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3
CHANGELOG.md
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@ -2,8 +2,9 @@
IMPROVEMENTS:
* agent: Blocking queries on service-specific health and catalog endpoints now return a per-service `X-Consul-Index` improving watch performance on very busy clusters. [[GH-3890](https://github.com/hashicorp/consul/issues/3890)]
* agent: Blocking queries on service-specific health and catalog endpoints now return a per-service `X-Consul-Index` improving watch performance on very busy clusters. [[GH-3890](https://github.com/hashicorp/consul/issues/3890)]. **Note this may break blocking clients that relied on undocumented implementation details** as noted in the [upgrade docs](https://github.com/hashicorp/consul/blob/master/website/source/docs/upgrading.html.md#upgrade-from-version-106-to-higher).
* dns: Introduced a new config param to limit the number of A/AAAA records returned. [[GH-3940](https://github.com/hashicorp/consul/issues/3940)]
BUG FIXES:
* agent: Fixed an issue where the coordinate update endpoint was not correctly parsing the ACL token. [[GH-3892](https://github.com/hashicorp/consul/issues/3892)]

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website/source/docs/commands/index.html.md
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@ -27,15 +27,15 @@ usage: consul [--version] [--help] <command> [<args>]
Available commands are:
agent Runs a Consul agent
configtest Validate config file
catalog Interact with the catalog
event Fire a new event
exec Executes a command on Consul nodes
force-leave Forces a member of the cluster to enter the "left" state
info Provides debugging information for operators
info Provides debugging information for operators.
join Tell Consul agent to join cluster
keygen Generates a new encryption key
keyring Manages gossip layer encryption keys
kv Interact with the KV store
kv Interact with the key-value store
leave Gracefully leaves the Consul cluster and shuts down
lock Execute a command holding a lock
maint Controls node or service maintenance mode
@ -44,6 +44,8 @@ Available commands are:
operator Provides cluster-level tools for Consul operators
reload Triggers the agent to reload configuration files
rtt Estimates network round trip time between nodes
snapshot Saves, restores and inspects snapshots of Consul server state
validate Validate config files/directories
version Prints the Consul version
watch Watch for changes in Consul
```

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website/source/docs/guides/dns-cache.html.md
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## Stale Reads
Stale reads can be used to reduce latency and increase the throughput
of DNS queries. By default, all reads are serviced by a
[single leader node](/docs/internals/consensus.html).
These reads are strongly consistent but are limited by the throughput
of a single node. Doing a stale read allows any Consul server to
of DNS queries. The [settings](/docs/agent/options.html) used to control stale reads
are [`dns_config.allow_stale`](/docs/agent/options.html#allow_stale),
which must be set to enable stale reads, and [`dns_config.max_stale`](/docs/agent/options.html#max_stale)
which limits how stale results are allowed to be.
Since Consul 0.7.1, [`allow_stale`](/docs/agent/options.html#allow_stale)
is enabled by default, using a [`max_stale`](/docs/agent/options.html#max_stale)
value that defaults to a near-indefinite threshold (10 years) to allow DNS queries to continue to be served in the event
of a long outage with no leader. A new telemetry counter has also been added at
`consul.dns.stale_queries` to track when agents serve DNS queries that are stale
by more than 5 seconds.
Doing a stale read allows any Consul server to
service a query, but non-leader nodes may return data that is
out-of-date. By allowing data to be slightly stale, we get horizontal
read scalability. Now any Consul server can service the request, so we
increase throughput by the number of servers in a cluster.
The [settings](/docs/agent/options.html) used to control stale reads
are [`dns_config.allow_stale`](/docs/agent/options.html#allow_stale),
which must be set to enable stale reads, and
[`dns_config.max_stale`](/docs/agent/options.html#max_stale)
which limits how stale results are allowed to be.
Starting from Consul 0.7, [`allow_stale`](/docs/agent/options.html#allow_stale)
is enabled by default, using a [`max_stale`](/docs/agent/options.html#max_stale)
value that defaults to 5 seconds, meaning that we will use data from
any Consul server that is within 5 seconds of the leader. In Consul 0.7.1, the
default for `max_stale` was been increased from 5 seconds to a near-indefinite
threshold (10 years) to allow DNS queries to continue to be served in the event
of a long outage with no leader. A new telemetry counter has also been added at
`consul.dns.stale_queries` to track when agents serve DNS queries that are stale
by more than 5 seconds.
If you want to prevent
stale reads or limit how stale they can be, you can set `allow_stale`
to false or use a lower value for `max_stale`. Doing the first will ensure that
all reads are serviced by a [single leader node](/docs/internals/consensus.html).
The reads will then be strongly consistent but will be limited by the throughput
of a single node.
## Negative Response Caching