Re: async-calls squid3/src debug.cc,1.18.4.4,1.18.4.5 Debug.h,1.10.4.3,1.10.4.4 main.cc,1.89.4.7,1.89.4.8 structs.h,1.116.4.3,1.116.4.4 cf.data.pre,1.155.4.3,1.155.4.4

On Sat, 2008-02-23 at 03:34 -0700, Adrian Chadd wrote:
> Can someone please explain the logic behind this?
> I think I understand, but I'd like to know what people are trying
> to achieve.

The overall goal is robustness: make production Squid installations
crash less often. In this particular case, we are trying to kill the
transaction or job that hit an internal error (a.k.a., assertion) rather
than killing the whole Squid. If our attempts to isolate the failure
fail, Squid aborts as before.

The assert_burst_max configuration knob controls whether Squid tries to
be robust and how hard it tries to do that. The logic is experimental
and is likely to change once we get more experience with this feature.

HTH,

Alex.

> On Sat, Feb 23, 2008, chtsanti wrote:
> > Update of cvs.devel.squid-cache.org:/cvsroot/squid/squid3/src
> >
> > Modified Files:
> > Tag: async-calls
> > debug.cc Debug.h main.cc structs.h cf.data.pre
> > Log Message:
> > - Add TheAssertsPerStep counter to count the number of assertions per
> > single main loop iteration. This counter is reset to zero at the
> > beginning of every main loop iteration.
> >
> > - To reset the TheAssertsPerStep counter a new AsyncEngine based class used,
> > the XAssertsEngine.
> >
> > - Add "assert_burst_max <int>" to squid.conf. If TheAssertsPerStep
> > counter exceeds a non-negative assert_burst_max, we abort().
> > If set to zero, the first assertion aborts Squid, giving users the old
> > behavior. If set to a negative number, there is no limit.
> >
> >
> >
> > Index: cf.data.pre
> > ===================================================================
> > RCS file: /cvsroot/squid/squid3/src/cf.data.pre,v
> > retrieving revision 1.155.4.3
> > retrieving revision 1.155.4.4
> > diff -C2 -d -r1.155.4.3 -r1.155.4.4
> > *** cf.data.pre 12 Feb 2008 19:04:39 -0000 1.155.4.3
> > --- cf.data.pre 23 Feb 2008 10:31:18 -0000 1.155.4.4
> > ***************
> > *** 5610,5612 ****
> > --- 5610,5628 ----
> > DOC_END
> >
> > + NAME: assert_burst_max
> > + TYPE: int
> > + LOC: Config.assert_burst_max
> > + DEFAULT: 100
> > + DOC_START
> > + When this is set to a possitive number then Squid will abort
> > + if an assertions burst exceeds this number.
> > + If set to zero, the first assertion aborts Squid, giving users
> > + the old behavior. If set to a negative number, there is no
> > + limit.
> > + An asssertions burst defined as the number of assertions per
> > + single Squid main loop iteration.
> > + WARNING! This is an experimental feature and the definition
> > + of a "burst" can change
> > + DOC_END
> > +
> > EOF
> >
> > Index: main.cc
> > ===================================================================
> > RCS file: /cvsroot/squid/squid3/src/main.cc,v
> > retrieving revision 1.89.4.7
> > retrieving revision 1.89.4.8
> > diff -C2 -d -r1.89.4.7 -r1.89.4.8
> > *** main.cc 12 Feb 2008 19:05:00 -0000 1.89.4.7
> > --- main.cc 23 Feb 2008 10:31:18 -0000 1.89.4.8
> > ***************
> > *** 144,147 ****
> > --- 144,158 ----
> > };
> >
> > + class XAssertsEngine : public AsyncEngine
> > + {
> > +
> > + public:
> > + int checkEvents(int timeout)
> > + {
> > + TheAssertsPerStep = 0;
> > + return EVENT_IDLE;
> > + };
> > + };
> > +
> > class SignalEngine: public AsyncEngine
> > {
> > ***************
> > *** 1297,1300 ****
> > --- 1308,1314 ----
> > mainLoop.registerEngine(&signalEngine);
> >
> > + XAssertsEngine xassertsEngine;
> > + mainLoop.registerEngine(&xassertsEngine);
