Add the test/fork-test.c test program.
FossilOrigin-Name: 0611e2b0cf3f33c28cc9ff6c5da7ebba2033bcbda5b1072a30021a3e1fb4e738
This commit is contained in:
drh
parent
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11
manifest
11
manifest
@ -1,5 +1,5 @@
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C Add\sthe\sSQLITE_FCNTL_NULL_IO\sfile-control.
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D 2024-11-13T14:58:35.917
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C Add\sthe\stest/fork-test.c\stest\sprogram.
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D 2024-11-13T16:08:02.102
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F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
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F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
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F LICENSE.md e108e1e69ae8e8a59e93c455654b8ac9356a11720d3345df2a4743e9590fb20d
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@ -1154,6 +1154,7 @@ F test/fkey7.test 64fb28da03da5dfe3cdef5967aa7e832c2507bf7fb8f0780cacbca1f2338d0
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F test/fkey8.test 51deda7f1a1448bca95875e4a6e1a3a75b4bd7215e924e845bd60de60e4d84bf
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F test/fkey_malloc.test 594a7ea1fbab553c036c70813cd8bd9407d63749
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F test/fordelete.test ba98f14446b310f9c9d935b97ec748753d0144a28b356ba30d1f4f6958fdde5c
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F test/fork-test.c 9ac2e6423a1d38df3d6be0e8ac15608b545de21e2b19d9d876254c5931b63edb
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F test/format4.test eeae341953db8b6bda7f549044797c3278a6cc345d11ada81471671b654f8ef4
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F test/fp-speed-1.c b37de94eba034e1703668816225f54510ec60fb0685406608cc707afe6b8234d
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F test/fpconv1.test d5d8aa0c427533006c112fb1957cdd1ea68c1d0709470dabb9ca02c2e4c06ad8
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@ -2198,8 +2199,8 @@ F tool/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd7227350
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F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
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F tool/warnings.sh 49a486c5069de041aedcbde4de178293e0463ae9918ecad7539eedf0ec77a139
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F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
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R 6602510d12e6c22a0b1d041f1323efab
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U drh
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Z 9feaba1d713c9ff220e94d51317a455c
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Z a609b555f7a83a611caf3857959d5dfd
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# Remove this line to create a well-formed Fossil manifest.
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f0e917fcf51b59f8ccfe5b9341937341d0e6016eb275d6c33dcb10b0b301a9da
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0611e2b0cf3f33c28cc9ff6c5da7ebba2033bcbda5b1072a30021a3e1fb4e738
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310
test/fork-test.c
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310
test/fork-test.c
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/*
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** The program demonstrates how a child process created using fork()
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** can continue to use SQLite for a database that the parent had opened and
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** and was writing into when the fork() occurred.
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**
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** This program executes the following steps:
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**
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** 1. Create a new database file. Open it, and populate it.
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** 2. Start a transaction and make changes.
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** ^-- close the transaction prior to fork() if --commit-before-fork
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** 3. Fork()
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** 4. In the child, close the database connection. Special procedures
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** are needed to close the database connection in the child. See the
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** implementation below.
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** 5. Commit the transaction in the parent.
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** 6. Verify that the transaction committed in the parent.
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** 7. In the child, after a delay to allow time for (5) and (6),
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** open a new database connection and verify that the transaction
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** committed by (5) is seen.
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** 8. Add make further changes and commit them in the child, using the
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** new database connection.
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** 9. In the parent, after a delay to account for (8), verify that
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** the new transaction added by (8) can be seen.
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**
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** Usage:
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**
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** fork-test FILENAME [options]
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**
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** Options:
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**
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** --wal Run the database in WAL mode
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** --vfstrace Enable VFS tracing for debugging
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** --commit-before-fork COMMIT prior to the fork() in step 3
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** --delay-after-4 N Pause for N seconds after step 4
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**
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** How To Compile:
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**
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** gcc -O0 -g -Wall -I$(SQLITESRC) \
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** f1.c $(SQLITESRC)/ext/misc/vfstrace.c $(SQLITESRC/sqlite3.c \
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** -ldl -lpthread -lm
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**
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** Test procedure:
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**
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** (1) Run "fork-test x1.db". Verify no I/O errors occur and that
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** both parent and child see all three rows in the t1 table.
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**
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** (2) Repeat (1) adding the --wal option.
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**
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** (3) Repeat (1) and (2) adding the --commit-before-fork option.
