stats: remove symbol table interface

envoy/stats/BUILD

@@ -52,10 +52,6 @@ envoy_cc_library(
 envoy_cc_library(
     name = "symbol_table_interface",
     hdrs = ["symbol_table.h"],
-    external_deps = ["abseil_inlined_vector"],
-    deps = [
-        "//source/common/common:hash_lib",
-    ],
 )
 
 envoy_cc_library(

envoy/stats/symbol_table.h

@@ -1,235 +1,20 @@
 #pragma once
 
-#include <functional>
-#include <memory>
-#include <utility>
-#include <vector>
-
-#include "envoy/common/pure.h"
-
-#include "absl/container/inlined_vector.h"
-#include "absl/strings/string_view.h"
-
 namespace Envoy {
 namespace Stats {
 
-/**
- * Runtime representation of an encoded stat name. This is predeclared only in
- * the interface without abstract methods, because (a) the underlying class
- * representation is common to both implementations of SymbolTable, and (b)
- * we do not want or need the overhead of a vptr per StatName. The common
- * declaration for StatName is in source/common/stats/symbol_table_impl.h
- */
-class StatName;
-using StatNameVec = absl::InlinedVector<StatName, 8>;
-
-class StatNameList;
-class StatNameSet;
-
-using StatNameSetPtr = std::unique_ptr<StatNameSet>;
+// Forward declarations for the symbol table classes. See
+// source/common/stats/symbol_table_impl.h" for the class definitions.
 
 /**
- * Holds a range of indexes indicating which parts of a stat-name are
- * dynamic. This is used to transfer stats from hot-restart parent to child,
- * retaining the same name structure.
+ * Runtime representation of an encoded stat name.
  */
-using DynamicSpan = std::pair<uint32_t, uint32_t>;
-using DynamicSpans = std::vector<DynamicSpan>;
+class StatName;
 
