src/iocore/cache/CacheVC.h

/** @file

  A brief file description

  @section license License

  Licensed to the Apache Software Foundation (ASF) under one
  or more contributor license agreements.  See the NOTICE file
  distributed with this work for additional information
  regarding copyright ownership.  The ASF licenses this file
  to you under the Apache License, Version 2.0 (the
  "License"); you may not use this file except in compliance
  with the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
 */

#pragma once

#include "iocore/aio/AIO.h"
#include "iocore/eventsystem/Action.h"
#include "iocore/eventsystem/Continuation.h"
#include "iocore/eventsystem/Event.h"
#include "iocore/eventsystem/IOBuffer.h"
#include "iocore/eventsystem/VIO.h"
#include "iocore/cache/Cache.h"
#include "P_CacheDoc.h"
#include "Stripe.h"
#include "StripeSM.h"
#include "tscore/ink_hrtime.h"
#include "tscore/List.h"
#include "tscore/Ptr.h"

#include <cstdint>

class Stripe;
class HttpConfigAccessor;

struct CacheVC : public CacheVConnection {
  CacheVC();

  VIO *do_io_read(Continuation *c, int64_t nbytes, MIOBuffer *buf) override;
  VIO *do_io_pread(Continuation *c, int64_t nbytes, MIOBuffer *buf, int64_t offset) override;
  VIO *do_io_write(Continuation *c, int64_t nbytes, IOBufferReader *buf, bool owner = false) override;
  void do_io_close(int lerrno = -1) override;
  void reenable(VIO *avio) override;
  void reenable_re(VIO *avio) override;
  bool get_data(int i, void *data) override;
  bool set_data(int i, void *data) override;

  bool
  is_ram_cache_hit() const override
  {
    ink_assert(vio.op == VIO::READ);
    return f.doc_from_ram_cache;
  }

  int
  get_header(void **ptr, int *len) override
  {
    if (first_buf) {
      Doc *doc = reinterpret_cast<Doc *>(first_buf->data());
      *ptr     = doc->hdr();
      *len     = doc->hlen;
      return 0;
    }

    return -1;
  }

  int
  set_header(void *ptr, int len) override
  {
    header_to_write     = ptr;
    header_to_write_len = len;
    return 0;
  }

  int
  get_single_data(void **ptr, int *len) override
  {
    if (first_buf) {
      Doc *doc = reinterpret_cast<Doc *>(first_buf->data());
      if (doc->data_len() == doc->total_len) {
        *ptr = doc->data();
        *len = doc->data_len();
        return 0;
      }
    }

    return -1;
  }

  int
  get_volume_number() const override
  {
    if (stripe && stripe->cache_vol) {
      return stripe->cache_vol->vol_number;
    }

    return -1;
  }

  const char *
  get_disk_path() const override
  {
    if (stripe && stripe->disk) {
      return stripe->disk->path;
    }

    return nullptr;
  }

  bool
  is_compressed_in_ram() const override
  {
    ink_assert(vio.op == VIO::READ);
    return f.compressed_in_ram;
  }

  bool writer_done();
  int  calluser(int event);
  int  callcont(int event);
  int  die();
  int  dead(int event, Event *e);

  int  handleReadDone(int event, Event *e);
  int  handleRead(int event, Event *e);
  bool load_from_ram_cache();
  bool load_from_last_open_read_call();
  bool load_from_aggregation_buffer();
  int  do_read_call(CacheKey *akey);
  int  handleWrite(int event, Event *e);
  int  handleWriteLock(int event, Event *e);
  int  do_write_call();
  int  do_write_lock();
  int  do_write_lock_call();
  int  do_sync(uint32_t target_write_serial);

  int openReadClose(int event, Event *e);
  int openReadReadDone(int event, Event *e);
  int openReadMain(int event, Event *e);
  int openReadStartEarliest(int event, Event *e);
  int openReadVecWrite(int event, Event *e);
  int openReadStartHead(int event, Event *e);
  int openReadFromWriter(int event, Event *e);
  int openReadFromWriterMain(int event, Event *e);
  int openReadFromWriterFailure(int event, Event *);
  int openReadChooseWriter(int event, Event *e);
  int openReadDirDelete(int event, Event *e);

  int openWriteCloseDir(int event, Event *e);
  int openWriteCloseHeadDone(int event, Event *e);
  int openWriteCloseHead(int event, Event *e);
  int openWriteCloseDataDone(int event, Event *e);
  int openWriteClose(int event, Event *e);
  int openWriteWriteDone(int event, Event *e);
  int openWriteOverwrite(int event, Event *e);
  int openWriteMain(int event, Event *e);
  int openWriteStartDone(int event, Event *e);
  int openWriteStartBegin(int event, Event *e);

  int updateVector(int event, Event *e);

  int removeEvent(int event, Event *e);

  int scanStripe(int event, Event *e);
  int scanObject(int event, Event *e);
  int scanUpdateDone(int event, Event *e);
  int scanOpenWrite(int event, Event *e);
  int scanRemoveDone(int event, Event *e);

  int
  is_io_in_progress()
  {
    return io.aiocb.aio_fildes != AIO_NOT_IN_PROGRESS;
  }
  void
  set_io_not_in_progress()
  {
    io.aiocb.aio_fildes = AIO_NOT_IN_PROGRESS;
  }
  void
  set_agg_write_in_progress()
  {
    io.aiocb.aio_fildes = AIO_AGG_WRITE_IN_PROGRESS;
  }

  void    cancel_trigger();
  int64_t get_object_size() override;
  void    set_http_info(CacheHTTPInfo *info) override;
  void    get_http_info(CacheHTTPInfo **info) override;
  /** Get the fragment table.
      @return The address of the start of the fragment table,
      or @c nullptr if there is no fragment table.
  */
  virtual HTTPInfo::FragOffset *get_frag_table();
  /** Load alt pointers and do fixups if needed.
      @return Length of header data used for alternates.
   */
  virtual uint32_t load_http_info(CacheHTTPInfoVector *info, struct Doc *doc, RefCountObj *block_ptr = nullptr);
  bool             is_pread_capable() override;
  bool             set_pin_in_cache(time_t time_pin) override;
  time_t           get_pin_in_cache() override;

