Ekka - Autocluster for EMQ X Broker. Ekka helps building a new distribution layer for EMQ X R2.3+.
---------- ----------
| EMQX |<--- MQTT--->| EMQX |
|--------| |--------|
| Ekka |<----RPC---->| Ekka |
|--------| |--------|
| Mnesia |<--Cluster-->| Mnesia |
|--------| |--------|
| Kernel |<----TCP---->| Kernel |
---------- ----------
Ekka supports erlang node discovery and autocluster using various strategies:
| Strategy | Description |
|---|---|
| manual | Join cluster manually |
| static | Static node list |
| mcast | IP Multicast |
| dns | DNS A Records |
| etcd | etcd |
| k8s | Kubernetes |
The configuration example files are under 'etc/' folder.
Cuttlefish style config:
cluster.discovery = static
cluster.static.seeds = [email protected],[email protected]
Erlang config:
{cluster_discovery,
{static, [
{seeds, ['[email protected]', '[email protected]']}
]}},
Cuttlefish style config:
cluster.discovery = mcast
## IP Multicast Address.
##
## Value: IP Address
cluster.mcast.addr = 239.192.0.1
## Multicast Ports.
##
## Value: Port List
cluster.mcast.ports = 4369,4370
## Multicast Iface.
##
## Value: Iface Address
##
## Default: 0.0.0.0
cluster.mcast.iface = 0.0.0.0
## Multicast Ttl.
##
## Value: 0-255
cluster.mcast.ttl = 255
## Multicast loop.
##
## Value: on | off
cluster.mcast.loop = on
Erlang config:
{cluster_discovery,
{mcast, [
{addr, {239,192,0,1}},
{ports, [4369,4370]},
{iface, {0,0,0,0}},
{ttl, 255},
{loop, true}
]}},
Cuttlefish style config:
cluster.discovery = dns
## DNS name.
##
## Value: String
cluster.dns.name = localhost
## The App name is used to build 'node.name' with IP address.
##
## Value: String
cluster.dns.app = ekka
Erlang config:
{cluster_discovery,
{dns, [
{name, "localhost"},
{app, "ekka"}
]}},
Cuttlefish style config:
cluster.discovery = etcd
## Etcd server list, seperated by ','.
##
## Value: String
cluster.etcd.server = http://127.0.0.1:2379
## The prefix helps build nodes path in etcd. Each node in the cluster
## will create a path in etcd: v2/keys/<prefix>/<cluster.name>/<node.name>
##
## Value: String
cluster.etcd.prefix = ekkacl
## The TTL for node's path in etcd.
##
## Value: Duration
##
## Default: 1m, 1 minute
cluster.etcd.node_ttl = 1m
## Path to a file containing the client's private PEM-encoded key.
##
## Value: File
##
## cluster.etcd.keyfile = {{platform_etc_dir}}/certs/client-key.pem
## Path to the file containing the client's certificate
##
## Value: File
##
## cluster.etcd.certfile = {{platform_etc_dir}}/certs/client.pem
## Path to the file containing PEM-encoded CA certificates. The CA certificates
## are used during server authentication and when building the client certificate chain.
##
## Value: File
##
## cluster.etcd.cacertfile = {{platform_etc_dir}}/certs/ca.pem
Erlang config:
{cluster_discovery,
{etcd, [
{server, ["http://127.0.0.1:2379"]},
{prefix, "ekkacluster"},
%%{ssl_options, [
%% {keyfile, "path/to/client-key.pem"},
%% {certfile, "path/to/client.pem"},
%% {cacertfile, "path/to/ca.pem"}
%%]},
{node_ttl, 60000}
]}},
Cuttlefish style config:
cluster.discovery = k8s
## Kubernates API server list, seperated by ','.
##
## Value: String
## cluster.k8s.apiserver = http://10.110.111.204:8080
## The service name helps lookup EMQ nodes in the cluster.
##
## Value: String
## cluster.k8s.service_name = ekka
## The name space of k8s
##
## Value: String
## cluster.k8s.namespace = default
## The address type is used to extract host from k8s service.
##
## Value: ip | dns | hostname
## cluster.k8s.address_type = ip
## The app name helps build 'node.name'.
##
## Value: String
## cluster.k8s.app_name = ekka
## The suffix added to dns and hostname get from k8s service
##
## Value: String
## cluster.k8s.suffix = pod.cluster.local
Erlang config:
{cluster_discovery,
{k8s, [
{apiserver, "http://10.110.111.204:8080"},
{namespace, "default"},
{service_name, "ekka"},
{address_type, ip},
{app_name, "ekka"},
{suffix, "pod.cluster.local"}
]}}
When network partition occurs, the following steps to heal the cluster if autoheal is enabled:
-
Node reports the partitions to a leader node which has the oldest guid.
-
Leader node create a global netsplit view and choose one node in the majority as coordinator.
-
Leader node requests the coordinator to autoheal the network partition.
-
Coordinator node reboots all the nodes in the minority side.
Erlang config:
{cluster_autoheal, true},
Cuttlefish style config:
cluster.autoheal = on
Ekka implements a simple distributed lock service in 0.3 release. The Lock APIs:
Acquire lock:
-spec(acquire(resource()) -> {boolean(), [node()]}).
ekka_locker:acquire(Resource).
-spec(acquire(atom(), resource(), lock_type()) -> lock_result()).
ekka_locker:acquire(ekka_locker, Resource, Type).
Release lock:
-spec(release(resource()) -> lock_result()).
ekka_locker:release(Resource).
-spec(release(atom(), resource()) -> lock_result()).
ekka_locker:release(Name, Resource).
The lock type:
-type(lock_type() :: local | leader | quorum | all).
The ekka 0.6.0 release implements erlang distribiton without epmd.
See: http://erlang.org/pipermail/erlang-questions/2015-December/087013.html
For example:
## Dist port: 4370
erl -pa ebin -pa _build/default/lib/*/ebin -proto_dist ekka -start_epmd false -epmd_module ekka_epmd -name [email protected] -s ekka
## Dist port: 4371
erl -pa ebin -pa _build/default/lib/*/ebin -proto_dist ekka -start_epmd false -epmd_module ekka_epmd -name [email protected] -s ekka
## Dist port: 4372
erl -pa ebin -pa _build/default/lib/*/ebin -proto_dist ekka -start_epmd false -epmd_module ekka_epmd -name [email protected] -s ekka
The erlang distribution port can be tuned by ekka inet_dist_base_port env. The default port is 4370.
Apache License Version 2.0
EMQ X Team.
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