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c141455049
Our documentation has a history of using a document's name as a way to link to it, such as "See [workers.md]() for details". This makes sense when you're traversing a directory of files, but less sense when the files are abstracted away - as they are on the documentation website. This PR changes the links to various documentation pages to something that fits better into the surrounding sentence, as you would when making any hyperlink on the web.
37 lines
1.5 KiB
Markdown
37 lines
1.5 KiB
Markdown
# Replication Architecture
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## Motivation
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We'd like to be able to split some of the work that synapse does into
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multiple python processes. In theory multiple synapse processes could
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share a single postgresql database and we\'d scale up by running more
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synapse processes. However much of synapse assumes that only one process
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is interacting with the database, both for assigning unique identifiers
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when inserting into tables, notifying components about new updates, and
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for invalidating its caches.
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So running multiple copies of the current code isn't an option. One way
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to run multiple processes would be to have a single writer process and
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multiple reader processes connected to the same database. In order to do
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this we'd need a way for the reader process to invalidate its in-memory
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caches when an update happens on the writer. One way to do this is for
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the writer to present an append-only log of updates which the readers
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can consume to invalidate their caches and to push updates to listening
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clients or pushers.
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Synapse already stores much of its data as an append-only log so that it
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can correctly respond to `/sync` requests so the amount of code changes
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needed to expose the append-only log to the readers should be fairly
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minimal.
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## Architecture
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### The Replication Protocol
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See [the TCP replication documentation](tcp_replication.md).
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### The Slaved DataStore
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There are read-only version of the synapse storage layer in
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`synapse/replication/slave/storage` that use the response of the
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replication API to invalidate their caches.
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