Thank you Brandon. It worked perfectly. :)
From: Brandon Whaley [mailto:redkr...@gmail.com] Sent: Thursday, September 10, 2015 7:10 PM To: Felix Almeida; fab-user@nongnu.org Subject: Re: [Fab-user] Can't save output to a CSV file if running task in parallel I'm fairly sure this is what you want: import csv from fabric.api import env, task, runs_once, parallel, execute, run, puts, hide env.abort_on_prompts = True env.always_use_pty = False env.command_timeout = 3 env.disable_known_hosts = True env.eagerly_disconnect = True env.timeout = 3 env.use_shell = False env.warn_only = True @parallel(pool_size=5) def _run(): try: with hide('output', 'running'): out = run('uname') except SystemExit: msg = 'error: a password is being requested' else: msg = str(out) puts(msg) return msg @task @runs_once def run_uname(hosts_file=None): if hosts_file: with open(hosts_file) as input_: host_list = [line.strip() for line in input_] env.hosts.extend(host_list) with open('output.csv', 'wb') as output: writer = csv.writer(output) writer.writerow(['HOSTNAME', 'UNAME']) with hide('running', 'status'): outputs = execute(run) for host, output in outputs.iteritems(): writer.writerow([host, output]) The changes are that msg is returned (instead of out) and that no writing is attempted in parallel, an operation is done on the return dictionary of execute() as explained in my first email. On Thu, Sep 10, 2015 at 7:03 PM Felix Almeida <felix.alme...@rci.rogers.com<mailto:felix.alme...@rci.rogers.com>> wrote: Thanks Brandon! But that's what I thought I was doing when I decorated my master task with "runs _once" and used the "parallel" decorator only on my subtask (which I call with "execute")... since I open the CSV file in the master task I assumed (incorrectly, I guess) it would work. Please, what do you think it would be a good approach here? Create a queue in the master task and make the subtask send messages to it? -------- Original message -------- From: Brandon Whaley <redkr...@gmail.com<mailto:redkr...@gmail.com>> Date: 2015-09-10 5:10 PM (GMT-05:00) To: Felix Almeida <felix.alme...@rci.rogers.com<mailto:felix.alme...@rci.rogers.com>>, fab-user@nongnu.org<mailto:fab-user@nongnu.org> Subject: Re: [Fab-user] Can't save output to a CSV file if running task in parallel Parallel uses multiprocessing, so you're opening output.csv in write mode once per host. You'll need to have a master task consolidate the return values of your parallel subtask (use execute) and write the csv once everything is done. Remember that execute returns a dictionary whose keys are the host_strings of each host and the values are the return value of the function you're executing. On Thu, Sep 10, 2015 at 4:46 PM Felix Almeida <felix.alme...@rci.rogers.com<mailto:felix.alme...@rci.rogers.com>> wrote: Hi all, I'm trying to run a simple task in parallel that captures the OS type (Linux, AIX, HP-UX, etc.) of a set of UNIX servers and save this information into a CSV file. However, if I add the @parallel decorator to the task the CSV file is left empty (only the header is saved), but if I remove the @parallel decorator then everything goes well. Note that the output to the screen via puts works fine in both cases. Please, any ideas of what I'm doing wrong? Perhaps this is not even a fabric question but a Python one (I'm not sure, sorry). Here is the complete code: import csv from fabric.api import env, task, runs_once, parallel, execute, run, puts, hide env.abort_on_prompts = True env.always_use_pty = False env.command_timeout = 3 env.disable_known_hosts = True env.eagerly_disconnect = True env.timeout = 3 env.use_shell = False env.warn_only = True @parallel(pool_size=5) def _run(csv_output): try: with hide('output', 'running'): out = run('uname') except SystemExit: msg = 'error: a password is being requested' else: msg = str(out) puts(msg) csv_output.writerow([env.host, msg]) return str(out) @task @runs_once def run_uname(hosts_file=None): if hosts_file: with open(hosts_file) as input_: host_list = [line.strip() for line in input_] env.hosts.extend(host_list) with open('output.csv', 'wb') as output: writer = csv.writer(output) writer.writerow(['HOSTNAME', 'UNAME']) with hide('running', 'status'): execute(_run, writer) I run it like this: fab run_uname:test_hosts.txt My environment is this: RHEL4, Python 2.7.10, Fabric 1.10.2, Paramiko 1.15.2 Thank you! 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