Add TLS support for ZooKeeper

This adds a script to generate TLS certs for zookeeper.

It also adds new config file options for specifying certs for a
TLS connection, adds a howto document to advise admins on how
to configure ZK for TLS.

It also removes the 'required' flag for the SASL auth parameters,
since they are not actually required.

Include the default openssl.cnf file since some distros modify it
to specify paths that are incompatbile with the zk-ca.sh script.

Change-Id: Icd976cc32dfd9f75f8cfb1c9ad11e08af31723d6
This commit is contained in:
James E. Blair 2020-03-11 11:31:51 -07:00
parent e0aea3bb4e
commit 93ec3daf47
10 changed files with 629 additions and 18 deletions

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@ -64,7 +64,7 @@ TCP port 4730 by default.
The Zuul scheduler communicates with Nodepool via the ZooKeeper
protocol. Nodepool requires an external ZooKeeper cluster, and the
Zuul scheduler needs to be able to connect to the hosts in that
cluster on TCP port 2181.
cluster on TCP port 2181 or 2281.
Both the Nodepool launchers and Zuul executors need to be able to
communicate with the hosts which nodepool provides. If these are on
@ -193,6 +193,17 @@ The following sections of ``zuul.conf`` are used by all Zuul components:
The ZooKeeper session timeout, in seconds.
.. attr:: tls_cert
If using TLS, the path to the PEM encoded certificate file.
.. attr:: tls_key
If using TLS, the path to the PEM encoded key file.
.. attr:: tls_ca
If using TLS, the path to the PEM encoded CA certificate file.
.. _scheduler:

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@ -7,3 +7,4 @@ Admin How-to Guides
installation
zuul-from-scratch
troubleshooting
zookeeper

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@ -0,0 +1,118 @@
ZooKeeper Administration
========================
This section will cover some basic tasks and recommendations when
setting up ZooKeeper for use with Zuul. A complete tutorial for
ZooKeeper is out of scope for this documentation.
Configuration
-------------
The following general configuration setting in
``/etc/zookeeper/zoo.cfg`` is recommended:
.. code-block::
autopurge.purgeInterval=6
This instructs ZooKeeper to purge old snapshots every 6 hours. This
will avoid filling the disk.
Encrypted Connections
---------------------
ZooKeeper version 3.5.1 or greater is required for TLS support.
ZooKeeper performs hostname validation for all ZooKeeper servers
("quorum members"), therefore each member of the ZooKeeper cluster
should have its own certificate. This does not apply to clients which
may share a certificate.
ZooKeeper performs certificate validation on all connections (server
and client). If you use a private Certificate Authority (CA) (which
is generally recommended and discussed below), then these TLS
certificates not only serve to encrypt traffic, but also to
authenticate and authorize clients to the cluster. Only clients with
certificates authorized by a CA explicitly trusted by your ZooKeeper
installation will be able to connect.
.. note:: The instructions below direct you to sign certificates with
a CA that you create specifically for Zuul's ZooKeeper
cluster. If you use a CA you share with other users in your
organization, any certificate signed by that CA will be able
to connect to your ZooKeeper cluster. In this case, you may
need to take additional steps such as network isolation to
protect your ZooKeeper cluster. These are beyond the scope
of this document.
The ``tools/zk-ca.sh`` script in the Zuul source code repository can
be used to quickly and easily generate self-signed certificates for
all ZooKeeper cluster members and clients.
Make a directory for it to store the certificates and CA data, and run
it once for each client:
.. code-block::
mkdir /etc/zookeeper/ca
tools/zk-ca.sh /etc/zookeeper/ca zookeeper1.example.com
tools/zk-ca.sh /etc/zookeeper/ca zookeeper2.example.com
tools/zk-ca.sh /etc/zookeeper/ca zookeeper3.example.com
Add the following to ``/etc/zookeeper/zoo.cfg``:
.. code-block::
# Necessary for TLS support
serverCnxnFactory=org.apache.zookeeper.server.NettyServerCnxnFactory
# Client TLS configuration
secureClientPort=2281
ssl.keyStore.location=/etc/zookeeper/ca/keystores/zookeeper1.example.com.jks
ssl.keyStore.password=keystorepassword
ssl.trustStore.location=/etc/zookeeper/ca/certs/cacert.pem
# Server TLS configuration
sslQuorum=true
ssl.quorum.keyStore.location=/etc/zookeeper/ca/keystores/zookeeper1.example.com.jks
ssl.quorum.keyStore.password=keystorepassword
ssl.quorum.trustStore.location=/etc/zookeeper/ca/certs/cacert.pem
Change the name of the certificate filenames as appropriate for the
host (e.g., ``zookeeper1.example.com.jks``). Note that the keystore
password ``keystorepassword``, which is set by the ``zk-ca.sh``
script, does not need to be changed as long as file permissions
provide sufficient protection. The password is present because many
Java utilities misbehave when interacting with keystores with empty or
missing passwords.
In order to disable plaintext connections, ensure that the
``clientPort`` option does not appear in ``zoo.cfg``. Use the new
method of specifying Zookeeper quorum servers, which looks like this:
.. code-block::
server.1=zookeeper1.example.com:2888:3888
server.2=zookeeper2.example.com:2888:3888
server.3=zookeeper3.example.com:2888:3888
This format normally includes ``;2181`` at the end of each line,
signifying that the server should listen on port 2181 for plaintext
client connections (this is equivalent to the ``clientPort`` option).
Omit it to disable plaintext connections. The earlier addition of
``secureClientPort`` to the config file instructs ZooKeeper to listen
for encrypted connections on port 2281.
Be sure to specify port 2281 rather than the standard 2181 in the
:attr:`zookeeper.hosts` setting in ``zuul.conf``.
Finally, add the :attr:`zookeeper.tls_cert`,
:attr:`zookeeper.tls_key`, and :attr:`zookeeper.tls_ca` options. Your
``zuul.conf`` file should look like:
.. code-block::
[zookeeper]
hosts=zookeeper1.example.com:2281,zookeeper2.example.com:2281,zookeeper3.example.com:2281
tls_cert=/etc/zookeeper/ca/certs/client.pem
tls_key=/etc/zookeeper/ca/keys/clientkey.pem
tls_ca=/etc/zookeeper/ca/certs/cacert.pem