  // number of bytes to memset to 0 in the CacheVC when we free
  // it. All member variables starting from vio are memset to 0.
  // This variable is initialized in CacheVC constructor.
  static int size_to_init;

  // Start Region A
  // This set of variables are not reset when the cacheVC is freed.
  // A CacheVC must set these to the correct values whenever needed
  // These are variables that are always set to the correct values
  // before being used by the CacheVC
  CacheKey key, first_key, earliest_key, update_key;
  Dir      dir, earliest_dir, overwrite_dir, first_dir;
  // end Region A

  // Start Region B
  // These variables are individually cleared or reset when the
  // CacheVC is freed. All these variables must be reset/cleared
  // in free_CacheVC.
  Action              _action;
  CacheHTTPHdr        request;
  CacheHTTPInfoVector vector;
  CacheHTTPInfo       alternate;
  Ptr<IOBufferData>   buf;
  Ptr<IOBufferData>   first_buf;
  Ptr<IOBufferBlock>  blocks; // data available to write
  Ptr<IOBufferBlock>  writer_buf;

  OpenDirEntry *od = nullptr;
  AIOCallback   io;
  int           alternate_index = CACHE_ALT_INDEX_DEFAULT; // preferred position in vector
  LINK(CacheVC, opendir_link);
  // end Region B

  // Start Region C
  // These variables are memset to 0 when the structure is freed.
  // The size of this region is size_to_init which is initialized
  // in the CacheVC constructor. It assumes that vio is the start
  // of this region.
  // NOTE: NOTE: NOTE: If vio is NOT the start, then CHANGE the
  // size_to_init initialization
  VIO                       vio;
  CacheFragType             frag_type;
  CacheHTTPInfo            *info;
  CacheHTTPInfoVector      *write_vector;
  const HttpConfigAccessor *params;
  int                       header_len;   // for communicating with agg_copy
  int                       frag_len;     // for communicating with agg_copy
  uint32_t                  write_len;    // for communicating with agg_copy
  uint32_t                  agg_len;      // for communicating with aggWrite
  uint32_t                  write_serial; // serial of the final write for SYNC
  StripeSM                 *stripe;
  Dir                      *last_collision;
  Event                    *trigger;
  CacheKey                 *read_key;
  ContinuationHandler       save_handler;
  uint32_t                  pin_in_cache;
  ink_hrtime                start_time;
  int                       op_type; // Index into the metrics array for this operation, rather than a CacheOpType (fewer casts)
  int                       recursive;
  int                       read_recursive;
  int                       closed;
  uint64_t                  seek_to;       // pread offset
  int64_t                   offset;        // offset into 'blocks' of data to write
  int64_t                   writer_offset; // offset of the writer for reading from a writer
  int64_t                   length;        // length of data available to write
  int64_t                   doc_pos;       // read position in 'buf'
  uint64_t                  write_pos;     // length written
  uint64_t                  total_len;     // total length written and available to write
  uint64_t                  doc_len;       // total_length (of the selected alternate for HTTP)
  uint64_t                  update_len;
  int                       fragment;
  int                       scan_msec_delay;
  CacheVC                  *write_vc;
  std::string_view          hostname;
  int                       header_to_write_len;
  void                     *header_to_write;
  short                     writer_lock_retry;
  union {
    uint32_t flags;
    struct {
      unsigned int use_first_key           : 1;
      unsigned int overwrite               : 1; // overwrite first_key Dir if it exists
      unsigned int close_complete          : 1; // WRITE_COMPLETE is final
      unsigned int sync                    : 1; // write to be committed to durable storage before WRITE_COMPLETE
      unsigned int evacuator               : 1;
      unsigned int single_fragment         : 1;
      unsigned int evac_vector             : 1;
      unsigned int lookup                  : 1;
      unsigned int update                  : 1;
      unsigned int remove                  : 1;
      unsigned int remove_aborted_writers  : 1;
      unsigned int open_read_timeout       : 1; // UNUSED
      unsigned int data_done               : 1;
      unsigned int read_from_writer_called : 1;
      unsigned int rewrite_resident_alt    : 1;
      unsigned int readers                 : 1;
      unsigned int doc_from_ram_cache      : 1;
      unsigned int hit_evacuate            : 1;
      unsigned int compressed_in_ram       : 1; // compressed state in ram cache
      unsigned int allow_empty_doc         : 1; // used for cache empty http document
    } f;
  };
  // BTF optimization used to skip reading stuff in cache partition that doesn't contain any
  // dir entries.
  char *scan_stripe_map;
  // BTF fix to handle objects that overlapped over two different reads,
  // this is how much we need to back up the buffer to get the start of the overlapping object.
  off_t scan_fix_buffer_offset;
  // end region C
};

LINK_DEFINITION(CacheVC, opendir_link)