On Fri, Jul 5, 2013 at 5:26 AM, Evgeny Turnaev <[email protected]> wrote: > Hi Keyur, > First of i am not really expert in curl. But reading through > documentation i can't find evidence that curl_multi_perform should > return CURLM_CALL_MULTI_PERFORM untill connection succeeds. Connection > can take very long time. Why don't you change your application code so > that it selects (poll or whatever) on curl sockets and when there is > action - call curl_multi_perform again. I suppose this is a typical > usage. Someone please correct me if i am wrong. >
Hi Evgeny, Thanks for the response. The issue is the inconsistency of the response code. In the localhost case, when curl_multi_perform returns CURLM_OK, the TCP connection is done, the HTTP connection is done, and the request has been sent over. If I call a select() on the FDs returned by curl_multi_fdset(), I'm actually waiting for a response for the server. I don't want this because I want to execute other code while the async request is being procesed. Whereas in the slow-remote-host case, even the TCP connection is not done when CURLM_OK is returned by curl_multi_perform(). So when I call a select(), I am still waiting for the TCP connect to go through. There is no way for my code to know which of the two scenarios is it currently experiencing. Once curl_multi_perform() has a TCP connection it returns CURML_CALL_MULTI_PERFORM until the request is sent over. It seems like a miss to not return the same when the TCP connection has not yet gone through. Hope that makes sense. Thanks, Keyur. > 2013/7/5 Keyur Govande <[email protected]>: >> Hello, >> >> We're using cURL to do some asynchronous programming in PHP. >> >> The code fires off a multi-curl request to get some data from a remote >> server. Once the request is sent i.e. curl_multi_exec() (PHP's wrapper >> around curl_multi_perform() ) returns CURLM_OK, the code continues its >> processing and once it is all done and ready, it checks the multi-curl >> request for a response. >> >> We're seeing some unusual behavior that might be a bug. We're >> currently on 7.19.7-26.el6_1.2, but I checked the code and the same >> behavior is in the latest version as well. >> >> If the curl request tries to connect to a host that is slow to respond >> to the initial connect, then curl_multi_perform() returns CURLM_OK, >> even though the connection is not completed and the request not sent. >> >> Here's a couple of sample straces showing both conditions. The PHP code is: >> >> // Set up the multi-curl >> do { >> $cme = curl_multi_exec($this->mc_handle, $this->mc_running); >> } while ($cme === CURLM_CALL_MULTI_PERFORM); >> // For purposes of the test, sleep. This is where other code would execute >> sleep(2); >> >> Connection to localhost where connect() is super fast: >> 1372871818.596930 socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 61 <0.000024> >> 1372871818.596990 fcntl(61, F_GETFL) = 0x2 (flags O_RDWR) <0.000023> >> 1372871818.597044 fcntl(61, F_SETFL, O_RDWR|O_NONBLOCK) = 0 <0.000015> >> 1372871818.597086 connect(61, {sa_family=AF_INET, sin_port=htons(80), >> sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now >> in progress) <0.000186> >> 1372871818.597315 poll([{fd=61, events=POLLOUT|POLLWRNORM}], 1, 0) = 1 >> ([{fd=61, revents=POLLOUT|POLLWRNORM}]) <0.000017> >> 1372871818.597370 getsockopt(61, SOL_SOCKET, SO_ERROR, [0], [4]) = 0 >> <0.000016> >> 1372871818.597902 socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 62 <0.000020> >> 1372871818.597960 fcntl(62, F_GETFL) = 0x2 (flags O_RDWR) <0.000016> >> 1372871818.598005 fcntl(62, F_SETFL, O_RDWR|O_NONBLOCK) = 0 <0.000018> >> 1372871818.598060 