62 lines
2.4 KiB
Plaintext
62 lines
2.4 KiB
Plaintext
---
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layout: commands
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page_title: 'Commands: Event'
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description: >-
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The event command provides a mechanism to fire a custom user event to an
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entire datacenter. These events are opaque to Consul, but they can be used to
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build scripting infrastructure to do automated deploys, restart services, or
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perform any other orchestration action. Events can be handled by using a
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watch.
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---
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# Consul Event
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Command: `consul event`
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The `event` command provides a mechanism to fire a custom user event to an
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entire datacenter. These events are opaque to Consul, but they can be used
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to build scripting infrastructure to do automated deploys, restart services,
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or perform any other orchestration action. Events can be handled by
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[using a watch](/docs/agent/watches).
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Under the hood, events are propagated using the [gossip protocol](/docs/internals/gossip).
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While the details are not important for using events, an understanding of
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the semantics is useful. The gossip layer will make a best-effort to deliver
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the event, but there is **no guaranteed delivery**. Unlike most Consul data, which is
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replicated using [consensus](/docs/internals/consensus), event data
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is purely peer-to-peer over gossip. This means it is not persisted and does
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not have a total ordering. In practice, this means you cannot rely on the
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order of message delivery. An advantage however is that events can still
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be used even in the absence of server nodes or during an outage.
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The underlying gossip also sets limits on the size of a user event
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message. It is hard to give an exact number, as it depends on various
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parameters of the event, but the payload should be kept very small
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(< 100 bytes). Specifying too large of an event will return an error.
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## Usage
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Usage: `consul event [options] [payload]`
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The only required option is `-name` which specifies the event name. An optional
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payload can be provided as the final argument.
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#### API Options
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@include 'http_api_options_client.mdx'
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@include 'http_api_options_server.mdx'
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#### Command Options
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- `-name` - The name of the event.
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- `-node` - Regular expression to filter nodes which should evaluate the event.
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- `-service` - Regular expression to filter to only nodes with matching services.
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- `-tag` - Regular expression to filter to only nodes with a service that has
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a matching tag. This must be used with `-service`. As an example, you may
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do `-service mysql -tag secondary`.
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