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**
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** (4) Repeat all prior steps adding the --delay-after-4 option with
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** a timeout of 15 seconds or so. Then, while both parent and child
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** are paused, run the CLI against the x1.db database from a separate
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** window and verify that all the correct file locks are still working
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** correctly.
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**
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** Take-Aways:
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**
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** * If a process has open SQLite database connections when it fork()s,
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** the child can call exec() and all it well. Nothing special needs
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** to happen.
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**
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** * If a process has open SQLite database connections when it fork()s,
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** the child can do anything that does not involve using SQLite without
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** causing problems in the parent. No special actions are needed in
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** the child.
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**
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** * If a process has open SQLite database connections when it fork()s,
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** the child can call sqlite3_close() on those database connections
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** as long as there were no pending write transactions when the fork()
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** occurred.
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**
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** * If a process has open SQLite database connections that are in the
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** middle of a write transaction and then the processes fork()s, the
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** child process should close the database connections using the
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** procedures demonstrated in Step 4 below before trying to do anything
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** else with SQLite.
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**
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** * If a child process can safely close SQLite database connections that
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** it inherited via fork() using the procedures shown in Step 4 below
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** even if the database connections were not involved in a write
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** transaction at the time of the fork(). The special procedures are
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** required if a write transaction was active. They are optional
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** otherwise. No harm results from using the special procedures when
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** they are not necessary.
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**
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** * Child processes that use SQLite should open their own database
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** connections. They should not attempt to use a database connection
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** that is inherited from the parent.
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*/
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#include <stdio.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <errno.h>
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#include "sqlite3.h"
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/*
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** Process ID of the parent
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*/
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static pid_t parentPid = 0;
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/*
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** Return either "parent" or "child", as appropriate.
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*/
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static const char *whoAmI(void){
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return getpid()==parentPid ? "parent" : "child";
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}
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/*
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** This is an sqlite3_exec() callback routine that prints all results.
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*/
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static int execCallback(void *pNotUsed, int nCol, char **aVal, char **aCol){
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int i;
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const char *zWho = whoAmI();
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for(i=0; i<nCol; i++){
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const char *zVal = aVal[i];
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const char *zCol = aCol[i];
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if( zVal==0 ) zVal = "NULL";
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if( zCol==0 ) zCol = "NULL";
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printf("%s: %s = %s\n", zWho, zCol, zVal);
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fflush(stdout);
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}
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return 0;
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}
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/*
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** Execute one or more SQL statements.
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*/
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static void sqlExec(sqlite3 *db, const char *zSql, int bCallback){
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int rc;
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char *zErr = 0;
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printf("%s: %s\n", whoAmI(), zSql);
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fflush(stdout);
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rc = sqlite3_exec(db, zSql, bCallback ? execCallback : 0, 0, &zErr);
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if( rc || zErr!=0 ){
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printf("%s: %s: rc=%d: %s\n",
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whoAmI(), zSql, rc, zErr);
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exit(1);
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}
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}
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/*
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** Trace callback for the vfstrace extension.
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*/
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static int vfsTraceCallback(const char *zMsg, void *pNotUsed){
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printf("%s: %s", whoAmI(), zMsg);
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fflush(stdout);
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return 0;
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}
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/* External VFS module provided by ext/misc/vfstrace.c
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*/
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extern int vfstrace_register(
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const char *zTraceName, // Name of the newly constructed VFS
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const char *zOldVfsName, // Name of the underlying VFS
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int (*xOut)(const char*,void*), // Output routine. ex: fputs
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void *pOutArg, // 2nd argument to xOut. ex: stderr
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int makeDefault // Make the new VFS the default
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);
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int main(int argc, char **argv){
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sqlite3 *db;
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int rc;
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int i;
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int useWal = 0;
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const char *zFilename = 0;
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pid_t child = 0, c2;
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int status;
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int bCommitBeforeFork = 0;
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int nDelayAfter4 = 0;
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for(i=1; i<argc; i++){
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const char *z = argv[i];
