Allow CLI flags to be specified by environment variable #152
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Allow the flags: * `--postgres-url` * `--schema` * `--pgroll-schema` To be set via these env vars: * `PGROLL_PG_URL` * `PGROLL_SCHEMA` * `PGROLL_STATE_SCHEMA`
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Change LGTM, can you update the docs to explain the new env vars? |
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The docs for the env vars are included in the new |
Set the session `lock_timeout` for the connection used by `pgroll` to run DDL operations. The need to set `lock_timeout` for DDL operations to achieve zero downtime migrations is well documented [[1](https://xata.io/blog/postgres-schema-changes-pita#locking-gotchas)], [[2](https://medium.com/paypal-tech/postgresql-at-scale-database-schema-changes-without-downtime-20d3749ed680#00dc)]. When a DDL transaction attempts to take an `ACCESS EXCLUSIVE` lock on a table while another transaction holds a conflicting lock (such as a long-running `SELECT` query's `ACCESS SHARE` lock), other queries will queue up behind the DDL transaction until it is able to obtain the exclusive lock thus locking out reads from the table and causing downtime. By setting a `lock_timeout` the DDL transaction will abort if it is unable to acquire the lock before the timeout, freeing any other queries that were queued behind it. The approach taken here is to set the `lock_timeout` at the session level. This assumes that `pgroll` has a direct connection to the Postgres instance rather than going through a connection pooler like PGBouncer. PGBouncer's statement or transaction mode may swap out the connection between transactions/statements meaning that the lock timeout may not be applied correctly. See [[3](https://jpcamara.com/2023/04/12/pgbouncer-is-useful.html)] for a more detailed discussion of PGBouncer's behaviour here. The new `--lock-timeout` flag (and `PGROLL_LOCK_TIMEOUT` env var) is used to control the timeout duration. Fixes #65
exekias
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andrew-farries
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Fix the `pgroll status` command so that it shows the status for the correct schema (ie the one set by the `--schema` flag, or `"public"` by default). Prior to this the command would show the status for the `--pgroll-schema` (`"pgroll"` by default). This appears to have been broken since #152.
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Bind command line arguments to env vars. Allow the flags:
--postgres-url--schema--pgroll-schemaTo be set via these env vars:
PGROLL_PG_URLPGROLL_SCHEMAPGROLL_STATE_SCHEMAIf a flag is specified both via a CLI flag and an env var the CLI flag takes priority.