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Allow offload daemon to work without a cache.
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This is largely for offloading from a memory-heavy Apache to a small process
 that serves large static files.
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@icculus
icculus committed Oct 13, 2008
1 parent 62cfe09 commit 94db086
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Showing 2 changed files with 171 additions and 128 deletions.
275 changes: 147 additions & 128 deletions nph-offload.c
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Expand Up @@ -181,11 +181,15 @@ static const char *GUserAgent = NULL;
static const char *GReqVersion = NULL;
static const char *GReqMethod = NULL;
static char *GFilePath = NULL;
static char *GMetaDataPath = NULL;
static void *GSemaphore = NULL;
static int GSemaphoreOwned = 0;
static FILE *GDebugFilePointer = NULL;

#if !GNOCACHE
static char *GMetaDataPath = NULL;
#endif


static void failure_location(const char *, const char *, const char *);
static inline void failure(const char *httperr, const char *errmsg)
{
Expand Down Expand Up @@ -503,14 +507,6 @@ static int64 atoi64(const char *str)
} // atoi64


static const char *makeNum(int64 num)
{
static char buf[64];
snprintf(buf, sizeof (buf), "%lld", (long long) num);
return buf;
} // makeNum


static void *xmalloc(const size_t len)
{
void *ptr = malloc(len);
Expand Down Expand Up @@ -719,125 +715,6 @@ static void terminate(void)
exit(0);
} // terminate


static list *loadMetadata(const char *fname)
{
list *retval = NULL;
struct stat statbuf;
int fd = open(fname, O_RDONLY);
if (fd == -1)
return NULL;

if (fstat(fd, &statbuf) == -1)
{
close(fd);
return NULL;
} // if

char *buf = (char *) xmalloc(statbuf.st_size + 1);
if (read(fd, buf, statbuf.st_size) != statbuf.st_size)
{
free(buf);
close(fd);
return NULL;
} // if

buf[statbuf.st_size] = '\0';
close(fd);

char *ptr = buf;
int total = 0;
while (1)
{
char *key = ptr;
ptr = strchr(ptr, '\n');
if (ptr == NULL)
break;
*(ptr++) = '\0';
char *value = ptr;
ptr = strchr(ptr, '\n');
if (ptr == NULL)
break;
*(ptr++) = '\0';
if (*key != '\0')
listSet(&retval, key, value);
debugEcho("Loaded metadata '%s' => '%s'", key, value);
total++;
} // while

free(buf);
debugEcho("Loaded %d metadata pair(s).", total);

return retval;
} // loadMetadata


static int cachedMetadataMostRecent(const list *metadata, const list *head)
{
const char *contentlength = listFind(metadata, "Content-Length");
if (!contentlength)
return 0;

const char *etag = listFind(metadata, "ETag");
if (!etag)
return 0;

const char *lastmodified = listFind(metadata, "Last-Modified");
if (!lastmodified)
return 0;

if (strcmp(contentlength, listFind(head, "Content-Length")) != 0)
return 0;

if (strcmp(etag, listFind(head, "ETag")) != 0)
return 0;

if (strcmp(lastmodified, listFind(head, "Last-Modified")) != 0)
{
const char *isweak = listFind(metadata, "X-Offload-Is-Weak");
if ( (!isweak) || (strcmp(isweak, "0") != 0) )
return 0;
} // if

// See if file size != Content-Length, and if it isn't,
// see if X-Offload-Caching-PID still exists. If process
// is missing, assume transfer died and recache.
struct stat statbuf;
if (stat(GFilePath, &statbuf) == -1)
return 0;

const int64 fsize = statbuf.st_size;
if (fsize != atoi64(contentlength))
{
// whoa, we were supposed to cache this!
const char *cacher = listFind(metadata, "X-Offload-Caching-PID");
if (!cacher)
return 0;

const int cacherpid = atoi(cacher);
if (process_dead(cacherpid))
{
debugEcho("Caching process ID died!");
return 0;
} // if
} // if

return 1;
} // cachedMetadataMostRecent


static void nukeRequestFromCache(void)
{
debugEcho("Nuking request from cache...");
getSemaphore();
if (GMetaDataPath != NULL)
unlink(GMetaDataPath);
if (GFilePath != NULL)
unlink(GFilePath);
putSemaphore();
} // nukeRequestFromCache


static void failure_location(const char *httperr, const char *errmsg,
const char *location)
{
Expand Down Expand Up @@ -1108,6 +985,7 @@ static void http_head(list **head)
} // http_head


#if !GNOCACHE
static int http_get(list **head)
{
list *headers = NULL;
Expand All @@ -1122,6 +1000,132 @@ static int http_get(list **head)
} // http_get


static const char *makeNum(int64 num)
{
static char buf[64];
snprintf(buf, sizeof (buf), "%lld", (long long) num);
return buf;
} // makeNum


static list *loadMetadata(const char *fname)
{
list *retval = NULL;
struct stat statbuf;
int fd = open(fname, O_RDONLY);
if (fd == -1)
return NULL;

if (fstat(fd, &statbuf) == -1)
{
close(fd);
return NULL;
} // if

char *buf = (char *) xmalloc(statbuf.st_size + 1);
if (read(fd, buf, statbuf.st_size) != statbuf.st_size)
{
free(buf);
close(fd);
return NULL;
} // if

buf[statbuf.st_size] = '\0';
close(fd);

