gianm commented on a change in pull request #6916: Add master/data/query server concepts to docs/packaging URL: https://github.com/apache/incubator-druid/pull/6916#discussion_r252392994
########## File path: docs/content/design/processes.md ########## @@ -0,0 +1,129 @@ +--- +layout: doc_page +title: "Druid Processes and Servers" +--- + +<!-- + ~ 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. + --> + +# Druid Processes and Servers + +## Process Types + +Druid has several process types: + +* [Coordinator](../design/coordinator.html) +* [Overlord](../design/overlord.html) +* [Broker](../design/broker.html) +* [Historical](../design/historical.html) +* [MiddleManager](../design/middlemanager.html) and [Peons](../design/peons.html) +* [Router (Optional)](../development/router.html) + +## Server Types + +Druid processes can be deployed any way you like, but for ease of deployment we suggest organizing them into three server types: + +* **Master** +* **Query** +* **Data** + +<img src="../../img/druid-architecture.png" width="800"/> + +This section describes the Druid processes and the suggested Master/Query/Data server organization, as shown in the architecture diagram above. + +### Master server + +A Master server manages data ingestion and availability: it is responsible for starting new ingestion jobs and coordinating availability of data on the "Data servers" described below. + +Within a Master server, functionality is split between two processes, the Coordinator and Overlord. + +#### Coordinator process + +[**Coordinator**](../design/coordinator.html) processes watch over the Historical processes on the Data servers. They are responsible for assigning segments to specific servers, and for ensuring segments are well-balanced across Historicals. + +#### Overlord process + +[**Overlord**](../design/overlord.html) processes watch over the MiddleManager processes on the Data servers and are the controllers of data ingestion into Druid. They are responsible for assigning ingestion tasks to MiddleManagers and for coordinating segment publishing. + +### Query server + +A Query server provides the endpoints that users and client applications interact with, routing queries to Data servers or other Query servers (and optionally proxied Master server requests as well). + +Within a Query server, functionality is split between two processes, the Broker and Router. + +#### Broker process + +[**Broker**](../design/broker.html) processes receive queries from external clients and forward those queries to Data servers. When Brokers receive results from those subqueries, they merge those results and return them to the +caller. End users typically query Brokers rather than querying Historicals or MiddleManagers processes on Data servers directly. + +#### Router process (optional) + +[**Router**](../development/router.html) processes are _optional_ processes that provide a unified API gateway in front of Druid Brokers, +Overlords, and Coordinators. They are optional since you can also simply contact the Druid Brokers, Overlords, and +Coordinators directly. + +### Data server + +A Data server executes ingestion jobs and stores queryable data. + +Within a Data server, functionality is split between two processes, the Historical and MiddleManager. + +### Historical process + +[**Historical**](../design/historical.html) processes are the workhorses that handle storage and querying on "historical" data +(including any streaming data that has been in the system long enough to be committed). Historical processes +download segments from deep storage and respond to queries about these segments. They don't accept writes. + +### Middle Manager process + +[**MiddleManager**](../design/middlemanager.html) processes handle ingestion of new data into the cluster. They are responsible +for reading from external data sources and publishing new Druid segments. + +#### Peon processes + +[**Peon**](../design/peons.html) processes are task execution engines spawned by MiddleManagers. Each Peon runs a separate JVM and is responsible for executing a single task. Peons always run on the same host as the MiddleManager that spawned them. + +## Process Colocation Review comment: The title here is counter-intuitive: it's mostly talking about when you would _not_ want to colocate. (The previous section is detailing the case for colocation.) How about re-titling it to "Pros and cons of colocation". ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on 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
