(shortfin-sd) Validate size of downloaded artifacts. (#560)

This commit introduces simple filesize/content-length comparison for a
simple validation of downloaded artifacts.
While I'm not sold on this as a long-term validation solution, it is
certainly better than nothing.

shortfin/python/shortfin_apps/sd/components/builders.py

@@ -5,9 +5,10 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 from iree.build import *
-from iree.build.executor import FileNamespace
+from iree.build.executor import FileNamespace, BuildAction, BuildContext, BuildFile
 import itertools
 import os
+import urllib
 import shortfin.array as sfnp
 import copy
 
@@ -162,25 +163,23 @@ def needs_update(ctx):
     return False
 
 
-def needs_file(filename, ctx, namespace=FileNamespace.GEN):
+def needs_file(filename, ctx, url=None, namespace=FileNamespace.GEN):
     out_file = ctx.allocate_file(filename, namespace=namespace).get_fs_path()
     if os.path.exists(out_file):
-        needed = False
-    else:
-        # name_path = "bin" if namespace == FileNamespace.BIN else ""
-        # if name_path:
-        #     filename = os.path.join(name_path, filename)
-        filekey = os.path.join(ctx.path, filename)
-        ctx.executor.all[filekey] = None
-        needed = True
-    return needed
+        if url:
+            needed = not is_valid_size(out_file, url)
+        if not needed:
+            return False
+    filekey = os.path.join(ctx.path, filename)
+    ctx.executor.all[filekey] = None
+    return True
 
 
 def needs_compile(filename, target, ctx):
     device = "amdgpu" if "gfx" in target else "llvmcpu"
     vmfb_name = f"{filename}_{device}-{target}.vmfb"
     namespace = FileNamespace.BIN
-    return needs_file(vmfb_name, ctx, namespace)
+    return needs_file(vmfb_name, ctx, namespace=namespace)
 
 
 def get_cached_vmfb(filename, target, ctx):
@@ -190,6 +189,69 @@ def get_cached_vmfb(filename, target, ctx):
     return ctx.file(vmfb_name)
 
 
+def is_valid_size(file_path, url):
+    if not url:
+        return True
+    with urllib.request.urlopen(url) as response:
+        content_length = response.getheader("Content-Length")
+    local_size = get_file_size(str(file_path))
+    if content_length:
+        content_length = int(content_length)
+        if content_length != local_size:
+            return False
+    return True
+
+
+def get_file_size(file_path):
+    """Gets the size of a local file in bytes as an integer."""
+
+    file_stats = os.stat(file_path)
+    return file_stats.st_size
+
+
+def fetch_http_check_size(*, name: str, url: str) -> BuildFile:
+    context = BuildContext.current()
+    output_file = context.allocate_file(name)
+    action = FetchHttpWithCheckAction(
+        url=url, output_file=output_file, desc=f"Fetch {url}", executor=context.executor
+    )
+    output_file.deps.add(action)
+    return output_file
+
+
+class FetchHttpWithCheckAction(BuildAction):
+    def __init__(self, url: str, output_file: BuildFile, **kwargs):
+        super().__init__(**kwargs)
+        self.url = url
+        self.output_file = output_file
+
+    def _invoke(self, retries=4):
+        path = self.output_file.get_fs_path()
+        self.executor.write_status(f"Fetching URL: {self.url} -> {path}")
+        try:
+            urllib.request.urlretrieve(self.url, str(path))
+        except urllib.error.HTTPError as e:
+            if retries > 0:
+                retries -= 1
+                self._invoke(retries=retries)
+            else:
+                raise IOError(f"Failed to fetch URL '{self.url}': {e}") from None
+        local_size = get_file_size(str(path))
+        try:
+            with urllib.request.urlopen(self.url) as response:
+                content_length = response.getheader("Content-Length")
+            if content_length:
+                content_length = int(content_length)
+                if content_length != local_size:
+                    raise IOError(
+                        f"Size of downloaded artifact does not match content-length header! {content_length} != {local_size}"
+                    )
+        except IOError:
+            if retries > 0:
+                retries -= 1
+                self._invoke(retries=retries)
+
+
 @entrypoint(description="Retreives a set of SDXL submodels.")
 def sdxl(
     model_json=cl_arg(
@@ -224,7 +286,7 @@ def sdxl(
     mlir_filenames = get_mlir_filenames(model_params, model)
     mlir_urls = get_url_map(mlir_filenames, mlir_bucket)
     for f, url in mlir_urls.items():
-        if update or needs_file(f, ctx):
+        if update or needs_file(f, ctx, url):
             fetch_http(name=f, url=url)
 
     vmfb_filenames = get_vmfb_filenames(model_params, model=model, target=target)
@@ -244,15 +306,14 @@ def sdxl(
                 vmfb_filenames[idx] = get_cached_vmfb(file_stem, target, ctx)
     else:
         for f, url in vmfb_urls.items():
-            if update or needs_file(f, ctx):
+            if update or needs_file(f, ctx, url):
                 fetch_http(name=f, url=url)
 
     params_filenames = get_params_filenames(model_params, model=model, splat=splat)
     params_urls = get_url_map(params_filenames, SDXL_WEIGHTS_BUCKET)
     for f, url in params_urls.items():
-        out_file = os.path.join(ctx.executor.output_dir, f)
-        if needs_file(f, ctx):
-            fetch_http(name=f, url=url)
+        if needs_file(f, ctx, url):
+            fetch_http_check_size(name=f, url=url)
     filenames = [*vmfb_filenames, *params_filenames, *mlir_filenames]
     return filenames