filter: Add HttpCache interface and helpers (#9878)

Signed-off-by: Todd Greer <tgreer@google.com>

source/common/http/headers.h

@@ -117,6 +117,7 @@ class HeaderValues {
   const LowerCaseString EnvoyDecoratorOperation{absl::StrCat(prefix(), "-decorator-operation")};
   const LowerCaseString Etag{"etag"};
   const LowerCaseString Expect{"expect"};
+  const LowerCaseString Expires{"expires"};
   const LowerCaseString ForwardedClientCert{"x-forwarded-client-cert"};
   const LowerCaseString ForwardedFor{"x-forwarded-for"};
   const LowerCaseString ForwardedHost{"x-forwarded-host"};

source/extensions/filters/http/cache/BUILD

@@ -7,10 +7,34 @@ load(
     "envoy_cc_extension",
     "envoy_cc_library",
     "envoy_package",
+    "envoy_proto_library",
 )
 
 envoy_package()
 
+envoy_proto_library(
+    name = "key",
+    srcs = ["key.proto"],
+)
+
+envoy_cc_library(
+    name = "http_cache_lib",
+    srcs = ["http_cache.cc"],
+    hdrs = ["http_cache.h"],
+    deps = [
+        ":http_cache_utils_lib",
+        ":key_cc_proto",
+        "//include/envoy/buffer:buffer_interface",
+        "//include/envoy/common:time_interface",
+        "//include/envoy/config:typed_config_interface",
+        "//include/envoy/http:codes_interface",
+        "//include/envoy/http:header_map_interface",
+        "//source/common/common:assert_lib",
+        "//source/common/http:headers_lib",
+        "//source/common/protobuf:utility_lib",
+    ],
+)
+
 envoy_cc_library(
     name = "http_cache_utils_lib",
     srcs = ["http_cache_utils.cc"],

