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copied!<p>i had nearly the same problem with servers hosted by acquia.</p> <p>A way to solve it was to : - set the backend IPs from the hoster servers by acquia in a separate vcl - build a croned script that regulary updates that vcl if the backend changed - restart the varnish to put the new backends in production</p> <pre><code>#!/usr/bin/python2.7 import socket import subprocess import re # # Do a nslookup and return the list of the IPs # def _nslookup(host): ips = "" ips = socket.getaddrinfo(host ,0,0,0,0) ip_list = [] for result in ips: ip_list.append(result[-1][0]) ip_list = list(set(ip_list)) return ip_list # # Compare current backends with the list returned by nslookup # def _compare_backends_vcl(host_name, group_name): current_ips = [] current_ips = _nslookup(host_name) # Get current backends current_backends = [] list = subprocess.Popen("/usr/bin/varnishadm backend.list | grep " + group_name + " | awk '{print $1}'", shell=True, stdout=subprocess.PIPE) backend = "" for backend in list.stdout: current_backends.append(re.sub(r'^.*\((.*),.*,.*$\n', r'\1', backend)) # Due to varnish bug that is not removing backends (old ones are still declared in backend.list # we are forced to add backends # So the nslookup should be part of the current set of backends # if set(current_ips).symmetric_difference(current_backends): if set(current_ips).difference(current_backends): # List is present so difference exist print "_compare: We have to update " + group_name return True else: return False # # Write the corresponding file # def _write_backends_vcl(host_name, group_name): TEMPLATE_NODE = '''backend %s { \t.host = "%s"; \t.port = "80"; \t.probe = %s; }''' vcl_file = open("/etc/varnish/" + group_name + "_backends.vcl", 'w') host_num = 1 hosts = _nslookup(host_name) for host in hosts: vcl_file.write(TEMPLATE_NODE % (group_name + "_" + str(host_num), host, group_name + "_probe")) vcl_file.write("\n\n") host_num +=1 vcl_file.write("director " + group_name + "_default round-robin {\n") for i in range(len(hosts)): node = group_name + "_" + str(i+1) vcl_file.write("\t{ .backend = %s; }\n" % node) vcl_file.write("}\n") vcl_file.close() # Main do_reload = "" if _compare_backends_vcl("myhost.prod.acquia-sites.com", "MYHOST_CONFIG"): do_reload = True _write_backends_vcl("myhost.prod.acquia-sites.com", "MYHOST_CONFIG") if do_reload: print "Reloading varnish" subprocess.Popen(['sudo', '/etc/init.d/varnish', 'reload']) exit(1) else: # print "Everything is ok" exit(0) </code></pre> <p>then, the corresponding vcl looks like :</p> <pre><code>backend MYHOST_CONFIG_1 { .host = "XX.XX.XX.XX"; .port = "80"; .probe = MYHOST_CONFIG_probe; } backend MYHOST_CONFIG_2 { .host = "XX.XX.XX.XX"; .port = "80"; .probe = MYHOST_CONFIG_probe; } director MYHOST_CONFIG_default round-robin { { .backend = MYHOST_CONFIG_1; } { .backend = MYHOST_CONFIG_2; } } </code></pre> <p>You have to setup the MYHOST_CONFIG_probe probe and to set MYHOST_CONFIG_default as a director for your config. Beware that varnish stores all the backend, and so you have to restart it regularly to purge the defective servers</p>

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