 /**
- * SymbolTable manages a namespace optimized for stat names, exploiting their
- * typical composition from "."-separated tokens, with a significant overlap
- * between the tokens. The interface is designed to balance optimal storage
- * at scale with hiding details from users. We seek to provide the most abstract
- * interface possible that avoids adding per-stat overhead or taking locks in
- * the hot path.
+ * Holds a set of symbols used to compose hierarhical names.
  */
-class SymbolTable {
-public:
-  /**
-   * Efficient byte-encoded storage of an array of tokens. The most common
-   * tokens are typically < 127, and are represented directly. tokens >= 128
-   * spill into the next byte, allowing for tokens of arbitrary numeric value to
-   * be stored. As long as the most common tokens are low-valued, the
-   * representation is space-efficient. This scheme is similar to UTF-8. The
-   * token ordering is dependent on the order in which stat-names are encoded
-   * into the SymbolTable, which will not be optimal, but in practice appears
-   * to be pretty good.
-   *
-   * This is exposed in the interface for the benefit of join(), which is
-   * used in the hot-path to append two stat-names into a temp without taking
-   * locks. This is used then in thread-local cache lookup, so that once warm,
-   * no locks are taken when looking up stats.
-   */
-  using Storage = uint8_t[];
-  using StoragePtr = std::unique_ptr<Storage>;
-
-  virtual ~SymbolTable() = default;
-
-  /**
-   * @return uint64_t the number of symbols in the symbol table.
-   */
-  virtual uint64_t numSymbols() const PURE;
-
-  /**
-   * Decodes a vector of symbols back into its period-delimited stat name. If
-   * decoding fails on any part of the symbol_vec, we release_assert and crash,
-   * since this should never happen, and we don't want to continue running
-   * with a corrupt stats set.
-   *
-   * @param stat_name the stat name.
-   * @return std::string stringified stat_name.
-   */
-  virtual std::string toString(const StatName& stat_name) const PURE;
-
-  /**
-   * Determines whether one StatName lexically precedes another. Note that
-   * the lexical order may not exactly match the lexical order of the
-   * elaborated strings. For example, stat-name of "-.-" would lexically
-   * sort after "---" but when encoded as a StatName would come lexically
-   * earlier. In practice this is unlikely to matter as those are not
-   * reasonable names for Envoy stats.
-   *
-   * Note that this operation has to be performed with the context of the
-   * SymbolTable so that the individual Symbol objects can be converted
-   * into strings for lexical comparison.
-   *
-   * @param a the first stat name
-   * @param b the second stat name
-   * @return bool true if a lexically precedes b.
-   */
-  virtual bool lessThan(const StatName& a, const StatName& b) const PURE;
-
-  /**
-   * Joins two or more StatNames. For example if we have StatNames for {"a.b",
-   * "c.d", "e.f"} then the joined stat-name matches "a.b.c.d.e.f". The
-   * advantage of using this representation is that it avoids having to
-   * decode/encode into the elaborated form, and does not require locking the
-   * SymbolTable.
-   *
-   * Note that this method does not bump reference counts on the referenced
-   * Symbols in the SymbolTable, so it's only valid as long for the lifetime of
-   * the joined StatNames.
-   *
-   * This is intended for use doing cached name lookups of scoped stats, where
-   * the scope prefix and the names to combine it with are already in StatName
-   * form. Using this class, they can be combined without accessing the
-   * SymbolTable or, in particular, taking its lock.
-   *
-   * @param stat_names the names to join.
-   * @return Storage allocated for the joined name.
-   */
-  virtual StoragePtr join(const StatNameVec& stat_names) const PURE;
-
-  /**
-   * Populates a StatNameList from a list of encodings. This is not done at
-   * construction time to enable StatNameList to be instantiated directly in
-   * a class that doesn't have a live SymbolTable when it is constructed.
-   *
-   * @param names A pointer to the first name in an array, allocated by the caller.
-   * @param num_names The number of names.
-   * @param list The StatNameList representing the stat names.
-   */
-  virtual void populateList(const StatName* names, uint32_t num_names, StatNameList& list) PURE;
-
-#ifndef ENVOY_CONFIG_COVERAGE
-  virtual void debugPrint() const PURE;
-#endif
-
-  using RecentLookupsFn = std::function<void(absl::string_view, uint64_t)>;
-
-  /**
-   * Calls the provided function with the name of the most recently looked-up
-   * symbols, including lookups on any StatNameSets, and with a count of
-   * the recent lookups on that symbol.
-   *
-   * @param iter the function to call for every recent item.
-   */
-  virtual uint64_t getRecentLookups(const RecentLookupsFn& iter) const PURE;
-
-  /**
-   * Clears the recent-lookups structures.
-   */
-  virtual void clearRecentLookups() PURE;
-
-  /**
-   * Sets the recent-lookup capacity.
-   */
-  virtual void setRecentLookupCapacity(uint64_t capacity) PURE;
-
-  /**
-   * @return The configured recent-lookup tracking capacity.
-   */
-  virtual uint64_t recentLookupCapacity() const PURE;
-
-  /**
-   * Creates a StatNameSet.
-   *
-   * @param name the name of the set.
-   * @return the set.
-   */
-  virtual StatNameSetPtr makeSet(absl::string_view name) PURE;
-
-  /**
-   * Identifies the dynamic components of a stat_name into an array of integer
-   * pairs, indicating the begin/end of spans of tokens in the stat-name that
-   * are created from StatNameDynamicStore or StatNameDynamicPool.
-   *
-   * This can be used to reconstruct the same exact StatNames in
-   * StatNames::mergeStats(), to enable stat continuity across hot-restart.
-   *
-   * @param stat_name the input stat name.
-   * @return the array of pairs indicating the bounds.
-   */
-  virtual DynamicSpans getDynamicSpans(StatName stat_name) const PURE;
-
-private:
-  friend struct HeapStatData;
-  friend class StatNameDynamicStorage;
-  friend class StatNameStorage;
-  friend class StatNameList;
-  friend class StatNameSet;
-
-  // The following methods are private, but are called by friend classes
-  // StatNameStorage and StatNameList, which must be friendly with SymbolTable
-  // in order to manage the reference-counted symbols they own.
-
-  /**
-   * Since SymbolTable does manual reference counting, a client of SymbolTable
-   * must manually call free(symbol_vec) when it is freeing the backing store
-   * for a StatName. This way, the symbol table will grow and shrink
-   * dynamically, instead of being write-only.
-   *
-   * @param stat_name the stat name.
-   */
-  virtual void free(const StatName& stat_name) PURE;
-
-  /**
-   * StatName backing-store can be managed by callers in a variety of ways
-   * to minimize overhead. But any persistent reference to a StatName needs
-   * to hold onto its own reference-counts for all symbols. This method
-   * helps callers ensure the symbol-storage is maintained for the lifetime
-   * of a reference.
-   *
-   * @param stat_name the stat name.
-   */
-  virtual void incRefCount(const StatName& stat_name) PURE;
-
-  /**
-   * Encodes 'name' into the symbol table. Bumps reference counts for referenced
-   * symbols. The caller must manage the storage, and is responsible for calling
-   * SymbolTable::free() to release the reference counts.
-   *
-   * @param name The name to encode.
-   * @return The encoded name, transferring ownership to the caller.
-   *
-   */
-  virtual StoragePtr encode(absl::string_view name) PURE;
-
-  virtual StoragePtr makeDynamicStorage(absl::string_view name) PURE;
-};
-
-using SymbolTablePtr = std::unique_ptr<SymbolTable>;
+class SymbolTable;
 
 } // namespace Stats
 } // namespace Envoy

source/common/stats/BUILD

@@ -89,7 +89,6 @@ envoy_cc_library(
     deps = [
         ":symbol_table_lib",
         "//envoy/stats:stats_interface",
-        "//envoy/stats:symbol_table_interface",
         "//source/common/config:well_known_names",
     ],
 )
@@ -190,7 +189,10 @@ envoy_cc_library(
     name = "symbol_table_lib",
     srcs = ["symbol_table_impl.cc"],
     hdrs = ["symbol_table_impl.h"],
-    external_deps = ["abseil_base"],
+    external_deps = [
+        "abseil_base",
+        "abseil_inlined_vector",
+    ],
     deps = [
         ":recent_lookups_lib",
         "//envoy/stats:symbol_table_interface",

source/common/stats/allocator_impl.cc

@@ -5,7 +5,6 @@
 
 #include "envoy/stats/sink.h"
 #include "envoy/stats/stats.h"
-#include "envoy/stats/symbol_table.h"
 
 #include "source/common/common/hash.h"
 #include "source/common/common/lock_guard.h"