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@ -3193,6 +3193,7 @@ class ZuulWebFixture(fixtures.Fixture):
info=self.info,
connections=self.connections,
zk_hosts=self.zk_hosts,
zk_timeout=10,
command_socket=os.path.join(self.test_root, 'web.socket'),
authenticators=self.authenticators)
self.web.start()

352
tools/openssl.cnf Normal file
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@ -0,0 +1,352 @@
#
# OpenSSL example configuration file.
# This is mostly being used for generation of certificate requests.
#
# Note that you can include other files from the main configuration
# file using the .include directive.
#.include filename
# This definition stops the following lines choking if HOME isn't
# defined.
HOME = .
RANDFILE = $ENV::HOME/.rnd
# Extra OBJECT IDENTIFIER info:
#oid_file = $ENV::HOME/.oid
oid_section = new_oids
# To use this configuration file with the "-extfile" option of the
# "openssl x509" utility, name here the section containing the
# X.509v3 extensions to use:
# extensions =
# (Alternatively, use a configuration file that has only
# X.509v3 extensions in its main [= default] section.)
[ new_oids ]
# We can add new OIDs in here for use by 'ca', 'req' and 'ts'.
# Add a simple OID like this:
# testoid1=1.2.3.4
# Or use config file substitution like this:
# testoid2=${testoid1}.5.6
# Policies used by the TSA examples.
tsa_policy1 = 1.2.3.4.1
tsa_policy2 = 1.2.3.4.5.6
tsa_policy3 = 1.2.3.4.5.7
####################################################################
[ ca ]
default_ca = CA_default # The default ca section
####################################################################
[ CA_default ]
dir = ./demoCA # Where everything is kept
certs = $dir/certs # Where the issued certs are kept
crl_dir = $dir/crl # Where the issued crl are kept
database = $dir/index.txt # database index file.
#unique_subject = no # Set to 'no' to allow creation of
# several certs with same subject.
new_certs_dir = $dir/newcerts # default place for new certs.
certificate = $dir/cacert.pem # The CA certificate
serial = $dir/serial # The current serial number
crlnumber = $dir/crlnumber # the current crl number
# must be commented out to leave a V1 CRL
crl = $dir/crl.pem # The current CRL
private_key = $dir/private/cakey.pem# The private key
RANDFILE = $dir/private/.rand # private random number file
x509_extensions = usr_cert # The extensions to add to the cert
# Comment out the following two lines for the "traditional"
# (and highly broken) format.
name_opt = ca_default # Subject Name options
cert_opt = ca_default # Certificate field options
# Extension copying option: use with caution.
# copy_extensions = copy
# Extensions to add to a CRL. Note: Netscape communicator chokes on V2 CRLs
# so this is commented out by default to leave a V1 CRL.
# crlnumber must also be commented out to leave a V1 CRL.
# crl_extensions = crl_ext
default_days = 365 # how long to certify for
default_crl_days= 30 # how long before next CRL
default_md = default # use public key default MD
preserve = no # keep passed DN ordering
# A few difference way of specifying how similar the request should look
# For type CA, the listed attributes must be the same, and the optional
# and supplied fields are just that :-)
policy = policy_match
# For the CA policy
[ policy_match ]
countryName = match
stateOrProvinceName = match
organizationName = match
organizationalUnitName = optional
commonName = supplied
emailAddress = optional
# For the 'anything' policy
# At this point in time, you must list all acceptable 'object'
# types.
[ policy_anything ]
countryName = optional
stateOrProvinceName = optional
localityName = optional
organizationName = optional
organizationalUnitName = optional
