Re: [zeromq-dev] will receive fail if TCP goes down in REQ socket
@Matt,,
I like the inband heartbeats better than the pirate patterns in ZMQ guide.
@Justin,
Yes, a DEALER socket can be used but will the reconnect not work? It is
simpler and actual reconnects will be rare so it isn't really less
performant.
On Sun, Dec 15, 2013 at 11:05 AM, Justin Karneges jus...@affinix.comwrote:
Cool. Is there a reason the relaxed behavior is to close and reconnect
in order to reset the state? I'd think all you'd need to do here is
change a local state variable in the client and just reuse the same
connection. As it stands, I'd still want to roll my own REQ over a
DEALER socket unless I'm missing something.
On 12/13/2013 10:24 PM, Pieter Hintjens wrote:
The ZMQ_REQ_RELAXED option on ZeroMQ v4, lets you resend requests.
On Sat, Dec 14, 2013 at 3:46 AM, Justin Karneges jus...@affinix.com
wrote:
ZeroMQ does not resend messages, so while the reconnect/queuing logic
will protect you to some degree, you still need to account for message
loss.
If you're using REQ then you'll need to timeout the request, otherwise
if a request or response message is lost then you'll never be able to
make a request on the socket ever again. So don't just indefinitely
block on a send or receive. Further, ZeroMQ historically hasn't had a
way to get a REQ socket out of the waiting for response state in the
event of a timeout other than by closing the socket and starting over.
This means the REQ type is not really usable in production. Better to
use DEALER and format a REQ-compatible message yourself. REP does not
suffer from these problems, so you can keep on using that and have
DEALER talk to REP.
Note: it is possible that very recent versions of ZeroMQ allow REQ
sockets to revert state on error but I haven't been following this
closely.
On 12/13/2013 04:17 PM, Sean Robertson wrote:
I believe the REQ will simply wait for the REP to come back up,
re-bind and send something.
On Fri, Dec 13, 2013 at 2:53 PM, Mohit Jaggi mohitja...@gmail.com
wrote:
Hi,
In most ZMQ sockets, the underlying TCP socket can change
transparently.
Does that apply to REQ-REP sockets as well? Or will the receive call
to ZMQ
socket fail?
sock = new REQ socket;
connect(sock);
while(1) {
request = receive(...);
...
send(response);
}
For example in the above code, let us say that the server with REP
socket on
the other side crashed and restarted. What will happen?
Thanks,
Mohit.
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Re: [zeromq-dev] will receive fail if TCP goes down in REQ socket
Cool. Is there a reason the relaxed behavior is to close and reconnect
in order to reset the state? I'd think all you'd need to do here is
change a local state variable in the client and just reuse the same
connection. As it stands, I'd still want to roll my own REQ over a
DEALER socket unless I'm missing something.
On 12/13/2013 10:24 PM, Pieter Hintjens wrote:
The ZMQ_REQ_RELAXED option on ZeroMQ v4, lets you resend requests.
On Sat, Dec 14, 2013 at 3:46 AM, Justin Karneges jus...@affinix.com wrote:
ZeroMQ does not resend messages, so while the reconnect/queuing logic
will protect you to some degree, you still need to account for message loss.
If you're using REQ then you'll need to timeout the request, otherwise
if a request or response message is lost then you'll never be able to
make a request on the socket ever again. So don't just indefinitely
block on a send or receive. Further, ZeroMQ historically hasn't had a
way to get a REQ socket out of the waiting for response state in the
event of a timeout other than by closing the socket and starting over.
This means the REQ type is not really usable in production. Better to
use DEALER and format a REQ-compatible message yourself. REP does not
suffer from these problems, so you can keep on using that and have
DEALER talk to REP.
Note: it is possible that very recent versions of ZeroMQ allow REQ
sockets to revert state on error but I haven't been following this closely.
