Update compute_installed_extensions metric: (#9891)

add owned_by_superuser field to filter out system extensions.

While on it, also correct related code:
- fix the metric setting: use set() instead of inc() in a loop.
inc() is not idempotent and can lead to incorrect results
if the function called multiple times. Currently it is only called at
compute start, but this will change soon.
- fix the return type of the installed_extensions endpoint
to match the metric. Currently it is only used in the test.

compute_tools/src/http/openapi_spec.yaml

@@ -537,12 +537,14 @@ components:
             properties:
               extname:
                 type: string
-              versions:
-                type: array
+              version:
+                type: string
                 items:
                   type: string
               n_databases:
                 type: integer
+              owned_by_superuser:
+                type: integer
 
     SetRoleGrantsRequest:
       type: object

compute_tools/src/installed_extensions.rs

@@ -1,7 +1,6 @@
 use compute_api::responses::{InstalledExtension, InstalledExtensions};
 use metrics::proto::MetricFamily;
 use std::collections::HashMap;
-use std::collections::HashSet;
 
 use anyhow::Result;
 use postgres::{Client, NoTls};
@@ -38,61 +37,77 @@ fn list_dbs(client: &mut Client) -> Result<Vec<String>> {
 /// Connect to every database (see list_dbs above) and get the list of installed extensions.
 ///
 /// Same extension can be installed in multiple databases with different versions,
-/// we only keep the highest and lowest version across all databases.
+/// so we report a separate metric (number of databases where it is installed)
+/// for each extension version.
 pub fn get_installed_extensions(mut conf: postgres::config::Config) -> Result<InstalledExtensions> {
     conf.application_name("compute_ctl:get_installed_extensions");
     let mut client = conf.connect(NoTls)?;
-
     let databases: Vec<String> = list_dbs(&mut client)?;
 
-    let mut extensions_map: HashMap<String, InstalledExtension> = HashMap::new();
+    let mut extensions_map: HashMap<(String, String, String), InstalledExtension> = HashMap::new();
     for db in databases.iter() {
         conf.dbname(db);
         let mut db_client = conf.connect(NoTls)?;
-        let extensions: Vec<(String, String)> = db_client
+        let extensions: Vec<(String, String, i32)> = db_client
             .query(
-                "SELECT extname, extversion FROM pg_catalog.pg_extension;",
+                "SELECT extname, extversion, extowner::integer FROM pg_catalog.pg_extension",
                 &[],
             )?
             .iter()
-            .map(|row| (row.get("extname"), row.get("extversion")))
+            .map(|row| {
+                (
+                    row.get("extname"),
+                    row.get("extversion"),
+                    row.get("extowner"),
+                )
+            })
             .collect();
 
-        for (extname, v) in extensions.iter() {
+        for (extname, v, extowner) in extensions.iter() {
             let version = v.to_string();
 
-            // increment the number of databases where the version of extension is installed
-            INSTALLED_EXTENSIONS
-                .with_label_values(&[extname, &version])
-                .inc();
+            // check if the extension is owned by superuser
+            // 10 is the oid of superuser
+            let owned_by_superuser = if *extowner == 10 { "1" } else { "0" };
 
             extensions_map
-                .entry(extname.to_string())
+                .entry((
+                    extname.to_string(),
+                    version.clone(),
+                    owned_by_superuser.to_string(),
+                ))
                 .and_modify(|e| {
-                    e.versions.insert(version.clone());
                     // count the number of databases where the extension is installed
                     e.n_databases += 1;
                 })
                 .or_insert(InstalledExtension {
                     extname: extname.to_string(),
-                    versions: HashSet::from([version.clone()]),
+                    version: version.clone(),
                     n_databases: 1,
+                    owned_by_superuser: owned_by_superuser.to_string(),
                 });
         }
     }
 
-    let res = InstalledExtensions {
-        extensions: extensions_map.into_values().collect(),
-    };
+    for (key, ext) in extensions_map.iter() {
+        let (extname, version, owned_by_superuser) = key;
+        let n_databases = ext.n_databases as u64;
 
-    Ok(res)
+        INSTALLED_EXTENSIONS
+            .with_label_values(&[extname, version, owned_by_superuser])
+            .set(n_databases);
+    }
+
+    Ok(InstalledExtensions {
+        extensions: extensions_map.into_values().collect(),
+    })
 }
 
 static INSTALLED_EXTENSIONS: Lazy<UIntGaugeVec> = Lazy::new(|| {
     register_uint_gauge_vec!(
         "compute_installed_extensions",
         "Number of databases where the version of extension is installed",
-        &["extension_name", "version"]
+        &["extension_name", "version", "owned_by_superuser"]
     )
     .expect("failed to define a metric")
 });