gianm commented on a change in pull request #8245: Add docs for CliIndexer as an experimental feature URL: https://github.com/apache/incubator-druid/pull/8245#discussion_r310888120
########## File path: docs/content/development/indexer.md ########## @@ -0,0 +1,152 @@ +--- +layout: doc_page +title: "Indexer Process" +--- + +<!-- + ~ 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. + --> + +# Indexer Process + +<div class="note info"> +The Indexer is an optional and <a href="../development/experimental.html">experimental</a> feature. Its memory management system is still under development and will be significantly enhanced in later releases. +</div> + +The Apache Druid (incubating) Indexer process is an alternative to the MiddleManager + Peon task execution system. Instead of forking a separate JVM process per-task, the Indexer runs tasks as separate threads within a single JVM process. + +The Indexer is designed to be easier to configure and deploy compared to the MiddleManager + Peon system. + +## Running + +``` +org.apache.druid.cli.Main server indexer +``` + +## Task Resource Sharing + +The following resources are shared across all tasks running inside an Indexer process: + +### Query resources + +The query processing threads and buffers are shared across all tasks. The Indexer will serve queries from a single endpoint shared by all tasks. + +### Server HTTP threads + +The Indexer maintains two equally sized pools of HTTP threads. + +One pool is exclusively used for task control messages between the Overlord and the Indexer ("chat handler threads"). The other pool is used for handling all other HTTP requests. + +The size of the pools are configured by the `druid.server.http.numThreads` configuration (e.g., if this is set to 10, there will be 10 chat handler threads and 10 non-chat handler threads). + +In addition to these two pools, 2 separate threads are allocated for lookup handling. If lookups are not used, these threads will not be used. + +### Memory Sharing + +The Indexer uses the `druid.worker.globalIngestionHeapLimitBytes` configuration to impose a global heap limit across all of the tasks it is running. + +This global limit is evenly divided across the number of task slots configured by `druid.worker.capacity`. + +To apply the per-task heap limit, the Indexer will override `maxBytesInMemory` in task tuning configs (i.e., ignoring the default value or any user configured value). `maxRowsInMemory` will also be overridden to an essentially unlimited value: the Indexer does not support row limits. + +By default, `druid.worker.globalIngestionHeapLimitBytes` is set to 60% of the available JVM heap. The remaining portion of the heap is reserved for query processing and segment persist/merge operations, and miscellaneous heap usage. + +#### Concurrent Segment Persist/Merge Limits + +To help reduce peak memory usage, the Indexer imposes a limit on the number of concurrent segment persist/merge operations across all running tasks. + +By default, the number of concurrent persist/merge operations is limited to (`druid.worker.capacity` / 2), rounded down. This limit can be configured with the `druid.worker.numConcurrentMerges` property. + +## Runtime Configuration + +In addition to the [common configurations](../configuration/index.html#common-configurations), the Indexer accepts the following configurations: + +|Property|Description|Default| +|--------|-----------|-------| +|`druid.worker.version`|Version identifier for the MiddleManager.|0| Review comment: This line, and a few other places, say "MiddleManager" when they should say "Indexer". ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@druid.apache.org For additional commands, e-mail: commits-h...@druid.apache.org
