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NETWORK_ALIASES.md

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Network aliases required for CCM

CCM needs a local ip address for each Cassandra node it creates. By default CCM assumes each node's ip address is 127.0.0.x, where x is the node id.

For example if you populated your cluster with 3 nodes, create interfaces for 127.0.0.2 and 127.0.0.3 (the first node of course uses 127.0.0.1).

Relevant CCM logs:

  • Missing an alias:
    (...) Inet address 127.0.0.2:9042 is not available; a cluster may already be running or you may need to add the loopback alias
  • Another node is already using a specific alias:
    (...) Inet address 127.0.0.2:9042 is not available: [Errno 48] Address already in use

Mac OSX temporary network aliases

To get up and running right now, create a temporary alias for every node except the first:

sudo ifconfig lo0 alias 127.0.0.2
sudo ifconfig lo0 alias 127.0.0.3

Note that these aliases are only temporary and will disappear on reboot.

Mac OSX persistent network aliases

Persist network aliases if you use CCM often or so infrequently you forget this step.

To persist a network alias on Mac OSX you need to create a RunAtLoad launch daemon which OSX automatically loads on startup. For example:

Create a shell script:

sudo vim /Library/LaunchDaemons/com.ccm.lo0.alias.sh

Contents of the script:

#!/bin/sh
sudo /sbin/ifconfig lo0 alias 127.0.0.2;
sudo /sbin/ifconfig lo0 alias 127.0.0.3;

Set access of the script:

sudo chmod 755 /Library/LaunchDaemons/com.ccm.lo0.alias.sh

Create a plist to launch the script:

sudo vim /Library/LaunchDaemons/com.ccm.lo0.alias.plist

Contents of the plist:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>com.ccm.lo0.alias</string>
    <key>RunAtLoad</key>
    <true/>
    <key>ProgramArguments</key>
    <array>
      <string>/Library/LaunchDaemons/com.ccm.lo0.alias.sh</string>
    </array>
    <key>StandardErrorPath</key>
    <string>/var/log/loopback-alias.log</string>
    <key>StandardOutPath</key>
    <string>/var/log/loopback-alias.log</string>
</dict>
</plist>

Set access of the plist:

sudo chmod 0644 /Library/LaunchDaemons/com.ccm.lo0.alias.plist
sudo chown root:staff /Library/LaunchDaemons/com.ccm.lo0.alias.plist

Launch the daemon now. OSX will automatically reload it on startup.

sudo launchctl load /Library/LaunchDaemons/com.ccm.lo0.alias.plist

Verify you can ping 127.0.0.2 and 127.0.0.3.

If you ever want to permanently kill the daemon, simply delete its plist from /Library/LaunchDaemons/.