curl: retry delays in parallel mode no longer sleeps blocking

The previous sleep for retries would block all other concurrent
transfers. Starting now, the retry will instead be properly marked to
not get restarted until after the delay time but other transfers can
still continue in the mean time.

Closes #5917

src/tool_operate.c

@@ -333,7 +333,8 @@ static CURLcode pre_transfer(struct GlobalConfig *global,
 static CURLcode post_per_transfer(struct GlobalConfig *global,
                                   struct per_transfer *per,
                                   CURLcode result,
-                                  bool *retryp)
+                                  bool *retryp,
+                                  long *delay) /* milliseconds! */
 {
   struct OutStruct *outs = &per->outs;
   CURL *curl = per->curl;
@@ -343,6 +344,7 @@ static CURLcode post_per_transfer(struct GlobalConfig *global,
     return result;
 
   *retryp = FALSE;
+  *delay = 0; /* for no retry, keep it zero */
 
   if(per->infdopen)
     close(per->infd);
@@ -535,7 +537,6 @@ static CURLcode post_per_transfer(struct GlobalConfig *global,
             m[retry], sleeptime/1000L, per->retry_numretries);
 
       per->retry_numretries--;
-      tool_go_sleep(sleeptime);
       if(!config->retry_delay) {
         per->retry_sleep *= 2;
         if(per->retry_sleep > RETRY_SLEEP_MAX)
@@ -578,7 +579,8 @@ static CURLcode post_per_transfer(struct GlobalConfig *global,
         }
         outs->bytes = 0; /* clear for next round */
       }
-      *retryp = TRUE; /* curl_easy_perform loop */
+      *retryp = TRUE;
+      *delay = sleeptime;
       return CURLE_OK;
     }
   } /* if retry_numretries */
@@ -2152,6 +2154,7 @@ static CURLcode add_parallel_transfers(struct GlobalConfig *global,
   struct per_transfer *per;
   CURLcode result = CURLE_OK;
   CURLMcode mcode;
+  bool sleeping = FALSE;
   *addedp = FALSE;
   *morep = FALSE;
   result = create_transfer(global, share, addedp);
@@ -2163,6 +2166,11 @@ static CURLcode add_parallel_transfers(struct GlobalConfig *global,
     if(per->added)
       /* already added */
       continue;
+    if(per->startat && (time(NULL) < per->startat)) {
+      /* this is still delaying */
+      sleeping = TRUE;
+      continue;
+    }
 
     result = pre_transfer(global, per);
     if(result)
@@ -2187,7 +2195,7 @@ static CURLcode add_parallel_transfers(struct GlobalConfig *global,
     all_added++;
     *addedp = TRUE;
   }
-  *morep = per ? TRUE : FALSE;
+  *morep = (per || sleeping) ? TRUE : FALSE;
   return CURLE_OK;
 }
 
@@ -2201,6 +2209,7 @@ static CURLcode parallel_transfers(struct GlobalConfig *global,
   struct timeval start = tvnow();
   bool more_transfers;
   bool added_transfers;
+  time_t tick = time(NULL);
 
   multi = curl_multi_init();
   if(!multi)
@@ -2223,28 +2232,39 @@ static CURLcode parallel_transfers(struct GlobalConfig *global,
     if(!mcode) {
       int rc;
       CURLMsg *msg;
-      bool removed = FALSE;
+      bool checkmore = FALSE;
       do {
         msg = curl_multi_info_read(multi, &rc);
         if(msg) {
           bool retry;
+          long delay;
           struct per_transfer *ended;
           CURL *easy = msg->easy_handle;
           result = msg->data.result;
           curl_easy_getinfo(easy, CURLINFO_PRIVATE, (void *)&ended);
           curl_multi_remove_handle(multi, easy);
 
-          result = post_per_transfer(global, ended, result, &retry);
+          result = post_per_transfer(global, ended, result, &retry, &delay);
           progress_finalize(ended); /* before it goes away */
           all_added--; /* one fewer added */
-          removed = TRUE;
-          if(retry)
+          checkmore = TRUE;
+          if(retry) {
             ended->added = FALSE; /* add it again */
+            /* we delay retries in full integer seconds only */
+            ended->startat = delay ? time(NULL) + delay/1000 : 0;
+          }
           else
             (void)del_per_transfer(ended);
         }
       } while(msg);
-      if(removed) {
+      if(!checkmore) {
+        time_t tock = time(NULL);
+        if(tick != tock) {
+          checkmore = TRUE;
+          tick = tock;
+        }
+      }
+      if(checkmore) {
         /* one or more transfers completed, add more! */
         (void)add_parallel_transfers(global, multi, share,
                                      &more_transfers,
@@ -2284,6 +2304,7 @@ static CURLcode serial_transfers(struct GlobalConfig *global,
     return result;
   for(per = transfers; per;) {
     bool retry;
+    long delay;
     bool bailout = FALSE;
     result = pre_transfer(global, per);
     if(result)
@@ -2306,9 +2327,11 @@ static CURLcode serial_transfers(struct GlobalConfig *global,
     /* store the result of the actual transfer */
     returncode = result;
 
-    result = post_per_transfer(global, per, result, &retry);
-    if(retry)
+    result = post_per_transfer(global, per, result, &retry, &delay);
+    if(retry) {
+      tool_go_sleep(delay);
       continue;
+    }
 
     /* Bail out upon critical errors or --fail-early */
     if(result || is_fatal_error(returncode) ||
@@ -2483,7 +2506,8 @@ static CURLcode run_all_transfers(struct GlobalConfig *global,
   /* cleanup if there are any left */
   for(per = transfers; per;) {
     bool retry;
-    CURLcode result2 = post_per_transfer(global, per, result, &retry);
+    long delay;
+    CURLcode result2 = post_per_transfer(global, per, result, &retry, &delay);
     if(!result)
       /* don't overwrite the original error */
       result = result2;

src/tool_operate.h

@@ -54,6 +54,9 @@ struct per_transfer {
   char errorbuffer[CURL_ERROR_SIZE];
 
   bool added; /* set TRUE when added to the multi handle */
+  time_t startat; /* when doing parallel transfers, this is a retry transfer
+                     that has been set to sleep until this time before it
+                     should get started (again) */
 
   /* for parallel progress bar */
   curl_off_t dltotal;