On 12/13/2013 04:17 PM, Sean Robertson wrote:
I believe the REQ will simply wait for the REP to come back up,
re-bind and send something.
On Fri, Dec 13, 2013 at 2:53 PM, Mohit Jaggi mohitja...@gmail.com wrote:
Hi,
In most ZMQ sockets, the underlying TCP socket can change transparently.
Does that apply to REQ-REP sockets as well? Or will the receive call to ZMQ
socket fail?
sock = new REQ socket;
connect(sock);
while(1) {
request = receive(...);
...
send(response);
}
For example in the above code, let us say that the server with REP socket
on
the other side crashed and restarted. What will happen?
Thanks,
Mohit.
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Re: [zeromq-dev] will receive fail if TCP goes down in REQ socket
Thanks all for your comments. I should clarify my use case better. I am
using the lbbroker3 pattern, where the worker uses a REQ socket to connect
to a ROUTER socket on the broker. It sends I'm READY to let the broker
know that it can serve a request. After the first request, the response
serves as the I'm READY indication to the broker. Now, if the broker
restarts it will wait for an I'm READY message but worker won't send any.
How can worker know that broker restarted?
On Fri, Dec 13, 2013 at 10:24 PM, Pieter Hintjens p...@imatix.com wrote:
The ZMQ_REQ_RELAXED option on ZeroMQ v4, lets you resend requests.
On Sat, Dec 14, 2013 at 3:46 AM, Justin Karneges jus...@affinix.com
wrote:
ZeroMQ does not resend messages, so while the reconnect/queuing logic
will protect you to some degree, you still need to account for message
loss.
If you're using REQ then you'll need to timeout the request, otherwise
if a request or response message is lost then you'll never be able to
make a request on the socket ever again. So don't just indefinitely
block on a send or receive. Further, ZeroMQ historically hasn't had a
way to get a REQ socket out of the waiting for response state in the
event of a timeout other than by closing the socket and starting over.
This means the REQ type is not really usable in production. Better to
use DEALER and format a REQ-compatible message yourself. REP does not
suffer from these problems, so you can keep on using that and have
DEALER talk to REP.
Note: it is possible that very recent versions of ZeroMQ allow REQ
sockets to revert state on error but I haven't been following this
closely.
On 12/13/2013 04:17 PM, Sean Robertson wrote:
I believe the REQ will simply wait for the REP to come back up,
re-bind and send something.
On Fri, Dec 13, 2013 at 2:53 PM, Mohit Jaggi mohitja...@gmail.com
wrote:
Hi,
In most ZMQ sockets, the underlying TCP socket can change
transparently.
Does that apply to REQ-REP sockets as well? Or will the receive call
to ZMQ
socket fail?
sock = new REQ socket;
connect(sock);
while(1) {
request = receive(...);
...
send(response);
}
For example in the above code, let us say that the server with REP
socket on
the other side crashed and restarted. What will happen?
Thanks,
Mohit.
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Re: [zeromq-dev] will receive fail if TCP goes down in REQ socket
Hi Mohit,
I went through the same thing recently. Not only does the worker need to know
if the broker has gone, the broker also needs to know the worker has gone:
1. worker connects to broker (based on lbbroker3 example)
2. worker sends “ready” command and waits for work.
3. broker sends idle commands every X seconds when there is no work to do.
4. worker replies to idle commands immediately.
In this way both the worker and broker know that they are still connected to
each other.
The broker removes the worker from being available until it replies from the
idle command.
If the worker doesn’t receive an idle command, it closes the socket and makes a
new connection.
This allows the worker to use a simple REQ socket. There is always one request
to one response over the connection.
If the broker can exit gracefully (deliberate shutdown, onto a crash), it could
also send a message to the workers to tell them to close their sockets and make
a new connection with another ready command.
Regards,
Matt.
