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Updated sync_agent() to be less ridiculous. Still ridiculous, though.

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This commit is contained in:
Jacob Leverich 2013-03-13 16:58:36 -07:00
parent 08b2e81c86
commit 86ad565956
1 changed files with 39 additions and 24 deletions
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63
mutilate.cc
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@ -53,7 +53,7 @@ zmq::context_t context(1);
struct thread_data {
const vector<string> *servers;
options_t *options;
bool master;
bool master; // Thread #0, not to be confused with agent master.
#ifdef HAVE_LIBZMQ
zmq::socket_t *socket;
#endif
@ -298,21 +298,20 @@ void finish_agent(ConnectionStats &stats) {
}
/*
* For each agent:
* Master -> Agent: sync1
* Agent -> Master: sync
* This synchronization routine is ridiculous because the master only
* has a ZMQ_REQ socket to the agents, but it needs to wait for a
* message from each agent before it releases them. In order to get
* the ZMQ socket into a state where it'll allow the agent to send it
* a message, it must first send a message ("sync_req"). In order to
* not leave the socket dangling with an incomplete transaction, the
* agent must send a reply ("ack").
*
* This is a *TERRIBLE* barrier implementation and I am ashamed. This
* not only causes a lot of skew, but it also allows agents to
* continue before the master has spoken with all other agents. This
* is why you see sync_agent() repeated several times in mutilate.cc.
*
* It should be:
* Without this stupid complication it would be:
*
* For each agent:
* Agent -> Master: sync
* For each agent:
* Master -> Agent: sync1
* Master -> Agent: proceed
*
* In this way, all agents must arrive at the barrier and the master
* must receive a message from each of them before it continues. It
@ -324,13 +323,31 @@ void sync_agent(zmq::socket_t* socket) {
// V("agent: synchronizing");
if (args.agent_given) {
for (auto s: agent_sockets) {
s_send(*s, "sync1");
string rep = s_recv(*s);
}
for (auto s: agent_sockets)
s_send(*s, "sync_req");
/* The real sync */
for (auto s: agent_sockets)
if (s_recv(*s).compare(string("sync")))
DIE("sync_agent[M]: out of sync [1]");
for (auto s: agent_sockets)
s_send(*s, "proceed");
/* End sync */
for (auto s: agent_sockets)
if (s_recv(*s).compare(string("ack")))
DIE("sync_agent[M]: out of sync [2]");
} else if (args.agentmode_given) {
string req = s_recv(*socket);
if (s_recv(*socket).compare(string("sync_req")))
DIE("sync_agent[A]: out of sync [1]");
/* The real sync */
s_send(*socket, "sync");
if (s_recv(*socket).compare(string("proceed")))
DIE("sync_agent[A]: out of sync [2]");
/* End sync */
s_send(*socket, "ack");
}
// V("agent: synchronized");
@ -667,7 +684,6 @@ void go(const vector<string>& servers, options_t& options,
#ifdef HAVE_LIBZMQ
if (args.agent_given) {
sync_agent(socket);
sync_agent(socket);
}
#endif
}
@ -809,13 +825,14 @@ void do_mutilate(const vector<string>& servers, options_t& options,
#ifdef HAVE_LIBZMQ
if (args.agent_given || args.agentmode_given) {
if (master) V("Synchronizing.");
// 1. thread barrier: make sure our threads ready before syncing agents
// 2. sync agents: all threads across all agents are now ready
// 3. thread barrier: don't release our threads until all agents ready
pthread_barrier_wait(&barrier);
if (master) sync_agent(socket);
pthread_barrier_wait(&barrier);
if (master) sync_agent(socket);
pthread_barrier_wait(&barrier);
if (master) V("Synchronized.");
}
#endif
@ -900,13 +917,11 @@ void do_mutilate(const vector<string>& servers, options_t& options,
#ifdef HAVE_LIBZMQ
if (args.agent_given || args.agentmode_given) {
if (master) V("Synchronizing.");
if (master) sync_agent(socket);
pthread_barrier_wait(&barrier);
if (master) sync_agent(socket);
pthread_barrier_wait(&barrier);
if (master) V("Synchronized.");
}
#endif