[Laurence]
Sorry if this is a faq or otherwise covered elsewhere, but I've encountered quite a big problem with Zeo in my environment.
I'm running FreeBSD 5.2.1 (Current as of last night) with Zope 2.7.0, Postgresql 7.4.2, Python 2.3.3 and psycopg-1.1.13.
We have been developing with Zope using a single Zope server without Zeo and the time have come to migrate onto Zeo. Everything seemed to come accross smoothly (We brought up the new server in a single Data.fs config) and everything seemed fine so we moved onto setting up Zeo with the Data.fs.
It seems that if we nest ZPT's more then three deep (ZPTA includes ZPTB which includes ZPTC) we get a seg fault and the Zope process dies (The Zeo server is fine). If we load ZPTB or comment out the inclusion of ZPTC everything works fine. It's when we encounter 3 or more layers that the server seg faults.
"3 deep blows up, 2 deep doesn't" sure makes it sound like the notorious "FreeBSD allocates tiny stacks for threads" business. Google on freebsd zope stack for many hits on this. Haven't used FreeBSD myself, and don't know what the current favored way to increase the thread stack size on FreeBSD might be. BTW, using ZEO increases the stack space you need, to deal with the extra (compared to not using ZEO) layers of across-the-network communication needed.