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reconnect: Implement "passive mode".

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This allows the reconnect library to support clients that want to listen
for an incoming connection.
This commit is contained in:
Ben Pfaff
2010-03-24 13:09:38 -07:00
parent 024b7728cc
commit 19df7f512c
4 changed files with 261 additions and 18 deletions
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130
lib/reconnect.c
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@@ -31,7 +31,8 @@
STATE(CONNECT_IN_PROGRESS, 1 << 3) \
STATE(ACTIVE, 1 << 4) \
STATE(IDLE, 1 << 5) \
STATE(RECONNECT, 1 << 6)
STATE(RECONNECT, 1 << 6) \
STATE(LISTENING, 1 << 7)
enum state {
#define STATE(NAME, VALUE) S_##NAME = VALUE,
STATES
@@ -50,6 +51,7 @@ struct reconnect {
int min_backoff;
int max_backoff;
int probe_interval;
bool passive;
/* State. */
enum state state;
@@ -95,6 +97,7 @@ reconnect_create(long long int now)
fsm->min_backoff = 1000;
fsm->max_backoff = 8000;
fsm->probe_interval = 5000;
fsm->passive = false;
fsm->state = S_VOID;
fsm->state_entered = now;
@@ -218,6 +221,32 @@ reconnect_set_probe_interval(struct reconnect *fsm, int probe_interval)
fsm->probe_interval = probe_interval ? MAX(1000, probe_interval) : 0;
}
/* Returns true if 'fsm' is in passive mode, false if 'fsm' is in active mode
* (the default). */
bool
reconnect_is_passive(const struct reconnect *fsm)
{
return fsm->passive;
}
/* Configures 'fsm' for active or passive mode. In active mode (the default),
* the FSM is attempting to connect to a remote host. In passive mode, the FSM
* is listening for connections from a remote host. */
void
reconnect_set_passive(struct reconnect *fsm, bool passive, long long int now)
{
if (fsm->passive != passive) {
fsm->passive = passive;
if (passive
? fsm->state & (S_CONNECT_IN_PROGRESS | S_RECONNECT)
: fsm->state == S_LISTENING && reconnect_may_retry(fsm)) {
reconnect_transition__(fsm, now, S_BACKOFF);
fsm->backoff = 0;
}
}
}
/* Returns true if 'fsm' has been enabled with reconnect_enable(). Calling
* another function that indicates a change in connection state, such as
* reconnect_disconnected() or reconnect_force_reconnect(), will also enable
@@ -284,19 +313,28 @@ reconnect_disconnected(struct reconnect *fsm, long long int now, int error)
} else {
VLOG_INFO("%s: connection dropped", fsm->name);
}
} else {
} else if (fsm->state == S_LISTENING) {
if (error > 0) {
VLOG_WARN("%s: connection attempt failed (%s)",
VLOG_WARN("%s: error listening for connections (%s)",
fsm->name, strerror(error));
} else {
VLOG_INFO("%s: connection attempt timed out", fsm->name);
VLOG_INFO("%s: error listening for connections", fsm->name);
}
} else {
const char *type = fsm->passive ? "listen" : "connection";
if (error > 0) {
VLOG_WARN("%s: %s attempt failed (%s)",
fsm->name, type, strerror(error));
} else {
VLOG_INFO("%s: %s attempt timed out", fsm->name, type);
}
}
/* Back off. */
if (fsm->state & (S_ACTIVE | S_IDLE)
&& fsm->last_received - fsm->last_connected >= fsm->backoff) {
fsm->backoff = fsm->min_backoff;
&& (fsm->last_received - fsm->last_connected >= fsm->backoff
|| fsm->passive)) {
fsm->backoff = fsm->passive ? 0 : fsm->min_backoff;
} else {
if (fsm->backoff < fsm->min_backoff) {
fsm->backoff = fsm->min_backoff;
@@ -305,8 +343,13 @@ reconnect_disconnected(struct reconnect *fsm, long long int now, int error)
} else {
fsm->backoff *= 2;
}
VLOG_INFO("%s: waiting %.3g seconds before reconnect\n",
fsm->name, fsm->backoff / 1000.0);
if (fsm->passive) {
VLOG_INFO("%s: waiting %.3g seconds before trying to "
"listen again", fsm->name, fsm->backoff / 1000.0);
} else {
VLOG_INFO("%s: waiting %.3g seconds before reconnect",
fsm->name, fsm->backoff / 1000.0);
}
}
reconnect_transition__(fsm, now,
@@ -314,19 +357,58 @@ reconnect_disconnected(struct reconnect *fsm, long long int now, int error)
}
}
/* Tell 'fsm' that a connection attempt is in progress.
