file_poller: added error checking and reporting

- Updated poller binary to propery check for errors (e.g. on attempting
  to open a file) and report them to stderr
- Updated the file_poller instrument to collect poller stderr output
  into a log file and to check the log for errors or warnings on
  completion of an iteration.

wlauto/instrumentation/poller/__init__.py

@@ -12,9 +12,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # pylint: disable=access-member-before-definition,attribute-defined-outside-init,unused-argument
+import os
 
 from wlauto import Instrument, Parameter, Executable
-from wlauto.exceptions import ConfigError
+from wlauto.exceptions import ConfigError, InstrumentError
 from wlauto.utils.types import list_or_string
 
 
@@ -27,8 +28,8 @@ class FilePoller(Instrument):
     This file will contain a timestamp column which will be in uS, the rest of the columns
     will be the contents of the polled files at that time.
 
-    This instrument can poll any file whos contents do not contain a new line since this
-    breaks the CSV formatting.
+    This instrument will strip any commas or new lines for the files' values
+    before writing them.
     """
 
     parameters = [
@@ -56,7 +57,7 @@ class FilePoller(Instrument):
             raise ConfigError('The device is not rooted, cannot run poller as root.')
         host_poller = context.resolver.get(Executable(self, self.device.abi,
                                                       "poller"))
-        target_poller = self.device.install_if_needed(host_poller)
+        target_poller = self.device.install(host_poller)
 
         expanded_paths = []
         for path in self.files:
@@ -70,11 +71,13 @@ class FilePoller(Instrument):
             self.labels = self._generate_labels()
 
         self.target_output_path = self.device.path.join(self.device.working_directory, 'poller.csv')
-        self.command = '{} -t {} -l {} {} > {}'.format(target_poller,
-                                                       self.sample_interval * 1000,
-                                                       ','.join(self.labels),
-                                                       ' '.join(self.files),
-                                                       self.target_output_path)
+        self.target_log_path = self.device.path.join(self.device.working_directory, 'poller.log')
+        self.command = '{} -t {} -l {} {} > {} 2>{}'.format(target_poller,
+                                                            self.sample_interval * 1000,
+                                                            ','.join(self.labels),
+                                                            ' '.join(self.files),
+                                                            self.target_output_path,
+                                                            self.target_log_path)
 
     def start(self, context):
         self.device.kick_off(self.command, as_root=self.as_root)
@@ -83,10 +86,23 @@ class FilePoller(Instrument):
         self.device.killall('poller', signal='TERM', as_root=self.as_root)
 
     def update_result(self, context):
-        self.device.pull_file(self.target_output_path, context.output_directory)
+        host_output_file = os.path.join(context.output_directory, 'poller.csv')
+        self.device.pull_file(self.target_output_path, host_output_file)
+        context.add_artifact('poller_output', host_output_file, kind='data')
+        host_log_file = os.path.join(context.output_directory, 'poller.log')
+        self.device.pull_file(self.target_log_path, host_log_file)
+        context.add_artifact('poller_log', host_log_file, kind='log')
+
+        with open(host_log_file) as fh:
+            for line in fh:
+                if 'ERROR' in line:
+                    raise InstrumentError(line.strip())
+                if 'WARNING' in line:
+                    self.logger.warning(line.strip())
 
     def teardown(self, context):
         self.device.delete_file(self.target_output_path)
+        self.device.delete_file(self.target_log_path)
 
     def _generate_labels(self):
         # Split paths into their parts

wlauto/instrumentation/poller/poller.c

@@ -14,7 +14,6 @@ void term(int signum)
     done = 1;
 }
 
-// From: http://stackoverflow.com/questions/1515195/how-to-remove-n-or-t-from-a-given-string-in-c
 void strip(char *s) {
     char *stripped_s = s;
     while(*s != '\0') {
@@ -27,6 +26,11 @@ void strip(char *s) {
     *stripped_s = '\0';
 }
 
