[FFmpeg-devel] [PATCH 4/6] avformat/http: Add support for Retry-After header

[Derek Buitenhuis]

429 and 503 codes can, and often do (e.g. all Google Cloud
Storage URLs can), return a Retry-After header with the error,
indicating how long to wait, in seconds, before retrying again.
If it is not respected by, for example, using our default backoff
stratetgy instead, chances of success are very unlikely.

This adds an AVOption to respect that header.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis at gmail.com>
---
 libavformat/http.c    | 12 ++++++++++++
 libavformat/version.h |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/libavformat/http.c b/libavformat/http.c
index e7603037f4..8f092f108d 100644
--- a/libavformat/http.c
+++ b/libavformat/http.c
@@ -138,6 +138,8 @@ typedef struct HTTPContext {
     char *new_location;
     AVDictionary *redirect_cache;
     uint64_t filesize_from_content_range;
+    int respect_retry_after;
+    int retry_after;
 } HTTPContext;
 
 #define OFFSET(x) offsetof(HTTPContext, x)
@@ -176,6 +178,7 @@ static const AVOption options[] = {
     { "reconnect_on_http_error", "list of http status codes to reconnect on", OFFSET(reconnect_on_http_error), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, D },
     { "reconnect_streamed", "auto reconnect streamed / non seekable streams", OFFSET(reconnect_streamed), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, D },
     { "reconnect_delay_max", "max reconnect delay in seconds after which to give up", OFFSET(reconnect_delay_max), AV_OPT_TYPE_INT, { .i64 = 120 }, 0, UINT_MAX/1000/1000, D },
+    { "respect_retry_after", "respect the Retry-After header when retrying connections", OFFSET(respect_retry_after), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, D },
     { "listen", "listen on HTTP", OFFSET(listen), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 2, D | E },
     { "resource", "The resource requested by a client", OFFSET(resource), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, E },
     { "reply_code", "The http status code to return to a client", OFFSET(reply_code), AV_OPT_TYPE_INT, { .i64 = 200}, INT_MIN, 599, E},
@@ -386,6 +389,13 @@ redo:
             reconnect_delay > s->reconnect_delay_max)
             goto fail;
 
+        if (s->respect_retry_after && s->retry_after > 0) {
+            reconnect_delay = s->retry_after;
+            if (reconnect_delay > s->reconnect_delay_max)
+                goto fail;
+            s->retry_after = 0;
+        }
+
         av_log(h, AV_LOG_WARNING, "Will reconnect at %"PRIu64" in %d second(s).\n", off, reconnect_delay);
         ret = ff_network_sleep_interruptible(1000U * 1000 * reconnect_delay, &h->interrupt_callback);
         if (ret != AVERROR(ETIMEDOUT))
@@ -1231,6 +1241,8 @@ static int process_line(URLContext *h, char *line, int line_count, int *parsed_h
             parse_expires(s, p);
         } else if (!av_strcasecmp(tag, "Cache-Control")) {
             parse_cache_control(s, p);
+        } else if (!av_strcasecmp(tag, "Retry-After")) {
+            s->retry_after = strtoull(p, NULL, 10);
         }
     }
     return 1;
diff --git a/libavformat/version.h b/libavformat/version.h
index 7ff1483912..ee91990360 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -32,7 +32,7 @@
 #include "version_major.h"
 
 #define LIBAVFORMAT_VERSION_MINOR   3
-#define LIBAVFORMAT_VERSION_MICRO 100
+#define LIBAVFORMAT_VERSION_MICRO 101
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
                                                LIBAVFORMAT_VERSION_MINOR, \
-- 
2.43.0