This is readme for ossh (One SSH to rule them all) tool.
This tool can be used to run commands via ssh on multiple hosts. It was inspired by the knife utility from chef configuration management system. Ossh tool was created by me at Hulu. It was used to run commands on thousands of machines in parallel.
$ ossh -?
Usage: ossh [-?AinPv] [-c COMMAND] [-C COMMAND_FILE] [-H HOST_STRING] [-h HOST_FILE] [-I FILTER] [-k PRIVATE_KEY] [-l USER] [-o PORT] [-p PARALLELISM] [-T TIMEOUT] [-t TIMEOUT] [parameters ...]
-?, --help Show help
-A, --askpass Prompt for a password for ssh connects
-c, --command=COMMAND
Command to run
-C, --command-file=COMMAND_FILE
file with commands to run
-H, --host=HOST_STRING
Add the given HOST_STRING to the list of hosts
-h, --hosts=HOST_FILE
Read hosts from file
-i, --ignore-failures
Ignore connection failures in the preconnect mode
-I, --inventory=FILTER
Use FILTER expression to select hosts from inventory
-k, --key=PRIVATE_KEY
Use this private key
-l, --user=USER Username for connections [$LOGNAME]
-n, --showip In the output show ips instead of names
-o, --port=PORT Port to connect to [22]
-p, --par=PARALLELISM
How many hosts to run simultaneously [512]
-P, --preconnect Connect to all hosts before running command
-T, --connect-timeout=TIMEOUT
Connect timeout in seconds [60]
-t, --timeout=TIMEOUT
Run timeout in seconds
-v, --verbose Verbose output
$
HOST_STRING can specify non standard port e.g. host.com:2222.
HOST_FILE can use #-style comments.
Brace expansion can be used. E.g. "host{1,3..5}.com" would expand to "host1.com host3.com host4.com host5.com"
$ ossh -H "db01 db02 web05 web06" -l root -c 'uptime'
db01 15:59:30 up 305 days, 21:04, 1 user, load average: 0.00, 0.00, 0.00
db02 15:59:30 up 263 days, 4:05, 1 user, load average: 0.00, 0.00, 0.00
web05 15:59:30 up 107 days, 16:02, 1 user, load average: 0.08, 0.03, 0.05
web06 15:59:30 up 371 days, 23:25, 1 user, load average: 0.00, 0.00, 0.00
$ ossh -H "web05 web06" -c "tail -f -c 0 /var/log/nginx/access.log|grep --line-buffered Wget"
web05 192.168.1.23 - - [22/Jun/2016:12:24:02 -0700] "GET / HTTP/1.1" 200 1532 "-" "Wget/1.15 (linux-gnu)"
web05 192.168.1.49 - - [22/Jun/2016:12:24:07 -0700] "GET / HTTP/1.1" 200 1532 "-" "Wget/1.15 (linux-gnu)"
web06 192.168.1.117 - - [22/Jun/2016:12:24:23 -0700] "GET / HTTP/1.1" 200 1532 "-" "Wget/1.15 (linux-gnu)"
web05 192.168.1.29 - - [22/Jun/2016:12:24:30 -0700] "GET / HTTP/1.1" 200 1532 "-" "Wget/1.15 (linux-gnu)"
$ ossh -p 1 -H "test0{1..3}" -c "sleep 10 && date"
test01 Wed Jun 22 12:38:24 PDT 2016
test02 Wed Jun 22 12:38:34 PDT 2016
test03 Wed Jun 22 12:38:44 PDT 2016
$ wc -l /tmp/ossh.ips
21418 /tmp/ossh.ips
$ time ossh -n -h /tmp/ossh.ips -c uptime -p 1000 >/tmp/ossh.out
real 3m10.310s
user 0m30.970s
sys 0m19.282s
$
$ grep 'load average' /tmp/ossh.out | sort -n -k5 | tail -n1
10.23.91.97 [1] 13:37:55 up 828 days, 2:34, 0 users, load average: 8.29, 4.45, 3.90
$
If you have inventory system of your own you can easily use it with ossh. To do this you need to have in
the PATH program named ossh-inventory that being given host specification (argument of -I option)
will return list of strings in the form
host-label host-address
where host-label can be any string (without whitespaces), host-address can be ip address or dns name.
$ cd <this repository> && go build -o ossh && strip ossh
Usually unix process can open not more than 1024 files. For ossh this means that in the preconnect mode you can't work with more than 1020 hosts. To temporary increase number of file handles you can use the following trick:
ubuntu@ip-172-16-0-5:~⟫ whoami && ulimit -n
ubuntu
1024
ubuntu@ip-172-16-0-5:~⟫ sudo sh -c "ulimit -n 65535 && sudo -i -u $LOGNAME"
ubuntu@ip-172-16-0-5:~$ whoami && ulimit -n
ubuntu
65535
ubuntu@ip-172-16-0-5:~$