flux-restore: add --size-limit=SIZE option

Problem: an archive that includes blobs too large to be
stored to the content cache cannot be restored, since failure
to restore a blob is treated as a fatal error.

Add a --size-limit=SIZE option that instructs flux-restore to
skip restoring blobs that exceed the specified size.

Author: garlick

src/cmd/builtin/restore.c

@@ -37,6 +37,7 @@ static int content_flags;
 static time_t restore_timestamp;
 static int blobcount;
 static int keycount;
+static int blob_size_limit;
 
 static void progress (int delta_blob, int delta_keys)
 {
@@ -270,6 +271,17 @@ static json_t *restore_snapshot (struct archive *ar, flux_t *h)
         else if (type == AE_IFREG) {
             int size = archive_entry_size (entry);
 
+            if (blob_size_limit > 0 && size > blob_size_limit) {
+                fprintf (stderr,
+                         "%s%s size %d exceeds %d limit, skipping\n",
+                         (!quiet && !verbose) ? "\r" : "",
+                         path,
+                         size,
+                         blob_size_limit);
+                // N.B.  archive_read_next_header() skips unconsumed data
+                //   automatically so it is safe to "continue" here.
+                continue;
+            }
             if (size > bufsize) {
                 void *newbuf;
                 if (!(newbuf = realloc (buf, size)))
@@ -354,6 +366,7 @@ static int cmd_restore (optparse_t *p, int ac, char *av[])
         content_flags |= CONTENT_FLAG_CACHE_BYPASS;
         kvs_checkpoint_flags |= KVS_CHECKPOINT_FLAG_CACHE_BYPASS;
     }
+    blob_size_limit = optparse_get_int (p, "size-limit", 0);
 
     h = builtin_get_flux_handle (p);
     ar = restore_create (infile);
@@ -458,6 +471,9 @@ static struct optparse_option restore_opts[] = {
     { .name = "no-cache", .has_arg = 0,
       .usage = "Bypass the broker content cache",
     },
+    { .name = "size-limit", .has_arg = 1, .arginfo = "SIZE",
+      .usage = "Do not restore blobs greater than SIZE bytes",
+    },
     OPTPARSE_TABLE_END
 };