script to slowly repair the primary vnode ranges for a node. If it fails you can restart from last sucessfull range. It waits between ranges to avoid buildup of compactions.

repair.py

#!/usr/bin/env python

import os, sys, re, subprocess, time

def usage():
    print "Usage:"
    print "  repair hostname keyspace [offset]\n"
    exit(1)

'''Grab the hostid guid from nodetool info'''
def get_hostid(host):
    p = subprocess.Popen([ "nodetool", "--host", host, "info"], stdin=subprocess.PIPE, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
    for line in p.stdout:
        id = re.search("id\s+:\s+([a-f0-9\-]+)",line, re.I)
        if id:
            return id.group(1);
    raise RuntimeError("Missing hostid");

'''Grab the ip matching the hostid in nodetool status'''
def get_ip(hostid):
    p = subprocess.Popen([ "nodetool", "--host", host, "status"], stdin=subprocess.PIPE, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
    for line in p.stdout:
        if hostid in line:
            return re.search("(\d+\.\d+.\d+.\d+)",line).group(1);
    raise RuntimeError("Missing ip for hostid");

'''Find the primary token ranges for specified ip'''
#!/usr/bin/python -u

from datetime import datetime
import os, sys, re, subprocess, time

def usage():
    print "Usage:"
    print "  repair hostname keyspace [offset]\n"
    exit(1)

'''Grab the hostid guid from nodetool info'''
def get_hostid(host):
    p = subprocess.Popen([ "nodetool", "--host", host, "info"], stdin=subprocess.PIPE, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
    for line in p.stdout:
        id = re.search("id\s+:\s+([a-f0-9\-]+)",line, re.I)
        if id:
            return id.group(1);
    raise RuntimeError("Missing hostid");

'''Grab the ip matching the hostid in nodetool status'''
def get_ip(hostid):
    p = subprocess.Popen([ "nodetool", "--host", host, "status"], stdin=subprocess.PIPE, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
    for line in p.stdout:
        if hostid in line:
            return re.search("(\d+\.\d+.\d+.\d+)",line).group(1);
    raise RuntimeError("Missing ip for hostid");

'''Find the primary token ranges for specified ip'''
def get_tokens(ip, keyspace):
    p = subprocess.Popen([ "nodetool", "--host", host, "describering", keyspace], stdin=subprocess.PIPE, stderr=subprocess.PIPE, stdout=subprocess.PIPE);
    tokens = [];
    for line in p.stdout:
        if "endpoints:["+ip in line:
            ranges = re.search("start_token:([\-\d]+),\s+end_token:([\-\d]+)",line);
            if ranges:
                tokens.append([ranges.group(1), ranges.group(2)]);
    if len(tokens) == 0:
        raise RuntimeError("No primary tokens for ip"+p.stdout.read());
    return tokens;

'''Gets the pending compactions for a node'''
def get_pending_compactions(host):
    p = subprocess.Popen([ "nodetool", "--host", host, "compactionstats", keyspace], stdin=subprocess.PIPE, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
    for line in p.stdout:
        if "pending tasks" in line:
            return re.search("^pending tasks:\s*(\d+)",line).group(1);

'''Kicks off repair in primary vnode ranges'''
def repair(host,keyspace,offset):
    ranges = get_tokens(get_ip(get_hostid(host)), keyspace);
    coffset = offset;
    for range in ranges[offset:]:
        p = subprocess.Popen(["nodetool", "--host", host, "repair", "-pr", "-st",range[0],"-et",range[1],"-local"], stdin=subprocess.PIPE, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
        print "repairing range "+str(coffset)+" "+str(datetime.now());
        e = p.wait();
        if e != 0:
            raise RuntimeError("Error encountered: "+p.stderr.readline());

        while(1):
            pending = get_pending_compactions(host);
            if int(pending) > 10:
                print "waiting for compactions to drop: "+str(pending)
                time.sleep(10);
            else:
                break;
        coffset += 1;

if len(sys.argv) < 3:
    usage();

host = sys.argv[1];
keyspace = sys.argv[2];
offset = 0;

if len(sys.argv) == 4:
    offset = int(sys.argv[3]);

repair(host,keyspace,offset);