer))
+  {
+    EVEL_DEBUG("Reading event from buffer");
+    msg = ring_buffer_read(&event_buffer);
+    evel_free_event(msg);
+  }
+  evt_handler_state = EVT_HANDLER_TERMINATED;
+  EVEL_INFO("Event handler thread stopped");
+
+  return (NULL);
+}
+
+/**************************************************************************//**
+ * Handle a JSON response from the listener, contained in a ::MEMORY_CHUNK.
+ *
+ * Tokenize the response, and decode any tokens found.
+ *
+ * @param chunk         The memory chunk containing the response.
+ * @param post          The memory chunk in which to place any resulting POST.
+ *****************************************************************************/
+void evel_handle_event_response(const MEMORY_CHUNK * const chunk,
+                                MEMORY_CHUNK * const post)
+{
+  jsmn_parser json_parser;
+  jsmntok_t json_tokens[EVEL_MAX_RESPONSE_TOKENS];
+  int num_tokens = 0;
+
+  EVEL_ENTER();
+
+  /***************************************************************************/
+  /* Check preconditions.                                                    */
+  /***************************************************************************/
+  assert(chunk != NULL);
+  assert(priority_post.memory == NULL);
+
+  EVEL_DEBUG("Response size = %d", chunk->size);
+  EVEL_DEBUG("Response = %s", chunk->memory);
+
+  /***************************************************************************/
+  /* Initialize the parser and tokenize the response.                        */
+  /***************************************************************************/
+  jsmn_init(&json_parser);
+  num_tokens = jsmn_parse(&json_parser,
+                          chunk->memory,
+                          chunk->size,
+                          json_tokens,
+                          EVEL_MAX_RESPONSE_TOKENS);
+
+  if (num_tokens < 0)
+  {
+    EVEL_ERROR("Failed to parse JSON response.  "
+               "Error code=%d", num_tokens);
+  }
+  else if (num_tokens == 0)
+  {
+    EVEL_DEBUG("No tokens found in JSON response");
+  }
+  else
+  {
+    EVEL_DEBUG("Decode JSON response tokens");
+    if (!evel_handle_response_tokens(chunk, json_tokens, num_tokens, post))
+    {
+      EVEL_ERROR("Failed to handle JSON response.");
+    }
+  }
+
+  EVEL_EXIT();
+}
+
+/**************************************************************************//**
+ * Handle a JSON response from the listener, as a list of tokens from JSMN.
+ *
+ * @param chunk         Memory chunk containing the JSON buffer.
+ * @param json_tokens   Array of tokens to handle.
+ * @param num_tokens    The number of tokens to handle.
+ * @param post          The memory chunk in which to place any resulting POST.
+ * @return true if we handled the response, false otherwise.
+ *****************************************************************************/
+bool evel_handle_response_tokens(const MEMORY_CHUNK * const chunk,
+                                 const jsmntok_t * const json_tokens,
+                                 const int num_tokens,
+                                 MEMORY_CHUNK * const post)
+{
+  bool json_ok = false;
+
+  EVEL_ENTER();
+
+  /***************************************************************************/
+  /* Check preconditions.                                                    */
+  /***************************************************************************/
+  assert(chunk != NULL);
+  assert(json_tokens != NULL);
+  assert(num_tokens < EVEL_MAX_RESPONSE_TOKENS);
+
+  /***************************************************************************/
+  /* Peek at the tokens to decide what the response it, then call the        */
+  /* appropriate handler to handle it.  There is only one handler at this    */
+  /* point.                                                                  */
+  /***************************************************************************/
+  if (evel_tokens_match_command_list(chunk, json_tokens, num_tokens))
+  {
+    json_ok = evel_handle_command_list(chunk, json_tokens, num_tokens, post);
+  }
+
+  EVEL_EXIT();
+
+  return json_ok;
+}
+
+/**************************************************************************//**
+ * Determine whether a list of tokens looks like a "commandList" response.
+ *
+ * @param chunk         Memory chunk containing the JSON buffer.
+ * @param json_tokens   Token to check.
+ * @param num_tokens    The number of tokens to handle.
+ * @return true if the tokens look like a "commandList" match, or false.
+ *****************************************************************************/
+bool evel_tokens_match_command_list(const MEMORY_CHUNK * const chunk,
+                                    const jsmntok_t * const json_tokens,
+                                    const int num_tokens)
+{
+  bool result = false;
+
+  EVEL_ENTER();
+
+  /***************************************************************************/
+  /* Make some checks on the basic layout of the commandList.                */
+  /***************************************************************************/
+  if ((num_tokens > 3) &&
+      (json_tokens[0].type == JSMN_OBJECT) &&
+      (json_tokens[1].type == JSMN_STRING) &&
+      (json_tokens[2].type == JSMN_ARRAY) &&
+      (evel_token_equals_string(chunk, &json_tokens[1], "commandList")))
+  {
+    result = true;
+  }
+
+  EVEL_EXIT();
+
+  return result;
+}
+
+/**************************************************************************//**
+ * Check that a string token matches a given input string.
+ *
+ * @param chunk         Memory chunk containing the JSON buffer.
+ * @param json_token    Token to check.
+ * @param check_string  String to check it against.
+ * @return true if the strings match, or false.
+ *****************************************************************************/
+bool evel_token_equals_string(const MEMORY_CHUNK * const chunk,
+                              const jsmntok_t * json_token,
+                              const char * check_string)
+{
+  bool result = false;
+
+  EVEL_ENTER();
+
+  const int token_length = json_token->end - json_token->start;
+  const char * const token_string = chunk->memory + json_token->start;
+
+  if (token_length == (int)strlen(check_string))
+  {
+    result = (strncmp(token_string, check_string, token_length) == 0);
+  }
+
+  EVEL_EXIT();
+
+  return result;
+}