Cannot open a Memcached cache settings in Lucee Administrator

Redtopia · May 17, 2026, 11:01pm

I’ve got a couple Memcached caches that I created in .CFConfig.json that I cannot view in the Lucee Administrator. When I try to open either of the cache settings, I get the error:

Cannot invoke “java.util.List.size()” because the return value of “lucee.commons.io.cache.Cache.keys()” is null

I tried to create a brand new Memcached cache through the administrator, and I still cannot open the settings page for it.

I’m running Memcached extension: org.lucee.memcached.extension (4.0.0.14)

The Lucee stack trace (this is really interesting!):

The Error Occurred in
/admin/services.cache.create.cfm: line 79
called from /admin/services.cache.cfm: line 41
called from /admin/web.cfm: line 521
called from /admin/web.cfm: line 515
called from /var/my-app/www/admin/index.cfm: line 3

Notice the bottom line in the stack trace. I put in “my-app” as a placeholder, but it really is the path to the app I’m running, and that directory does exist. I suspect this could be part of the problem.

In addition, the Java stacktrace is:

lucee.runtime.exp.NativeException: Cannot invoke "java.util.List.size()" because the return value of "lucee.commons.io.cache.Cache.keys()" is null
 at lucee.runtime.functions.cache.CacheCount.call(CacheCount.java:42)
 at services_cache_create_cfm1104$cf.call(/admin/services.cache.create.cfm:79)
 at lucee.runtime.PageContextImpl._doInclude(PageContextImpl.java:1118)
 at lucee.runtime.PageContextImpl._doInclude(PageContextImpl.java:1012)
 at lucee.runtime.PageContextImpl.doInclude(PageContextImpl.java:993)
 at services_cache_cfm414$cf.call(/admin/services.cache.cfm:41)
 at lucee.runtime.PageContextImpl._doInclude(PageContextImpl.java:1118)
 at lucee.runtime.PageContextImpl._doInclude(PageContextImpl.java:1012)
 at lucee.runtime.PageContextImpl.doInclude(PageContextImpl.java:993)
 at web_cfm$cf.call_000007(/admin/web.cfm:521)
 at web_cfm$cf.call(/admin/web.cfm:515)
 at lucee.runtime.PageContextImpl._doInclude(PageContextImpl.java:1118)
 at lucee.runtime.PageContextImpl._doInclude(PageContextImpl.java:1012)
 at lucee.runtime.PageContextImpl.doInclude(PageContextImpl.java:993)
 at index_cfm$cf.call(/admin/index.cfm:3)
 at lucee.runtime.PageContextImpl._doInclude(PageContextImpl.java:1118)
 at lucee.runtime.PageContextImpl._doInclude(PageContextImpl.java:1012)
 at lucee.runtime.listener.ModernAppListener._onRequest(ModernAppListener.java:215)
 at lucee.runtime.listener.ModernAppListener.onRequest(ModernAppListener.java:102)
 at lucee.runtime.PageContextImpl.execute(PageContextImpl.java:2816)
 at lucee.runtime.PageContextImpl._execute(PageContextImpl.java:2803)
 at lucee.runtime.PageContextImpl.executeCFML(PageContextImpl.java:2774)
 at lucee.runtime.engine.Request.exe(Request.java:45)
 at lucee.runtime.engine.CFMLEngineImpl._service(CFMLEngineImpl.java:1113)
 at lucee.runtime.engine.CFMLEngineImpl.serviceCFML(CFMLEngineImpl.java:1070)
 at lucee.loader.engine.CFMLEngineWrapper.serviceCFML(CFMLEngineWrapper.java:97)
 at lucee.loader.servlet.jakarta.CFMLServlet.service(CFMLServlet.java:52)
 at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:710)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:128)
 at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:107)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:165)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:77)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:492)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:113)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:83)
 at org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:685)
 at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:654)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:72)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:341)
 at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:397)
 at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63)
 at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:903)
 at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1801)
 at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52)
 at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:946)
 at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:480)
 at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:57)
 at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: java.lang.NullPointerException: Cannot invoke "java.util.List.size()" because the return value of "lucee.commons.io.cache.Cache.keys()" is null
 ... 49 more

OS: Ubuntu 24.04 (Noble)
Java: OpenJDK 21
Tomcat Version: 11.0.6
Lucee Version: 6.2.6.19
Memcached: org.lucee.memcached.extension (4.0.0.14)

Redtopia · May 18, 2026, 4:12pm

I’m thinking I should file a bug report on this. The extension seems to be trying to load the request from my app:

From error stack:

called from /var/my-app/www/admin/index.cfm: line 3

Waiting for confirmation and I’ll be happy to log the bug report.

Zackster · May 18, 2026, 4:36pm

there’s a few layers this one!

memcached doesn’t support enumerating cache keys, which leads to a few different problems, as the loader cache api, fetches keys and counts them, as there is no size api. hacky stuff like returning an empty collection for the count, but that brakes other things

the admin workaround is brittle ( case in point)

https://luceeserver.atlassian.net/browse/LDEV-4422

memcached returns null, so I’m thinking about handling that and just having cacheCount() / cfobjectcache size simply both return -1 which makes sense and isn’t a NPE ? wanna file a ticket for that?

the admin can then gracefully handle that, rather than bombing

Redtopia · May 18, 2026, 6:54pm

New ticket here: LDEV-6323

Zackster · May 19, 2026, 10:32am

github.com

lucee/extension-memcached/blob/master/README.md

# Lucee Memcached Extension

Issues: https://luceeserver.atlassian.net/issues/?jql=labels%20%3D%20memcached

Docs: https://docs.lucee.org/categories/cache.html

## Limitations

Memcached's protocol doesn't expose key enumeration, so any CFML cache feature that needs to list or count keys is constrained:

- `cacheCount(cacheName)` returns `-1` — the documented "count not available" sentinel from the `Cache` interface. Use `if ( cacheCount(cn) GTE 0 )` before relying on the value. ([LDEV-6324](https://luceeserver.atlassian.net/browse/LDEV-6324))
- `cacheGetAllIds(filter, cacheName)` returns an empty array.
- `cacheGetAll(filter, cacheName)` is currently broken against memcached and throws — see [LDEV-2275](https://luceeserver.atlassian.net/browse/LDEV-2275).
- `cacheClear(filter, cacheName)` returns `-1`; the filter is ignored because keys can't be enumerated. `cacheClear()` without a filter performs a cache-wide flush and works.
- The Lucee Admin cache edit page shows `Clear cache (count unsupported)` for memcached connections instead of an item count.

Single-key operations work normally: `cachePut`, `cacheGet`, `cacheGetMetadata`, `cacheKeyExists`, `cacheRemove`.