Drop support for Python < 3.6

The Python syntax is upgrade accordingly by enabling
pyupgrade in Ruff configuration.

The following commands were executed:
 - `ruff check --fix`
 - `ruff check --fix --unsafe-fixes`
 - `ruff format`

We added python 3.7 in the lint tests job in CI. And we also check for
obvious syntax errors on Python3.6.

.github/workflows/python_lint.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.12"]
+        python-version: ["3.7", "3.12"]
     steps:
     - name: Checkout repository
       uses: actions/checkout@v4
@@ -27,3 +27,29 @@ jobs:
       run: |
         ruff check --output-format=github .
         ruff format --check
+
+  python36:
+    # This job will detect InvalidSyntax error on Python 3.6.
+    # A success doesn't necessarily mean that PoWA works.
+    runs-on: ubuntu-20.04
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v4
+
+    - name: Set Python Version
+      uses: actions/setup-python@v5
+      with:
+        python-version: 3.6
+
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -r requirements.txt
+
+    - name: Configure PoWA
+      run: |
+        cp powa-web.conf-dist powa-web.conf
+
+    - name: Check for syntax errors
+      run: |
+        timeout 1 python run_powa.py || code=$?; if [[ $code -ne 124 && $code -ne 0 ]]; then exit $code; fi

.ruff.toml

@@ -8,7 +8,8 @@ line-length = 79
 # In addition, we also enable:
 # `Q` for "flake8-quotes"
 # `I` for "isort"
-extend-select = ["Q", "I"]
+# `UP` for "pyupgrade"
+extend-select = ["Q", "I", "UP"]
 
 [lint.per-file-ignores]
 "powa/__init__.py" = ["E402"]

powa/__init__.py

@@ -1,5 +1,3 @@
-from __future__ import print_function
-
 """
 Powa main application.
 """
@@ -63,36 +61,36 @@ def make_app(**kwargs):
     parse_options()
 
     URLS = [
-        U(r"%slogin/" % options.url_prefix, LoginHandler, name="login"),
-        U(r"%slogout/" % options.url_prefix, LogoutHandler, name="logout"),
+        U(rf"{options.url_prefix}login/", LoginHandler, name="login"),
+        U(rf"{options.url_prefix}logout/", LogoutHandler, name="logout"),
         U(
-            r"%sreload_collector/" % options.url_prefix,
+            rf"{options.url_prefix}reload_collector/",
             CollectorReloadHandler,
             name="reload_collector",
         ),
         U(
-            r"%sforce_snapshot/(\d+)" % options.url_prefix,
+            rf"{options.url_prefix}force_snapshot/(\d+)",
             CollectorForceSnapshotHandler,
             name="force_snapshot",
         ),
         U(
-            r"%srefresh_db_cat/" % options.url_prefix,
+            rf"{options.url_prefix}refresh_db_cat/",
             CollectorDbCatRefreshHandler,
             name="refresh_db_cat",
         ),
         U(
-            r"%sserver/select" % options.url_prefix,
+            rf"{options.url_prefix}server/select",
             ServerSelector,
             name="server_selector",
         ),
         U(
-            r"%sdatabase/select" % options.url_prefix,
+            rf"{options.url_prefix}database/select",
             DatabaseSelector,
             name="database_selector",
         ),
-        U(r"%s" % options.url_prefix, IndexHandler, name="index"),
+        U(rf"{options.url_prefix}", IndexHandler, name="index"),
         U(
-            r"%sserver/(\d+)/database/([^\/]+)/suggest/" % options.url_prefix,
+            rf"{options.url_prefix}server/(\d+)/database/([^\/]+)/suggest/",
             IndexSuggestionHandler,
             name="index_suggestion",
         ),
@@ -124,9 +122,9 @@ def make_app(**kwargs):
         URLS,
         ui_modules=ui_modules,
         ui_methods=ui_methods,
-        login_url=("%slogin/" % options.url_prefix),
+        login_url=(f"{options.url_prefix}login/"),
         static_path=os.path.join(POWA_ROOT, "static"),
-        static_url_prefix=("%sstatic/" % options.url_prefix),
+        static_url_prefix=(f"{options.url_prefix}static/"),
         cookie_secret=options.cookie_secret,
         template_path=os.path.join(POWA_ROOT, "templates"),
         **kwargs,

powa/collector.py

@@ -3,8 +3,6 @@
 collector handling.
 """
 
-from __future__ import absolute_import
-
 import json
 from powa.dashboards import MetricGroupDef
 from powa.framework import AuthHandler

powa/compat.py

@@ -6,8 +6,6 @@
 
 """
 
-from __future__ import absolute_import
-
 import json
 import psycopg2
 from psycopg2 import extensions
@@ -37,7 +35,7 @@ def __new__(cls, name, _, d):
     return type.__new__(metaclass, "temporary_class", (), {})
 
 
-class classproperty(object):
+class classproperty:
     """
     A descriptor similar to property, but using the class.
     """

powa/config.py

@@ -2,8 +2,6 @@
 Dashboard for the configuration summary page.
 """
 
