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Today there are a few places in the transport layer docs where we talk about communication between nodes _within a cluster_. We also use the transport layer for remote cluster connections, and these statements also apply there, but this is not clear from today's docs. This commit generalises these statements to make it clear that they apply to remote cluster connections too. It also adds a link from the docs on configuring TCP retries to the (deeply-buried) docs on preserving long-lived connections.
202 lines
8.3 KiB
Plaintext
202 lines
8.3 KiB
Plaintext
[[modules-transport]]
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=== Transport
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REST clients send requests to your {es} cluster over <<modules-http,HTTP>>, but
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the node that receives a client request cannot always handle it alone and must
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normally pass it on to other nodes for further processing. It does this using
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the transport networking layer. The transport layer is used for all internal
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communication between nodes within a cluster, all communication with the nodes
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of a <<modules-remote-clusters,remote cluster>>, and also by the
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`TransportClient` in the {es} Java API.
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[[transport-settings]]
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==== Transport settings
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The following settings can be configured for the internal transport that
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communicates over TCP. These settings also use the common
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<<modules-network,network settings>>.
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`transport.port`::
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A bind port range. Defaults to `9300-9400`.
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`transport.publish_port`::
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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`::
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The host address to bind the transport service to. Defaults to
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`transport.host` (if set) or `network.bind_host`.
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`transport.publish_host`::
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The host address to publish for nodes in the cluster to connect to.
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Defaults to `transport.host` (if set) or `network.publish_host`.
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`transport.host`::
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Used to set the `transport.bind_host` and the `transport.publish_host`.
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`transport.connect_timeout`::
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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`::
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Set to `true` to enable compression (`DEFLATE`) between
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all nodes. Defaults to `false`.
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`transport.ping_schedule`::
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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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`transport.tcp.no_delay`::
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Enable or disable the https://en.wikipedia.org/wiki/Nagle%27s_algorithm[TCP no delay]
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setting. Defaults to `network.tcp.no_delay`.
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`transport.tcp.keep_alive`::
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Configures the `SO_KEEPALIVE` option for this socket, which
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determines whether it sends TCP keepalive probes.
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Defaults to `network.tcp.keep_alive`.
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`transport.tcp.keep_idle`::
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Configures the `TCP_KEEPIDLE` option for this socket, which
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determines the time in seconds that a connection must be idle before
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starting to send TCP keepalive probes. Defaults to `network.tcp.keep_idle` if set,
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or the system default otherwise.
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This value cannot exceed `300` seconds. In cases where the system default
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is higher than `300`, the value is automatically lowered to `300`. Only applicable on
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Linux and macOS, and requires Java 11 or newer.
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`transport.tcp.keep_interval`::
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Configures the `TCP_KEEPINTVL` option for this socket,
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which determines the time in seconds between sending TCP keepalive probes.
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Defaults to `network.tcp.keep_interval` if set, or the system default otherwise.
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This value cannot exceed `300` seconds. In cases where the system default is higher than `300`,
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the value is automatically lowered to `300`. Only applicable on Linux and macOS,
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and requires Java 11 or newer.
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`transport.tcp.keep_count`::
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Configures the `TCP_KEEPCNT` option for this socket, which
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determines the number of unacknowledged TCP keepalive probes that may be
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sent on a connection before it is dropped. Defaults to `network.tcp.keep_count`
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if set, or the system default otherwise. Only applicable on Linux and macOS, and
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requires Java 11 or newer.
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transport.tcp.reuse_address::
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Should an address be reused or not. Defaults to `network.tcp.reuse_address`.
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`transport.tcp.send_buffer_size`::
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The size of the TCP send buffer (specified with <<size-units,size units>>).
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Defaults to `network.tcp.send_buffer_size`.
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`transport.tcp.receive_buffer_size`::
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The size of the TCP receive buffer (specified with <<size-units,size units>>).
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Defaults to `network.tcp.receive_buffer_size`.
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[[transport-profiles]]
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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 which to bind.
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* `bind_host`: The host to which to bind.
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* `publish_host`: The host which is published in informational APIs.
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Profiles also support all the other transport settings specified in the
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<<transport-settings,transport settings>> section, and use these as defaults.
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For example, `transport.profiles.client.tcp.reuse_address` can be explicitly
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configured, and defaults otherwise to `transport.tcp.reuse_address`.
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[[long-lived-connections]]
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===== Long-lived idle connections
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A transport connection between two nodes is made up of a number of long-lived
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TCP connections, some of which may be idle for an extended period of time.
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Nonetheless, Elasticsearch requires these connections to remain open, and it
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can disrupt the operation of your cluster if any inter-node connections are
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closed by an external influence such as a firewall. It is important to
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configure your network to preserve long-lived idle connections between
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Elasticsearch nodes, for instance by leaving `tcp.keep_alive` enabled and
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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. Devices which drop connections when they reach
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a certain age are a common source of problems to Elasticsearch clusters, and
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must not be used.
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[[request-compression]]
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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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[[response-compression]]
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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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[[transport-tracer]]
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==== Transport tracer
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The transport layer 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 setting the level of the `org.elasticsearch.transport.TransportService.tracer` logger to `TRACE`:
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[source,console]
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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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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,console]
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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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