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Module API for Forking

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* create module API for forking child processes.
* refactor duplicate code around creating and tracking forks by AOF and RDB.
* child processes listen to SIGUSR1 and dies exitFromChild in order to
  eliminate a valgrind warning of unhandled signal.
* note that BGSAVE error reply has changed.

valgrind error is:
  Process terminating with default action of signal 10 (SIGUSR1)
This commit is contained in:
Oran Agra
2019-07-17 08:51:02 +03:00
parent 4b2579a064
commit 56258c6b7d
15 changed files with 342 additions and 91 deletions
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84
tests/modules/fork.c Normal file
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#define REDISMODULE_EXPERIMENTAL_API
#include "redismodule.h"
#include <string.h>
#include <assert.h>
#include <unistd.h>
#define UNUSED(V) ((void) V)
int child_pid = -1;
int exitted_with_code = -1;
void done_handler(int exitcode, int bysignal, void *user_data) {
child_pid = -1;
exitted_with_code = exitcode;
assert(user_data==(void*)0xdeadbeef);
UNUSED(bysignal);
}
int fork_create(RedisModuleCtx *ctx, RedisModuleString **argv, int argc)
{
long long code_to_exit_with;
if (argc != 2) {
RedisModule_WrongArity(ctx);
return REDISMODULE_OK;
}
RedisModule_StringToLongLong(argv[1], &code_to_exit_with);
exitted_with_code = -1;
child_pid = RedisModule_Fork(done_handler, (void*)0xdeadbeef);
if (child_pid < 0) {
RedisModule_ReplyWithError(ctx, "Fork failed");
return REDISMODULE_OK;
} else if (child_pid > 0) {
/* parent */
RedisModule_ReplyWithLongLong(ctx, child_pid);
return REDISMODULE_OK;
}
/* child */
RedisModule_Log(ctx, "notice", "fork child started");
usleep(200000);
RedisModule_Log(ctx, "notice", "fork child exiting");
RedisModule_ExitFromChild(code_to_exit_with);
/* unreachable */
return 0;
}
int fork_exitcode(RedisModuleCtx *ctx, RedisModuleString **argv, int argc)
{
UNUSED(argv);
UNUSED(argc);
RedisModule_ReplyWithLongLong(ctx, exitted_with_code);
return REDISMODULE_OK;
}
int fork_kill(RedisModuleCtx *ctx, RedisModuleString **argv, int argc)
{
UNUSED(argv);
UNUSED(argc);
if (RedisModule_KillForkChild(child_pid) != REDISMODULE_OK)
RedisModule_ReplyWithError(ctx, "KillForkChild failed");
else
RedisModule_ReplyWithLongLong(ctx, 1);
child_pid = -1;
return REDISMODULE_OK;
}
int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
UNUSED(argv);
UNUSED(argc);
if (RedisModule_Init(ctx,"fork",1,REDISMODULE_APIVER_1)== REDISMODULE_ERR)
return REDISMODULE_ERR;
if (RedisModule_CreateCommand(ctx,"fork.create", fork_create,"",0,0,0) == REDISMODULE_ERR)
return REDISMODULE_ERR;
if (RedisModule_CreateCommand(ctx,"fork.exitcode", fork_exitcode,"",0,0,0) == REDISMODULE_ERR)
return REDISMODULE_ERR;
if (RedisModule_CreateCommand(ctx,"fork.kill", fork_kill,"",0,0,0) == REDISMODULE_ERR)
return REDISMODULE_ERR;
return REDISMODULE_OK;
}