It is generated JSON file of serf dynamically by etcd. I made it experimentally, but do not maintain it recently.

serf-etcdconf.pl

#!/usr/bin/perl

# Serf configuration generator with Etcd
#
# MIT License
# 2014 Masahito Zembutsu

use JSON::XS;
use Net::HTTP;
use Data::Dumper;

my $target = '/serf/manager';

# etcd
my $etcd_host = '127.0.0.1';
my $etcd_port = '4001';
my $etcd_ver  = 'v2';

# no buffering
$| = 1;

# define as objects
my $config_obj = 'event_handlers|start_join';

# debug
$ERR = 0;

# get JSON data
my $json_str = &etcd_request($target);

# checking format
#if (valid_json ($json_str)) {
#       #print "valid json: $@\n";
#} else{
#       #print "invalid json: $@\n";
#}

# decode JSON
$config = JSON::XS->new->utf8->decode($json_str);

my @nodes = @{$config->{'node'}->{'nodes'}};
$target = $config->{'node'}->{'key'};
$target .= '/' if ( $target !~ /(\/)$/ );
my %OUTPUT;

foreach my $key (@nodes) {
        $key->{'key'} =~ s/$target//;
        if ($key->{dir} == 1 ) {
                my @data = @{$key->{'nodes'}};
                if ($key->{'key'} =~ /$config_obj/) {
                        my @newdata;
                } elsif ($key->{'key'} eq 'keys' ) {
                        my %newdata;
                }
                foreach my $tmp (@data) {
                        my $cut = $target.$key->{key}.'/';
                        $tmp->{key} =~ s/$cut//;
                        if ($key->{'key'} =~ /$config_obj/) {
                                push @newdata, $tmp->{'value'};
                        } elsif ($key->{'key'} eq 'keys' ) {
                                $newdata{$tmp->{'key'}} = $tmp->{'value'};
                        }
                }
                if ($key->{'key'} =~ /$config_obj/) {
                        $key->{'value'}  = \@newdata;
                } elsif ($key->{'key'} eq 'keys' ) {
                        $key->{'value'}  = \%newdata;
                }
        }
        $OUTPUT{$key->{'key'}} = $key->{'value'};
}

# Display output
my $NEWJSON = JSON::XS->new->utf8->encode( \%OUTPUT );
print $NEWJSON,"\n";

exit;


sub etcd_request {

        my $request = shift;
        %headers = ('Content-Type' => 'application/json-rpc');

        my $nh = Net::HTTP->new(Host => $etcd_host, PeerPort => $etcd_port) or $ERR = 1;
        my $req = '/'.$etcd_ver.'/keys'.$request.'?recursive=true&sorted=true';
        $nh->write_request('GET', $req  , %headers , '') or $ERR = 2;
        my ($code, $mess, %headers) = $nh->read_response_headers();

        if ($code eq '200') {
                my $bufm;
                while (1) {
                        my $buf;
                        my $nread = $nh->read_entity_body($buf, 1024);
                        die "read failed: $!" unless defined $nread;
                        last unless $nread;
                        $bufm .= $buf;
                }
                return $bufm if ($bufm);
        } else {
                print "ERROR: failed, code: $code, response: $mess\n";
        }
        return;
}

1;

push must do information to correspond to /serf/ beforehand on kvs of etcd.
In addition, this script does not support the registration of the setting information for etcd.