commonName = supplied
emailAddress = optional
####################################################################
[ req ]
default_bits = 2048
default_keyfile = privkey.pem
distinguished_name = req_distinguished_name
attributes = req_attributes
x509_extensions = v3_ca # The extensions to add to the self signed cert
# Passwords for private keys if not present they will be prompted for
# input_password = secret
# output_password = secret
# This sets a mask for permitted string types. There are several options.
# default: PrintableString, T61String, BMPString.
# pkix : PrintableString, BMPString (PKIX recommendation before 2004)
# utf8only: only UTF8Strings (PKIX recommendation after 2004).
# nombstr : PrintableString, T61String (no BMPStrings or UTF8Strings).
# MASK:XXXX a literal mask value.
# WARNING: ancient versions of Netscape crash on BMPStrings or UTF8Strings.
string_mask = utf8only
# req_extensions = v3_req # The extensions to add to a certificate request
[ req_distinguished_name ]
countryName = Country Name (2 letter code)
countryName_default = AU
countryName_min = 2
countryName_max = 2
stateOrProvinceName = State or Province Name (full name)
stateOrProvinceName_default = Some-State
localityName = Locality Name (eg, city)
0.organizationName = Organization Name (eg, company)
0.organizationName_default = Internet Widgits Pty Ltd
# we can do this but it is not needed normally :-)
#1.organizationName = Second Organization Name (eg, company)
#1.organizationName_default = World Wide Web Pty Ltd
organizationalUnitName = Organizational Unit Name (eg, section)
#organizationalUnitName_default =
commonName = Common Name (e.g. server FQDN or YOUR name)
commonName_max = 64
emailAddress = Email Address
emailAddress_max = 64
# SET-ex3 = SET extension number 3
[ req_attributes ]
challengePassword = A challenge password
challengePassword_min = 4
challengePassword_max = 20
unstructuredName = An optional company name
[ usr_cert ]
# These extensions are added when 'ca' signs a request.
# This goes against PKIX guidelines but some CAs do it and some software
# requires this to avoid interpreting an end user certificate as a CA.
basicConstraints=CA:FALSE
# Here are some examples of the usage of nsCertType. If it is omitted
# the certificate can be used for anything *except* object signing.
# This is OK for an SSL server.
# nsCertType = server
# For an object signing certificate this would be used.
# nsCertType = objsign
# For normal client use this is typical
# nsCertType = client, email
# and for everything including object signing:
# nsCertType = client, email, objsign
# This is typical in keyUsage for a client certificate.
# keyUsage = nonRepudiation, digitalSignature, keyEncipherment
# This will be displayed in Netscape's comment listbox.
nsComment = "OpenSSL Generated Certificate"
# PKIX recommendations harmless if included in all certificates.
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid,issuer
# This stuff is for subjectAltName and issuerAltname.
# Import the email address.
# subjectAltName=email:copy
# An alternative to produce certificates that aren't
# deprecated according to PKIX.
# subjectAltName=email:move
# Copy subject details
# issuerAltName=issuer:copy
#nsCaRevocationUrl = http://www.domain.dom/ca-crl.pem
#nsBaseUrl
#nsRevocationUrl
#nsRenewalUrl
#nsCaPolicyUrl
#nsSslServerName
# This is required for TSA certificates.
# extendedKeyUsage = critical,timeStamping
[ v3_req ]
# Extensions to add to a certificate request
basicConstraints = CA:FALSE
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
[ v3_ca ]
# Extensions for a typical CA
# PKIX recommendation.
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid:always,issuer
basicConstraints = critical,CA:true
