Log CompactOnDeletionCollectorFactory parameters on DB open (#6686)

Summary:
Log it in the info log to help in troubleshooting. It is logged as follows -
```
2020/04/10-10:51:39.886662 7ffff7fef340                   Options.table_properties_collectors: CompactOnDeletionCollector (Sliding window size = 100 Deletion trigger = 90);
```

Tests:
make check
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6686

Reviewed By: ltamasi

Differential Revision: D21002442

Pulled By: anand1976

fbshipit-source-id: 7adf0dbae7f1febcb00ce61fea5097118ede5c6a

include/rocksdb/table_properties.h

@@ -136,6 +136,11 @@ class TablePropertiesCollectorFactory {
 
   // The name of the properties collector can be used for debugging purpose.
   virtual const char* Name() const = 0;
+
+  // Can be overridden by sub-classes to return the Name, followed by
+  // configuration info that will // be logged to the info log when the
+  // DB is opened
+  virtual std::string ToString() const { return Name(); }
 };
 
 // TableProperties contains a bunch of read-only properties of its associated

include/rocksdb/utilities/table_properties_collectors.h

@@ -18,9 +18,9 @@ namespace ROCKSDB_NAMESPACE {
 class CompactOnDeletionCollectorFactory
     : public TablePropertiesCollectorFactory {
  public:
-  virtual ~CompactOnDeletionCollectorFactory() {}
+  ~CompactOnDeletionCollectorFactory() {}
 
-  virtual TablePropertiesCollector* CreateTablePropertiesCollector(
+  TablePropertiesCollector* CreateTablePropertiesCollector(
       TablePropertiesCollectorFactory::Context context) override;
 
   // Change the value of sliding_window_size "N"
@@ -34,10 +34,12 @@ class CompactOnDeletionCollectorFactory
     deletion_trigger_.store(deletion_trigger);
   }
 
-  virtual const char* Name() const override {
+  const char* Name() const override {
     return "CompactOnDeletionCollector";
   }
 
+  std::string ToString() const override;
+
  private:
   friend std::shared_ptr<CompactOnDeletionCollectorFactory>
   NewCompactOnDeletionCollectorFactory(size_t sliding_window_size,

options/options.cc

@@ -319,14 +319,13 @@ void ColumnFamilyOptions::Dump(Logger* log) const {
     ROCKS_LOG_HEADER(log,
                      "Options.compaction_options_fifo.allow_compaction: %d",
                      compaction_options_fifo.allow_compaction);
-    std::string collector_names;
+    std::ostringstream collector_info;
     for (const auto& collector_factory : table_properties_collector_factories) {
-      collector_names.append(collector_factory->Name());
+      collector_info << collector_factory->ToString() << ';';
-      collector_names.append("; ");
     }
     ROCKS_LOG_HEADER(
         log, "                  Options.table_properties_collectors: %s",
-        collector_names.c_str());
+        collector_info.str().c_str());
     ROCKS_LOG_HEADER(log,
                      "                  Options.inplace_update_support: %d",
                      inplace_update_support);

utilities/table_properties_collectors/compact_on_deletion_collector.cc

@@ -7,6 +7,7 @@
 #include "utilities/table_properties_collectors/compact_on_deletion_collector.h"
 
 #include <memory>
+#include <sstream>
 #include "rocksdb/utilities/table_properties_collectors.h"
 
 namespace ROCKSDB_NAMESPACE {
@@ -78,6 +79,13 @@ CompactOnDeletionCollectorFactory::CreateTablePropertiesCollector(
       sliding_window_size_.load(), deletion_trigger_.load());
 }
 
+std::string CompactOnDeletionCollectorFactory::ToString() const {
+  std::ostringstream cfg;
+  cfg << Name() << " (Sliding window size = " << sliding_window_size_.load()
+       << " Deletion trigger = " << deletion_trigger_.load() << ')';
+  return cfg.str();
+}
+
 std::shared_ptr<CompactOnDeletionCollectorFactory>
     NewCompactOnDeletionCollectorFactory(
         size_t sliding_window_size,