What is it
The messenger v2 protocol, or msgr2, is the second major revision on Ceph’s on-wire protocol. It brings with it several key features:
A secure mode that encrypts all data passing over the network
Improved encapsulation of authentication payloads, enabling future integration of new authentication modes like Kerberos
Improved earlier feature advertisement and negotiation, enabling future protocol revisions
Ceph daemons can now bind to multiple ports, allowing both legacy Ceph clients and new v2-capable clients to connect to the same cluster.
By default, monitors now bind to the new IANA-assigned port
(ce4h or 0xce4) for the new v2 protocol, while also binding to the
old default port
6789 for the legacy v1 protocol.
Prior to Nautilus, all network addresses were rendered like
18.104.22.168:567/89012 where there was an IP address, a port, and a
nonce to uniquely identify a client or daemon on the network.
Starting with Nautilus, we now have three different address types:
v2:22.214.171.124:578/89012identifies a daemon binding to a port speaking the new v2 protocol
v1:126.96.36.199:578/89012identifies a daemon binding to a port speaking the legacy v1 protocol. Any address that was previously shown with any prefix is now shown as a
any:188.8.131.52:578/89012identifies a client that can speak either version of the protocol. Prior to nautilus, clients would appear as
184.108.40.206:0/123456, where the port of 0 indicates they are clients and do not accept incoming connections. Starting with Nautilus, these clients are now internally represented by a TYPE_ANY address, and still shown with no prefix, because they may connect to daemons using the v2 or v1 protocol, depending on what protocol(s) the daemons are using.
Because daemons now bind to multiple ports, they are now described by a vector of addresses instead of a single address. For example, dumping the monitor map on a Nautilus cluster now includes lines like:
last_changed 2019-02-25 11:10:46.700821
created 2019-02-25 11:10:46.700821
min_mon_release 14 (nautilus)
0: [v2:10.0.0.10:3300/0,v1:10.0.0.10:6789/0] mon.foo
1: [v2:10.0.0.11:3300/0,v1:10.0.0.11:6789/0] mon.bar
2: [v2:10.0.0.12:3300/0,v1:10.0.0.12:6789/0] mon.baz
The bracketed list or vector of addresses means that the same daemon can be reached on multiple ports (and protocols). Any client or other daemon connecting to that daemon will use the v2 protocol (listed first) if possible; otherwise it will back to the legacy v1 protocol. Legacy clients will only see the v1 addresses and will continue to connect as they did before, with the v1 protocol.
Starting in Nautilus, the
mon_host configuration option and
<mon-host> command line options support the same bracketed address
Bind configuration options
Two new configuration options control whether the v1 and/or v2 protocol is used:
ms_bind_msgr1[default: true] controls whether a daemon binds to a port speaking the v1 protocol
ms_bind_msgr2[default: true] controls whether a daemon binds to a port speaking the v2 protocol
Similarly, two options control whether IPv4 and IPv6 addresses are used:
The ability to bind to multiple ports has paved the way for dual-stack IPv4 and IPv6 support. That said, dual-stack operation is not yet supported as of Quincy v17.2.0.
The v2 protocol supports two connection modes:
crc mode provides:
a strong initial authentication when the connection is established (with cephx, mutual authentication of both parties with protection from a man-in-the-middle or eavesdropper), and
a crc32c integrity check to protect against bit flips due to flaky hardware or cosmic rays
crc mode does not provide:
secrecy (an eavesdropper on the network can see all post-authentication traffic as it goes by) or
protection from a malicious man-in-the-middle (who can deliberate modify traffic as it goes by, as long as they are careful to adjust the crc32c values to match)
secure mode provides:
full encryption of all post-authentication traffic, including a cryptographic integrity check.
In Nautilus, secure mode uses the AES-GCM stream cipher, which is generally very fast on modern processors (e.g., faster than a SHA-256 cryptographic hash).
Connection mode configuration options
For most connections, there are options that control which modes are used:
There are a parallel set of options that apply specifically to monitors, allowing administrators to set different (usually more secure) requirements on communication with the monitors.
The v2 protocol supports two compression modes:
force mode provides:
In multi-availability zones deployment, compressing replication messages between OSDs saves latency.
In the public cloud, inter-AZ communications are expensive. Thus, minimizing message size reduces network costs to cloud provider.
When using instance storage on AWS (probably other public clouds as well) the instances with NVMe provide low network bandwidth relative to the device bandwidth. In this case, NW compression can improve the overall performance since this is clearly the bottleneck.
none mode provides:
messages are transmitted without compression.
Compression mode configuration options
For all connections, there is an option that controls compression usage in secure mode
Combining encryption with compression reduces the level of security of messages between peers. In case both encryption and compression are enabled, compression setting will be ignored and message will not be compressed. This behaviour can be override using this setting.
- see also
There is a parallel set of options that apply specifically to OSDs, allowing administrators to set different requirements on communication between OSDs.
Compression policy to use in Messenger for communicating with OSD
- valid choices
- see also
Minimal message size eligable for on-wire compression
- see also
Transitioning from v1-only to v2-plus-v1
ms_bind_msgr2 is true starting with Nautilus 14.2.z.
However, until the monitors start using v2, only limited services will
start advertising v2 addresses.
For most users, the monitors are binding to the default legacy port
for the v1 protocol. When this is the case, enabling v2 is as simple as:
ceph mon enable-msgr2
If the monitors are bound to non-standard ports, you will need to
specify an additional port for v2 explicitly. For example, if your
mon.a binds to
220.127.116.11:1111, and you want to add v2 on
ceph mon set-addrs a [v2:18.104.22.168:1112,v1:22.214.171.124:1111]
Once the monitors bind to v2, each daemon will start advertising a v2 address when it is next restarted.
Updating ceph.conf and mon_host
Prior to Nautilus, a CLI user or daemon will normally discover the
monitors via the
mon_host option in
syntax for this option has expanded starting with Nautilus to allow
support the new bracketed list format. For example, an old line
mon_host = 10.0.0.1:6789,10.0.0.2:6789,10.0.0.3:6789
Can be changed to:
mon_host = [v2:10.0.0.1:3300/0,v1:10.0.0.1:6789/0],[v2:10.0.0.2:3300/0,v1:10.0.0.2:6789/0],[v2:10.0.0.3:3300/0,v1:10.0.0.3:6789/0]
However, when default ports are used (
6789), they can
mon_host = 10.0.0.1,10.0.0.2,10.0.0.3
Once v2 has been enabled on the monitors,
ceph.conf may need to be
updated to either specify no ports (this is usually simplest), or
explicitly specify both the v2 and v1 addresses. Note, however, that
the new bracketed syntax is only understood by Nautilus and later, so
do not make that change on hosts that have not yet had their ceph
When you are updating
ceph.conf, note the new
generate-minimal-conf command (which generates a barebones config
file with just enough information to reach the monitors) and the
ceph config assimilate-conf (which moves config file options into
the monitors’ configuration database) may be helpful. For example,:
# ceph config assimilate-conf < /etc/ceph/ceph.conf
# ceph config generate-minimal-config > /etc/ceph/ceph.conf.new
# cat /etc/ceph/ceph.conf.new
# minimal ceph.conf for 0e5a806b-0ce5-4bc6-b949-aa6f68f5c2a3
fsid = 0e5a806b-0ce5-4bc6-b949-aa6f68f5c2a3
mon_host = [v2:10.0.0.1:3300/0,v1:10.0.0.1:6789/0]
# mv /etc/ceph/ceph.conf.new /etc/ceph/ceph.conf
For a detailed description of the v2 wire protocol, see msgr2 protocol (msgr2.0 and msgr2.1).