+typedef struct {
+        int fd;
+        char *path;
+} poll_source_t;
+
 int main(int argc, char ** argv) {
 
     extern char *optarg;
@@ -38,9 +42,9 @@ int main(int argc, char ** argv) {
     memset(buf, 0, sizeof(buf));
     struct timeval current_time;
     double time_float;
-    int files_to_poll[argc-optind];
     char *labels;
     int labelCount = 0;
+
     static char usage[] = "usage: %s [-h] [-t INTERVAL] FILE [FILE ...]\n"
                           "polls FILE(s) every INTERVAL microseconds and outputs\n"
                           "the results in CSV format including a timestamp to STDOUT\n"
@@ -79,16 +83,18 @@ int main(int argc, char ** argv) {
     }
 
     if (optind >= argc) {
-        fprintf(stderr, "%s: missiing file path(s)\n", argv[0]);
+        fprintf(stderr, "ERROR: %s: missing file path(s)\n", argv[0]);
         fprintf(stderr, usage, argv[0]);
         exit(1);
     }
 
-    if (labelCount && labelCount != argc-optind)
+    int num_files = argc - optind;
+    poll_source_t files_to_poll[num_files];
+
+    if (labelCount && labelCount != num_files)
     {
-        fprintf(stderr, "%s: %d labels specified but %d files specified\n", argv[0],
-                                                                            labelCount,
-                                                                            argc-optind);
+        fprintf(stderr, "ERROR: %s: %d labels specified but %d files specified\n",
+                argv[0], labelCount, num_files);
         fprintf(stderr, usage, argv[0]);
         exit(1);
     }
@@ -100,9 +106,16 @@ int main(int argc, char ** argv) {
         printf(",%s", labels);
     }
     int i;
-    for (i = 0; i < (argc - optind); i++)
+    for (i = 0; i < num_files; i++)
     {
-        files_to_poll[i] = open(argv[optind + i], O_RDONLY);
+        files_to_poll[i].path = argv[optind + i];
+        files_to_poll[i].fd = open(files_to_poll[i].path, O_RDONLY);
+        if (files_to_poll[i].fd == -1) {
+            fprintf(stderr, "ERROR: Could not open \"%s\", got: %s\n",
+                    files_to_poll[i].path, strerror(errno));
+            exit(2);
+        }
+
         if(!labelCount) {
             printf(",%s", argv[optind + i]);
         }
@@ -115,15 +128,24 @@ int main(int argc, char ** argv) {
     action.sa_handler = term;
     sigaction(SIGTERM, &action, NULL);
 
-    //Poll files
+    //Poll files 
+    int bytes_read = 0;
     while (!done) {
         gettimeofday(&current_time, NULL);
         time_float = (double)current_time.tv_sec;
         time_float += ((double)current_time.tv_usec)/1000/1000;
         printf("%f", time_float);
-        for (i = 0; i < (argc - optind); i++) {
-            read(files_to_poll[i], buf, 1024);
-            lseek(files_to_poll[i], 0, SEEK_SET);
+        for (i = 0; i < num_files; i++) {
+            lseek(files_to_poll[i].fd, 0, SEEK_SET);
+            bytes_read = read(files_to_poll[i].fd, buf, 1024);
+
+            if (bytes_read < 0) {
+                fprintf(stderr, "WARNING: Read nothing from \"%s\"\n",
+                        files_to_poll[i].path);
+                printf(",");
+                continue;
+            }
+
             strip(buf);
             printf(",%s", buf);
             buf[0] = '\0'; // "Empty" buffer
@@ -133,9 +155,9 @@ int main(int argc, char ** argv) {
     }
 
     //Close files
-    for (i = 0; i < (argc - optind); i++)
+    for (i = 0; i < num_files; i++)
     {
-        files_to_poll[i] = open(argv[optind + i], O_RDONLY);
+        close(files_to_poll[i].fd);
     }
     exit(0);
 }