Transport
editTransport
editREST clients send requests to your Elasticsearch cluster over HTTP, but
the node that receives a client request cannot always handle it alone and must
normally pass it on to other nodes for further processing. It does this using
the transport networking layer. The transport layer is used for all internal
communication between nodes within a cluster, all communication with the nodes
of a remote cluster, and also by the
TransportClient
in the Elasticsearch Java API.
Transport settings
editThe internal transport communicates over TCP. You can configure it with the following settings:
-
transport.port
-
(Static)
A bind port range. Defaults to
9300-9400
. -
transport.publish_port
-
(Static)
The port that other nodes in the cluster
should use when communicating with this node. Useful when a cluster node
is behind a proxy or firewall and the
transport.port
is not directly addressable from the outside. Defaults to the actual port assigned viatransport.port
. -
transport.bind_host
-
(Static)
The host address to bind the transport service to. Defaults to
transport.host
(if set) ornetwork.bind_host
. -
transport.publish_host
-
(Static)
The host address to publish for nodes in the cluster to connect to.
Defaults to
transport.host
(if set) ornetwork.publish_host
. -
transport.host
-
(Static)
Used to set the
transport.bind_host
and thetransport.publish_host
. -
transport.connect_timeout
-
(Static)
The connect timeout for initiating a new connection (in
time setting format). Defaults to
30s
. -
transport.compress
-
(Static)
Set to
true
to enable compression (DEFLATE
) between all nodes. Defaults tofalse
. -
transport.ping_schedule
-
(Static)
Schedule a regular application-level ping message
to ensure that transport connections between nodes are kept alive. Defaults to
5s
in the transport client and-1
(disabled) elsewhere. It is preferable to correctly configure TCP keep-alives instead of using this feature, because TCP keep-alives apply to all kinds of long-lived connections and not just to transport connections.
It also uses the common network settings.
Transport profiles
editElasticsearch allows you to bind to multiple ports on different interfaces by the use of transport profiles. See this example configuration
transport.profiles.default.port: 9300-9400 transport.profiles.default.bind_host: 10.0.0.1 transport.profiles.client.port: 9500-9600 transport.profiles.client.bind_host: 192.168.0.1 transport.profiles.dmz.port: 9700-9800 transport.profiles.dmz.bind_host: 172.16.1.2
The default
profile is special. It is used as a fallback for any other
profiles, if those do not have a specific configuration setting set, and is how
this node connects to other nodes in the cluster.
The following parameters can be configured on each transport profile, as in the example above:
-
port
: The port to bind to -
bind_host
: The host to bind -
publish_host
: The host which is published in informational APIs -
tcp.no_delay
: Configures theTCP_NO_DELAY
option for this socket -
tcp.keep_alive
: Configures theSO_KEEPALIVE
option for this socket -
tcp.keep_idle
: Configures theTCP_KEEPIDLE
option for this socket, which determines the time in seconds that a connection must be idle before starting to send TCP keepalive probes. Only applicable on Linux and Mac, and requires JDK 11 or newer. Defaults to -1, which does not set this option at the socket level, but uses default system configuration instead. -
tcp.keep_interval
: Configures theTCP_KEEPINTVL
option for this socket, which determines the time in seconds between sending TCP keepalive probes. Only applicable on Linux and Mac, and requires JDK 11 or newer. Defaults to -1, which does not set this option at the socket level, but uses default system configuration instead. -
tcp.keep_count
: Configures theTCP_KEEPCNT
option for this socket, which determines the number of unacknowledged TCP keepalive probes that may be sent on a connection before it is dropped. Only applicable on Linux and Mac, and requires JDK 11 or newer. Defaults to -1, which does not set this option at the socket level, but uses default system configuration instead. -
tcp.reuse_address
: Configures theSO_REUSEADDR
option for this socket -
tcp.send_buffer_size
: Configures the send buffer size of the socket -
tcp.receive_buffer_size
: Configures the receive buffer size of the socket
Long-lived idle connections
editA transport connection between two nodes is made up of a number of long-lived
TCP connections, some of which may be idle for an extended period of time.
Nonetheless, Elasticsearch requires these connections to remain open, and it
can disrupt the operation of your cluster if any inter-node connections are
closed by an external influence such as a firewall. It is important to
configure your network to preserve long-lived idle connections between
Elasticsearch nodes, for instance by leaving tcp.keep_alive
enabled and
ensuring that the keepalive interval is shorter than any timeout that might
cause idle connections to be closed, or by setting transport.ping_schedule
if
keepalives cannot be configured. Devices which drop connections when they reach
a certain age are a common source of problems to Elasticsearch clusters, and
must not be used.
Request compression
editBy default, the transport.compress
setting is false
and network-level
request compression is disabled between nodes in the cluster. This default
normally makes sense for local cluster communication as compression has a
noticeable CPU cost and local clusters tend to be set up with fast network
connections between nodes.
The transport.compress
setting always configures local cluster request
compression and is the fallback setting for remote cluster request compression.
If you want to configure remote request compression differently than local
request compression, you can set it on a per-remote cluster basis using the
cluster.remote.${cluster_alias}.transport.compress
setting.
Response compression
editThe compression settings do not configure compression for responses. Elasticsearch will compress a response if the inbound request was compressed—even when compression is not enabled. Similarly, Elasticsearch will not compress a response if the inbound request was uncompressed—even when compression is enabled.
Transport tracer
editThe transport layer has a dedicated tracer logger which, when activated, logs incoming and out going requests. The log can be dynamically activated
by setting the level of the org.elasticsearch.transport.TransportService.tracer
logger to TRACE
:
PUT _cluster/settings { "transient" : { "logger.org.elasticsearch.transport.TransportService.tracer" : "TRACE" } }
You can also control which actions will be traced, using a set of include and exclude wildcard patterns. By default every request will be traced except for fault detection pings:
PUT _cluster/settings { "transient" : { "transport.tracer.include" : "*", "transport.tracer.exclude" : "internal:coordination/fault_detection/*" } }