[cron.d] Add cron job to periodically clean-up core files (#3449)

* [cron.d] Create cron job to periodically clean-up core files
* Create script to scan /var/core and clean-up older core files
* Create cron job to run clean-up script

Signed-off-by: Danny Allen <daall@microsoft.com>

* Update interval for running cron job

* Respond to feedback

* Change syslog id

build_debian.sh

@@ -440,6 +440,9 @@ build_number: ${BUILD_NUMBER:-0}
 built_by: $USER@$BUILD_HOSTNAME
 EOF
 
+## Copy over clean-up script
+sudo cp ./files/scripts/core_cleanup.py $FILESYSTEM_ROOT/usr/bin/core_cleanup.py
+
 ## Copy ASIC config checksum
 python files/build_scripts/generate_asic_config_checksum.py
 if [[ ! -f './asic_config_checksum' ]]; then

files/image_config/cron.d/core_cleanup

@@ -0,0 +1,3 @@
+# Attempts to clean up core files every 2 hours
+* */2 * * * root /usr/bin/core_cleanup.py > /dev/null 2>&1
+

files/scripts/core_cleanup.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python
+
+import syslog
+import os
+
+from collections import defaultdict
+from datetime import datetime
+
+SYSLOG_IDENTIFIER = 'core_cleanup.py'
+CORE_FILE_DIR = os.path.basename(__file__)
+MAX_CORE_FILES = 4
+
+def log_info(msg):
+    syslog.openlog(SYSLOG_IDENTIFIER)
+    syslog.syslog(syslog.LOG_INFO, msg)
+    syslog.closelog()
+
+def log_error(msg):
+    syslog.openlog(SYSLOG_IDENTIFIER)
+    syslog.syslog(syslog.LOG_ERR, msg)
+    syslog.closelog()
+
+def main():
+    if os.getuid() != 0:
+        log_error('Root required to clean up core files')
+        return
+
+    log_info('Cleaning up core files')
+    core_files = [f for f in os.listdir(CORE_FILE_DIR) if os.path.isfile(os.path.join(CORE_FILE_DIR, f))]
+
+    core_files_by_process = defaultdict(list)
+    for f in core_files:
+        process = f.split('.')[0]
+        curr_files = core_files_by_process[process]
+        curr_files.append(f)
+
+        if len(curr_files) > MAX_CORE_FILES:
+            curr_files.sort(reverse = True, key = lambda x: datetime.utcfromtimestamp(int(x.split('.')[1])))
+            oldest_core = curr_files[MAX_CORE_FILES]
+            log_info('Deleting {}'.format(oldest_core))
+            try:
+                os.remove(os.path.join(CORE_FILE_DIR, oldest_core))
+            except:
+                log_error('Unexpected error occured trying to delete {}'.format(oldest_core))
+            core_files_by_process[process] = curr_files[0:MAX_CORE_FILES]
+
+    log_info('Finished cleaning up core files')
+
+if __name__ == '__main__':
+    main()
+