# Key usage: this is typical for a CA certificate. However since it will
# prevent it being used as an test self-signed certificate it is best
# left out by default.
# keyUsage = cRLSign, keyCertSign
# Some might want this also
# nsCertType = sslCA, emailCA
# Include email address in subject alt name: another PKIX recommendation
# subjectAltName=email:copy
# Copy issuer details
# issuerAltName=issuer:copy
# DER hex encoding of an extension: beware experts only!
# obj=DER:02:03
# Where 'obj' is a standard or added object
# You can even override a supported extension:
# basicConstraints= critical, DER:30:03:01:01:FF
[ crl_ext ]
# CRL extensions.
# Only issuerAltName and authorityKeyIdentifier make any sense in a CRL.
# issuerAltName=issuer:copy
authorityKeyIdentifier=keyid:always
[ proxy_cert_ext ]
# These extensions should be added when creating a proxy certificate
# This goes against PKIX guidelines but some CAs do it and some software
# requires this to avoid interpreting an end user certificate as a CA.
basicConstraints=CA:FALSE
# Here are some examples of the usage of nsCertType. If it is omitted
# the certificate can be used for anything *except* object signing.
# This is OK for an SSL server.
# nsCertType = server
# For an object signing certificate this would be used.
# nsCertType = objsign
# For normal client use this is typical
# nsCertType = client, email
# and for everything including object signing:
# nsCertType = client, email, objsign
# This is typical in keyUsage for a client certificate.
# keyUsage = nonRepudiation, digitalSignature, keyEncipherment
# This will be displayed in Netscape's comment listbox.
nsComment = "OpenSSL Generated Certificate"
# PKIX recommendations harmless if included in all certificates.
subjectKeyIdentifier=hash
authorityKeyIdentifier=keyid,issuer
# This stuff is for subjectAltName and issuerAltname.
# Import the email address.
# subjectAltName=email:copy
# An alternative to produce certificates that aren't
# deprecated according to PKIX.
# subjectAltName=email:move
# Copy subject details
# issuerAltName=issuer:copy
#nsCaRevocationUrl = http://www.domain.dom/ca-crl.pem
#nsBaseUrl
#nsRevocationUrl
#nsRenewalUrl
#nsCaPolicyUrl
#nsSslServerName
# This really needs to be in place for it to be a proxy certificate.
proxyCertInfo=critical,language:id-ppl-anyLanguage,pathlen:3,policy:foo
####################################################################
[ tsa ]
default_tsa = tsa_config1 # the default TSA section
[ tsa_config1 ]
# These are used by the TSA reply generation only.
dir = ./demoCA # TSA root directory
serial = $dir/tsaserial # The current serial number (mandatory)
crypto_device = builtin # OpenSSL engine to use for signing
signer_cert = $dir/tsacert.pem # The TSA signing certificate
# (optional)
certs = $dir/cacert.pem # Certificate chain to include in reply
# (optional)
signer_key = $dir/private/tsakey.pem # The TSA private key (optional)
signer_digest = sha256 # Signing digest to use. (Optional)
default_policy = tsa_policy1 # Policy if request did not specify it
# (optional)
other_policies = tsa_policy2, tsa_policy3 # acceptable policies (optional)
digests = sha1, sha256, sha384, sha512 # Acceptable message digests (mandatory)
accuracy = secs:1, millisecs:500, microsecs:100 # (optional)
clock_precision_digits = 0 # number of digits after dot. (optional)
ordering = yes # Is ordering defined for timestamps?
# (optional, default: no)
tsa_name = yes # Must the TSA name be included in the reply?
# (optional, default: no)
ess_cert_id_chain = no # Must the ESS cert id chain be included?
# (optional, default: no)
ess_cert_id_alg = sha1 # algorithm to compute certificate
# identifier (optional, default: sha1)

