//
// Clone server Model Six
//
// Lets us build this source without creating a library
#include "bstar.c"
#include "kvmsg.c"
// Bstar reactor handlers
static int s_snapshots (zloop_t *loop, void *socket, void *args);
static int s_collector (zloop_t *loop, void *socket, void *args);
static int s_flush_ttl (zloop_t *loop, void *socket, void *args);
static int s_send_hugz (zloop_t *loop, void *socket, void *args);
static int s_new_master (zloop_t *loop, void *unused, void *args);
static int s_new_slave (zloop_t *loop, void *unused, void *args);
static int s_subscriber (zloop_t *loop, void *socket, void *args);
// Our server is defined by these properties
typedef struct {
zctx_t *ctx; // Context wrapper
zhash_t *kvmap; // Key-value store
bstar_t *bstar; // Bstar reactor core
int64_t sequence; // How many updates we're at
int port; // Main port we're working on
int peer; // Main port of our peer
void *publisher; // Publish updates and hugz
void *collector; // Collect updates from clients
void *subscriber; // Get updates from peer
zlist_t *pending; // Pending updates from clients
Bool primary; // TRUE if we're primary
Bool master; // TRUE if we're master
Bool slave; // TRUE if we're slave
} clonesrv_t;
int main (int argc, char *argv [])
{
clonesrv_t *self = (clonesrv_t *) zmalloc (sizeof (clonesrv_t));
if (argc == 2 && streq (argv [1], "-p")) {
zclock_log ("I: primary master, waiting for backup (slave)");
self->bstar = bstar_new (BSTAR_PRIMARY, "tcp://*:5003",
"tcp://localhost:5004");
bstar_voter (self->bstar, "tcp://*:5556", ZMQ_ROUTER,
s_snapshots, self);
self->port = 5556;
self->peer = 5566;
self->primary = TRUE;
}
else
if (argc == 2 && streq (argv [1], "-b")) {
zclock_log ("I: backup slave, waiting for primary (master)");
self->bstar = bstar_new (BSTAR_BACKUP, "tcp://*:5004",
"tcp://localhost:5003");
bstar_voter (self->bstar, "tcp://*:5566", ZMQ_ROUTER,
s_snapshots, self);
self->port = 5566;
self->peer = 5556;
self->primary = FALSE;
}
else {
printf ("Usage: clonesrv4 { -p | -b }\n");
free (self);
exit (0);
}
// Primary server will become first master
if (self->primary)
self->kvmap = zhash_new ();
self->ctx = zctx_new ();
self->pending = zlist_new ();
bstar_set_verbose (self->bstar, TRUE);
// Set up our clone server sockets
self->publisher = zsocket_new (self->ctx, ZMQ_PUB);
self->collector = zsocket_new (self->ctx, ZMQ_SUB);
zsocket_bind (self->publisher, "tcp://*:%d", self->port + 1);
zsocket_bind (self->collector, "tcp://*:%d", self->port + 2);
// Set up our own clone client interface to peer
self->subscriber = zsocket_new (self->ctx, ZMQ_SUB);
zsocket_connect (self->subscriber, "tcp://localhost:%d", self->peer + 1);
// Register state change handlers
bstar_new_master (self->bstar, s_new_master, self);
bstar_new_slave (self->bstar, s_new_slave, self);
// Register our other handlers with the bstar reactor
zloop_reader (bstar_zloop (self->bstar), self->collector, s_collector, self);
zloop_timer (bstar_zloop (self->bstar), 1000, 0, s_flush_ttl, self);
zloop_timer (bstar_zloop (self->bstar), 1000, 0, s_send_hugz, self);
// Start the Bstar reactor
bstar_start (self->bstar);
// Interrupted, so shut down
while (zlist_size (self->pending)) {
kvmsg_t *kvmsg = (kvmsg_t *) zlist_pop (self->pending);
kvmsg_destroy (&kvmsg);
}
zlist_destroy (&self->pending);
bstar_destroy (&self->bstar);
zhash_destroy (&self->kvmap);
zctx_destroy (&self->ctx);
free (self);
return 0;
}
// ---------------------------------------------------------------------
// Send snapshots to clients who ask for them
static int s_send_single (char *key, void *data, void *args);
// Routing information for a key-value snapshot
typedef struct {
void *socket; // ROUTER socket to send to
zframe_t *identity; // Identity of peer who requested state
char *subtree; // Client subtree specification
} kvroute_t;
static int
s_snapshots (zloop_t *loop, void *snapshot, void *args)
{
clonesrv_t *self = (clonesrv_t *) args;
zframe_t *identity = zframe_recv (snapshot);
if (identity) {
// Request is in second frame of message
char *request = zstr_recv (snapshot);
char *subtree = NULL;
if (streq (request, "ICANHAZ?")) {
free (request);