connect(62, {sa_family=AF_INET, sin_port=htons(80), >> sin_addr=inet_addr("127.0.0.1")}, 16) = -1 EINPROGRESS (Operation now >> in progress) <0.000057> >> 1372871818.598162 poll([{fd=62, events=POLLOUT|POLLWRNORM}], 1, 0) = 1 >> ([{fd=62, revents=POLLOUT|POLLWRNORM}]) <0.000016> >> 1372871818.598212 getsockopt(62, SOL_SOCKET, SO_ERROR, [0], [4]) = 0 >> <0.000015> >> 1372871818.598665 sendto(61, "GET /rpc_test.php?sleep=1 >> HTTP/1.1\r\nAccept: */*\r\nHost: www.example.com\r\n\r\n", 75, >> MSG_NOSIGNAL, NULL, 0) = 75 <0.000159> >> 1372871818.599054 sendto(62, "GET /rpc_test.php?sleep=1 >> HTTP/1.1\r\nAccept: */*\r\nHost: www.example.com\r\n\r\n", 75, >> MSG_NOSIGNAL, NULL, 0) = 75 <0.000072> >> 1372871818.601071 nanosleep({2, 0}, 0x7fff7ce2f4c0) = 0 <2.000130> >> >> Connecting to a slow remote host: >> 1372871825.806179 connect(61, {sa_family=AF_INET, sin_port=htons(80), >> sin_addr=inet_addr("10.255.58.37")}, 16) = -1 EINPROGRESS (Operation >> now in progress) <0.000195> >> 1372871825.806417 poll([{fd=61, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 >> (Timeout) <0.000017> >> 1372871825.806919 socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 62 <0.000024> >> 1372871825.806976 fcntl(62, F_GETFL) = 0x2 (flags O_RDWR) <0.000016> >> 1372871825.807020 fcntl(62, F_SETFL, O_RDWR|O_NONBLOCK) = 0 <0.000016> >> 1372871825.807064 connect(62, {sa_family=AF_INET, sin_port=htons(80), >> sin_addr=inet_addr("10.255.58.37")}, 16) = -1 EINPROGRESS (Operation >> now in progress) <0.000173> >> 1372871825.807278 poll([{fd=62, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 >> (Timeout) <0.000021> >> 1372871825.807688 poll([{fd=61, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 >> (Timeout) <0.000016> >> 1372871825.807824 poll([{fd=62, events=POLLOUT|POLLWRNORM}], 1, 0) = 0 >> (Timeout) <0.000016> >> 1372871825.809776 nanosleep({2, 0}, 0x7fff04b17530) = 0 <2.000174> >> >> For the slow remote host, the sleep is getting triggered even though >> the GET request was not yet sent. >> >> Reading through the code in lib/multi.c, in the >> CURLM_STATE_WAITCONNECT block, if connected is false, then the result >> should be CURLM_CALL_MULTI_PERFORM in order to keep calling poll until >> the connections are established and the requests flushed out. >> >> Here's the diff on the 7.19.7 branch that I think will fix the issue. >> The patch for 7.31.0 would be exactly the same: >> diff --git a/lib/multi.c b/lib/multi.c >> index 48df928..dc5ec48 100644 >> --- a/lib/multi.c >> +++ b/lib/multi.c >> @@ -1077,6 +1077,7 @@ static CURLMcode multi_runsingle(struct Curl_multi >> *multi, >> break; >> } >> >> + result = CURLM_CALL_MULTI_PERFORM; >> if(connected) { >> if(!protocol_connect) { >> /* We have a TCP connection, but 'protocol_connect' may be false >> @@ -1095,8 +1096,6 @@ static CURLMcode multi_runsingle(struct Curl_multi >> *multi, >> /* after the connect has completed, go WAITDO or DO */ >> multistate(easy, multi->pipelining_enabled? >> CURLM_STATE_WAITDO:CURLM_STATE_DO); >> - >> - result = CURLM_CALL_MULTI_PERFORM; >> } >> } >> break; >> >> Is there anything I'm missing, or another way to accomplish this? >> >> Thanks, >> Keyur. >> ------------------------------------------------------------------- >> List admin: http://cool.haxx.se/list/listinfo/curl-library >> Etiquette: http://curl.haxx.se/mail/etiquette.html > ------------------------------------------------------------------- > List admin: http://cool.haxx.se/list/listinfo/curl-library > Etiquette: http://curl.haxx.se/mail/etiquette.html ------------------------------------------------------------------- List admin: http://cool.haxx.se/list/listinfo/curl-library Etiquette: http://curl.haxx.se/mail/etiquette.html