103
tools/zk-ca.sh Executable file
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@ -0,0 +1,103 @@
#!/bin/sh -e
# Copyright 2020 Red Hat, Inc
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
# Manage a CA for Zookeeper
CAROOT=$1
SERVER=$2
SUBJECT='/C=US/ST=California/L=Oakland/O=Company Name/OU=Org'
TOOLSDIR=$(dirname $0)
CONFIG="-config $TOOLSDIR/openssl.cnf"
make_ca() {
mkdir $CAROOT/demoCA
mkdir $CAROOT/demoCA/reqs
mkdir $CAROOT/demoCA/newcerts
mkdir $CAROOT/demoCA/crl
mkdir $CAROOT/demoCA/private
chmod 700 $CAROOT/demoCA/private
touch $CAROOT/demoCA/index.txt
touch $CAROOT/demoCA/index.txt.attr
mkdir $CAROOT/certs
mkdir $CAROOT/keys
mkdir $CAROOT/keystores
chmod 700 $CAROOT/keys
chmod 700 $CAROOT/keystores
openssl req $CONFIG -new -nodes -subj "$SUBJECT/CN=caroot" \
-keyout $CAROOT/demoCA/private/cakey.pem \
-out $CAROOT/demoCA/reqs/careq.pem
openssl ca $CONFIG -create_serial -days 3560 -batch -selfsign -extensions v3_ca \
-out $CAROOT/demoCA/cacert.pem \
-keyfile $CAROOT/demoCA/private/cakey.pem \
-infiles $CAROOT/demoCA/reqs/careq.pem
cp $CAROOT/demoCA/cacert.pem $CAROOT/certs
}
make_client() {
openssl req $CONFIG -new -nodes -subj "$SUBJECT/CN=client" \
-keyout $CAROOT/keys/clientkey.pem \
-out $CAROOT/demoCA/reqs/clientreq.pem
openssl ca $CONFIG -batch -policy policy_anything -days 3560 \
-out $CAROOT/certs/client.pem \
-infiles $CAROOT/demoCA/reqs/clientreq.pem
}
make_server() {
openssl req $CONFIG -new -nodes -subj "$SUBJECT/CN=$SERVER" \
-keyout $CAROOT/keys/${SERVER}key.pem \
-out $CAROOT/demoCA/reqs/${SERVER}req.pem
openssl ca $CONFIG -batch -policy policy_anything -days 3560 \
-out $CAROOT/certs/$SERVER.pem \
-infiles $CAROOT/demoCA/reqs/${SERVER}req.pem
cat $CAROOT/certs/$SERVER.pem $CAROOT/keys/${SERVER}key.pem \
> $CAROOT/keystores/$SERVER.pem
}
help() {
echo "$0 CAROOT [SERVER]"
echo
echo " CAROOT is the path to a directory in which to store the CA"
echo " and certificates."
echo " SERVER is the FQDN of a server for which a certificate should"
echo " be generated"
}
if [ ! -d "$CAROOT" ]; then
echo "CAROOT must be a directory"
help
exit 1
fi
cd $CAROOT
CAROOT=`pwd`
if [ ! -d "$CAROOT/demoCA" ]; then
echo 'Generate CA'
make_ca
echo 'Generate client certificate'
make_client
fi
if [ -f "$CAROOT/certs/$SERVER.pem" ]; then
echo "Certificate for $SERVER already exists"
exit 0
fi
if [ "$SERVER" != "" ]; then
make_server
fi

