Re: [PATCH 03/13] http: use new headers for each object request

[Patrick Steinhardt <ps@pks.im>]

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On Sun, Mar 24, 2024 at 01:12:51AM +0000, brian m. carlson wrote:
> Currently we create one set of headers for all object requests and reuse
> it.  However, we'll need to adjust the headers for authentication
> purposes in the future, so let's create a new set for each request so
> that we can adjust them if the authentication changes.
> 
> Note that the cost of allocation here is tiny compared to the fact that
> we're making a network call, not to mention probably a full TLS
> connection, so this shouldn't have a significant impact on performance.
> Moreover, nobody who cares about performance is using the dumb HTTP
> protocol anyway, since it often makes huge numbers of requests compared
> to the smart protocol.
> 
> Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
> ---
>  http.c | 19 +++++++++++--------
>  http.h |  2 ++
>  2 files changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/http.c b/http.c
> index e73b136e58..1c2200da77 100644
> --- a/http.c
> +++ b/http.c
> @@ -128,7 +128,6 @@ static unsigned long empty_auth_useless =
>  	| CURLAUTH_DIGEST;
>  
>  static struct curl_slist *pragma_header;
> -static struct curl_slist *no_pragma_header;
>  static struct string_list extra_http_headers = STRING_LIST_INIT_DUP;
>  
>  static struct curl_slist *host_resolutions;

Nice to see that this also allows us to get rid of one more global
variable.

> @@ -299,6 +298,11 @@ size_t fwrite_null(char *ptr UNUSED, size_t eltsize UNUSED, size_t nmemb,
>  	return nmemb;
>  }
>  
> +static struct curl_slist *object_request_headers(void)
> +{
> +	return curl_slist_append(http_copy_default_headers(), "Pragma:");
> +}
> +
>  static void closedown_active_slot(struct active_request_slot *slot)
>  {
>  	active_requests--;
> @@ -1275,8 +1279,6 @@ void http_init(struct remote *remote, const char *url, int proactive_auth)
>  
>  	pragma_header = curl_slist_append(http_copy_default_headers(),
>  		"Pragma: no-cache");
> -	no_pragma_header = curl_slist_append(http_copy_default_headers(),
> -		"Pragma:");
>  
>  	{
>  		char *http_max_requests = getenv("GIT_HTTP_MAX_REQUESTS");
> @@ -1360,8 +1362,6 @@ void http_cleanup(void)
>  	curl_slist_free_all(pragma_header);
>  	pragma_header = NULL;
>  
> -	curl_slist_free_all(no_pragma_header);
> -	no_pragma_header = NULL;
>  

Nit: this leaves behind two consecutive empty lines.

Patrick

>  	curl_slist_free_all(host_resolutions);
>  	host_resolutions = NULL;
> @@ -2370,6 +2370,7 @@ void release_http_pack_request(struct http_pack_request *preq)
>  	}
>  	preq->slot = NULL;
>  	strbuf_release(&preq->tmpfile);
> +	curl_slist_free_all(preq->headers);
>  	free(preq->url);
>  	free(preq);
>  }
> @@ -2454,11 +2455,11 @@ struct http_pack_request *new_direct_http_pack_request(
>  	}
>  
>  	preq->slot = get_active_slot();
> +	preq->headers = object_request_headers();
>  	curl_easy_setopt(preq->slot->curl, CURLOPT_WRITEDATA, preq->packfile);
>  	curl_easy_setopt(preq->slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
>  	curl_easy_setopt(preq->slot->curl, CURLOPT_URL, preq->url);
> -	curl_easy_setopt(preq->slot->curl, CURLOPT_HTTPHEADER,
> -		no_pragma_header);
> +	curl_easy_setopt(preq->slot->curl, CURLOPT_HTTPHEADER, preq->headers);
>  
>  	/*
>  	 * If there is data present from a previous transfer attempt,
> @@ -2624,13 +2625,14 @@ struct http_object_request *new_http_object_request(const char *base_url,
>  	}
>  
>  	freq->slot = get_active_slot();
> +	freq->headers = object_request_headers();
>  
>  	curl_easy_setopt(freq->slot->curl, CURLOPT_WRITEDATA, freq);
>  	curl_easy_setopt(freq->slot->curl, CURLOPT_FAILONERROR, 0);
>  	curl_easy_setopt(freq->slot->curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
>  	curl_easy_setopt(freq->slot->curl, CURLOPT_ERRORBUFFER, freq->errorstr);
>  	curl_easy_setopt(freq->slot->curl, CURLOPT_URL, freq->url);
> -	curl_easy_setopt(freq->slot->curl, CURLOPT_HTTPHEADER, no_pragma_header);
> +	curl_easy_setopt(freq->slot->curl, CURLOPT_HTTPHEADER, freq->headers);
>  
>  	/*
>  	 * If we have successfully processed data from a previous fetch
> @@ -2718,5 +2720,6 @@ void release_http_object_request(struct http_object_request *freq)
>  		release_active_slot(freq->slot);
>  		freq->slot = NULL;
>  	}
> +	curl_slist_free_all(freq->headers);
>  	strbuf_release(&freq->tmpfile);
>  }
> diff --git a/http.h b/http.h
> index 3af19a8bf5..c5f8cc4620 100644
> --- a/http.h
> +++ b/http.h
> @@ -196,6 +196,7 @@ struct http_pack_request {
>  	FILE *packfile;
>  	struct strbuf tmpfile;
>  	struct active_request_slot *slot;
> +	struct curl_slist *headers;
>  };
>  
>  struct http_pack_request *new_http_pack_request(
> @@ -229,6 +230,7 @@ struct http_object_request {
>  	int zret;
>  	int rename;
>  	struct active_request_slot *slot;
> +	struct curl_slist *headers;
>  };
>  
>  struct http_object_request *new_http_object_request(
> 

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