subtree = zstr_recv (snapshot);
}
else
printf ("E: bad request, aborting\n");
if (subtree) {
// Send state socket to client
kvroute_t routing = { snapshot, identity, subtree };
zhash_foreach (self->kvmap, s_send_single, &routing);
// Now send END message with sequence number
zclock_log ("I: sending shapshot=%d", (int) self->sequence);
zframe_send (&identity, snapshot, ZFRAME_MORE);
kvmsg_t *kvmsg = kvmsg_new (self->sequence);
kvmsg_set_key (kvmsg, "KTHXBAI");
kvmsg_set_body (kvmsg, (byte *) subtree, 0);
kvmsg_send (kvmsg, snapshot);
kvmsg_destroy (&kvmsg);
free (subtree);
}
}
return 0;
}
// Send one state snapshot key-value pair to a socket
// Hash item data is our kvmsg object, ready to send
static int
s_send_single (char *key, void *data, void *args)
{
kvroute_t *kvroute = (kvroute_t *) args;
kvmsg_t *kvmsg = (kvmsg_t *) data;
if (strlen (kvroute->subtree) <= strlen (kvmsg_key (kvmsg))
&& memcmp (kvroute->subtree,
kvmsg_key (kvmsg), strlen (kvroute->subtree)) == 0) {
// Send identity of recipient first
zframe_send (&kvroute->identity,
kvroute->socket, ZFRAME_MORE + ZFRAME_REUSE);
kvmsg_send (kvmsg, kvroute->socket);
}
return 0;
}
// ---------------------------------------------------------------------
// Collect updates from clients
// If we're master, we apply these to the kvmap
// If we're slave, or unsure, we queue them on our pending list
static int s_was_pending (clonesrv_t *self, kvmsg_t *kvmsg);
static int
s_collector (zloop_t *loop, void *collector, void *args)
{
clonesrv_t *self = (clonesrv_t *) args;
kvmsg_t *kvmsg = kvmsg_recv (collector);
kvmsg_dump (kvmsg);
if (kvmsg) {
if (self->master) {
kvmsg_set_sequence (kvmsg, ++self->sequence);
kvmsg_send (kvmsg, self->publisher);
int ttl = atoi (kvmsg_get_prop (kvmsg, "ttl"));
if (ttl)
kvmsg_set_prop (kvmsg, "ttl",
"%" PRId64, zclock_time () + ttl * 1000);
kvmsg_store (&kvmsg, self->kvmap);
zclock_log ("I: publishing update=%d", (int) self->sequence);
}
else {
// If we already got message from master, drop it, else
// hold on pending list
if (s_was_pending (self, kvmsg))
kvmsg_destroy (&kvmsg);
else
zlist_append (self->pending, kvmsg);
}
}
return 0;
}
// If message was already on pending list, remove it and
// return TRUE, else return FALSE.
static int
s_was_pending (clonesrv_t *self, kvmsg_t *kvmsg)
{
kvmsg_t *held = (kvmsg_t *) zlist_first (self->pending);
while (held) {
if (memcmp (kvmsg_uuid (kvmsg),
kvmsg_uuid (held), sizeof (uuid_t)) == 0) {
zlist_remove (self->pending, held);
return TRUE;
}
held = (kvmsg_t *) zlist_next (self->pending);
}
return FALSE;
}
// ---------------------------------------------------------------------
// Purge ephemeral values that have expired
static int s_flush_single (char *key, void *data, void *args);
static int
s_flush_ttl (zloop_t *loop, void *unused, void *args)
{
clonesrv_t *self = (clonesrv_t *) args;
zhash_foreach (self->kvmap, s_flush_single, args);
return 0;
}
// If key-value pair has expired, delete it and publish the
// fact to listening clients.
static int
s_flush_single (char *key, void *data, void *args)
{
clonesrv_t *self = (clonesrv_t *) args;
kvmsg_t *kvmsg = (kvmsg_t *) data;
int64_t ttl;
sscanf (kvmsg_get_prop (kvmsg, "ttl"), "%" PRId64, &ttl);
if (ttl && zclock_time () >= ttl) {
kvmsg_set_sequence (kvmsg, ++self->sequence);
kvmsg_set_body (kvmsg, (byte *) "", 0);
kvmsg_send (kvmsg, self->publisher);
kvmsg_store (&kvmsg, self->kvmap);
zclock_log ("I: publishing delete=%d", (int) self->sequence);
}
return 0;
}
// ---------------------------------------------------------------------
// Send hugz to anyone listening on the publisher socket
static int
s_send_hugz (zloop_t *loop, void *unused, void *args)
{
clonesrv_t *self = (clonesrv_t *) args;
kvmsg_t *kvmsg = kvmsg_new (self->sequence);
kvmsg_set_key (kvmsg, "HUGZ");
kvmsg_set_body (kvmsg, (byte *) "", 0);
kvmsg_send (kvmsg, self->publisher);
kvmsg_destroy (&kvmsg);
return 0;
}
// ---------------------------------------------------------------------
// State change handlers
// We're becoming master
//
// The backup server applies its pending list to its own hash table,
// and then starts to process state snapshot requests.