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@ -149,10 +149,17 @@ class Scheduler(zuul.cmd.ZuulDaemonApp):
zookeeper_hosts = get_default(self.config, 'zookeeper', 'hosts', None)
if not zookeeper_hosts:
raise Exception("The zookeeper hosts config value is required")
zookeeper_tls_key = get_default(self.config, 'zookeeper', 'tls_key')
zookeeper_tls_cert = get_default(self.config, 'zookeeper', 'tls_cert')
zookeeper_tls_ca = get_default(self.config, 'zookeeper', 'tls_ca')
zookeeper_timeout = float(get_default(self.config, 'zookeeper',
'session_timeout', 10.0))
zookeeper.connect(zookeeper_hosts, timeout=zookeeper_timeout)
zookeeper.connect(
zookeeper_hosts,
timeout=zookeeper_timeout,
tls_cert=zookeeper_tls_cert,
tls_key=zookeeper_tls_key,
tls_ca=zookeeper_tls_ca)
self.configure_connections()
self.sched.setExecutor(gearman)

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@ -86,6 +86,12 @@ class WebServer(zuul.cmd.ZuulDaemonApp):
self.config, 'zookeeper', 'hosts', None)
if not params["zk_hosts"]:
raise Exception("The zookeeper hosts config value is required")
params["zk_tls_key"] = get_default(self.config, 'zookeeper', 'tls_key')
params["zk_tls_cert"] = get_default(self.config,
'zookeeper', 'tls_cert')
params["zk_tls_ca"] = get_default(self.config, 'zookeeper', 'tls_ca')
params["zk_timeout"] = float(get_default(self.config, 'zookeeper',
'session_timeout', 10.0))
try:
self.web = zuul.web.ZuulWeb(**params)

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@ -1069,17 +1069,13 @@ class StreamManager(object):
class ZuulWeb(object):
log = logging.getLogger("zuul.web.ZuulWeb")
def __init__(self, listen_address, listen_port,
gear_server, gear_port,
ssl_key=None, ssl_cert=None, ssl_ca=None,
static_cache_expiry=3600,
connections=None,
info=None,
static_path=None,
zk_hosts=None,
authenticators=None,
command_socket=None,
):
def __init__(self, listen_address, listen_port, gear_server,
gear_port, ssl_key=None, ssl_cert=None, ssl_ca=None,
static_cache_expiry=3600, connections=None,
info=None, static_path=None, zk_hosts=None,
zk_timeout=None, zk_tls_cert=None, zk_tls_key=None,
zk_tls_ca=None, authenticators=None,
command_socket=None):
self.start_time = time.time()
self.listen_address = listen_address
self.listen_port = listen_port
@ -1095,7 +1091,10 @@ class ZuulWeb(object):
client_id='Zuul Web Server')
self.zk = zuul.zk.ZooKeeper(enable_cache=True)
if zk_hosts:
self.zk.connect(hosts=zk_hosts, read_only=True)
self.zk.connect(hosts=zk_hosts, read_only=True,
timeout=zk_timeout, tls_cert=zk_tls_cert,
tls_key=zk_tls_key, tls_ca=zk_tls_ca)
self.connections = connections
self.authenticators = authenticators
self.stream_manager = StreamManager()

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@ -115,7 +115,8 @@ class ZooKeeper(object):
self.log.warning("Retrying zookeeper connection")
self._last_retry_log = now
def connect(self, hosts, read_only=False, timeout=10.0):
def connect(self, hosts, read_only=False, timeout=10.0,
tls_cert=None, tls_key=None, tls_ca=None):
'''
Establish a connection with ZooKeeper cluster.
@ -127,10 +128,22 @@ class ZooKeeper(object):
:param bool read_only: If True, establishes a read-only connection.
:param float timeout: The ZooKeeper session timeout, in
seconds (default: 10.0).
:param str tls_key: Path to TLS key
:param str tls_cert: Path to TLS cert
:param str tls_ca: Path to TLS CA cert
'''
if self.client is None:
self.client = KazooClient(hosts=hosts, read_only=read_only,
timeout=timeout)
args = dict(hosts=hosts,
read_only=read_only,
timeout=timeout,
)
if tls_key:
args['use_ssl'] = True
args['keyfile'] = tls_key
args['certfile'] = tls_cert
args['ca'] = tls_ca
self.client = KazooClient(**args)
self.client.add_listener(self._connection_listener)
# Manually retry initial connection attempt
while True: