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Change if to switch, add more descriptions

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pull/14122/head
Yuchen Zeng 7 years ago
parent 6a15e4f15b
commit a041e0f3ae
1 changed files with 57 additions and 26 deletions
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  1. 83
      src/core/ext/filters/max_age/max_age_filter.cc

83
src/core/ext/filters/max_age/max_age_filter.cc
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@ -91,6 +91,7 @@ struct channel_data {
grpc_connectivity_state connectivity_state;
/* Number of active calls */
gpr_atm call_count;
/* TODO(zyc): C++lize this state machine */
/* 'idle_state' holds the states of max_idle_timer and channel idleness.
It can contain one of the following values:
+--------------------------------+----------------+---------+
@ -101,10 +102,32 @@ struct channel_data {
| MAX_IDLE_STATE_SEEN_EXIT_IDLE | set, invalid | busy |
| MAX_IDLE_STATE_SEEN_ENTER_IDLE | set, invalid | idle |
+--------------------------------+----------------+---------+
MAX_IDLE_STATE_INIT: The initial and final state of 'idle_state'. The
channel has 1 or 1+ active calls, and the the timer is not set. Note that
we may put a virtual call to hold this state at channel initialization or
shutdown, so that the channel won't enter other states.
MAX_IDLE_STATE_TIMER_SET: The state after the timer is set and no calls
have arrived after the timer is set. The channel must have 0 active call in
this state. If the timer is fired in this state, we will close the channel
due to idleness.
MAX_IDLE_STATE_SEEN_EXIT_IDLE: The state after the timer is set and at
least one call has arrived after the timer is set. The channel must have 1
or 1+ active calls in this state. If the timer is fired in this state, we
won't reschudle it.
MAX_IDLE_STATE_SEEN_ENTER_IDLE: The state after the timer is set and the at
least one call has arrived after the timer is set, BUT the channel
currently has 1 or 1+ active calls. If the timer is fired in this state, we
will reschudle it.
max_idle_timer will not be cancelled (unless the channel is shutting down).
If the timer callback is called when the max_idle_timer is valid (i.e.
idle_state is MAX_IDLE_STATE_TIMER_SET), the channel will be closed due to
idleness, otherwise the channel won't be changed.
State transitions:
MAX_IDLE_STATE_INIT <-------3------ MAX_IDLE_STATE_SEEN_EXIT_IDLE
^ | ^ ^ |
@ -113,6 +136,7 @@ struct channel_data {
| | | | |
| v | | v
MAX_IDLE_STATE_TIMER_SET <----5------ MAX_IDLE_STATE_SEEN_ENTER_IDLE
For 1, 3, 5 : See max_idle_timer_cb() function
For 2, 7 : See decrease_call_count() function
For 4, 6 : See increase_call_count() function */
@ -240,34 +264,41 @@ static void close_max_idle_channel(channel_data* chand) {
static void max_idle_timer_cb(void* arg, grpc_error* error) {
channel_data* chand = (channel_data*)arg;
if (error == GRPC_ERROR_NONE) {
while (true) {
bool try_again = true;
while (try_again) {
gpr_atm idle_state = gpr_atm_acq_load(&chand->idle_state);
if (idle_state == MAX_IDLE_STATE_TIMER_SET) {
close_max_idle_channel(chand);
/* This MAX_IDLE_STATE_INIT is a final state, we don't have to check if
* idle_state has been changed */
gpr_atm_rel_store(&chand->idle_state, MAX_IDLE_STATE_INIT);
break;
} else if (idle_state == MAX_IDLE_STATE_SEEN_EXIT_IDLE) {
if (gpr_atm_rel_cas(&chand->idle_state, MAX_IDLE_STATE_SEEN_EXIT_IDLE,
MAX_IDLE_STATE_INIT)) {
switch (idle_state) {
case MAX_IDLE_STATE_TIMER_SET:
close_max_idle_channel(chand);
/* This MAX_IDLE_STATE_INIT is a final state, we don't have to check
* if idle_state has been changed */
gpr_atm_rel_store(&chand->idle_state, MAX_IDLE_STATE_INIT);
try_again = false;
break;
case MAX_IDLE_STATE_SEEN_EXIT_IDLE:
if (gpr_atm_rel_cas(&chand->idle_state, MAX_IDLE_STATE_SEEN_EXIT_IDLE,
MAX_IDLE_STATE_INIT)) {
try_again = false;
}
break;
case MAX_IDLE_STATE_SEEN_ENTER_IDLE:
GRPC_CHANNEL_STACK_REF(chand->channel_stack,
"max_age max_idle_timer");
grpc_timer_init(&chand->max_idle_timer,
(grpc_millis)gpr_atm_no_barrier_load(
&chand->last_enter_idle_time_millis) +
chand->max_connection_idle,
&chand->max_idle_timer_cb);
/* idle_state may have already been set to
MAX_IDLE_STATE_SEEN_EXIT_IDLE by increase_call_count(), in this
case, we don't need to set it to MAX_IDLE_STATE_TIMER_SET */
gpr_atm_rel_cas(&chand->idle_state, MAX_IDLE_STATE_SEEN_ENTER_IDLE,
MAX_IDLE_STATE_TIMER_SET);
try_again = false;
break;
default:
/* try again */
break;
}
} else if (idle_state == MAX_IDLE_STATE_SEEN_ENTER_IDLE) {
GRPC_CHANNEL_STACK_REF(chand->channel_stack, "max_age max_idle_timer");
grpc_timer_init(&chand->max_idle_timer,
(grpc_millis)gpr_atm_no_barrier_load(
&chand->last_enter_idle_time_millis) +
chand->max_connection_idle,
&chand->max_idle_timer_cb);
/* idle_state may have already been set to MAX_IDLE_STATE_SEEN_EXIT_IDLE
by increase_call_count(), in this case, we don't need to set it to
MAX_IDLE_STATE_TIMER_SET */
gpr_atm_rel_cas(&chand->idle_state, MAX_IDLE_STATE_SEEN_ENTER_IDLE,
MAX_IDLE_STATE_TIMER_SET);
break;
} else {
/* try again */
}
}
}

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