SSH connection is not being reused when sending multiple commands #2966
Description
cmds.sh connects through SSH and executes several commands:
#!/usr/bin/env python3
import docker
if __name__ == "__main__":
client = docker.DockerClient("ssh://localhost", use_ssh_client=True)
client.ping()
client.images.list()
client.containers.list()
Running this script spawns a new ssh connection for each command which takes a lot of time because the whole login sequence is repeated:
$ strace -fs256 ./cmds.py 2>&1 | grep exec.*ssh
[pid 35337] execve("/bin/sh", ["/bin/sh", "-c", "ssh -p 22 -- localhost docker system dial-stdio"], 0x14d3a90 /* 72 vars */ <unfinished ...>
[pid 35338] execve("/usr/bin/ssh", ["ssh", "-p", "22", "--", "localhost", "docker", "system", "dial-stdio"], 0x561272c46448 /* 72 vars */ <unfinished ...>
[pid 35405] execve("/bin/sh", ["/bin/sh", "-c", "ssh -p 22 -- localhost docker system dial-stdio"], 0x14d8090 /* 72 vars */ <unfinished ...>
[pid 35406] execve("/usr/bin/ssh", ["ssh", "-p", "22", "--", "localhost", "docker", "system", "dial-stdio"], 0x55c16b5e1448 /* 72 vars */ <unfinished ...>
[pid 35465] execve("/bin/sh", ["/bin/sh", "-c", "ssh -p 22 -- localhost docker system dial-stdio"], 0x14d8090 /* 72 vars */ <unfinished ...>
[pid 35466] execve("/usr/bin/ssh", ["ssh", "-p", "22", "--", "localhost", "docker", "system", "dial-stdio"], 0x55c40c8e4448 /* 72 vars */ <unfinished ...>
[pid 35524] execve("/bin/sh", ["/bin/sh", "-c", "ssh -p 22 -- localhost docker system dial-stdio"], 0x14d8090 /* 72 vars */ <unfinished ...>
[pid 35525] execve("/usr/bin/ssh", ["ssh", "-p", "22", "--", "localhost", "docker", "system", "dial-stdio"], 0x55ae78291448 /* 72 vars */ <unfinished ...>
[pid 35583] execve("/bin/sh", ["/bin/sh", "-c", "ssh -p 22 -- localhost docker system dial-stdio"], 0x14dcfd0 /* 72 vars */ <unfinished ...>
[pid 35584] execve("/usr/bin/ssh", ["ssh", "-p", "22", "--", "localhost", "docker", "system", "dial-stdio"], 0x55b6878d6448 /* 72 vars */ <unfinished ...>
[pid 35642] execve("/bin/sh", ["/bin/sh", "-c", "ssh -p 22 -- localhost docker system dial-stdio"], 0x14dabc0 /* 72 vars */ <unfinished ...>
[pid 35643] execve("/usr/bin/ssh", ["ssh", "-p", "22", "--", "localhost", "docker", "system", "dial-stdio"], 0x562746674448 /* 72 vars */ <unfinished ...>
[pid 35702] execve("/bin/sh", ["/bin/sh", "-c", "ssh -p 22 -- localhost docker system dial-stdio"], 0x14d8090 /* 72 vars */ <unfinished ...>
[pid 35703] execve("/usr/bin/ssh", ["ssh", "-p", "22", "--", "localhost", "docker", "system", "dial-stdio"], 0x555dd2d9a448 /* 72 vars */ <unfinished ...>
I expected it to reuse the same pipe for all commands.
Even using the paramiko client (use_ssh_client=False) seems to be similar because SSHConnectionPool are created for every URL. Those URLs are different for every request.
So I don't really understand how this was supposed to work efficiently. Is there something fundamental that precludes the reuse of the SSH connection?
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