static int
s_new_master (zloop_t *loop, void *unused, void *args)
{
clonesrv_t *self = (clonesrv_t *) args;
self->master = TRUE;
self->slave = FALSE;
zloop_cancel (bstar_zloop (self->bstar), self->subscriber);
// Apply pending list to own hash table
while (zlist_size (self->pending)) {
kvmsg_t *kvmsg = (kvmsg_t *) zlist_pop (self->pending);
kvmsg_set_sequence (kvmsg, ++self->sequence);
kvmsg_send (kvmsg, self->publisher);
kvmsg_store (&kvmsg, self->kvmap);
zclock_log ("I: publishing pending=%d", (int) self->sequence);
}
return 0;
}
// ---------------------------------------------------------------------
// We're becoming slave
static int
s_new_slave (zloop_t *loop, void *unused, void *args)
{
clonesrv_t *self = (clonesrv_t *) args;
zhash_destroy (&self->kvmap);
self->master = FALSE;
self->slave = TRUE;
zloop_reader (bstar_zloop (self->bstar), self->subscriber,
s_subscriber, self);
return 0;
}
// ---------------------------------------------------------------------
// Collect updates from peer (master)
// We're always slave when we get these updates
static int
s_subscriber (zloop_t *loop, void *subscriber, void *args)
{
clonesrv_t *self = (clonesrv_t *) args;
// Get state snapshot if necessary
if (self->kvmap == NULL) {
self->kvmap = zhash_new ();
void *snapshot = zsocket_new (self->ctx, ZMQ_DEALER);
zsocket_connect (snapshot, "tcp://localhost:%d", self->peer);
zclock_log ("I: asking for snapshot from: tcp://localhost:%d",
self->peer);
zstr_send (snapshot, "ICANHAZ?");
while (TRUE) {
kvmsg_t *kvmsg = kvmsg_recv (snapshot);
if (!kvmsg)
break; // Interrupted
if (streq (kvmsg_key (kvmsg), "KTHXBAI")) {
self->sequence = kvmsg_sequence (kvmsg);
kvmsg_destroy (&kvmsg);
break; // Done
}
kvmsg_store (&kvmsg, self->kvmap);
}
zclock_log ("I: received snapshot=%d", (int) self->sequence);
zsocket_destroy (self->ctx, snapshot);
}
// Find and remove update off pending list
kvmsg_t *kvmsg = kvmsg_recv (subscriber);
if (!kvmsg)
return 0;
if (strneq (kvmsg_key (kvmsg), "HUGZ")) {
if (!s_was_pending (self, kvmsg)) {
// If master update came before client update, flip it
// around, store master update (with sequence) on pending
// list and use to clear client update when it comes later
zlist_append (self->pending, kvmsg_dup (kvmsg));
}
// If update is more recent than our kvmap, apply it
if (kvmsg_sequence (kvmsg) > self->sequence) {
self->sequence = kvmsg_sequence (kvmsg);
kvmsg_store (&kvmsg, self->kvmap);
zclock_log ("I: received update=%d", (int) self->sequence);
}
else
kvmsg_destroy (&kvmsg);
}
else
kvmsg_destroy (&kvmsg);
return 0;
}
代码不短，不过作者的牢骚更长。（貌似花了一周的时间）
当然作为一个靠谱的模型，总会制定一些规范给某些不太靠谱的人： http://rfc.zeromq.org/spec:12
至此，整个教程算是告一段落了。（之所以这最后一个模型分了三段，着实是代码多了些）
教程结束了，学习才刚开始。至于会不会再有后续，诚如guide结尾：
More coming soon…
结言：
虽然知道翻译技术文章有难度，但着实还是吓着了，在写第一章的时候就打了退堂鼓。终究在自我安慰、勉励下完成了这个系列的笔记(退一步)。好吧，我承认代码、图示占了大比例，不过，好歹算是有始有终的完成了。
原计划一周时间结束的，由于诸多原因(磨蹭，消极，退堂鼓)前后竟然跨了两个多月，总算咬牙坚持了下来，其实不敢说学到了很多，自从中部python的代码不再时，几乎就没有再自己验证代码的可行和逻辑了。写本系列，更多的是自个儿跟自个儿过不去(俺就不信写不完了！)折腾到最后，多少也是有些收获的(谁折腾谁知道～)
回首看看，也就这样了，倒是有些"天凉好个秋"的意味。
也罢，哦了～