-from __future__ import absolute_import
-
 import json
 from powa.collector import CollectorServerDetail
 from powa.dashboards import (
@@ -418,7 +416,7 @@ def post_process(self, data, server, **kwargs):
             data["messages"] = {
                 "alert": [
                     "Could not retrieve extensions"
-                    + " on remote server: %s" % errmsg
+                    + f" on remote server: {errmsg}"
                 ]
             }
             return data
@@ -528,7 +526,7 @@ def post_process(self, data, server, **kwargs):
             data["messages"] = {
                 "alert": [
                     "Could not retrieve extensions"
-                    + " on remote server: %s" % errmsg
+                    + f" on remote server: {errmsg}"
                 ]
             }
             return data

powa/dashboards.py

@@ -275,7 +275,7 @@ def url_name(cls):
         """
         Returns the default url_name for this data source.
         """
-        return "datasource_%s" % cls.__name__
+        return f"datasource_{cls.__name__}"
 
     @classproperty
     def parameterized_json(cls, handler, **parms):
@@ -310,14 +310,14 @@ def bind(self, group):
         """
 
         if self._group is not None:
-            raise ValueError("Already bound to %s" % self._group)
+            raise ValueError(f"Already bound to {self._group}")
         self._group = group
 
     def _fqn(self):
         """
         Return the fully qualified name of this metric.
         """
-        return "%s.%s" % (self._group.name, self.name)
+        return f"{self._group.name}.{self.name}"
 
 
 class Dashboard(JSONizable):
@@ -502,7 +502,7 @@ def _validate(self):
             if any(m._group != mg1 for m in self.metrics):
                 raise ValueError(
                     "A grid is not allowed to have metrics from different "
-                    "groups. (title: %s)" % self.title
+                    f"groups. (title: {self.title})"
                 )
 
     def to_json(self):
@@ -559,7 +559,7 @@ def to_json(self):
         return values
 
 
-class Declarative(object):
+class Declarative:
     """
     Base class for declarative classes.
     """
@@ -606,12 +606,12 @@ def __new__(meta, name, bases, dct):
             if isinstance(val, Metric):
                 dct.pop(key)
                 dct["metrics"][key] = val
-        return super(MetaMetricGroup, meta).__new__(meta, name, bases, dct)
+        return super().__new__(meta, name, bases, dct)
 
     def __init__(cls, name, bases, dct):
         for metric in dct.get("metrics").values():
             metric.bind(cls)
-        super(MetaMetricGroup, cls).__init__(name, bases, dct)
+        super().__init__(name, bases, dct)
 
     def __getattr__(cls, key):
         if key not in cls.metrics:
@@ -705,7 +705,7 @@ def metrics(self):
         return self._metrics
 
 
-class DashboardPage(object):
+class DashboardPage:
     """
     A Dashboard page ties together a set of datasources, and a dashboard.
 
@@ -745,7 +745,7 @@ def url_specs(cls, url_prefix):
         url_specs = []
         url_specs.append(
             URLSpec(
-                r"%s%s/" % (url_prefix, cls.base_url.strip("/")),
+                r"{}{}/".format(url_prefix, cls.base_url.strip("/")),
                 type(cls.__name__, (cls.dashboard_handler_cls, cls), {}),
                 {"template": cls.template, "params": cls.params},
                 name=cls.__name__,
@@ -754,12 +754,13 @@ def url_specs(cls, url_prefix):
         for datasource in cls.datasources:
             if datasource.data_url is None:
                 raise KeyError(
-                    "A Datasource must have a data_url: %s"
-                    % datasource.__name__
+                    f"A Datasource must have a data_url: {datasource.__name__}"
                 )
             url_specs.append(
                 URLSpec(
-                    r"%s%s/" % (url_prefix, datasource.data_url.strip("/")),
+                    r"{}{}/".format(
+                        url_prefix, datasource.data_url.strip("/")
+                    ),
                     type(
                         datasource.__name__,
                         (datasource, datasource.datasource_handler_cls),

powa/database.py

@@ -305,7 +305,7 @@ def query(self):
         from_clause = query
 
         if self.has_extension(self.path_args[0], "pg_stat_kcache"):
-            from_clause = "({query}) AS sub2".format(query=query)
+            from_clause = f"({query}) AS sub2"
 
             # Add system metrics from pg_stat_kcache,
             kcache_query = kcache_getstatdata_sample(
@@ -344,10 +344,8 @@ def query(self):
                 ]
             )
 
-            from_clause += """
-            LEFT JOIN ({kcache_query}) AS kc USING (dbid, ts, srvid)""".format(
-                kcache_query=kcache_query
-            )
+            from_clause += f"""
+            LEFT JOIN ({kcache_query}) AS kc USING (dbid, ts, srvid)"""
 
         return """SELECT {cols}
         FROM (
@@ -505,7 +503,7 @@ def query(self):
                 wps("count_io"),
             ]
 
-        from_clause = "({query}) AS sub".format(query=query)
+        from_clause = f"({query}) AS sub"
 
         return """SELECT {cols}
         FROM {from_clause}
@@ -887,12 +885,12 @@ def query(self):
                 ]
             )
 
-        from_clause = """(
+        from_clause = f"""(
                 {inner_query}
             ) AS sub
             JOIN {{powa}}.powa_statements AS ps
                 USING (srvid, queryid, userid, dbid)
-            CROSS JOIN {bs}""".format(inner_query=inner_query, bs=block_size)
+            CROSS JOIN {block_size}"""
 
         return """SELECT {cols}
                 FROM {from_clause}
@@ -936,11 +934,11 @@ def query(self):
             "sum(count) AS counts",
         ]
 
-        from_clause = """(
+        from_clause = f"""(
             {inner_query}
         ) AS sub
             JOIN {{powa}}.powa_statements AS ps
-                USING (srvid, queryid, dbid)""".format(inner_query=inner_query)
+                USING (srvid, queryid, dbid)"""
 
         return """SELECT {cols}
             FROM {from_clause}