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Modifications to make mod_unique_id thread safe. This should work on Windows,

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but no guarantees.  I haven't verified it will always give a unique ID, but
the logic is good.  I'll write some test cases to see if I can make it fail
later.

Submitted by:	Ryan Bloom


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@83789 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Roy T. Fielding
1999-08-26 17:22:35 +00:00
parent dc349534f3
commit 3dfd8e0dc3
1 changed files with 28 additions and 12 deletions
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40
modules/metadata/mod_unique_id.c
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@@ -65,19 +65,25 @@
#include "httpd.h"
#include "http_config.h"
#include "http_log.h"
#include "multithread.h"
#ifdef MULTITHREAD
#error sorry this module does not support multithreaded servers yet
#endif
typedef struct {
unsigned int stamp;
unsigned int in_addr;
unsigned int pid;
unsigned short counter;
unsigned int thread_index;
} unique_id_rec;
/* We are using thread_index (the index into the scoreboard), because we
* cannont garauntee the thread_id will be an integer.
*
* This code looks like it won't give a unique ID with the new thread logic.
* It will. The reason is, we don't increment the counter in a thread_safe
* manner. Because the thread_index is also in the unique ID now, this does
* not matter. In order for the id to not be unique, the same thread would
* have to get the same counter twice in the same second.
*/
/* Comments:
*
* We want an identifier which is unique across all hits, everywhere.
@@ -143,12 +149,12 @@ typedef struct {
static unsigned global_in_addr;
static APACHE_TLS unique_id_rec cur_unique_id;
static unique_id_rec cur_unique_id;
/*
* Number of elements in the structure unique_id_rec.
*/
#define UNIQUE_ID_REC_MAX 4
#define UNIQUE_ID_REC_MAX 5
static unsigned short unique_id_rec_offset[UNIQUE_ID_REC_MAX],
unique_id_rec_size[UNIQUE_ID_REC_MAX],
@@ -177,8 +183,11 @@ static void unique_id_global_init(server_rec *s, pool *p)
unique_id_rec_size[2] = sizeof(cur_unique_id.pid);
unique_id_rec_offset[3] = XtOffsetOf(unique_id_rec, counter);
unique_id_rec_size[3] = sizeof(cur_unique_id.counter);
unique_id_rec_offset[4] = XtOffsetOf(unique_id_rec, thread_index);
unique_id_rec_size[4] = sizeof(cur_unique_id.thread_index);
unique_id_rec_total_size = unique_id_rec_size[0] + unique_id_rec_size[1] +
unique_id_rec_size[2] + unique_id_rec_size[3];
unique_id_rec_size[2] + unique_id_rec_size[3] +
unique_id_rec_size[4];
/*
* Calculate the size of the structure when encoded.
@@ -316,6 +325,7 @@ static int gen_unique_id(request_rec *r)
* Buffer padded with two final bytes, used to copy the unique_id_red
* structure without the internal paddings that it could have.
*/
unique_id_rec new_unique_id;
struct {
unique_id_rec foo;
unsigned char pad[2];
@@ -332,16 +342,21 @@ static int gen_unique_id(request_rec *r)
ap_table_setn(r->subprocess_env, "UNIQUE_ID", e);
return DECLINED;
}
new_unique_id.in_addr = cur_unique_id.in_addr;
new_unique_id.pid = cur_unique_id.pid;
new_unique_id.counter = cur_unique_id.counter;
cur_unique_id.stamp = htonl((unsigned int)r->request_time);
new_unique_id.stamp = htonl((unsigned int)r->request_time);
new_unique_id.thread_index = htonl((unsigned int)r->connection->thread_num);
/* we'll use a temporal buffer to avoid uuencoding the possible internal
* paddings of the original structure */
x = (unsigned char *) &paddedbuf;
y = (unsigned char *) &cur_unique_id;
y = (unsigned char *) &new_unique_id;
k = 0;
for (i = 0; i < UNIQUE_ID_REC_MAX; i++) {
y = ((unsigned char *) &cur_unique_id) + unique_id_rec_offset[i];
y = ((unsigned char *) &new_unique_id) + unique_id_rec_offset[i];
for (j = 0; j < unique_id_rec_size[i]; j++, k++) {
x[k] = y[j];
}
@@ -370,7 +385,8 @@ static int gen_unique_id(request_rec *r)
ap_table_setn(r->subprocess_env, "UNIQUE_ID", str);
/* and increment the identifier for the next call */
counter = ntohs(cur_unique_id.counter) + 1;
counter = ntohs(new_unique_id.counter) + 1;
cur_unique_id.counter = htons(counter);
return DECLINED;