source/extensions/filters/http/cache/http_cache.cc

@@ -0,0 +1,160 @@
+#include "extensions/filters/http/cache/http_cache.h"
+
+#include <algorithm>
+#include <ostream>
+
+#include "envoy/http/codes.h"
+
+#include "common/http/headers.h"
+#include "common/protobuf/utility.h"
+
+#include "extensions/filters/http/cache/http_cache_utils.h"
+
+#include "absl/time/time.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace HttpFilters {
+namespace Cache {
+
+std::ostream& operator<<(std::ostream& os, CacheEntryStatus status) {
+  switch (status) {
+  case CacheEntryStatus::Ok:
+    return os << "Ok";
+  case CacheEntryStatus::Unusable:
+    return os << "Unusable";
+  case CacheEntryStatus::RequiresValidation:
+    return os << "RequiresValidation";
+  case CacheEntryStatus::FoundNotModified:
+    return os << "FoundNotModified";
+  case CacheEntryStatus::UnsatisfiableRange:
+    return os << "UnsatisfiableRange";
+  }
+  NOT_REACHED_GCOVR_EXCL_LINE;
+}
+
+std::ostream& operator<<(std::ostream& os, const AdjustedByteRange& range) {
+  return os << "[" << range.begin() << "," << range.end() << ")";
+}
+
+LookupRequest::LookupRequest(const Http::HeaderMap& request_headers, SystemTime timestamp)
+    : timestamp_(timestamp),
+      request_cache_control_(request_headers.CacheControl() == nullptr
+                                 ? ""
+                                 : request_headers.CacheControl()->value().getStringView()) {
+  // These ASSERTs check prerequisites. A request without these headers can't be looked up in cache;
+  // CacheFilter doesn't create LookupRequests for such requests.
+  ASSERT(request_headers.Path(), "Can't form cache lookup key for malformed Http::HeaderMap "
+                                 "with null Path.");
+  ASSERT(request_headers.ForwardedProto(),
+         "Can't form cache lookup key for malformed Http::HeaderMap with null ForwardedProto.");
+  ASSERT(request_headers.Host(), "Can't form cache lookup key for malformed Http::HeaderMap "
+                                 "with null Host.");
+  const Http::HeaderString& forwarded_proto = request_headers.ForwardedProto()->value();
+  const auto& scheme_values = Http::Headers::get().SchemeValues;
+  ASSERT(forwarded_proto == scheme_values.Http || forwarded_proto == scheme_values.Https);
+  // TODO(toddmgreer): Let config determine whether to include forwarded_proto, host, and
+  // query params.
+  // TODO(toddmgreer): get cluster name.
+  // TODO(toddmgreer): Parse Range header into request_range_spec_, and handle the resultant
+  // vector<AdjustedByteRange> in CacheFilter::onOkHeaders.
+  key_.set_cluster_name("cluster_name_goes_here");
+  key_.set_host(std::string(request_headers.Host()->value().getStringView()));
+  key_.set_path(std::string(request_headers.Path()->value().getStringView()));
+  key_.set_clear_http(forwarded_proto == scheme_values.Http);
+}
+
+// Unless this API is still alpha, calls to stableHashKey() must always return
+// the same result, or a way must be provided to deal with a complete cache
+// flush. localHashKey however, can be changed at will.
+size_t stableHashKey(const Key& key) { return MessageUtil::hash(key); }
+size_t localHashKey(const Key& key) { return stableHashKey(key); }
+
+// Returns true if response_headers is fresh.
+bool LookupRequest::isFresh(const Http::HeaderMap& response_headers) const {
+  if (!response_headers.Date()) {
+    return false;
+  }
+  const Http::HeaderEntry* cache_control_header = response_headers.CacheControl();
+  if (cache_control_header) {
+    const SystemTime::duration effective_max_age =
+        Utils::effectiveMaxAge(cache_control_header->value().getStringView());
+    return timestamp_ - Utils::httpTime(response_headers.Date()) < effective_max_age;
+  }
+  // We didn't find a cache-control header with enough info to determine
+  // freshness, so fall back to the expires header.
+  return timestamp_ <= Utils::httpTime(response_headers.get(Http::Headers::get().Expires));
+}
+
+LookupResult LookupRequest::makeLookupResult(Http::HeaderMapPtr&& response_headers,
+                                             uint64_t content_length) const {
+  // TODO(toddmgreer): Implement all HTTP caching semantics.
+  ASSERT(response_headers);
+  LookupResult result;
+  result.cache_entry_status_ =
+      isFresh(*response_headers) ? CacheEntryStatus::Ok : CacheEntryStatus::RequiresValidation;
+  result.headers_ = std::move(response_headers);
+  result.content_length_ = content_length;
+  if (!adjustByteRangeSet(result.response_ranges_, request_range_spec_, content_length)) {
+    result.headers_->setStatus(static_cast<uint64_t>(Http::Code::RangeNotSatisfiable));
+  }
+  result.has_trailers_ = false;
+  return result;
+}
+
+bool adjustByteRangeSet(std::vector<AdjustedByteRange>& response_ranges,
+                        const std::vector<RawByteRange>& request_range_spec,
+                        uint64_t content_length) {
+  if (request_range_spec.empty()) {
+    // No range header, so the request can proceed.
+    return true;
+  }
+
+  if (content_length == 0) {
+    // There is a range header, but it's unsatisfiable.
+    return false;
+  }
+
+  for (const RawByteRange& spec : request_range_spec) {
+    if (spec.isSuffix()) {
+      // spec is a suffix-byte-range-spec
+      if (spec.suffixLength() == 0) {
+        // This range is unsatisfiable, so skip it.
+        continue;
+      }
+      if (spec.suffixLength() >= content_length) {
+        // All bytes are being requested, so we may as well send a '200
+        // OK' response.
+        response_ranges.clear();
+        return true;
+      }
+      response_ranges.emplace_back(content_length - spec.suffixLength(), content_length);
+    } else {
+      // spec is a byte-range-spec
+      if (spec.firstBytePos() >= content_length) {
+        // This range is unsatisfiable, so skip it.
+        continue;
+      }
+      if (spec.lastBytePos() >= content_length - 1) {
+        if (spec.firstBytePos() == 0) {
+          // All bytes are being requested, so we may as well send a '200
+          // OK' response.
+          response_ranges.clear();
+          return true;
+        }
+        response_ranges.emplace_back(spec.firstBytePos(), content_length);
+      } else {
+        response_ranges.emplace_back(spec.firstBytePos(), spec.lastBytePos() + 1);
+      }
+    }
+  }
+  if (response_ranges.empty()) {
+    // All ranges were unsatisfiable.
+    return false;
+  }
+  return true;
+}
+} // namespace Cache
+} // namespace HttpFilters
+} // namespace Extensions
+} // namespace Envoy