Update readme and openapi spec

pageserver/src/http/openapi_spec.yml

@@ -307,6 +307,7 @@ paths:
       description: |
         Create a timeline. Returns new timeline id on success.\
         If no new timeline id is specified in parameters, it would be generated. It's an error to recreate the same timeline.
+        If no pg_version is specified, assume DEFAULT_PG_VERSION hardcoded in the pageserver.
       requestBody:
         content:
           application/json:
@@ -322,6 +323,8 @@ paths:
                 ancestor_start_lsn:
                   type: string
                   format: hex
+                pg_version:
+                  type: integer
       responses:
         "201":
           description: TimelineInfo

test_runner/README.md

@@ -60,6 +60,12 @@ Useful environment variables:
 
 `NEON_BIN`: The directory where neon binaries can be found.
 `POSTGRES_DISTRIB_DIR`: The directory where postgres distribution can be found.
+Since pageserver supports several postgres versions, `POSTGRES_DISTRIB_DIR` must contain
+a subdirectory for each version with naming convention `v{PG_VERSION}/`.
+Inside that dir, a `bin/postgres` binary should be present.
+`DEFAULT_PG_VERSION`: The version of Postgres to use,
+This is used to construct full path to the postgres binaries.
+Format is 2-digit major version nubmer, i.e. `DEFAULT_PG_VERSION="14"`
 `TEST_OUTPUT`: Set the directory where test state and test output files
 should go.
 `TEST_SHARED_FIXTURES`: Try to re-use a single pageserver for all the tests.