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reftable-stack.h
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169 lines (137 loc) · 5.61 KB
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/*
* Copyright 2020 Google LLC
*
* Use of this source code is governed by a BSD-style
* license that can be found in the LICENSE file or at
* https://developers.google.com/open-source/licenses/bsd
*/
#ifndef REFTABLE_STACK_H
#define REFTABLE_STACK_H
#include "reftable-writer.h"
/*
* The stack presents an interface to a mutable sequence of reftables.
* A stack can be mutated by pushing a table to the top of the stack.
* The reftable_stack automatically compacts files on disk to ensure good
* amortized performance.
*
* For windows and other platforms that cannot have open files as rename
* destinations, concurrent access from multiple processes needs the rand()
* random seed to be randomized.
*/
struct reftable_stack;
/* open a new reftable stack. The tables along with the table list will be
* stored in 'dir'. Typically, this should be .git/reftables.
*/
int reftable_new_stack(struct reftable_stack **dest, const char *dir,
const struct reftable_write_options *opts);
/* returns the update_index at which a next table should be written. */
uint64_t reftable_stack_next_update_index(struct reftable_stack *st);
/* holds a transaction to add tables at the top of a stack. */
struct reftable_addition;
enum {
/*
* Reload the stack when the stack is out-of-date after locking it.
*/
REFTABLE_STACK_NEW_ADDITION_RELOAD = (1 << 0),
};
/*
* returns a new transaction to add reftables to the given stack. As a side
* effect, the ref database is locked. Accepts REFTABLE_STACK_NEW_ADDITION_*
* flags.
*/
int reftable_stack_new_addition(struct reftable_addition **dest,
struct reftable_stack *st,
unsigned int flags);
/* Adds a reftable to transaction. */
int reftable_addition_add(struct reftable_addition *add,
int (*write_table)(struct reftable_writer *wr,
void *arg),
void *arg);
/* Commits the transaction, releasing the lock. After calling this,
* reftable_addition_destroy should still be called.
*/
int reftable_addition_commit(struct reftable_addition *add);
/* Release all non-committed data from the transaction, and deallocate the
* transaction. Releases the lock if held. */
void reftable_addition_destroy(struct reftable_addition *add);
/*
* Add a new table to the stack. The write_table function must call
* reftable_writer_set_limits, add refs and return an error value.
* The flags are passed through to `reftable_stack_new_addition()`.
*/
int reftable_stack_add(struct reftable_stack *st,
int (*write_table)(struct reftable_writer *wr,
void *write_arg),
void *write_arg, unsigned flags);
struct reftable_iterator;
/*
* Initialize an iterator for the merged tables contained in the stack that can
* be used to iterate through refs. The iterator is valid until the next reload
* or write.
*/
int reftable_stack_init_ref_iterator(struct reftable_stack *st,
struct reftable_iterator *it);
/*
* Initialize an iterator for the merged tables contained in the stack that can
* be used to iterate through logs. The iterator is valid until the next reload
* or write.
*/
int reftable_stack_init_log_iterator(struct reftable_stack *st,
struct reftable_iterator *it);
/* returns the merged_table for seeking. This table is valid until the
* next write or reload, and should not be closed or deleted.
*/
struct reftable_merged_table *
reftable_stack_merged_table(struct reftable_stack *st);
/* frees all resources associated with the stack. */
void reftable_stack_destroy(struct reftable_stack *st);
/* Reloads the stack if necessary. This is very cheap to run if the stack was up
* to date */
int reftable_stack_reload(struct reftable_stack *st);
/* Policy for expiring reflog entries. */
struct reftable_log_expiry_config {
/* Drop entries older than this timestamp */
uint64_t time;
/* Drop older entries */
uint64_t min_update_index;
};
/* compacts all reftables into a giant table. Expire reflog entries if config is
* non-NULL */
int reftable_stack_compact_all(struct reftable_stack *st,
struct reftable_log_expiry_config *config);
/*
* Check if compaction is required.
*
* When `use_heuristics` is false, check if all tables can be compacted to a
* single table. If true, use heuristics to determine if the tables need to be
* compacted to maintain geometric progression.
*/
int reftable_stack_compaction_required(struct reftable_stack *st,
bool use_heuristics,
bool *required);
/* heuristically compact unbalanced table stack. */
int reftable_stack_auto_compact(struct reftable_stack *st);
/* delete stale .ref tables. */
int reftable_stack_clean(struct reftable_stack *st);
/* convenience function to read a single ref. Returns < 0 for error, 0 for
* success, and 1 if ref not found. */
int reftable_stack_read_ref(struct reftable_stack *st, const char *refname,
struct reftable_ref_record *ref);
/* convenience function to read a single log. Returns < 0 for error, 0 for
* success, and 1 if ref not found. */
int reftable_stack_read_log(struct reftable_stack *st, const char *refname,
struct reftable_log_record *log);
/* statistics on past compactions. */
struct reftable_compaction_stats {
uint64_t bytes; /* total number of bytes written */
uint64_t entries_written; /* total number of entries written, including
failures. */
int attempts; /* how often we tried to compact */
int failures; /* failures happen on concurrent updates */
};
/* return statistics for compaction up till now. */
struct reftable_compaction_stats *
reftable_stack_compaction_stats(struct reftable_stack *st);
/* Return the hash of the stack. */
enum reftable_hash reftable_stack_hash_id(struct reftable_stack *st);
#endif