char *ptr = buf;
int total = 0;
while (1)
{
char *key = ptr;
ptr = strchr(ptr, '\n');
if (ptr == NULL)
break;
*(ptr++) = '\0';
char *value = ptr;
ptr = strchr(ptr, '\n');
if (ptr == NULL)
break;
*(ptr++) = '\0';
if (*key != '\0')
listSet(&retval, key, value);
debugEcho("Loaded metadata '%s' => '%s'", key, value);
total++;
} // while

free(buf);
debugEcho("Loaded %d metadata pair(s).", total);

return retval;
} // loadMetadata


static int cachedMetadataMostRecent(const list *metadata, const list *head)
{
const char *contentlength = listFind(metadata, "Content-Length");
if (!contentlength)
return 0;

const char *etag = listFind(metadata, "ETag");
if (!etag)
return 0;

const char *lastmodified = listFind(metadata, "Last-Modified");
if (!lastmodified)
return 0;

if (strcmp(contentlength, listFind(head, "Content-Length")) != 0)
return 0;

if (strcmp(etag, listFind(head, "ETag")) != 0)
return 0;

if (strcmp(lastmodified, listFind(head, "Last-Modified")) != 0)
{
const char *isweak = listFind(metadata, "X-Offload-Is-Weak");
if ( (!isweak) || (strcmp(isweak, "0") != 0) )
return 0;
} // if

// See if file size != Content-Length, and if it isn't,
// see if X-Offload-Caching-PID still exists. If process
// is missing, assume transfer died and recache.
struct stat statbuf;
if (stat(GFilePath, &statbuf) == -1)
return 0;

const int64 fsize = statbuf.st_size;
if (fsize != atoi64(contentlength))
{
// whoa, we were supposed to cache this!
const char *cacher = listFind(metadata, "X-Offload-Caching-PID");
if (!cacher)
return 0;

const int cacherpid = atoi(cacher);
if (process_dead(cacherpid))
{
debugEcho("Caching process ID died!");
return 0;
} // if
} // if

return 1;
} // cachedMetadataMostRecent


static void nukeRequestFromCache(void)
{
debugEcho("Nuking request from cache...");
getSemaphore();
if (GMetaDataPath != NULL)
unlink(GMetaDataPath);
if (GFilePath != NULL)
unlink(GFilePath);
putSemaphore();
} // nukeRequestFromCache


static char *etagToCacheFname(const char *etag)
{
static const char chs[] = { ' ', '\t', 0x0B, '\"', '\'' };
Expand Down Expand Up @@ -1307,6 +1311,7 @@ static pid_t cacheFork(const int sock, FILE *cacheio, const int64 max)
terminate(); // always die.
return -1;
} // cacheFork
#endif // #if !GNOCACHE


static int serverMainline(int argc, char **argv, char **envp)
Expand Down Expand Up @@ -1469,6 +1474,18 @@ static int serverMainline(int argc, char **argv, char **envp)
if (invalidContentRange(startRange, endRange, max))
failure("400 Bad Request", "Bad content range requested.");

#if GNOCACHE

GFilePath = makeStr("%s%s", GOFFLOADDIR, Guri);
debugEcho("file to send is %s", GFilePath);
list *metadata = head;
head = NULL;
io = open(GFilePath, O_RDONLY);
if (io == -1)
failure("500 Internal Server Error", "Couldn't access cached data.");

#else

char *etagFname = etagToCacheFname(etag);
GFilePath = makeStr("%s/filedata-%s", GOFFLOADDIR, etagFname);
GMetaDataPath = makeStr("%s/metadata-%s", GOFFLOADDIR, etagFname);
Expand Down Expand Up @@ -1548,6 +1565,8 @@ static int serverMainline(int argc, char **argv, char **envp)
failure("500 Internal Server Error", "Couldn't access cached data.");
} // else

#endif

if (!GHttpStatus)
GHttpStatus = atoi(responseCode);

Expand Down
24 changes: 24 additions & 0 deletions offload_server_config.h
View file
Expand Up @@ -138,5 +138,29 @@
#define SHM_NAME "mod-offload"
#endif

// You probably should leave this alone if you don't know what you're doing.
// Set this to non-zero to disable caching. This can be useful if you just
// want a lightweight HTTP server to handle the heavy lifting for large
// static files. For example, you could have Apache running on port 80 to
// handle most requests, so you get all the PHP, SSL, mod_*, .htaccess, etc
// goodness, but Apache eats several megabytes of RAM per connection when
// serving static files. If you have a multi-gigabyte static file, a client
// might consume that server's RAM for several hours to complete the
// transfer. Since most of the memory Apache consumes is irrelevant to
// sending static files, it might make sense to offload it to a lightweight
// process like this, with a 302 Redirect, and free up those resources for
// dynamic content. Very quickly you find yourself saving hundreds of
// megabytes.
// GNOCACHE changes a few rules. This process will no longer cache files, and
// GOFFLOADDIR refers to the DocumentRoot where files are read from. We will
// still do HTTP HEAD requests to the GBASESERVER for metadata, and to verify
// that we have access to the file (since we do no authorization
// ourselves). We access the file directly, instead of caching over HTTP, so
// be careful about file permissions, URI aliases, etc. This probably is only
// useful with GLISTENPORT != 0.
#ifndef GNOCACHE
#define GNOCACHE 0
#endif

// end of offload_server_config.h ...

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