mirror of https://github.com/hashicorp/consul
47 lines
2.2 KiB
Markdown
47 lines
2.2 KiB
Markdown
---
|
|
layout: docs
|
|
page_title: Consul vs. SkyDNS
|
|
sidebar_title: SkyDNS
|
|
description: >-
|
|
SkyDNS is a tool designed to provide service discovery. It uses multiple
|
|
central servers that are strongly-consistent and fault-tolerant. Nodes
|
|
register services using an HTTP API, and queries can be made over HTTP or DNS
|
|
to perform discovery.
|
|
---
|
|
|
|
# Consul vs. SkyDNS
|
|
|
|
SkyDNS is a tool designed to provide service discovery.
|
|
It uses multiple central servers that are strongly-consistent and
|
|
fault-tolerant. Nodes register services using an HTTP API, and
|
|
queries can be made over HTTP or DNS to perform discovery.
|
|
|
|
Consul is very similar but provides a superset of features. Consul
|
|
also relies on multiple central servers to provide strong consistency
|
|
and fault tolerance. Nodes can use an HTTP API or use an agent to
|
|
register services, and queries are made over HTTP or DNS.
|
|
|
|
However, the systems differ in many ways. Consul provides a much richer
|
|
health checking framework with support for arbitrary checks and
|
|
a highly scalable failure detection scheme. SkyDNS relies on naive
|
|
heartbeating and TTLs, an approach which has known scalability issues.
|
|
Additionally, the heartbeat only provides a limited liveness check
|
|
versus the rich health checks that Consul performs.
|
|
|
|
Multiple datacenters can be supported by using "regions" in SkyDNS;
|
|
however, the data is managed and queried from a single cluster. If servers
|
|
are split between datacenters, the replication protocol will suffer from
|
|
very long commit times. If all the SkyDNS servers are in a central datacenter,
|
|
then connectivity issues can cause entire datacenters to lose availability.
|
|
Additionally, even without a connectivity issue, query performance will
|
|
suffer as requests must always be performed in a remote datacenter.
|
|
|
|
Consul supports multiple datacenters out of the box, and it purposely
|
|
scopes the managed data to be per-datacenter. This means each datacenter
|
|
runs an independent cluster of servers. Requests are forwarded to remote
|
|
datacenters if necessary; requests for services within a datacenter
|
|
never go over the WAN, and connectivity issues between datacenters do not
|
|
affect availability within a datacenter. Additionally, the unavailability
|
|
of one datacenter does not affect the discovery of services
|
|
in any other datacenter.
|