Retry sample insert after keeper cluster changes

In a [test run](#6508) we
saw that oximeter sample inserts failed because a keeper leader election
was occurring during an insert attempt. Wrap all inserts after keeper
cluster changes in a retry to make them resilient.

Fixes #6508

oximeter/db/tests/integration_test.rs

@@ -297,19 +297,20 @@ async fn test_cluster() -> anyhow::Result<()> {
         .expect("failed to get samples from client1");
 
     // We still have a quorum (2 of 3 keepers), so we should be able to insert
+    // Removing a node may require a new leader election which would require
+    // some polling, so we go ahead and do that.
     let samples = oximeter_test_utils::generate_test_samples(
         input.n_projects,
         input.n_instances,
         input.n_cpus,
         input.n_samples,
     );
-    client3
-        .insert_samples(&samples)
+    wait_for_insert(log, &client3, &samples)
         .await
         .expect("failed to insert samples at server3");
     wait_for_num_points(&log, &client2, samples.len() * 3)
         .await
-        .expect("failed to get samples from client1");
+        .expect("failed to get samples from client2");
 
     // Stop another keeper
     deployment.stop_keeper(1.into()).expect("failed to stop keeper 1");
@@ -355,7 +356,9 @@ async fn test_cluster() -> anyhow::Result<()> {
         input.n_cpus,
         input.n_samples,
     );
-    client1.insert_samples(&samples).await.expect("failed to insert samples");
+    wait_for_insert(log, &client1, &samples)
+        .await
+        .expect("failed to insert samples at server1");
     wait_for_num_points(&log, &client2, samples.len() * 4)
         .await
         .expect("failed to get samples from client1");
@@ -375,7 +378,9 @@ async fn test_cluster() -> anyhow::Result<()> {
         input.n_cpus,
         input.n_samples,
     );
-    client1.insert_samples(&samples).await.expect("failed to insert samples");
+    wait_for_insert(log, &client1, &samples)
+        .await
+        .expect("failed to insert samples at server1");
     wait_for_num_points(&log, &client2, samples.len() * 5)
         .await
         .expect("failed to get samples from client1");
@@ -519,3 +524,30 @@ async fn wait_for_ping(log: &Logger, client: &Client) -> anyhow::Result<()> {
     info!(log, "Clickhouse server ready: {}", client.url());
     Ok(())
 }
+
+/// Wait for insert to succeed after messing with keeper configuration
+async fn wait_for_insert(
+    log: &Logger,
+    client: &Client,
+    samples: &[Sample],
+) -> anyhow::Result<()> {
+    poll::wait_for_condition(
+        || async {
+            client
+                .insert_samples(&samples)
+                .await
+                .map_err(|_| poll::CondCheckError::<oximeter_db::Error>::NotYet)
+        },
+        &Duration::from_millis(1000),
+        &Duration::from_secs(60),
+    )
+    .await
+    .with_context(|| {
+        format!(
+            "failed to insert samples at clickhouse server: {}",
+            client.url()
+        )
+    })?;
+    info!(log, "inserted samples at clickhouse server: {}", client.url());
+    Ok(())
+}