Lianja

SSH Parallel Remote Commands on Multiple Servers

Demonstrates running the same command on several servers simultaneously. It is simply a matter of using one Ssh object per server, starting the command on each with QuickCmdSend, and then polling each connection with QuickCmdCheck until all have finished.

Background: This is the fan-out pattern behind configuration-management and monitoring tools: query or update a whole fleet in roughly the time the slowest single host takes, rather than the sum of all of them. Each server needs its own object because each has its own connection and authentication state. Note that results come back in whatever order the servers finish, which is why the example tracks completion per connection. Production code would keep the objects in arrays instead of repeating the logic per server.

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llSuccess = .F.

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  Demonstrates running the same command on several servers simultaneously.  It is simply a
//  matter of using one Ssh object per server.

loSsh1 = createobject("CkSsh")
loSsh2 = createobject("CkSsh")
loSsh3 = createobject("CkSsh")

lnPort = 22

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
lcPassword = "mySshPassword"

llSuccess = loSsh1.Connect("ssh-server1.example.com",lnPort)
if (llSuccess = .F.) then
    ? loSsh1.LastErrorText
    release loSsh1
    release loSsh2
    release loSsh3
    return
endif

llSuccess = loSsh1.AuthenticatePw("mySshLogin",lcPassword)
if (llSuccess = .F.) then
    ? loSsh1.LastErrorText
    release loSsh1
    release loSsh2
    release loSsh3
    return
endif

llSuccess = loSsh2.Connect("ssh-server2.example.com",lnPort)
if (llSuccess = .F.) then
    ? loSsh2.LastErrorText
    release loSsh1
    release loSsh2
    release loSsh3
    return
endif

llSuccess = loSsh2.AuthenticatePw("mySshLogin",lcPassword)
if (llSuccess = .F.) then
    ? loSsh2.LastErrorText
    release loSsh1
    release loSsh2
    release loSsh3
    return
endif

llSuccess = loSsh3.Connect("ssh-server3.example.com",lnPort)
if (llSuccess = .F.) then
    ? loSsh3.LastErrorText
    release loSsh1
    release loSsh2
    release loSsh3
    return
endif

llSuccess = loSsh3.AuthenticatePw("mySshLogin",lcPassword)
if (llSuccess = .F.) then
    ? loSsh3.LastErrorText
    release loSsh1
    release loSsh2
    release loSsh3
    return
endif

//  This command sleeps for 5 seconds and then prints the system date/time, making the parallel
//  execution easy to observe.
lcCmd = "sleep 5; date"

//  Start the command on each server.  QuickCmdSend returns immediately.
lnChannel1 = loSsh1.QuickCmdSend(lcCmd)
if (lnChannel1 < 0) then
    ? loSsh1.LastErrorText
    release loSsh1
    release loSsh2
    release loSsh3
    return
endif

lnChannel2 = loSsh2.QuickCmdSend(lcCmd)
if (lnChannel2 < 0) then
    ? loSsh2.LastErrorText
    release loSsh1
    release loSsh2
    release loSsh3
    return
endif

lnChannel3 = loSsh3.QuickCmdSend(lcCmd)
if (lnChannel3 < 0) then
    ? loSsh3.LastErrorText
    release loSsh1
    release loSsh2
    release loSsh3
    return
endif

//  The command is now running on all three servers at once.  Poll each connection until every
//  command has finished.  (Production code would keep the objects in arrays rather than
//  repeating the logic.)
lnPollTimeoutMs = 50
lnNumFinished = 0
llFinished1 = .F.
llFinished2 = .F.
llFinished3 = .F.

do while lnNumFinished < 3
    if (not llFinished1) then
        lnCh1 = loSsh1.QuickCmdCheck(lnPollTimeoutMs)
        if (lnCh1 = -2) then
            ? loSsh1.LastErrorText
            release loSsh1
            release loSsh2
            release loSsh3
            return
        endif

        if (lnCh1 >= 0) then
            ? "---- ssh1 channel " + str(lnCh1) + " finished ----"
            lcOut1 = loSsh1.GetReceivedText(lnCh1,"utf-8")
            if (loSsh1.LastMethodSuccess = .F.) then
                ? loSsh1.LastErrorText
                release loSsh1
                release loSsh2
                release loSsh3
                return
            endif

            ? lcOut1
            llFinished1 = .T.
            lnNumFinished = lnNumFinished + 1
        endif

    endif

    if (not llFinished2) then
        lnCh2 = loSsh2.QuickCmdCheck(lnPollTimeoutMs)
        if (lnCh2 = -2) then
            ? loSsh2.LastErrorText
            release loSsh1
            release loSsh2
            release loSsh3
            return
        endif

        if (lnCh2 >= 0) then
            ? "---- ssh2 channel " + str(lnCh2) + " finished ----"
            lcOut2 = loSsh2.GetReceivedText(lnCh2,"utf-8")
            if (loSsh2.LastMethodSuccess = .F.) then
                ? loSsh2.LastErrorText
                release loSsh1
                release loSsh2
                release loSsh3
                return
            endif

            ? lcOut2
            llFinished2 = .T.
            lnNumFinished = lnNumFinished + 1
        endif

    endif

    if (not llFinished3) then
        lnCh3 = loSsh3.QuickCmdCheck(lnPollTimeoutMs)
        if (lnCh3 = -2) then
            ? loSsh3.LastErrorText
            release loSsh1
            release loSsh2
            release loSsh3
            return
        endif

        if (lnCh3 >= 0) then
            ? "---- ssh3 channel " + str(lnCh3) + " finished ----"
            lcOut3 = loSsh3.GetReceivedText(lnCh3,"utf-8")
            if (loSsh3.LastMethodSuccess = .F.) then
                ? loSsh3.LastErrorText
                release loSsh1
                release loSsh2
                release loSsh3
                return
            endif

            ? lcOut3
            llFinished3 = .T.
            lnNumFinished = lnNumFinished + 1
        endif

    endif

enddo

loSsh1.Disconnect()
loSsh2.Disconnect()
loSsh3.Disconnect()


release loSsh1
release loSsh2
release loSsh3