From 4b7e7bf905873fd1c36f0d99ac8c84bdbcef2a70 Mon Sep 17 00:00:00 2001
From: Joseph Davis <joseph.davis@suse.com>
Date: Tue, 25 Jun 2019 12:25:03 -0700
Subject: [PATCH] Update all columns in metrics on an update to refresh TTL

Cassandra Time to Live (TTL) is applied per-column in a
row, and with a default TTL for the table.  The Cassandra
driver appears to have been written with a misunderstanding
that the TTL was per-row, and as a result the update
statements were written to avoid writing all cells.
But that results in some cells in the row not being updated,
and after their TTL expires they are removed, so a metric
query may result in partial data (updated_at set but
metric_id and created_at missing).

This fix changes the statement used when a new measurement
is received to use the same insert statement for the metric
row and thus refresh the TTL for all the columns.

A follow on patch should be created to remove the Update
statements for Measurements, and consider refactoring/removing
the caching model.

Change-Id: I6b7636a52e8bdb2ce8ad97f839acb6184cd58a8b
Story: 2005832
Task: 35872
---
 .../repository/cassandra/CassandraCluster.java      | 13 +++----------
 .../repository/cassandra/CassandraMetricRepo.java   |  4 +++-
 2 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/java/src/main/java/monasca/persister/repository/cassandra/CassandraCluster.java b/java/src/main/java/monasca/persister/repository/cassandra/CassandraCluster.java
index ac20b098..59527438 100644
--- a/java/src/main/java/monasca/persister/repository/cassandra/CassandraCluster.java
+++ b/java/src/main/java/monasca/persister/repository/cassandra/CassandraCluster.java
@@ -64,6 +64,7 @@ public class CassandraCluster {
       + "set value = ?, value_meta = ?, region = ?, tenant_id = ?, metric_name = ?, dimensions = ? "
       + "where metric_id = ? and time_stamp = ?";
 
+  // TODO: Remove update statements, TTL issues
   private static final String MEASUREMENT_UPDATE_CQL = "update monasca.measurements USING TTL ? "
       + "set value = ?, value_meta = ? " + "where metric_id = ? and time_stamp = ?";
 
@@ -71,10 +72,6 @@ public class CassandraCluster {
       + "set metric_id = ?, created_at = ?, updated_at = ? "
       + "where region = ? and tenant_id = ? and metric_name = ? and dimensions = ? and dimension_names = ?";
 
-  private static final String METRICS_UPDATE_CQL = "update monasca.metrics USING TTL ? "
-      + "set updated_at = ? "
-      + "where region = ? and tenant_id = ? and metric_name = ? and dimensions = ? and dimension_names = ?";
-
   private static final String DIMENSION_INSERT_CQL = "insert into  monasca.dimensions "
       + "(region, tenant_id, name, value) values (?, ?, ?, ?)";
 
@@ -115,7 +112,6 @@ public class CassandraCluster {
   private PreparedStatement measurementInsertStmt;
   private PreparedStatement measurementUpdateStmt;
   private PreparedStatement metricInsertStmt;
-  private PreparedStatement metricUpdateStmt;
   private PreparedStatement dimensionStmt;
   private PreparedStatement dimensionMetricStmt;
   private PreparedStatement metricDimensionStmt;
@@ -182,9 +178,9 @@ public class CassandraCluster {
     metricsSession = cluster.connect(dbConfig.getKeySpace());
 
     measurementInsertStmt = metricsSession.prepare(MEASUREMENT_INSERT_CQL).setIdempotent(true);
+    // TODO: Remove update statements, TTL issues
     measurementUpdateStmt = metricsSession.prepare(MEASUREMENT_UPDATE_CQL).setIdempotent(true);
     metricInsertStmt = metricsSession.prepare(METRICS_INSERT_CQL).setIdempotent(true);
-    metricUpdateStmt = metricsSession.prepare(METRICS_UPDATE_CQL).setIdempotent(true);
     dimensionStmt = metricsSession.prepare(DIMENSION_INSERT_CQL).setIdempotent(true);
     dimensionMetricStmt = metricsSession.prepare(DIMENSION_METRIC_INSERT_CQL).setIdempotent(true);
     metricDimensionStmt = metricsSession.prepare(METRIC_DIMENSION_INSERT_CQL).setIdempotent(true);
@@ -232,6 +228,7 @@ public class CassandraCluster {
     return measurementInsertStmt;
   }
 
+  // TODO: Remove update statements, TTL issues
   public PreparedStatement getMeasurementUpdateStmt() {
     return measurementUpdateStmt;
   }
@@ -240,10 +237,6 @@ public class CassandraCluster {
     return metricInsertStmt;
   }
 
-  public PreparedStatement getMetricUpdateStmt() {
-    return metricUpdateStmt;
-  }
-
   public PreparedStatement getDimensionStmt() {
     return dimensionStmt;
   }
diff --git a/java/src/main/java/monasca/persister/repository/cassandra/CassandraMetricRepo.java b/java/src/main/java/monasca/persister/repository/cassandra/CassandraMetricRepo.java
index d096e784..bef61618 100644
--- a/java/src/main/java/monasca/persister/repository/cassandra/CassandraMetricRepo.java
+++ b/java/src/main/java/monasca/persister/repository/cassandra/CassandraMetricRepo.java
@@ -155,7 +155,9 @@ public class CassandraMetricRepo extends CassandraRepo implements Repo<MetricEnv
           metric.getValue(), metric.getValueMeta(), region, tenantId, metricName, dimensions, id));
     } else {
       metricCacheHitMeter.mark();
-      batches.addMetricQuery(cluster.getMetricUpdateStmt().bind(retention,
+      // MUST update all relevant columns to ensure TTL consistency in a row
+      batches.addMetricQuery(cluster.getMetricInsertStmt().bind(retention,
+          defIdShaHash.getSha1HashByteBuffer(), new Timestamp(metric.getTimestamp()),
           new Timestamp(metric.getTimestamp()), region, tenantId, metricName,
           getDimensionList(dimensions), new ArrayList<>(dimensions.keySet())));
       batches.addMeasurementQuery(buildMeasurementUpdateQuery(defIdShaHash, metric.getTimestamp(),