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Website: very minor tweaks to docs/internals/anti-entropy.html.

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Ryan Breen 2015-03-29 10:53:49 -04:00
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website/source/docs/internals/anti-entropy.html.markdown
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@ -57,17 +57,20 @@ consolidated and consistent view of the cluster.
<a name="anti-entropy"></a> <a name="anti-entropy"></a>
### Anti-Entropy ### Anti-Entropy
Consul has a clear separation between the global service catalog and the agent Entropy is the tendency of systems to become increasingly disordered. Consul's
local state as discussed above. Reconciling these two is done using an anti-entropy mechanisms are designed to counter this tendency, to keep the
anti-entropy mechanism. state of the cluster ordered even through failures of its components.
Anti-entropy is a syncronization of the local agent state and the catalog. For Consul has a clear separation between the global service catalog and the agent
example, when a user registers a new service or check with the agent, the agent local state as discussed above. The anti-entropy mechanism reconciles these two
in turn notifies the catalog that this new check exists. Similarly, when a check views of the world: anti-entropy is a syncronization of the local agent state and
is deleted from the agent, it is consequently removed from the catalog as well. the catalog. For example, when a user registers a new service or check with the
agent, the agent in turn notifies the catalog that this new check exists.
Similarly, when a check is deleted from the agent, it is consequently removed from
the catalog as well.
Anti-entropy is also used to update availability information. As agents run Anti-entropy is also used to update availability information. As agents run
their health checks, their status may change, in which case their new status their health checks, their status may change in which case their new status
is synced to the catalog. Using this information, the catalog can respond is synced to the catalog. Using this information, the catalog can respond
intelligently to queries about its nodes and services based on their intelligently to queries about its nodes and services based on their
availability. availability.
@ -76,7 +79,7 @@ During this synchronization, the catalog is also checked for correctness. If
any services or checks exist in the catalog that the agent is not aware of, they any services or checks exist in the catalog that the agent is not aware of, they
will be automatically removed to make the catalog reflect the proper set of will be automatically removed to make the catalog reflect the proper set of
services and health information for that agent. Consul treats the state of the services and health information for that agent. Consul treats the state of the
agent as authoritative, meaning if there are any differences between the agent agent as authoritative; if there are any differences between the agent
and catalog view, the agent local view will always be used. and catalog view, the agent local view will always be used.
### Periodic Synchronization ### Periodic Synchronization
@ -87,9 +90,9 @@ status to the catalog. This ensures that the catalog closely matches the agent's
true state. This also allows Consul to re-populate the service catalog even in true state. This also allows Consul to re-populate the service catalog even in
the case of complete data loss. the case of complete data loss.
The amount of time between periodic anti-entropy runs will vary based on cluster To avoid saturation, the amount of time between periodic anti-entropy runs will
size to avoid saturation. The table below describes the periodic sync times and vary based on cluster size. The table below defines the relationship between
how they change as the Consul cluster grows. cluster size and sync interval:
<table class="table table-bordered table-striped"> <table class="table table-bordered table-striped">
<tr> <tr>