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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#include "PaxosService.h"
#include "common/Clock.h"
#include "Monitor.h"
#include "common/config.h"
#include "include/assert.h"
#include "global/debug.h"
#define dout_subsys ceph_subsys_paxos
#undef dout_prefix
#define dout_prefix _prefix(_dout, mon, paxos, paxos->machine_id)
static ostream& _prefix(std::ostream *_dout, Monitor *mon, Paxos *paxos, int machine_id) {
return *_dout << "mon." << mon->name << "@" << mon->rank
<< "(" << mon->get_state_name()
<< ").paxosservice(" << get_paxos_name(machine_id) << ") ";
}
const char *PaxosService::get_machine_name()
{
return paxos->get_machine_name();
}
bool PaxosService::dispatch(PaxosServiceMessage *m)
{
dout(10) << "dispatch " << *m << " from " << m->get_orig_source_inst() << dendl;
// make sure our map is readable and up to date
if (!paxos->is_readable(m->version)) {
dout(10) << " waiting for paxos -> readable (v" << m->version << ")" << dendl;
paxos->wait_for_readable(new C_RetryMessage(this, m));
return true;
}
// make sure service has latest from paxos.
update_from_paxos();
// preprocess
if (preprocess_query(m))
return true; // easy!
// leader?
if (!mon->is_leader()) {
mon->forward_request_leader(m);
return true;
}
// writeable?
if (!paxos->is_writeable()) {
dout(10) << " waiting for paxos -> writeable" << dendl;
paxos->wait_for_writeable(new C_RetryMessage(this, m));
return true;
}
// update
if (prepare_update(m)) {
double delay = 0.0;
if (should_propose(delay)) {
if (delay == 0.0) {
propose_pending();
} else {
// delay a bit
if (!proposal_timer) {
dout(10) << " setting propose timer with delay of " << delay << dendl;
proposal_timer = new C_Propose(this);
mon->timer.add_event_after(delay, proposal_timer);
} else {
dout(10) << " propose timer already set" << dendl;
}
}
} else {
dout(10) << " not proposing" << dendl;
}
}
return true;
}
bool PaxosService::should_propose(double& delay)
{
// simple default policy: quick startup, then some damping.
if (paxos->last_committed <= 1)
delay = 0.0;
else {
utime_t now = ceph_clock_now(g_ceph_context);
if ((now - paxos->last_commit_time) > g_conf->paxos_propose_interval)
delay = (double)g_conf->paxos_min_wait;
else
delay = (double)(g_conf->paxos_propose_interval + paxos->last_commit_time
- now);
}
return true;
}
void PaxosService::propose_pending()
{
dout(10) << "propose_pending" << dendl;
assert(have_pending);
assert(mon->is_leader() && paxos->is_active());
if (proposal_timer) {
mon->timer.cancel_event(proposal_timer);
proposal_timer = 0;
}
/**
* @note The value we propose is encoded in a bufferlist, passed to
* Paxos::propose_new_value and it is obtained by calling a
* function that must be implemented by the class implementing us.
* I.e., the function encode_pending will be the one responsible
* to encode whatever is pending on the implementation class into a
* bufferlist, so we can then propose that as a value through Paxos.
*/
bufferlist bl;
encode_pending(bl);
have_pending = false;
// apply to paxos
paxos->wait_for_commit_front(new C_Active(this));
paxos->propose_new_value(bl);
}
void PaxosService::restart()
{
dout(10) << "restart" << dendl;
if (proposal_timer) {
mon->timer.cancel_event(proposal_timer);
proposal_timer = 0;
}
on_restart();
}
void PaxosService::election_finished()
{
dout(10) << "election_finished" << dendl;
if (proposal_timer) {
mon->timer.cancel_event(proposal_timer);
proposal_timer = 0;
}
if (have_pending) {
discard_pending();
have_pending = false;
}
// make sure we update our state
if (paxos->is_active())
_active();
else
paxos->wait_for_active(new C_Active(this));
}
void PaxosService::_active()
{
if (!paxos->is_active()) {
dout(10) << "_active - not active" << dendl;
paxos->wait_for_active(new C_Active(this));
return;
}
dout(10) << "_active" << dendl;
// pull latest from paxos
update_from_paxos();
// create pending state?
if (mon->is_leader() && paxos->is_active()) {
dout(7) << "_active creating new pending" << dendl;
if (!have_pending) {
create_pending();
have_pending = true;
}
if (paxos->get_version() == 0) {
// create initial state
create_initial();
propose_pending();
return;
}
}
// NOTE: it's possible that this will get called twice if we commit
// an old paxos value. Implementations should be mindful of that.
if (paxos->is_active())
on_active();
}
void PaxosService::shutdown()
{
paxos->cancel_events();
paxos->shutdown();
if (proposal_timer) {
mon->timer.cancel_event(proposal_timer);
proposal_timer = 0;
}
}
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