On 15 Dec 2013, at 9:20 am, Mohit Jaggi mohitja...@gmail.com wrote:
Thanks all for your comments. I should clarify my use case better. I am using
the lbbroker3 pattern, where the worker uses a REQ socket to connect to a
ROUTER socket on the broker. It sends I'm READY to let the broker know that
it can serve a request. After the first request, the response serves as the
I'm READY indication to the broker. Now, if the broker restarts it will
wait for an I'm READY message but worker won't send any. How can worker
know that broker restarted?
On Fri, Dec 13, 2013 at 10:24 PM, Pieter Hintjens p...@imatix.com wrote:
The ZMQ_REQ_RELAXED option on ZeroMQ v4, lets you resend requests.
On Sat, Dec 14, 2013 at 3:46 AM, Justin Karneges jus...@affinix.com wrote:
ZeroMQ does not resend messages, so while the reconnect/queuing logic
will protect you to some degree, you still need to account for message loss.
If you're using REQ then you'll need to timeout the request, otherwise
if a request or response message is lost then you'll never be able to
make a request on the socket ever again. So don't just indefinitely
block on a send or receive. Further, ZeroMQ historically hasn't had a
way to get a REQ socket out of the waiting for response state in the
event of a timeout other than by closing the socket and starting over.
This means the REQ type is not really usable in production. Better to
use DEALER and format a REQ-compatible message yourself. REP does not
suffer from these problems, so you can keep on using that and have
DEALER talk to REP.
Note: it is possible that very recent versions of ZeroMQ allow REQ
sockets to revert state on error but I haven't been following this closely.
On 12/13/2013 04:17 PM, Sean Robertson wrote:
I believe the REQ will simply wait for the REP to come back up,
re-bind and send something.
On Fri, Dec 13, 2013 at 2:53 PM, Mohit Jaggi mohitja...@gmail.com wrote:
Hi,
In most ZMQ sockets, the underlying TCP socket can change transparently.
Does that apply to REQ-REP sockets as well? Or will the receive call to
ZMQ
socket fail?
sock = new REQ socket;
connect(sock);
while(1) {
request = receive(...);
...
send(response);
}
For example in the above code, let us say that the server with REP socket
on
the other side crashed and restarted. What will happen?
Thanks,
Mohit.
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[zeromq-dev] will receive fail if TCP goes down in REQ socket
Hi,
In most ZMQ sockets, the underlying TCP socket can change transparently.
Does that apply to REQ-REP sockets as well? Or will the receive call to ZMQ
socket fail?
sock = new REQ socket;
connect(sock);
while(1) {
request = receive(...);
...
send(response);
}
For example in the above code, let us say that the server with REP socket
on the other side crashed and restarted. What will happen?
Thanks,
Mohit.
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Re: [zeromq-dev] will receive fail if TCP goes down in REQ socket
I believe the REQ will simply wait for the REP to come back up,
re-bind and send something.
On Fri, Dec 13, 2013 at 2:53 PM, Mohit Jaggi mohitja...@gmail.com wrote:
Hi,
In most ZMQ sockets, the underlying TCP socket can change transparently.
Does that apply to REQ-REP sockets as well? Or will the receive call to ZMQ
socket fail?
sock = new REQ socket;
connect(sock);
while(1) {
request = receive(...);
...
send(response);
}
For example in the above code, let us say that the server with REP socket on
the other side crashed and restarted. What will happen?
Thanks,
Mohit.
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Re: [zeromq-dev] will receive fail if TCP goes down in REQ socket
ZeroMQ does not resend messages, so while the reconnect/queuing logic
will protect you to some degree, you still need to account for message loss.
If you're using REQ then you'll need to timeout the request, otherwise
if a request or response message is lost then you'll never be able to
make a request on the socket ever again. So don't just indefinitely
block on a send or receive. Further, ZeroMQ historically hasn't had a
way to get a REQ socket out of the waiting for response state in the
event of a timeout other than by closing the socket and starting over.
