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Commit8362be3

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Code review for superuser_reserved_connections patch. Don't try to do
database access outside a transaction; revert bogus performance improvementin SIBackendInit(); improve comments; add documentation (this part courtesyNeil Conway).
1 parent02d83d7 commit8362be3

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5 files changed

+90
-63
lines changed

5 files changed

+90
-63
lines changed

‎doc/src/sgml/runtime.sgml

Lines changed: 39 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.157 2002/11/2100:42:18 tgl Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.158 2002/11/2106:36:08 tgl Exp $
33
-->
44

55
<Chapter Id="runtime">
@@ -1902,6 +1902,28 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
19021902
</listitem>
19031903
</varlistentry>
19041904

1905+
<varlistentry>
1906+
<term><varname>SUPERUSER_RESERVED_CONNECTIONS</varname>
1907+
(<type>integer</type>)</term>
1908+
<listitem>
1909+
<para>
1910+
Determines the number of <quote>connection slots</quote> that
1911+
are reserved for connections by <productname>PostgreSQL</>
1912+
superusers. At most <varname>max_connections</> connections can
1913+
ever be active simultaneously. Whenever the number of active
1914+
concurrent connections is at least <varname>max_connections</> minus
1915+
<varname>superuser_reserved_connections</varname>, new connections
1916+
will be accepted only from superuser accounts.
1917+
</para>
1918+
1919+
<para>
1920+
The default value is 2. The value must be less than the value of
1921+
<varname>max_connections</varname>. This parameter can only be
1922+
set at server start.
1923+
</para>
1924+
</listitem>
1925+
</varlistentry>
1926+
19051927
<varlistentry>
19061928
<term><varname>TCPIP_SOCKET</varname> (<type>boolean</type>)</term>
19071929
<listitem>
@@ -2952,24 +2974,25 @@ $ <userinput>kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`</userinput
29522974
</para>
29532975

29542976
<para>
2955-
With SSL support compiled in, the <productname>PostgreSQL</> server
2956-
can be started with SSL support by setting the parameter
2957-
<varname>ssl</varname> to on in
2958-
<filename>postgresql.conf</filename>. When starting in SSL mode,
2959-
the server will look for the files <filename>server.key</> and
2960-
<filename>server.crt</>in the data directory. These files should
2961-
contain the server private key and certificate respectively. These
2962-
files must be set up correctly before an SSL-enabled server can
2963-
start. If the private key is protected with a passphrase, the
2964-
server will prompt for thepassphrase andwillnot start until it
2965-
has been entered.
2977+
With<acronym>SSL</> support compiled in, the
2978+
<productname>PostgreSQL</> servercan be started with
2979+
<acronym>SSL</> support by setting the parameter
2980+
<varname>ssl</varname> to on in <filename>postgresql.conf</>. When
2981+
starting in <acronym>SSL</> mode,the server will look for the
2982+
files<filename>server.key</>and <filename>server.crt</> in the
2983+
data directory. These files shouldcontain the server private key
2984+
and certificate respectively. Thesefiles must be set up correctly
2985+
before an <acronym>SSL</>-enabled server canstart. If the private key is
2986+
protected with a passphrase, theserverwillprompt for the
2987+
passphrase and will not start until ithas been entered.
29662988
</para>
29672989

29682990
<para>
2969-
The server will listen for both standard and SSL connections on the
2970-
same TCP/IP port, and will negotiate with any connecting client on
2971-
whether to use SSL. See <xref linkend="client-authentication"> about
2972-
how to force the server to only use of SSL for certain connections.
2991+
The server will listen for both standard and <acronym>SSL</>
2992+
connections on the same TCP/IP port, and will negotiate with any
2993+
connecting client on whether to use <acronym>SSL</>. See <xref
2994+
linkend="client-authentication"> about how to force the server to
2995+
require use of <acronym>SSL</> for certain connections.
29732996
</para>
29742997

29752998
<para>

‎src/backend/postmaster/postmaster.c

Lines changed: 19 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -37,7 +37,7 @@
3737
*
3838
*
3939
* IDENTIFICATION
40-
* $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.298 2002/11/18 00:40:46 tgl Exp $
40+
* $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.299 2002/11/21 06:36:08 tgl Exp $
4141
*
4242
* NOTES
4343
*
@@ -154,12 +154,11 @@ intMaxBackends = DEF_MAXBACKENDS;
154154
/*
155155
* ReservedBackends is the number of backends reserved for superuser use.
156156
* This number is taken out of the pool size given by MaxBackends so
157-
* number of backend slots available to none super users is
158-
* (MaxBackends - ReservedBackends). Note, existing super user
159-
* connections are not taken into account once this lower limit has
160-
* been reached, i.e. superuser connections made before the lower limit
161-
* is reached always count towards that limit and are not taken from
162-
* ReservedBackends.
157+
* number of backend slots available to non-superusers is
158+
* (MaxBackends - ReservedBackends). Note what this really means is
159+
* "if there are <= ReservedBackends connections available, only superusers
160+
* can make new connections" --- pre-existing superuser connections don't
161+
* count against the limit.
163162
*/
164163
intReservedBackends=2;
165164

