- $r = q("select * from fcontact where network = '%s' and addr = '%s' limit 1",
- dbesc(NETWORK_DIASPORA),
- dbesc($handle)
- );
- if(count($r)) {
- logger('find_diaspora_person_by handle: in cache ' . print_r($r,true), LOGGER_DEBUG);
- // update record occasionally so it doesn't get stale
- $d = strtotime($r[0]['updated'] . ' +00:00');
- if($d > strtotime('now - 14 days'))
- return $r[0];
- $update = true;
- }
- logger('find_diaspora_person_by_handle: refresh',LOGGER_DEBUG);
- require_once('include/Scrape.php');
- $r = probe_url($handle, PROBE_DIASPORA);
- if((count($r)) && ($r['network'] === NETWORK_DIASPORA)) {
- add_fcontact($r,$update);
- return ($r);
- }
- return false;
+ $got_lock = false;
+
+ $endlessloop = 0;
+ $maxloops = 10;
+
+ do {
+ $r = q("select * from fcontact where network = '%s' and addr = '%s' limit 1",
+ dbesc(NETWORK_DIASPORA),
+ dbesc($handle)
+ );
+ if(count($r)) {
+ $person = $r[0];
+ logger('find_diaspora_person_by handle: in cache ' . print_r($r,true), LOGGER_DEBUG);
+
+ // update record occasionally so it doesn't get stale
+ $d = strtotime($person['updated'] . ' +00:00');
+ if($d < strtotime('now - 14 days'))
+ $update = true;
+ }
+
+
+ // FETCHING PERSON INFORMATION FROM REMOTE SERVER
+ //
+ // If the person isn't in our 'fcontact' table, or if he/she is but
+ // his/her information hasn't been updated for more than 14 days, then
+ // we want to fetch the person's information from the remote server.
+ //
+ // Note that $person isn't changed by this block of code unless the
+ // person's information has been successfully fetched from the remote
+ // server. So if $person was 'false' to begin with (because he/she wasn't
+ // in the local cache), it'll stay false, and if $person held the local
+ // cache information to begin with, it'll keep that information. That way
+ // if there's a problem with the remote fetch, we can at least use our
+ // cached information--it's better than nothing.
+
+ if((! $person) || ($update)) {
+ // Lock the function to prevent race conditions if multiple items
+ // come in at the same time from a person who doesn't exist in
+ // fcontact
+ //
+ // Don't loop forever. On the last loop, try to create the contact
+ // whether the function is locked or not. Maybe the locking thread
+ // has died or something. At any rate, a duplicate in 'fcontact'
+ // is a much smaller problem than a deadlocked thread
+ $got_lock = lock_function('find_diaspora_person_by_handle', false);
+ if(($endlessloop + 1) >= $maxloops)
+ $got_lock = true;
+
+ if($got_lock) {
+ logger('find_diaspora_person_by_handle: create or refresh', LOGGER_DEBUG);
+ require_once('include/Scrape.php');
+ $r = probe_url($handle, PROBE_DIASPORA);
+
+ // Note that Friendica contacts can return a "Diaspora person"
+ // if Diaspora connectivity is enabled on their server
+ if((count($r)) && ($r['network'] === NETWORK_DIASPORA)) {
+ add_fcontact($r,$update);
+ $person = ($r);
+ }
+
+ unlock_function('find_diaspora_person_by_handle');
+ }
+ else {
+ logger('find_diaspora_person_by_handle: couldn\'t lock function', LOGGER_DEBUG);
+ if(! $person)
+ block_on_function_lock('find_diaspora_person_by_handle');
+ }
+ }
+ } while((! $person) && (! $got_lock) && (++$endlessloop < $maxloops));
+ // We need to try again if the person wasn't in 'fcontact' but the function was locked.
+ // The fact that the function was locked may mean that another process was creating the
+ // person's record. It could also mean another process was creating or updating an unrelated
+ // person.
+ //
+ // At any rate, we need to keep trying until we've either got the person or had a chance to
+ // try to fetch his/her remote information. But we don't want to block on locking the
+ // function, because if the other process is creating the record, then when we acquire the lock
+ // we'll dive right into creating another, duplicate record. We DO want to at least wait
+ // until the lock is released, so we don't flood the database with requests.
+ //
+ // If the person was in the 'fcontact' table, don't try again. It's not worth the time, since
+ // we do have some information for the person
+
+ return $person;