This means the REQ type is not really usable in production. Better to
use DEALER and format a REQ-compatible message yourself. REP does not
suffer from these problems, so you can keep on using that and have
DEALER talk to REP.
Note: it is possible that very recent versions of ZeroMQ allow REQ
sockets to revert state on error but I haven't been following this closely.
On 12/13/2013 04:17 PM, Sean Robertson wrote:
I believe the REQ will simply wait for the REP to come back up,
re-bind and send something.
On Fri, Dec 13, 2013 at 2:53 PM, Mohit Jaggi mohitja...@gmail.com wrote:
Hi,
In most ZMQ sockets, the underlying TCP socket can change transparently.
Does that apply to REQ-REP sockets as well? Or will the receive call to ZMQ
socket fail?
sock = new REQ socket;
connect(sock);
while(1) {
request = receive(...);
...
send(response);
}
For example in the above code, let us say that the server with REP socket on
the other side crashed and restarted. What will happen?
Thanks,
Mohit.
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Re: [zeromq-dev] will receive fail if TCP goes down in REQ socket
On 14 Dec 2013, at 11:46 am, Justin Karneges jus...@affinix.com wrote: ZeroMQ does not resend messages, so while the reconnect/queuing logic will protect you to some degree, you still need to account for message loss. If you're using REQ then you'll need to timeout the request, otherwise if a request or response message is lost then you'll never be able to make a request on the socket ever again. So don't just indefinitely block on a send or receive. Further, ZeroMQ historically hasn't had a way to get a REQ socket out of the waiting for response state in the event of a timeout other than by closing the socket and starting over. This means the REQ type is not really usable in production. Better to use DEALER and format a REQ-compatible message yourself. REP does not suffer from these problems, so you can keep on using that and have DEALER talk to REP. Surely REQ is still very useful in production: simply a client making a request. Connect, send request, wait for reply (or timeout) disconnect, job done. In the same way a HTTP connection would give you a single request and response. ? Of course the error handling on the client is to close the REQ socket and make a new one for a new request, but this is still fairly similar to a HTTP request. -Matt ___ zeromq-dev mailing list zeromq-dev@lists.zeromq.org http://lists.zeromq.org/mailman/listinfo/zeromq-dev
Re: [zeromq-dev] will receive fail if TCP goes down in REQ socket
The ZMQ_REQ_RELAXED option on ZeroMQ v4, lets you resend requests.
On Sat, Dec 14, 2013 at 3:46 AM, Justin Karneges jus...@affinix.com wrote:
ZeroMQ does not resend messages, so while the reconnect/queuing logic
will protect you to some degree, you still need to account for message loss.
If you're using REQ then you'll need to timeout the request, otherwise
if a request or response message is lost then you'll never be able to
make a request on the socket ever again. So don't just indefinitely
block on a send or receive. Further, ZeroMQ historically hasn't had a
way to get a REQ socket out of the waiting for response state in the
event of a timeout other than by closing the socket and starting over.
This means the REQ type is not really usable in production. Better to
use DEALER and format a REQ-compatible message yourself. REP does not
suffer from these problems, so you can keep on using that and have
DEALER talk to REP.
Note: it is possible that very recent versions of ZeroMQ allow REQ
sockets to revert state on error but I haven't been following this closely.
On 12/13/2013 04:17 PM, Sean Robertson wrote:
I believe the REQ will simply wait for the REP to come back up,
re-bind and send something.
On Fri, Dec 13, 2013 at 2:53 PM, Mohit Jaggi mohitja...@gmail.com wrote:
Hi,
In most ZMQ sockets, the underlying TCP socket can change transparently.
Does that apply to REQ-REP sockets as well? Or will the receive call to ZMQ
socket fail?
sock = new REQ socket;
connect(sock);
while(1) {
request = receive(...);
...
send(response);
}
For example in the above code, let us say that the server with REP socket on
the other side crashed and restarted. What will happen?
Thanks,
Mohit.
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