@@ -568,7 +567,15 @@ PostmasterMain(int argc, char *argv[])
568567
}
569568

570569
/*
571-
* Check for invalid combinations of switches
570+
* Now we can set the data directory, and then read postgresql.conf.
571+
*/
572+
checkDataDir(potential_DataDir);/* issues error messages */
573+
SetDataDir(potential_DataDir);
574+
575+
ProcessConfigFile(PGC_POSTMASTER);
576+
577+
/*
578+
* Check for invalid combinations of GUC settings.
572579
*/
573580
if (NBuffers<2*MaxBackends||NBuffers<16)
574581
{
@@ -581,16 +588,11 @@ PostmasterMain(int argc, char *argv[])
581588
ExitPostmaster(1);
582589
}
583590

584-
checkDataDir(potential_DataDir);/* issues error messages */
585-
SetDataDir(potential_DataDir);
586-
587-
ProcessConfigFile(PGC_POSTMASTER);
588-
589-
/*
590-
* Force an exit if ReservedBackends is not less than MaxBackends.
591-
*/
592591
if (ReservedBackends >=MaxBackends)
593-
elog(FATAL,"superuser_reserved_connections must be less than max_connections.");
592+
{
593+
postmaster_error("superuser_reserved_connections must be less than max_connections.");
594+
ExitPostmaster(1);
595+
}
594596

595597
/*
596598
* Now that we are done processing the postmaster arguments, reset

‎src/backend/storage/ipc/sinval.c

Lines changed: 6 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.52 2002/09/04 20:31:25 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.53 2002/11/21 06:36:08 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -542,12 +542,11 @@ BackendIdGetProc(BackendId procId)
542542
/*
543543
* CountEmptyBackendSlots - count empty slots in backend process table
544544
*
545-
* Doesn't count since the procState array could be large and we've already
546-
* allowed for that by running a freeBackends counter in the SI segment.
547-
* Unlike CountActiveBackends() we do not need to interrogate the
548-
* backends to determine the free slot count.
549-
* Goes for a lock despite being a trival look up in case other backends
550-
* are busy starting or exiting since there is scope for confusion.
545+
* We don't actually need to count, since sinvaladt.c maintains a
546+
* freeBackends counter in the SI segment.
547+
*
548+
* Acquiring the lock here is almost certainly overkill, but just in
549+
* case fetching an int is not atomic on your machine ...
551550
*/
552551
int
553552
CountEmptyBackendSlots(void)

‎src/backend/storage/ipc/sinvaladt.c

Lines changed: 13 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.48 2002/08/29 21:02:12 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.49 2002/11/21 06:36:08 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -92,13 +92,6 @@ SIBackendInit(SISeg *segP)
9292
intindex;
9393
ProcState*stateP=NULL;
9494

95-
if (segP->freeBackends==0)
96-
{
97-
/* out of procState slots */
98-
MyBackendId=InvalidBackendId;
99-
return0;
100-
}
101-
10295
/* Look for a free entry in the procState array */
10396
for (index=0;index<segP->lastBackend;index++)
10497
{
@@ -111,9 +104,18 @@ SIBackendInit(SISeg *segP)
111104

112105
if (stateP==NULL)
113106
{
114-
stateP=&segP->procState[segP->lastBackend];
115-
Assert(stateP->nextMsgNum<0);
116-
segP->lastBackend++;
107+
if (segP->lastBackend<segP->maxBackends)
108+
{
109+
stateP=&segP->procState[segP->lastBackend];
110+
Assert(stateP->nextMsgNum<0);
111+
segP->lastBackend++;
112+
}
113+
else
114+
{
115+
/* out of procState slots */
116+
MyBackendId=InvalidBackendId;
117+
return0;
118+
}
117119
}
118120

119121
MyBackendId= (stateP-&segP->procState[0])+1;

‎src/backend/utils/init/postinit.c

Lines changed: 13 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/utils/init/postinit.c,v 1.117 2002/10/03 19:19:09 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/utils/init/postinit.c,v 1.118 2002/11/21 06:36:08 tgl Exp $
1212
*
1313
*
1414
*-------------------------------------------------------------------------
@@ -377,6 +377,18 @@ InitPostgres(const char *dbname, const char *username)
377377
*/
378378
RelationCacheInitializePhase3();
379379

380+
/*
381+
* Check a normal user hasn't connected to a superuser reserved slot.
382+
* We can't do this till after we've read the user information, and
383+
* we must do it inside a transaction since checking superuserness
384+
* may require database access. The superuser check is probably the
385+
* most expensive part; don't do it until necessary.
386+
*/
387+
if (ReservedBackends>0&&
388+
CountEmptyBackendSlots()<ReservedBackends&&
389+
!superuser())
390+
elog(FATAL,"Non-superuser connection limit exceeded");
391+
380392
/*
381393
* Initialize various default states that can't be set up until we've
382394
* selected the active user and done ReverifyMyDatabase.
@@ -397,17 +409,6 @@ InitPostgres(const char *dbname, const char *username)
397409
/* close the transaction we started above */
398410
if (!bootstrap)
399411
CommitTransactionCommand(true);
400-
401-
/*
402-
* Check a normal user hasn't connected to a superuser reserved slot.
403-
* Do this here since we need the user information and that only
404-
* happens after we've started bringing the shared memory online. So
405-
* we wait until we've registered exit handlers and potentially shut
406-
* an open transaction down for an as safety conscious rejection as
407-
* possible.
408-
*/
409-
if (CountEmptyBackendSlots()<ReservedBackends&& !superuser())
410-
elog(ERROR,"Non-superuser connection limit exceeded");
411412
}
412413

413414
/*

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