> > +
> > /* TODO: stop requiring the singleton here */
> > mainLoop.registerEngine(EventScheduler::GetInstance());
> >
> > Index: debug.cc
> > ===================================================================
> > RCS file: /cvsroot/squid/squid3/src/debug.cc,v
> > retrieving revision 1.18.4.4
> > retrieving revision 1.18.4.5
> > diff -C2 -d -r1.18.4.4 -r1.18.4.5
> > *** debug.cc 16 Feb 2008 21:06:42 -0000 1.18.4.4
> > --- debug.cc 23 Feb 2008 10:31:18 -0000 1.18.4.5
> > ***************
> > *** 45,48 ****
> > --- 45,49 ----
> > int TheCascadingAsserts = 0;
> > int TheSalvagedAsserts = 0;
> > + int TheAssertsPerStep = 0;
> >
> > static char *debug_log_file = NULL;
> > ***************
> > *** 591,606 ****
> > xassert(const char *msg, const char *file, int line) {
> >
> > ! if (TheCascadingAsserts < MAX_CASCADING_ASSERTS && AsyncCall_Handling_Exceptions) {
> > TheCascadingAsserts++;
> > TheSalvagedAsserts++;
> > ! debugs(0, 0, "assertion failed: " << file << ":" << line << ": \"" << msg << "\". Trying to survive. Salvaged assertions: " << TheSalvagedAsserts);
> >
> > throw TextException(msg, file, line);
> > }
> >
> > - debugs(0, 0, "assertion failed: " << file << ":" << line << ": \"" << msg << "\"");
> >
> > if(TheCascadingAsserts >= MAX_CASCADING_ASSERTS)
> > ! debugs(0, 0, "I am dying after " << TheCascadingAsserts << "cascading assertions!" );
> >
> > if (!shutting_down)
> > --- 592,619 ----
> > xassert(const char *msg, const char *file, int line) {
> >
> > ! debugs(0, 0, "assertion failed: " << file << ":" << line << ": \"" << msg << "\"");
> > !
> > ! if (AsyncCall_Handling_Exceptions &&
> > ! TheCascadingAsserts < MAX_CASCADING_ASSERTS &&
> > ! ( Config.assert_burst_max < 0 ||
> > ! (Config.assert_burst_max > 0 && TheAssertsPerStep < Config.assert_burst_max)
> > ! )
> > ! ) {
> > TheCascadingAsserts++;
> > TheSalvagedAsserts++;
> > ! TheAssertsPerStep++;
> > !
> > ! debugs(0, 0, "salvaging assertion #" << TheSalvagedAsserts << " (" <<
> > ! TheAssertsPerStep << "/" << Config.assert_burst_max << ")");
> >
> > throw TextException(msg, file, line);
> > }
> >
> >
> > if(TheCascadingAsserts >= MAX_CASCADING_ASSERTS)
> > ! debugs(0, 0, "dying after " << TheCascadingAsserts << "cascading assertions" );
> > !
> > ! if(Config.assert_burst_max > 0 && TheAssertsPerStep >= Config.assert_burst_max)
> > ! debugs(0, 0, "dying after an " << TheAssertsPerStep << " assertions burst" );
> >
> > if (!shutting_down)
> >
> > Index: Debug.h
> > ===================================================================
> > RCS file: /cvsroot/squid/squid3/src/Debug.h,v
> > retrieving revision 1.10.4.3
> > retrieving revision 1.10.4.4
> > diff -C2 -d -r1.10.4.3 -r1.10.4.4
> > *** Debug.h 14 Feb 2008 21:46:38 -0000 1.10.4.3
> > --- Debug.h 23 Feb 2008 10:31:18 -0000 1.10.4.4
> > ***************
> > *** 55,58 ****
> > --- 55,60 ----
> > void WillCatchException(int debug_section, int debug_level, const char *who);
> > void WontCatchException();
> > + extern int TheSalvagedAsserts;
> > + extern int TheAssertsPerStep;
> >
> > /* defined names for Debug Levels */
> >
> > Index: structs.h
> > ===================================================================
> > RCS file: /cvsroot/squid/squid3/src/structs.h,v
> > retrieving revision 1.116.4.3
> > retrieving revision 1.116.4.4
> > diff -C2 -d -r1.116.4.3 -r1.116.4.4
> > *** structs.h 12 Feb 2008 19:05:14 -0000 1.116.4.3
> > --- structs.h 23 Feb 2008 10:31:18 -0000 1.116.4.4
> > ***************
> > *** 693,696 ****
> > --- 693,697 ----
> >
> > char *accept_filter;
> > + int assert_burst_max;
> > };
> >
Received on Mon Feb 25 2008 - 11:06:56 MST