167 lines
6.7 KiB
Plaintext
167 lines
6.7 KiB
Plaintext
[[modules-transport]]
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== Transport
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The transport module is used for internal communication between nodes
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within the cluster. Each call that goes from one node to the other uses
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the transport module (for example, when an HTTP GET request is processed
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by one node, and should actually be processed by another node that holds
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the data). The transport module is also used for the `TransportClient` in the
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{es} Java API.
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The transport mechanism is completely asynchronous in nature, meaning
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that there is no blocking thread waiting for a response. The benefit of
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using asynchronous communication is first solving the
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http://en.wikipedia.org/wiki/C10k_problem[C10k problem], as well as
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being the ideal solution for scatter (broadcast) / gather operations such
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as search in Elasticsearch.
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[float]
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=== Transport Settings
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The internal transport communicates over TCP. You can configure it with the
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following settings:
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[cols="<,<",options="header",]
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|=======================================================================
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|Setting |Description
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|`transport.port` |A bind port range. Defaults to `9300-9400`.
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|`transport.publish_port` |The port that other nodes in the cluster
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should use when communicating with this node. Useful when a cluster node
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is behind a proxy or firewall and the `transport.port` is not directly
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addressable from the outside. Defaults to the actual port assigned via
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`transport.port`.
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|`transport.bind_host` |The host address to bind the transport service to. Defaults to `transport.host` (if set) or `network.bind_host`.
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|`transport.publish_host` |The host address to publish for nodes in the cluster to connect to. Defaults to `transport.host` (if set) or `network.publish_host`.
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|`transport.host` |Used to set the `transport.bind_host` and the `transport.publish_host` Defaults to `transport.host` or `network.host`.
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|`transport.connect_timeout` |The connect timeout for initiating a new connection (in
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time setting format). Defaults to `30s`.
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|`transport.compress` |Set to `true` to enable compression (`DEFLATE`) between
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all nodes. Defaults to `false`.
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|`transport.ping_schedule` | Schedule a regular application-level ping message
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to ensure that transport connections between nodes are kept alive. Defaults to
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`5s` in the transport client and `-1` (disabled) elsewhere. It is preferable
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to correctly configure TCP keep-alives instead of using this feature, because
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TCP keep-alives apply to all kinds of long-lived connections and not just to
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transport connections.
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|=======================================================================
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It also uses the common
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<<modules-network,network settings>>.
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[float]
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==== Transport Profiles
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Elasticsearch allows you to bind to multiple ports on different interfaces by
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the use of transport profiles. See this example configuration
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[source,yaml]
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--------------
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transport.profiles.default.port: 9300-9400
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transport.profiles.default.bind_host: 10.0.0.1
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transport.profiles.client.port: 9500-9600
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transport.profiles.client.bind_host: 192.168.0.1
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transport.profiles.dmz.port: 9700-9800
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transport.profiles.dmz.bind_host: 172.16.1.2
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--------------
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The `default` profile is special. It is used as a fallback for any other
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profiles, if those do not have a specific configuration setting set, and is how
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this node connects to other nodes in the cluster.
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The following parameters can be configured on each transport profile, as in the
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example above:
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* `port`: The port to bind to
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* `bind_host`: The host to bind
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* `publish_host`: The host which is published in informational APIs
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* `tcp.no_delay`: Configures the `TCP_NO_DELAY` option for this socket
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* `tcp.keep_alive`: Configures the `SO_KEEPALIVE` option for this socket
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* `tcp.reuse_address`: Configures the `SO_REUSEADDR` option for this socket
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* `tcp.send_buffer_size`: Configures the send buffer size of the socket
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* `tcp.receive_buffer_size`: Configures the receive buffer size of the socket
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[float]
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==== Long-lived idle connections
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Elasticsearch opens a number of long-lived TCP connections between each pair of
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nodes in the cluster, and some of these connections may be idle for an extended
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period of time. Nonetheless, Elasticsearch requires these connections to remain
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open, and it can disrupt the operation of the cluster if any inter-node
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connections are closed by an external influence such as a firewall. It is
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important to configure your network to preserve long-lived idle connections
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between Elasticsearch nodes, for instance by leaving `tcp.keep_alive` enabled
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and ensuring that the keepalive interval is shorter than any timeout that might
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cause idle connections to be closed, or by setting `transport.ping_schedule` if
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keepalives cannot be configured.
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[float]
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==== Transport Compression
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[float]
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===== Request Compression
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By default, the `transport.compress` setting is `false` and network-level
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request compression is disabled between nodes in the cluster. This default
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normally makes sense for local cluster communication as compression has a
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noticeable CPU cost and local clusters tend to be set up with fast network
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connections between nodes.
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The `transport.compress` setting always configures local cluster request
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compression and is the fallback setting for remote cluster request compression.
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If you want to configure remote request compression differently than local
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request compression, you can set it on a per-remote cluster basis using the
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<<remote-cluster-settings,`cluster.remote.${cluster_alias}.transport.compress` setting>>.
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[float]
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===== Response Compression
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The compression settings do not configure compression for responses. {es} will
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compress a response if the inbound request was compressed--even when compression
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is not enabled. Similarly, {es} will not compress a response if the inbound
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request was uncompressed--even when compression is enabled.
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[float]
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=== Transport Tracer
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The transport module has a dedicated tracer logger which, when activated, logs incoming and out going requests. The log can be dynamically activated
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by settings the level of the `org.elasticsearch.transport.TransportService.tracer` logger to `TRACE`:
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[source,js]
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--------------------------------------------------
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PUT _cluster/settings
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{
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"transient" : {
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"logger.org.elasticsearch.transport.TransportService.tracer" : "TRACE"
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}
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}
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--------------------------------------------------
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// CONSOLE
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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
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except for fault detection pings:
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[source,js]
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--------------------------------------------------
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PUT _cluster/settings
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{
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"transient" : {
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"transport.tracer.include" : "*",
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"transport.tracer.exclude" : "internal:coordination/fault_detection/*"
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}
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}
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--------------------------------------------------
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// CONSOLE
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