49 lines
1.4 KiB
Markdown
49 lines
1.4 KiB
Markdown
---
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layout: "docs"
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page_title: "Consul Protocol Compatibility Promise"
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sidebar_current: "docs-upgrading-compatibility"
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---
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# Protocol Compatibility Promise
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We expect Consul to run in large clusters as long-running agents. Because
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upgrading agents in this sort of environment relies heavily on protocol
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compatibility, this page makes it clear on our promise to keeping different
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Consul versions compatible with each other.
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We promise that every subsequent release of Consul will remain backwards
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compatible with _at least_ one prior version. Concretely: version 0.5 can
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speak to 0.4 (and vice versa), but may not be able to speak to 0.1.
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The backwards compatibility is automatic unless otherwise noted. Consul agents by
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default will speak the latest protocol, but can understand earlier
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ones. If speaking an earlier protocol, _new features may not be available_.
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The ability for an agent to speak an earlier protocol is so that they
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can be upgraded without cluster disruption.
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This compatibility guarantee makes it possible to upgrade Consul agents one
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at a time, one version at a time. For more details on the specifics of
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upgrading, see the [upgrading page](/docs/upgrading.html).
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## Protocol Compatibility Table
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<table class="table table-bordered table-striped">
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<tr>
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<th>Version</th>
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<th>Protocol Compatibility</th>
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</tr>
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<tr>
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<td>0.1</td>
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<td>1</td>
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</tr>
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<tr>
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<td>0.2</td>
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<td>1</td>
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</tr>
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<tr>
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<td>0.3</td>
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<td>1, 2</td>
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</tr>
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</table>
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