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https://issues.apache.org/jira/browse/FLINK-7781?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16224662#comment-16224662
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ASF GitHub Bot commented on FLINK-7781:
---------------------------------------
Github user zentol commented on a diff in the pull request:
https://github.com/apache/flink/pull/4901#discussion_r147670970
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/rest/handler/legacy/metrics/SubtaskMetricsHandler.java
---
@@ -0,0 +1,70 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.runtime.rest.handler.legacy.metrics;
+
+import
org.apache.flink.runtime.rest.handler.legacy.SubtaskExecutionAttemptDetailsHandler;
+
+import java.util.Map;
+import java.util.concurrent.Executor;
+
+/**
+ * Request handler that returns, aggregated across all subtasks of a
single tasks, a list of all available metrics or the
+ * values for a set of metrics.
+ *
+ * <p>If the query parameters do not contain a "get" parameter the list of
all metrics is returned.
+ * {@code {"available": [ { "name" : "X", "id" : "X" } ] } }
+ *
+ * <p>If the query parameters do contain a "get" parameter, a
comma-separated list of metric names is expected as a value.
+ * {@code /metrics?get=X,Y}
+ * The handler will then return a list containing the values of the
requested metrics.
+ * {@code [ { "id" : "X", "value" : "S" }, { "id" : "Y", "value" : "T" } ]
}
+ *
+ * <p>The "agg" query parameter is used to define which aggregates should
be calculated. Available aggregations are
+ * "sum", "max", "min" and "avg".
+ */
+public class SubtaskMetricsHandler extends AbstractMetricsHandler {
+ private static final String SUBTASK_METRICS_REST_PATH =
"/jobs/:jobid/vertices/:vertexid/subtasks/:subtasknum/metrics";
+
+ public SubtaskMetricsHandler(Executor executor, MetricFetcher fetcher) {
+ super(executor, fetcher);
+ }
+
+ @Override
+ public String[] getPaths() {
+ return new String[]{SUBTASK_METRICS_REST_PATH};
+ }
+
+ @Override
+ protected Map<String, String> getMapFor(Map<String, String> pathParams,
MetricStore metrics) {
+ String subtaskNumString =
pathParams.get(SubtaskExecutionAttemptDetailsHandler.PARAMETER_SUBTASK_INDEX);
+ int subtaskNum;
+ try {
+ subtaskNum = Integer.valueOf(subtaskNumString);
+ } catch (NumberFormatException nfe) {
+ return null;
+ }
--- End diff --
An unknown subtask index will cause the method to return null
(```metrics.getSubtaskMetricStore(...)```), which is the same behavior as all
other metric handlers.
We can't provide an accurate message in this case; we only know that this
subtask index is unknown to the store, but not why. (does it exceed the
parallelism, metrics haven't arrived yet).
> Support simple on-demand metrics aggregation
> --------------------------------------------
>
> Key: FLINK-7781
> URL: https://issues.apache.org/jira/browse/FLINK-7781
> Project: Flink
> Issue Type: Improvement
> Components: Metrics, REST
> Affects Versions: 1.4.0
> Reporter: Chesnay Schepler
> Assignee: Chesnay Schepler
> Fix For: 1.4.0
>
>
> We should support aggregations (min, max, avg, sum) of metrics in the REST
> API. This is primarily about aggregating across subtasks, for example the
> number of incoming records across all subtasks.
> This is useful for simple use-cases where a dedicated metrics backend is
> overkill, and will allow us to provide better metrics in the web UI (since we
> can expose these aggregated as well).
> I propose to add a new query parameter "agg=[min,max,avg,sum]". As a start
> this parameter should only be used for task metrics. (This is simply the main
> use-case i have in mind)
> The aggregation should (naturally) only work for numeric metrics.
> We will need a HashSet of metrics that exist for subtasks of a given tasks
> that has to be updated in {{MetricStore#add}}.
> All task metrics are either stored as
> # {{<subtask-index>.<metric>}} or
> # {{<subtask-index>.<operator-name>.<metric>}}.
> If a user sends a request {{get=mymetric,agg=sum}}, only the metrics of the
> first kind are to be considered. Similarly, given a request
> {{get=myoperator.mymetric,agg=sum}} only metrics of the second kind are to be
> considered.
> Ideally, the name of the aggregated metric (i.e. the original name without
> subtask index) is also contained in the list of available metrics.
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