[GitHub] [trafficcontrol] ocket8888 commented on a change in pull request #6126: Distributed Traffic Monitor blueprint

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ocket8888 commented on a change in pull request #6126:
URL: https://github.com/apache/trafficcontrol/pull/6126#discussion_r692543391



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File path: blueprints/distributed-traffic-monitor.md
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+# Distributed Traffic Monitor
+
+## Problem Description
+Currently, TM polls all caches in a CDN. As CDNs grow, this becomes a major
+pain point as TM is limited by the amount of bandwidth and CPU it requires to
+receive and process data from every cache on the CDN, and scaling vertically by
+running it on better hardware is only feasible up to a certain point. Also, the
+performance of a cache observed by a TM which is very far away from it does not
+always reflect the performance observed by clients that are actually using the
+cache (because the clients are typically much closer to it).
+
+## Proposed Change
+TM should have the ability to poll only a subset of caches in a CDN and peer
+with other TMs which are monitoring other subsets in order to get a full view
+of the CDN's health. This would allow us to run TM in a more distributed manner
+across the CDN, giving us a view of cache health that is closer to what clients
+actually observe and enabling us to scale TM horizontally. Additionally, we
+would like to have the option to disable _stat polling_ in order for these
+distributed TMs to focus on _health polling_.
+
+### Traffic Portal Impact
+This proposal does not require any TP changes.
+
+### Traffic Ops Impact
+This proposal should have no impact on TO. The existing TO API endpoints
+already provide the data that TM will need to run in a distributed manner.

Review comment:
       will it affect the endpoints that call into TM, though? Like `cdns/{{name}}/health` just picks any random ONLINE TM and gets its `/publish/CrStates` but that won't actually be the whole CDN now, maybe.




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