rawlinp opened a new pull request #6527: URL: https://github.com/apache/trafficcontrol/pull/6527
Rather than having a single TM poll an entire CDN, the new `distributed_polling` config option allows a TM to poll a subset of the CDN and share its data to other TMs outside of its TM group (cachegroup). This separates TM peers into two different categories: - local peers - distributed peers A CDN is divided into N subsets, where N is the number of TM groups (cachegroups). Each TM in a TM group polls their assigned cachegroups, combining state with the other TMs in its group (its local peers), and polls TMs from every other TM group (its distributed peers) in order to get health availability for the entire CDN. Therefore, each TM is only responsible for polling a subset of the CDN yet still has a full view of the CDN's health. This means TR and the tc-health-client can still poll TM's /publish/CrStates endpoint to get availability for the entire CDN. <!-- Thank you for contributing! Please be sure to read our contribution guidelines: https://github.com/apache/trafficcontrol/blob/master/CONTRIBUTING.md If this closes or relates to an existing issue, please reference it using one of the following: Closes: #ISSUE Related: #ISSUE If this PR fixes a security vulnerability, DO NOT submit! Instead, contact the Apache Traffic Control Security Team at [email protected] and follow the guidelines at https://apache.org/security regarding vulnerability disclosure. --> <!-- **^ Add meaningful description above** --><hr/> ## Which Traffic Control components are affected by this PR? <!-- Please delete all components from this list that are NOT affected by this PR. Feel free to add the name of a tool or script that is affected but not on the list. --> - Documentation - Traffic Monitor ## What is the best way to verify this PR? <!-- Please include here ALL the steps necessary to test your PR. If your PR has tests (and most should), provide the steps needed to run the tests. If not, please provide step-by-step instructions to test the PR manually and explain why your PR does not need tests. --> Firstly, run Traffic Monitor without enabling `distributed_polling`. TM should continue to function normally in a non-distributed manner. Secondly, enable `distributed_polling` and ensure TM functions properly. In order to do this, you may need at least 4 TMs divided into two separate cachegroups (2 TMs per group) in Traffic Ops. Note: for local testing, I configured 9 TM servers in three different groups using IP addresses 127.0.0.2 - 127.0.0.10. On MacOS, you can use this command to configure these loopback addresses: ``` for i in {2..10}; do sudo ifconfig lo0 alias 127.0.0.$i up; done ``` Since TM uses hostnames instead of IP addresses for peer polling, I tried adding the TM FQDNs to `/etc/hosts`, but for some reason it seems Go on MacOS doesn't check that file (you may have better luck doing this on Linux). So instead I set up some A records in a lab DNS zone to return 127.0.0.2 - 127.0.0.10 so that TM makes real DNS requests which return these loopback addresses. ## PR submission checklist - [x] This PR has tests <!-- If not, please delete this text and explain why this PR does not need tests. --> - [x] This PR has documentation <!-- If not, please delete this text and explain why this PR does not need documentation. --> - [x] This PR has a CHANGELOG.md entry <!-- A fix for a bug from an ATC release, an improvement, or a new feature should have a changelog entry. --> - [x] This PR **DOES NOT FIX A SERIOUS SECURITY VULNERABILITY** (see [the Apache Software Foundation's security guidelines](https://apache.org/security) for details) <!-- 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. --> -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
