Hi, I ran the same experiment on version 3.7.0 and did not encounter any issues with long startup delays.
From: pritam kumar <kumarpritamm...@gmail.com> Date: Saturday, 2 August 2025 at 16:20 To: dev@kafka.apache.org <dev@kafka.apache.org> Subject: Re: Significant startup delay after upgrading kafka clients from 3.5.1 to 4.0.0 [You don't often get email from kumarpritamm...@gmail.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ] EXTERNAL SENDER. Do not click links or open attachments unless you recognize the sender and know the content is safe. DO NOT provide your username or password. Hi, Is this delay experienced on 3.7 versions also? This plugin discovery is the connect feature and recently a change was rolled out with different modes of plugin discovery. Is this because of that change? On Sat, 2 Aug 2025 at 7:24 PM, Kirk True <k...@kirktrue.pro> wrote: > Hi! > > I work on the Kafka Java client and I was not familiar with the concept of > plugin discovery, but found a writeup here: > > > https://gbr01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fkafka.apache.org%2Fdocumentation%2F%23connect_plugindiscovery&data=05%7C02%7CLove.Almgren%40kambi.com%7C071e458ee8c24fe1a80708ddd1cfb06c%7Ce3ec1ec4b9944e9e82e080234621871f%7C0%7C0%7C638897412159675530%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=8wYTAJi%2BFGqzfY4h6ER01YJBnRfIrr4eSeqQWnBucng%3D&reserved=0<https://kafka.apache.org/documentation/#connect_plugindiscovery> > > From reading through that, plugin discovery looks like a Connect feature. > Unfortunately, I'm not familiar with that area, so I can't provide any > immediate advice :( > > Are you seeing this slow behavior when using Connect, or do you see it > when using the AdminClient, Consumer, and/or Producer clients? > > I'm sure the developers working on Connect would like to know about this > performance behavior. Can you provide this information in a bug report at > https://gbr01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fissues.apache.org%2Fjira&data=05%7C02%7CLove.Almgren%40kambi.com%7C071e458ee8c24fe1a80708ddd1cfb06c%7Ce3ec1ec4b9944e9e82e080234621871f%7C0%7C0%7C638897412159695592%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=VVJ0cLHbHPAaP76Md13J2HjllIHh4SQeMKDBM6Y3yOg%3D&reserved=0?<https://issues.apache.org/jira> > If so, please use the Jira "Component" > value of "connect" so that the developers working in that area will be more > likely to see the issue. > > Thanks, > Kirk > > On Mon, Jul 28, 2025, at 12:10 AM, Love Almgren wrote: > > Hello Kafka devs, > > > > We’re in the process of upgrading our Kafka clients from version 3.5.1 > to 4.0.0, and have observed a significant increase in startup time related > to plugin loading. > > > > In version 3.5.1, plugin discovery completed in 30-40 seconds. After > upgrading to 4.0.0, the same step takes over 5 minutes. We also tested > version 3.9.0, where the delay was still 40 seconds. > > > > We were able to work around this issue by explicitly setting: > > > > plugin.discovery = service_load > > > > This brought the startup time back to expected levels. Still, we’d like > to better understand: > > > > 1. What might be causing the longer discovery times in newer versions? > > 2. Is this expected behavior, or might it be a regression? > > 3. Are there any risks to relying on service_load for plugin > discovery? > > > > Any insights or suggestions would be greatly appreciated. > > Thanks in advance, > > Love Almgren > > CONFIDENTIALITY NOTICE: This email message (and any attachment) is > intended only for the individual or entity to which it is addressed. The > information in this email is confidential and may contain information that > is legally privileged or exempt from disclosure under applicable law. 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