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Comparison · DevOps
Eclipse OpenJ9 vs Undertow
A side-by-side editorial comparison of Eclipse OpenJ9 and Undertow — release velocity, themes, recent moves, and the top alternatives to consider.
Eclipse OpenJ9 vs Undertow: at a glance
What is Eclipse OpenJ9?
OpenJ9 ships on the quarterly JDK security clock and says almost nothing on the way past
Eclipse OpenJ9 is an alternative JVM, released in lockstep with the quarterly OpenJDK update cycle. Its release entries are pointer pages: a link to the Eclipse release plan and off-site notes, the matrix of JDK levels each version works with, branch and commit SHAs, any CVEs resolved, and a standing link to the JITServer Helm chart. No feature descriptions appear in the feed at all.
What is Undertow?
Undertow 2.4.0 clears three CVEs and finally lands long-open HTTP/2 and timeout requests
Undertow's 2.4 line opened in May 2026 with a release that combines three CVE fixes with a backlog of feature requests, several of them years old judging by their issue numbers — in-flight request processing time tracking, comments in the predicate language, a configurable async context timeout replacing a hard-coded one, HTTP/2 GOAWAY connection management, a TLS protocol version exchange attribute, and a method to invalidate all cache paths. The two releases since have been small: a handful of Jiras in 2.4.1, and a 2.4.2 whose entire release note is the sentence that it was tagged.
Eclipse OpenJ9 vs Undertow: editorial side-by-side
Eclipse OpenJ9
2.5DEVOPS
OpenJ9 ships on the quarterly JDK security clock and says almost nothing on the way past
◆ Current state
Eclipse OpenJ9 is an alternative JVM, released in lockstep with the quarterly OpenJDK update cycle. Its release entries are pointer pages: a link to the Eclipse release plan and off-site notes, the matrix of JDK levels each version works with, branch and commit SHAs, any CVEs resolved, and a standing link to the JITServer Helm chart. No feature descriptions appear in the feed at all.
◆ Where it's heading
What the feed does reliably show is the JDK support matrix advancing together — 8u, 11, 17, 21, 25 and latterly 26 all stepping forward in each release — and which cycles carried security content. Three CVEs in 0.60.0 against one in 0.59.0 and one in 0.57.0 is the only variation in an otherwise uniform sequence. Interleaved with those are single-JDK releases like 0.55.0 and 0.58.0, which track a new Java version's arrival rather than the quarterly update.
◆ Prediction
The pattern points to the next release landing on the following quarterly OpenJDK update with a similar CVE roll-up and the JDK matrix advanced one patch level. What changes inside the JVM is not something this feed reveals.
Undertow
0.0DEVOPS
Undertow 2.4.0 clears three CVEs and finally lands long-open HTTP/2 and timeout requests
◆ Current state
Undertow's 2.4 line opened in May 2026 with a release that combines three CVE fixes with a backlog of feature requests, several of them years old judging by their issue numbers — in-flight request processing time tracking, comments in the predicate language, a configurable async context timeout replacing a hard-coded one, HTTP/2 GOAWAY connection management, a TLS protocol version exchange attribute, and a method to invalidate all cache paths. The two releases since have been small: a handful of Jiras in 2.4.1, and a 2.4.2 whose entire release note is the sentence that it was tagged.
◆ Where it's heading
The 2.4.0 pattern — a long-deferred feature backlog shipping in the same release as security fixes — suggests features move when a release has to happen anyway rather than on their own schedule. What did ship points at operational control: timeouts that were hard-coded becoming configurable, connection lifecycle handling for HTTP/2, and attributes exposing TLS and timing detail to whatever sits above the server. Enabling test runs on JDK 25 in 2.4.1 is the only forward-looking item in the two follow-up releases.
◆ Prediction
With three entries and one substantive release among them, there is little to extrapolate from; the JDK 25 test enablement is the one thread that implies more work, pointing at runtime compatibility rather than features as the near-term focus.
Alternatives to Eclipse OpenJ9 and Undertow
Other DevOps products tracked by Sparkpulse, ranked by recent ship velocity. Each card links to a full editorial trajectory and lets you pivot into a head-to-head comparison with either Eclipse OpenJ9 or Undertow.
OceanBase
OceanBase is rebuilding itself as a RAG backend without giving up the HTAP story
QGroundControl
QGroundControl rebuilt its flight UI around touch screens, then went quiet for ten months
Pelican
Pelican now ships roughly once a year, and 4.12 is theme housekeeping
WildFly
WildFly's quarterly train is really a stability ladder, and OIDC keeps climbing it
RESTEasy
Jakarta REST implementation in pure maintenance across two parallel branches.
See all Eclipse OpenJ9 alternatives → · See all Undertow alternatives →
Recent activity from Eclipse OpenJ9 and Undertow
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 11d agoEclipse OpenJ9OpenJ9 0.60 resolves three CVEs across six JDK levels
- 1mo agoUndertow2.4.2.Final
- 2mo agoUndertowUndertow 2.4.1 makes the HTTP/1.1 reason-phrase optional
- 2mo agoUndertowUndertow 2.4.0 fixes three CVEs and adds HTTP/2 GOAWAY handling
- 3mo agoEclipse OpenJ9OpenJ9 0.59 closes a CVE and steps the JDK matrix forward
- 4mo agoEclipse OpenJ9Eclipse OpenJ9 v0.58.0
- 6mo agoEclipse OpenJ9OpenJ9 0.57 delivers the quarterly security update
- 6mo agoEclipse OpenJ9Eclipse OpenJ9 v0.56.0
- 9mo agoEclipse OpenJ9Eclipse OpenJ9 v0.55.0
Frequently asked questions
What is the difference between Eclipse OpenJ9 and Undertow?
They serve adjacent needs but don't currently overlap on shipped themes. Eclipse OpenJ9 is currently shipping more aggressively (velocity 2.5 vs 0.0), with 0 editorial sparks in the last 30 days against 0. See the at-a-glance table above for a side-by-side breakdown of velocity, recent sparks, and editorial themes.
Is Eclipse OpenJ9 better than Undertow?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Eclipse OpenJ9 is currently shipping more aggressively (velocity 2.5 vs 0.0), with 0 editorial sparks in the last 30 days against 0. For your specific use case, the alternatives sections above list other DevOps products to evaluate alongside.
What are the best alternatives to Eclipse OpenJ9?
Top Eclipse OpenJ9 alternatives in DevOps are ranked by recent ship velocity. Browse the "Eclipse OpenJ9 alternatives" section above for the current picks, or visit /alternatives/eclipse-openj9 for the full list with editorial commentary on each.
What are the best alternatives to Undertow?
Top Undertow alternatives in DevOps are ranked by recent ship velocity. Browse the "Undertow alternatives" section above for the current picks, or visit /alternatives/undertow for the full list with editorial commentary on each.