mirror of https://github.com/hashicorp/consul
56 lines
2.9 KiB
Markdown
56 lines
2.9 KiB
Markdown
---
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layout: docs
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page_title: Consul vs. Serf
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sidebar_title: Serf
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description: >-
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Serf is a node discovery and orchestration tool and is the only tool discussed
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so far that is built on an eventually-consistent gossip model with no
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centralized servers. It provides a number of features, including group
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membership, failure detection, event broadcasts, and a query mechanism.
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However, Serf does not provide any high-level features such as service
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discovery, health checking or key/value storage. Consul is a complete system
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providing all of those features.
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---
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# Consul vs. Serf
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[Serf](https://www.serf.io) is a node discovery and orchestration tool and is the only
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tool discussed so far that is built on an eventually-consistent gossip model
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with no centralized servers. It provides a number of features, including group
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membership, failure detection, event broadcasts, and a query mechanism. However,
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Serf does not provide any high-level features such as service discovery, health
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checking or key/value storage. Consul is a complete system providing all of those
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features.
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The internal [gossip protocol](/docs/internals/gossip) used within Consul is in
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fact powered by the Serf library: Consul leverages the membership and failure detection
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features and builds upon them to add service discovery. By contrast, the discovery
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feature of Serf is at a node level, while Consul provides a service and node level
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abstraction.
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The health checking provided by Serf is very low level and only indicates if the
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agent is alive. Consul extends this to provide a rich health checking system
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that handles liveness in addition to arbitrary host and service-level checks.
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Health checks are integrated with a central catalog that operators can easily
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query to gain insight into the cluster.
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The membership provided by Serf is at a node level, while Consul focuses
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on the service level abstraction, mapping single nodes to multiple services.
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This can be simulated in Serf using tags, but it is much more limited and does
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not provide useful query interfaces. Consul also makes use of a strongly-consistent
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catalog while Serf is only eventually-consistent.
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In addition to the service level abstraction and improved health checking,
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Consul provides a key/value store and support for multiple datacenters.
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Serf can run across the WAN but with degraded performance. Consul makes use
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of [multiple gossip pools](/docs/internals/architecture) so that
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the performance of Serf over a LAN can be retained while still using it over
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a WAN for linking together multiple datacenters.
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Consul is opinionated in its usage while Serf is a more flexible and
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general purpose tool. In [CAP](https://en.wikipedia.org/wiki/CAP_theorem) terms,
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Consul uses a CP architecture, favoring consistency over availability. Serf is an
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AP system and sacrifices consistency for availability. This means Consul cannot
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operate if the central servers cannot form a quorum while Serf will continue to
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function under almost all circumstances.
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