/* Tell 'fsm' that a connection or listening attempt is in progress.
*
* The FSM will start a timer, after which the connection attempt will be
* aborted (by returning RECONNECT_DISCONNECT from reconect_run()). */
* The FSM will start a timer, after which the connection or listening attempt
* will be aborted (by returning RECONNECT_DISCONNECT from reconect_run()). */
void
reconnect_connecting(struct reconnect *fsm, long long int now)
{
if (fsm->state != S_CONNECT_IN_PROGRESS) {
VLOG_INFO("%s: connecting...", fsm->name);
if (fsm->passive) {
VLOG_INFO("%s: listening...", fsm->name);
} else {
VLOG_INFO("%s: connecting...", fsm->name);
}
reconnect_transition__(fsm, now, S_CONNECT_IN_PROGRESS);
}
}
/* Tell 'fsm' that the client is listening for connection attempts. This state
* last indefinitely until the client reports some change.
*
* The natural progression from this state is for the client to report that a
* connection has been accepted or is in progress of being accepted, by calling
* reconnect_connecting() or reconnect_connected().
*
* The client may also report that listening failed (e.g. accept() returned an
* unexpected error such as ENOMEM) by calling reconnect_listen_error(), in
* which case the FSM will back off and eventually return RECONNECT_CONNECT
* from reconnect_run() to tell the client to try listening again. */
void
reconnect_listening(struct reconnect *fsm, long long int now)
{
if (fsm->state != S_LISTENING) {
VLOG_INFO("%s: listening...", fsm->name);
reconnect_transition__(fsm, now, S_LISTENING);
}
}
/* Tell 'fsm' that the client's attempt to accept a connection failed
* (e.g. accept() returned an unexpected error such as ENOMEM).
*
* If the FSM is currently listening (reconnect_listening() was called), it
* will back off and eventually return RECONNECT_CONNECT from reconnect_run()
* to tell the client to try listening again. If there is an active
* connection, this will be delayed until that connection drops. */
void
reconnect_listen_error(struct reconnect *fsm, long long int now, int error)
{
if (fsm->state == S_LISTENING) {
reconnect_disconnected(fsm, now, error);
}
}
/* Tell 'fsm' that the connection was successful.
*
* The FSM will start the probe interval timer, which is reset by
@@ -395,6 +477,7 @@ reconnect_deadline__(const struct reconnect *fsm)
assert(fsm->state_entered != LLONG_MIN);
switch (fsm->state) {
case S_VOID:
case S_LISTENING:
return LLONG_MAX;
case S_BACKOFF:
@@ -425,9 +508,9 @@ reconnect_deadline__(const struct reconnect *fsm)
*
* - 0: The client need not take any action.
*
* - RECONNECT_CONNECT: The client should start a connection attempt and
* indicate this by calling reconnect_connecting(). If the connection
* attempt has definitely succeeded, it should call
* - Active client, RECONNECT_CONNECT: The client should start a connection
* attempt and indicate this by calling reconnect_connecting(). If the
* connection attempt has definitely succeeded, it should call
* reconnect_connected(). If the connection attempt has definitely
* failed, it should call reconnect_connect_failed().
*
@@ -437,9 +520,19 @@ reconnect_deadline__(const struct reconnect *fsm)
* (e.g. connect()) even if the connection might soon abort due to a
* failure at a high-level (e.g. SSL negotiation failure).
*
* - Passive client, RECONNECT_CONNECT: The client should try to listen for
* a connection, if it is not already listening. It should call
* reconnect_listening() if successful, otherwise reconnect_connecting()
* or reconnected_connect_failed() if the attempt is in progress or
* definitely failed, respectively.
*
* A listening passive client should constantly attempt to accept a new
* connection and report an accepted connection with
* reconnect_connected().
*
* - RECONNECT_DISCONNECT: The client should abort the current connection
* or connection attempt and call reconnect_disconnected() or
* reconnect_connect_failed() to indicate it.
* or connection attempt or listen attempt and call
* reconnect_disconnected() or reconnect_connect_failed() to indicate it.
*
* - RECONNECT_PROBE: The client should send some kind of request to the
* peer that will elicit a response, to ensure that the connection is
@@ -474,6 +567,9 @@ reconnect_run(struct reconnect *fsm, long long int now)
case S_RECONNECT:
return RECONNECT_DISCONNECT;
case S_LISTENING:
return 0;
}
NOT_REACHED();