Use _id for metrics collections.

The metrics collections are capped, so an _id is not required. However, starting
in MongoDB 2.0, you can no longer perform a multi-update without an object _id,
which caused metrics invalidation to fail. The fix is relatively simple, since
the metrics values already had an implicit unique id (expression, level, time
and optional group key): make the id explicit.

Note that this change is not backwards-compatible!

lib/cube/server/event.js

@@ -67,8 +67,8 @@ exports.putter = function(db) {
         var floor = tiers[tier].floor;
         metrics.update({
           i: false,
-          l: +tier,
-          t: {
+          "_id.l": +tier,
+          "_id.t": {
             $gte: floor(times[0]),
             $lte: floor(times[1])
           }

lib/cube/server/metric.js

@@ -4,10 +4,9 @@ var util = require("util"),
     types = require("./types"),
     reduces = require("./reduces");
 
-var metric_fields = {t: 1, g: 1, v: 1},
-    metric_options = {sort: {t: 1}, batchSize: 1000},
-    event_options = {sort: {t: 1}, batchSize: 1000},
-    update_options = {upsert: true};
+var metric_fields = {v: 1},
+    metric_options = {sort: {_id: 1}, batchSize: 1000},
+    event_options = {sort: {t: 1}, batchSize: 1000};
 
 // Query for metrics.
 // TODO use expression ids, and record how often expressions are queried?
@@ -68,9 +67,9 @@ exports.getter = function(db) {
       // Query for the desired metric in the cache.
       type.metrics.find({
         i: false,
-        e: expression.source,
-        l: tier.key,
-        t: {
+        "_id.e": expression.source,
+        "_id.l": tier.key,
+        "_id.t": {
           $gte: start,
           $lt: stop
         }
@@ -84,9 +83,9 @@ exports.getter = function(db) {
         cursor.each(function(error, row) {
           if (error) throw error;
           if (row) {
-            callback(row.t, row.v, row.g);
-            if (time < row.t) compute(time, row.t);
-            time = tier.step(row.t);
+            callback(row._id.t, row.v, row._id.g);
+            if (time < row._id.t) compute(time, row._id.t);
+            time = tier.step(row._id.t);
           } else {
             if (time < stop) compute(time, stop);
           }
@@ -203,31 +202,29 @@ exports.getter = function(db) {
 
       function saveGroup(time, value, group) {
         callback(time, value, group);
-        if (value) type.metrics.update({
-          e: expression.source,
-          l: tier.key,
-          t: time,
-          g: group
-        }, {
-          $set: {
-            i: false,
-            v: new Double(value)
-          }
-        }, update_options);
+        if (value) type.metrics.save({
+          _id: {
+            e: expression.source,
+            l: tier.key,
+            t: time,
+            g: group
+          },
+          i: false,
+          v: new Double(value)
+        });
       }
 
       function save(time, value) {
         callback(time, value);
-        if (value) type.metrics.update({
-          e: expression.source,
-          l: tier.key,
-          t: time
-        }, {
-          $set: {
-            i: false,
-            v: new Double(value)
-          }
-        }, update_options);
+        if (value) type.metrics.save({
+          _id: {
+            e: expression.source,
+            l: tier.key,
+            t: time
+          },
+          i: false,
+          v: new Double(value)
+        });
       }
     }
   }

schema/schema-create.js

@@ -1,11 +1,10 @@
 db.createCollection("boards");
 
-["random", "stock", "collectd_df", "collectd_load", "collectd_interface", "collectd_memory"].forEach(function(type) {
+["random", "collectd_df", "collectd_load", "collectd_interface", "collectd_memory"].forEach(function(type) {
   var event = type + "_events", metric = type + "_metrics";
   db.createCollection(event);
   db[event].ensureIndex({t: 1});
-  db.createCollection(metric, {capped: true, size: 1e6, autoIndexId: false});
-  db[metric].ensureIndex({e: 1, l: 1, t: 1, g: 1}, {unique: true});
-  db[metric].ensureIndex({i: 1, e: 1, l: 1, t: 1});
-  db[metric].ensureIndex({i: 1, l: 1, t: 1});
+  db.createCollection(metric, {capped: true, size: 1e7, autoIndexId: true});
+  db[metric].ensureIndex({"i": 1, "_id.e": 1, "_id.l": 1, "_id.t": 1});
+  db[metric].ensureIndex({"i": 1, "_id.l": 1, "_id.t": 1});
 });