Message-ID: <44298A73.9090303@tada.se>
Date: Tue, 28 Mar 2006 21:11:47 +0200
From: Thomas Hallgren <thomas@tada.se>
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To: Dave Cramer <pg@fastcrypt.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Simon Riggs <simon@2ndquadrant.com>,
	Martijn van Oosterhout <kleptog@svana.org>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>,
	PL/Java Development <Pljava-dev@gborg.postgresql.org>
Subject: Re: Shared memory
References: <4423CF32.3060406@tada.se> <20060324125851.GC8718@svana.org>
	<4427A8F1.3020009@tada.se> <14559.1143473507@sss.pgh.pa.us>
	<4428125D.7000707@tada.se>
	<1143541439.3839.323.camel@localhost.localdomain>
	<44295AB0.5060203@tada.se> <2966.1143563883@sss.pgh.pa.us>
	<44296E24.5010602@tada.se>
	<27F0779D-C696-4A39-9CA9-0228C6BABF56@fastcrypt.com>
In-Reply-To: <27F0779D-C696-4A39-9CA9-0228C6BABF56@fastcrypt.com>
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Dave Cramer wrote:
>
>>
>> I'm not too keen on the term FENCED, since it, in the PL/Java case 
>> will lead to poorer isolation. Multiple threads running in the same 
>> JVM will be able to share data and a JVM crash will affect all 
>> connected sessions.
> When was the last time you saw a JVM crash ? These are very rare now.
I think that's somewhat dependent on what JVM you're using. For the 
commercial ones, BEA, IBM, and Sun, i fully agree.

> In any case if it does fail, it's a JVM bug and can happen to any code 
> running and take the server down if it is in process.
Crash is perhaps not the right word. My point concerned level of 
isolation. Code that is badly written may have serious impact on other 
threads in the same JVM. Let's say you cause an OutOfMemoryException or 
an endless loop. The former will render the JVM completely useless and 
the latter will cause low scheduling prio. If the same thing happens 
using an in-process JVM, the problem is isolated to that one session.

Regards,
Thomas Hallgren