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