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Merge pull request #673 from ryanbreen/watches 

Very minor tweaks to docs/agent/watches
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Armon Dadgar 2015-02-05 09:43:54 -08:00
parent 7caedac17a f381aa554a
commit 7724fd8774
1 changed files with 26 additions and 25 deletions
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@ -3,19 +3,18 @@ layout: "docs"
page_title: "Watches"
sidebar_current: "docs-agent-watches"
description: |-
Watches are a way of specifying a view of data (list of nodes, KV pairs, health checks, etc) which is monitored for any updates. When an update is detected, an external handler is invoked. A handler can be any executable. As an example, you could watch the status of health checks and notify an external system when a check is critical.
Watches are a way of specifying a view of data (e.g. list of nodes, KV pairs, health checks) which is monitored for updates. When an update is detected, an external handler is invoked. A handler can be any executable. As an example, you could watch the status of health checks and notify an external system when a check is critical.
---
# Watches
Watches are a way of specifying a view of data (list of nodes, KV pairs,
health checks, etc) which is monitored for any updates. When an update
is detected, an external handler is invoked. A handler can be any
executable. As an example, you could watch the status of health checks and
notify an external system when a check is critical.
Watches are a way of specifying a view of data (e.g. list of nodes, KV pairs, health
checks) which is monitored for updates. When an update is detected, an external handler
is invoked. A handler can be any executable. As an example, you could watch the status
of health checks and notify an external system when a check is critical.
Watches are implemented using blocking queries in the [HTTP API](/docs/agent/http.html).
Agents automatically make the proper API calls to watch for changes,
Agents automatically make the proper API calls to watch for changes
and inform a handler when the data view has updated.
Watches can be configured as part of the [agent's configuration](/docs/agent/options.html),
@ -23,27 +22,28 @@ causing them to run once the agent is initialized. Reloading the agent configura
allows for adding or removing watches dynamically.
Alternatively, the [watch command](/docs/commands/watch.html) enables a watch to be
started outside of the agent. This can be used by an operator to inspect data in Consul,
started outside of the agent. This can be used by an operator to inspect data in Consul
or to easily pipe data into processes without being tied to the agent lifecycle.
In either case, the `type` of the watch must be specified. Each type of watch
supports different parameters, both required and optional. These options are specified
in a JSON body when using agent configuration, or as CLI flags for the watch command.
supports different parameters, some required and some optional. These options are specified
in a JSON body when using agent configuration or as CLI flags for the watch command.
## Handlers
The watch specification specifies the view of data to be monitored.
Once that view is updated the specified handler is invoked. The handler
The watch configuration specifies the view of data to be monitored.
Once that view is updated, the specified handler is invoked. The handler
can be any executable.
A handler should read its input from stdin, and expect to read
A handler should read its input from stdin and expect to read
JSON formatted data. The format of the data depends on the type of the
watch. Each watch type documents the format type, and because they
watch. Each watch type documents the format type. Because they
map directly to an HTTP API, handlers should expect the input to
match the format of the API.
Additionally, the `CONSUL_INDEX` environmental variable will be set.
This maps to the `X-Consul-Index` value from the [HTTP API](/docs/agent/http.html).
Additionally, the `CONSUL_INDEX` environment variable will be set.
This maps to the `X-Consul-Index` value in responses from the
[HTTP API](/docs/agent/http.html).
## Global Parameters
@ -56,7 +56,7 @@ are a few global parameters that all watches support:
## Watch Types
The following types are supported, with more documentation below:
The following types are supported. Detailed documentation on each is below:
* `key` - Watch a specific KV pair
* `keyprefix` - Watch a prefix in the KV store
@ -215,10 +215,11 @@ An example of the output of this command:
### Type: service
The "service" watch type is used to monitor the providers
of a single service. It requires the "service" parameter,
but optionally takes "tag" and "passingonly". The "tag" parameter
will filter by tag, and "passingonly" is a boolean that will
filter to only the instances passing all health checks.
of a single service. It requires the "service" parameter
and optionally takes the parameters "tag" and "passingonly".
The "tag" parameter will filter by tag, and "passingonly" is
a boolean that will filter to only the instances passing all
health checks.
This maps to the `/v1/health/service` API internally.
@ -281,10 +282,10 @@ An example of the output of this command:
The "checks" watch type is used to monitor the checks of a given
service or those in a specific state. It optionally takes the "service"
parameter to filter to a specific service, or "state" to filter
to a specific state. By default, it will watch all checks.
parameter to filter to a specific service or the "state" parameter to
filter to a specific state. By default, it will watch all checks.
This maps to the `/v1/health/state/` API if monitoring by state,
This maps to the `/v1/health/state/` API if monitoring by state
or `/v1/health/checks/` if monitoring by service.
An example of the output of this command:
@ -308,7 +309,7 @@ An example of the output of this command:
The "event" watch type is used to monitor for custom user
events. These are fired using the [consul event](/docs/commands/event.html) command.
It takes only a single optional "name" parameter, which restricts
It takes only a single optional "name" parameter which restricts
the watch to only events with the given name.
This maps to the `v1/event/list` API internally.