88addd71fc
Well, they still do go to that DB by default, but our docs give a better command to users, which would do the right thing.
85 lines
3.8 KiB
Markdown
85 lines
3.8 KiB
Markdown
# Importing an existing Postgres database from another installation (optional)
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Run this if you'd like to import your database from a previous installation.
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(don't forget to import your Synapse `media_store` files as well - see [the importing-synape-media-store guide](importing-synapse-media-store.md)).
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## Prerequisites
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For this to work, **the database name in Postgres must match** what this playbook uses.
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This playbook uses a Postgres database name of `synapse` by default (controlled by the `matrix_synapse_database_database` variable).
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If your database name differs, be sure to change `matrix_synapse_database_database` to your desired name and to re-run the playbook before proceeding.
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The playbook supports importing Postgres dump files in **text** (e.g. `pg_dump > dump.sql`) or **gzipped** formats (e.g. `pg_dump | gzip -c > dump.sql.gz`).
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Importing multiple databases (as dumped by `pg_dumpall`) is also supported.
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Before doing the actual import, **you need to upload your Postgres dump file to the server** (any path is okay).
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## Importing
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To import, run this command (make sure to replace `<server-path-to-postgres-dump.sql>` with a file path on your server):
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```sh
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ansible-playbook -i inventory/hosts setup.yml \
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--extra-vars='postgres_default_import_database=synapse server_path_postgres_dump=<server-path-to-postgres-dump.sql>' \
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--tags=import-postgres
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```
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We specify the `synapse` database as the default import database. If your dump is a single-database dump (`pg_dump`), then we need to tell it where to go to. If you're redefining `matrix_synapse_database_database` to something other than `synapse`, please adjust it here too. For database dumps spanning multiple databases (`pg_dumpall`), you can remove the `postgres_default_import_database` definition (but it doesn't hurt to keep it too).
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**Note**: `<server-path-to-postgres-dump.sql>` must be a file path to a Postgres dump file on the server (not on your local machine!).
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## Troubleshooting
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A table ownership issue can occur if you are importing from a Synapse installation which was both:
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- migrated from SQLite to Postgres, and
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- used a username other than 'synapse'
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In this case you may run into the following error during the import task:
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```
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"ERROR: role \"synapse_user\" does not exist"
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```
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where `synapse_user` is the database username from the previous Synapse installation.
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This can be verified by examining the dump for ALTER TABLE statements which set OWNER TO that username:
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```Shell
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$ grep "ALTER TABLE" homeserver.sql"
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ALTER TABLE public.access_tokens OWNER TO synapse_user;
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ALTER TABLE public.account_data OWNER TO synapse_user;
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ALTER TABLE public.account_data_max_stream_id OWNER TO synapse_user;
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ALTER TABLE public.account_validity OWNER TO synapse_user;
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ALTER TABLE public.application_services_state OWNER TO synapse_user;
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...
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```
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It can be worked around by changing the username to `synapse`, for example by using `sed`:
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```Shell
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$ sed -i "s/synapse_user/synapse/g" homeserver.sql"
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```
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This uses sed to perform an 'in-place' (`-i`) replacement globally (`/g`), searching for `synapse user` and replacing with `synapse` (`s/synapse_user/synapse`). If your database username was different, change `synapse_user` to that username instead.
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Note that if the previous import failed with an error it may have made changes which are incompatible with re-running the import task right away; if you do so it may fail with an error such as:
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```
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ERROR: relation \"access_tokens\" already exists
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```
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In this case you can use the command suggested in the import task to clear the database before retrying the import:
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```Shell
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# systemctl stop matrix-postgres
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# rm -rf /matrix/postgres/data/*
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# systemctl start matrix-postgres
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```
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Once the database is clear and the ownership of the tables has been fixed in the SQL file, the import task should succeed.
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