Are there any guidelines to speed up network connection by choosing the right curl opt headers with libcurl

[ganeshkamath89]

I am using libcurl to connect from my client to servers (internal and 3rd party).

While choosing curl opt headers :

1. How do I choose the headers if my priority is speed.
2. How do I choose headers if my priority is lesser TCP Retransmission / TCP ACK.
3. How do I choose the headers if I prefer more persistant communication by sacrificing speed.

If you can share examples of changing curl opt headers that have made a real difference in user experience, please share.

[jay]

Are you having performance issues? curl should perform well with default settings.

[ganeshkamath89]

Hi @jay. How is handle reuse being done in your example, is it happening from this this line:

curl_easy_setopt(easy, CURLOPT_PRIVATE, user);

In general, if I use the curl opt header CURLOPT_PRIVATE and pass the URL in the third parameter, will it create a reusable handle, if the date is the same?

For example, if my URL is associated with this line:
curl_easy_setopt(curl, CURLOPT_URL, cl->data.endpoint);

if I add the header and associate it with the same value as URL like this:

curl_easy_setopt(curl, CURLOPT_URL, cl->data.endpoint);
curl_easy_setopt(curl, CURLOPT_PRIVATE, cl->data.endpoint);

will it resuse the handle for future connections with the same URL?

Am I applying the code properly here?

[ganeshkamath89]

Hi @jay . Can you help me convert this file to easy with handle reuse?
File: https://github.com/Openwsman/openwsman/blob/master/src/lib/wsman-curl-client-transport.c

I don't know if we will be making multiple connections simultaneously to use multi with this file. I can try multi and check feasability with this file. But I don't know yet. Currently the handle reuse option seems promising.

I have added the PipeWait header "CURLOPT_PIPEWAIT" today, need to see how it affects performance. Thanks for this tip.

[jay]

Am I applying the code properly here?

The code was written only for the purpose of comparison of the different methods. I have added that information to the comments and also I added some code to show errors.

Can you help me convert this file to easy with handle reuse?

No. You would have to decide which method is appropriate for what you are doing and make those changes. The file you linked to is using curl_easy_perform. It is also possible to share connections in a single thread by using CURL_LOCK_DATA_CONNECT. For example if it's too much work to rewrite all that code to reuse the easy handle then you could reuse a shared object with connection sharing enabled instead. See example shared-connection-cache.c.

[ganeshkamath89]

Hi @jay.
We have observed that over VPN curl connection breaks. The pattern shared in the beginning of the discussion is seen more frequently on VPN based connections. Do you have any recommendations what I can do to establish the connection, longer or enable it to be more persistant? Do you have any recommendations for any particular Curl_Opt headers or other settings?

[jay]

Sorry no, it sounds like network issues and not a curl problem.