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if( z[0]=='-' && z[1]=='-' && z[2]!=0 ) z++;
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if( strcmp(z, "-wal")==0 ){
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useWal = 1;
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}else if( strcmp(z, "-commit-before-fork")==0 ){
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bCommitBeforeFork = 1;
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}else if( strcmp(z, "-delay-after-4")==0 && i+1<argc ){
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i++;
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nDelayAfter4 = atoi(argv[i]);
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}else if( strcmp(z, "-vfstrace")==0 ){
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vfstrace_register("vfstrace", 0, vfsTraceCallback, 0, 1);
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}else if( z[0]=='-' ){
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printf("unknown option: \"%s\"\n", argv[i]);
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exit(1);
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}else if( zFilename!=0 ){
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printf("unknown argument: \"%s\"\n", argv[i]);
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exit(1);
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}else{
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zFilename = argv[i];
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}
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}
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if( zFilename==0 ){
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printf("Usage: %s FILENAME\n", argv[0]);
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return 1;
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}
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/** Step 1 **/
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printf("Step 1:\n");
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parentPid = getpid();
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unlink(zFilename);
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rc = sqlite3_open(zFilename, &db);
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if( rc ){
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printf("sqlite3_open() returns %d\n", rc);
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exit(1);
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}
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if( useWal ){
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sqlExec(db, "PRAGMA journal_mode=WAL;", 0);
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}
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sqlExec(db, "CREATE TABLE t1(x);", 0);
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sqlExec(db, "INSERT INTO t1 VALUES('First row');", 0);
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sqlExec(db, "SELECT x FROM t1;", 1);
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/** Step 2 **/
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printf("Step 2:\n");
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sqlExec(db, "BEGIN IMMEDIATE;", 0);
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sqlExec(db, "INSERT INTO t1 VALUES('Second row');", 0);
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sqlExec(db, "SELECT x FROM t1;", 1);
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if( bCommitBeforeFork ) sqlExec(db, "COMMIT", 0);
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/** Step 3 **/
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printf("Step 3:\n"); fflush(stdout);
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child = fork();
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if( child!=0 ){
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printf("Parent = %d\nChild = %d\n", getpid(), child);
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}
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/** Step 4 **/
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if( child==0 ){
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int k;
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printf("Step 4:\n"); fflush(stdout);
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/***********************************************************************
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** The following block of code closes the database connection without
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** rolling back or changing any files on disk. This is necessary to
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** preservce the pending transaction in the parent.
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*/
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for(k=0; 1/*exit-by-break*/; k++){
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const char *zDbName = sqlite3_db_name(db, k);
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sqlite3_file *pJrnl = 0;
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if( k==1 ) continue;
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if( zDbName==0 ) break;
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sqlite3_file_control(db, zDbName, SQLITE_FCNTL_NULL_IO, 0);
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sqlite3_file_control(db, zDbName, SQLITE_FCNTL_JOURNAL_POINTER, &pJrnl);
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if( pJrnl && pJrnl->pMethods && pJrnl->pMethods->xFileControl ){
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pJrnl->pMethods->xFileControl(pJrnl, SQLITE_FCNTL_NULL_IO, 0);
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}
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}
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sqlite3_close(db);
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/*
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** End of special close procedures for SQLite database connections
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** inherited via fork().
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***********************************************************************/
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printf("%s: database connection closed\n", whoAmI()); fflush(stdout);
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}else{
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/* Pause the parent briefly to give the child a chance to close its
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** database connection */
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sleep(1);
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}
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if( nDelayAfter4>0 ){
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printf("%s: Delay for %d seconds\n", whoAmI(), nDelayAfter4);
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fflush(stdout);
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sleep(nDelayAfter4);
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printf("%s: Continue after %d delay\n", whoAmI(), nDelayAfter4);
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fflush(stdout);
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}
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/** Step 5 **/
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if( child!=0 ){
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printf("Step 5:\n");
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if( !bCommitBeforeFork ) sqlExec(db, "COMMIT", 0);
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sqlExec(db, "SELECT x FROM t1;", 1);
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}
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/** Step 7 **/
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if( child==0 ){
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sleep(2);
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printf("Steps 7 and 8:\n");
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rc = sqlite3_open(zFilename, &db);
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if( rc ){
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printf("Child unable to reopen the database. rc = %d\n", rc);
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exit(1);
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}
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sqlExec(db, "SELECT * FROM t1;", 1);
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/** Step 8 **/
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sqlExec(db, "INSERT INTO t1 VALUES('Third row');", 0);
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sqlExec(db, "SELECT * FROM t1;", 1);
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sleep(1);
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return 0;
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}
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c2 = wait(&status);
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printf("Process %d finished with status %d\n", c2, status);
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/** Step 9 */
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if( child!=0 ){
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printf("Step 9:\n");
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sqlExec(db, "SELECT * FROM t1;", 1);
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}
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return 0;
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}
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