From: Josep Puigdemont Date: Fri, 6 May 2016 03:28:26 +0200 Subject: [PATCH] common.py: allow specifying number of attempts in exec_cmd Some commands executed by exec_cmd may fail because of a temporary cause, and it may be desirable to retry the same command several times until it succeeds. One example of this are the ipmitool commands, which may fail temorarily on some targets if they get too many requests simultaneously. In this patch two new optional parameters are introduced to the function signature, which do not break backward compatibility: attempts: which indicates how many times the command should be run if it returns a non-zero value*, and defaults to 1 (as today). delay: which indicates the delay in seconds between attempts, and defaults to 5 seconds. verbose: It will print the remaining attempts left for the current command if set to True. * It may be desirable to add yet another parameter to indicate what return value should be considered an error, but zero for now seems a reasonable default Signed-off-by: Josep Puigdemont --- deploy/common.py | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/deploy/common.py b/deploy/common.py index 41b4e27..3cd3e0e 100644 --- a/deploy/common.py +++ b/deploy/common.py @@ -16,6 +16,7 @@ import argparse import shutil import stat import errno +import time N = {'id': 0, 'status': 1, 'name': 2, 'cluster': 3, 'ip': 4, 'mac': 5, 'roles': 6, 'pending_roles': 7, 'online': 8, 'group_id': 9} @@ -37,13 +38,22 @@ out_handler.setFormatter(formatter) LOG.addHandler(out_handler) os.chmod(LOGFILE, stat.S_IRWXU | stat.S_IRWXG | stat.S_IRWXO) -def exec_cmd(cmd, check=True): - process = subprocess.Popen(cmd, - stdout=subprocess.PIPE, - stderr=subprocess.PIPE, - shell=True) - (response, stderr) = process.communicate() - return_code = process.returncode +def exec_cmd(cmd, check=True, attempts=1, delay=5, verbose=False): + # a negative value means forever + while attempts != 0: + attempts = attempts - 1 + process = subprocess.Popen(cmd, + stdout=subprocess.PIPE, + stderr=subprocess.PIPE, + shell=True) + (response, stderr) = process.communicate() + return_code = process.returncode + if return_code == 0 or attempts == 0: + break + time.sleep(delay) + if verbose: + log('%d attempts left: %s' % (attempts, cmd)) + response = response.strip() if check: if return_code > 0: