[tor-commits] [tor/master] Add a 'consensus cache' type on top of storagedir.
nickm at torproject.org
nickm at torproject.org
Thu Apr 6 15:51:27 UTC 2017
commit 4404dc5756c929fccc5784a637014aee929bdfd1
Author: Nick Mathewson <nickm at torproject.org>
Date: Tue Apr 4 09:35:39 2017 -0400
Add a 'consensus cache' type on top of storagedir.
Every file in the cache is labeled. The labels are held in memory;
the bodies are mapped on demand.
---
src/or/conscache.c | 487 +++++++++++++++++++++++++++++++++++++++++++++++++++++
src/or/conscache.h | 48 ++++++
src/or/include.am | 2 +
3 files changed, 537 insertions(+)
diff --git a/src/or/conscache.c b/src/or/conscache.c
new file mode 100644
index 0000000..4bcf29c
--- /dev/null
+++ b/src/or/conscache.c
@@ -0,0 +1,487 @@
+/* Copyright (c) 2017, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#include "or.h"
+
+#include "config.h"
+#include "conscache.h"
+#include "storagedir.h"
+
+#define CCE_MAGIC 0x17162253
+
+/**
+ * A consensus_cache_entry_t is a reference-counted handle to an
+ * item in a consensus_cache_t. It can be mmapped into RAM, or not,
+ * depending whether it's currently in use.
+ */
+struct consensus_cache_entry_t {
+ uint32_t magic; /**< Must be set to CCE_MAGIC */
+ int32_t refcnt; /**< Reference count. */
+ unsigned can_remove : 1; /**< If true, we want to delete this file. */
+ /** If true, we intend to unmap this file as soon as we're done with it. */
+ unsigned release_aggressively : 1;
+
+ /** Filename for this object within the storage_dir_t */
+ char *fname;
+ /** Labels associated with this object. Immutable once the object
+ * is created. */
+ config_line_t *labels;
+ /** Pointer to the cache that includes this entry (if any). */
+ consensus_cache_t *in_cache;
+
+ /** Since what time has this object been mapped into RAM, but with the cache
+ * being the only having a reference to it? */
+ time_t unused_since;
+ /** mmaped contents of the underlying file. May be NULL */
+ tor_mmap_t *map;
+ /** Length of the body within <b>map</b>. */
+ size_t bodylen;
+ /** Pointer to the body within <b>map</b>. */
+ const uint8_t *body;
+};
+
+/**
+ * A consensus_cache_t holds a directory full of labeled items.
+ */
+struct consensus_cache_t {
+ /** Underling storage_dir_t to handle persistence */
+ storage_dir_t *dir;
+ /** List of all the entries in the directory. */
+ smartlist_t *entries;
+};
+
+static void consensus_cache_clear(consensus_cache_t *cache);
+static void consensus_cache_rescan(consensus_cache_t *);
+static void consensus_cache_entry_map(consensus_cache_t *,
+ consensus_cache_entry_t *);
+static void consensus_cache_entry_unmap(consensus_cache_entry_t *ent);
+
+/**
+ * Helper: Open a consensus cache in subdirectory <b>subdir</b> of the
+ * data directory, to hold up to <b>max_entries</b> of data.
+ */
+consensus_cache_t *
+consensus_cache_open(const char *subdir, int max_entries)
+{
+ consensus_cache_t *cache = tor_malloc_zero(sizeof(consensus_cache_t));
+ char *directory = get_datadir_fname(subdir);
+ cache->dir = storage_dir_new(directory, max_entries);
+ tor_free(directory);
+ if (!cache->dir) {
+ tor_free(cache);
+ return NULL;
+ }
+
+ consensus_cache_rescan(cache);
+ return cache;
+}
+
+/**
+ * Helper: clear all entries from <b>cache</b> (but do not delete
+ * any that aren't marked for removal
+ */
+static void
+consensus_cache_clear(consensus_cache_t *cache)
+{
+ consensus_cache_delete_pending(cache);
+
+ SMARTLIST_FOREACH_BEGIN(cache->entries, consensus_cache_entry_t *, ent) {
+ ent->in_cache = NULL;
+ consensus_cache_entry_decref(ent);
+ } SMARTLIST_FOREACH_END(ent);
+ smartlist_free(cache->entries);
+ cache->entries = NULL;
+}
+
+/**
+ * Drop all storage held by <b>cache</b>.
+ */
+void
+consensus_cache_free(consensus_cache_t *cache)
+{
+ if (! cache)
+ return;
+
+ if (cache->entries) {
+ consensus_cache_clear(cache);
+ }
+ storage_dir_free(cache->dir);
+ tor_free(cache);
+}
+
+/**
+ * Write <b>datalen</b> bytes of data at <b>data</b> into the <b>cache</b>,
+ * labeling that data with <b>labels</b>. On failure, return NULL. On
+ * success, return a newly created consensus_cache_entry_t.
+ *
+ * The returned value will be owned by the cache, and you will have a
+ * reference to it. Call consensus_cache_entry_decref() when you are
+ * done with it.
+ *
+ * The provided <b>labels</b> MUST have distinct keys: if they don't,
+ * this API does not specify which values (if any) for the duplicate keys
+ * will be considered.
+ */
+consensus_cache_entry_t *
+consensus_cache_add(consensus_cache_t *cache,
+ const config_line_t *labels,
+ const uint8_t *data,
+ size_t datalen)
+{
+ char *fname = NULL;
+ int r = storage_dir_save_labeled_to_file(cache->dir,
+ labels, data, datalen, &fname);
+ if (r < 0 || fname == NULL) {
+ return NULL;
+ }
+ consensus_cache_entry_t *ent =
+ tor_malloc_zero(sizeof(consensus_cache_entry_t));
+ ent->magic = CCE_MAGIC;
+ ent->fname = fname;
+ ent->labels = config_lines_dup(labels);
+ ent->in_cache = cache;
+ ent->unused_since = TIME_MAX;
+ smartlist_add(cache->entries, ent);
+ /* Start the reference count at 2: the caller owns one copy, and the
+ * cache owns another.
+ */
+ ent->refcnt = 2;
+
+ return ent;
+}
+
+/**
+ * Given a <b>cache</b>, return some entry for which <b>key</b>=<b>value</b>.
+ * Return NULL if no such entry exists.
+ *
+ * Does not adjust reference counts.
+ */
+consensus_cache_entry_t *
+consensus_cache_find_first(consensus_cache_t *cache,
+ const char *key,
+ const char *value)
+{
+ smartlist_t *tmp = smartlist_new();
+ consensus_cache_find_all(tmp, cache, key, value);
+ consensus_cache_entry_t *ent = NULL;
+ if (smartlist_len(tmp))
+ ent = smartlist_get(tmp, 0);
+ smartlist_free(tmp);
+ return ent;
+}
+
+/**
+ * Given a <b>cache</b>, add every entry to <b>out<b> for which
+ * <b>key</b>=<b>value</b>. If <b>key</b> is NULL, add every entry.
+ *
+ * Does not adjust reference counts.
+ */
+void
+consensus_cache_find_all(smartlist_t *out,
+ consensus_cache_t *cache,
+ const char *key,
+ const char *value)
+{
+ if (! key) {
+ smartlist_add_all(out, cache->entries);
+ return;
+ }
+
+ SMARTLIST_FOREACH_BEGIN(cache->entries, consensus_cache_entry_t *, ent) {
+ const char *found_val = consensus_cache_entry_get_value(ent, key);
+ if (found_val && !strcmp(value, found_val)) {
+ smartlist_add(out, ent);
+ }
+ } SMARTLIST_FOREACH_END(ent);
+}
+
+/**
+ * Given a list of consensus_cache_entry_t, remove all those entries
+ * that do not have <b>key</b>=<b>value</b> in their labels.
+ *
+ * Does not adjust reference counts.
+ */
+void
+consensus_cache_filter_list(smartlist_t *lst,
+ const char *key,
+ const char *value)
+{
+ if (BUG(lst == NULL))
+ return; // LCOV_EXCL_LINE
+ if (key == NULL)
+ return;
+ SMARTLIST_FOREACH_BEGIN(lst, consensus_cache_entry_t *, ent) {
+ const char *found_val = consensus_cache_entry_get_value(ent, key);
+ if (! found_val || strcmp(value, found_val)) {
+ SMARTLIST_DEL_CURRENT(lst, ent);
+ }
+ } SMARTLIST_FOREACH_END(ent);
+}
+
+/**
+ * If <b>ent</b> has a label with the given <b>key</b>, return its
+ * value. Otherwise return NULL.
+ *
+ * The return value is only guaranteed to be valid for as long as you
+ * hold a reference to <b>ent</b>.
+ */
+const char *
+consensus_cache_entry_get_value(const consensus_cache_entry_t *ent,
+ const char *key)
+{
+ const config_line_t *match = config_line_find(ent->labels, key);
+ if (match)
+ return match->value;
+ else
+ return NULL;
+}
+
+/**
+ * Return a pointer to the labels in <b>ent</b>.
+ *
+ * This pointer is only guaranteed to be valid for as long as you
+ * hold a reference to <b>ent</b>.
+ */
+const config_line_t *
+consensus_cache_entry_get_labels(const consensus_cache_entry_t *ent)
+{
+ return ent->labels;
+}
+
+/**
+ * Increase the reference count of <b>ent</b>.
+ */
+void
+consensus_cache_entry_incref(consensus_cache_entry_t *ent)
+{
+ if (BUG(ent->magic != CCE_MAGIC))
+ return; // LCOV_EXCL_LINE
+ ++ent->refcnt;
+ ent->unused_since = TIME_MAX;
+}
+
+/**
+ * Release a reference held to <b>ent</b>.
+ *
+ * If it was the last reference, ent will be freed. Therefore, you must not
+ * use <b>ent</b> after calling this function.
+ */
+void
+consensus_cache_entry_decref(consensus_cache_entry_t *ent)
+{
+ if (! ent)
+ return;
+ if (BUG(ent->refcnt <= 0))
+ return; // LCOV_EXCL_LINE
+ if (BUG(ent->magic != CCE_MAGIC))
+ return; // LCOV_EXCL_LINE
+
+ --ent->refcnt;
+
+ if (ent->refcnt == 1 && ent->in_cache) {
+ /* Only the cache has a reference: we don't need to keep the file
+ * mapped */
+ if (ent->map) {
+ if (ent->release_aggressively) {
+ consensus_cache_entry_unmap(ent);
+ } else {
+ ent->unused_since = approx_time();
+ }
+ }
+ return;
+ }
+
+ if (ent->refcnt > 0)
+ return;
+
+ /* Refcount is zero; we can free it. */
+ if (ent->map) {
+ consensus_cache_entry_unmap(ent);
+ }
+ tor_free(ent->fname);
+ config_free_lines(ent->labels);
+ memwipe(ent, 0, sizeof(consensus_cache_entry_t));
+ tor_free(ent);
+}
+
+/**
+ * Mark <b>ent</b> for deletion from the cache. Deletion will not occur
+ * until the cache is the only place that holds a reference to <b>ent</b>.
+ */
+void
+consensus_cache_entry_mark_for_removal(consensus_cache_entry_t *ent)
+{
+ ent->can_remove = 1;
+}
+
+/**
+ * Mark <b>ent</b> as the kind of entry that we don't need to keep mmap'd for
+ * any longer than we're actually using it.
+ */
+void
+consensus_cache_entry_mark_for_aggressive_release(consensus_cache_entry_t *ent)
+{
+ ent->release_aggressively = 1;
+}
+
+/**
+ * Try to read the body of <b>ent</b> into memory if it isn't already
+ * loaded. On success, set *<b>body_out</b> to the body, *<b>sz_out</b>
+ * to its size, and return 0. On failure return -1.
+ *
+ * The resulting body pointer will only be valid for as long as you
+ * hold a reference to <b>ent</b>.
+ */
+int
+consensus_cache_entry_get_body(const consensus_cache_entry_t *ent,
+ const uint8_t **body_out,
+ size_t *sz_out)
+{
+ if (BUG(ent->magic != CCE_MAGIC))
+ return -1; // LCOV_EXCL_LINE
+
+ if (! ent->map) {
+ if (! ent->in_cache)
+ return -1;
+
+ consensus_cache_entry_map((consensus_cache_t *)ent->in_cache,
+ (consensus_cache_entry_t *)ent);
+ if (! ent->map) {
+ return -1;
+ }
+ }
+
+ *body_out = ent->body;
+ *sz_out = ent->bodylen;
+ return 0;
+}
+
+/**
+ * Unmap every mmap'd element of <b>cache</b> that has been unused
+ * since <b>cutoff</b>.
+ */
+void
+consensus_cache_unmap_lazy(consensus_cache_t *cache, time_t cutoff)
+{
+ SMARTLIST_FOREACH_BEGIN(cache->entries, consensus_cache_entry_t *, ent) {
+ tor_assert_nonfatal(ent->in_cache == cache);
+ if (ent->refcnt > 1 || BUG(ent->in_cache == NULL)) {
+ /* Somebody is using this entry right now */
+ continue;
+ }
+ if (ent->unused_since > cutoff) {
+ /* Has been unused only for a little while */
+ continue;
+ }
+ if (ent->map == NULL) {
+ /* Not actually mapped. */
+ continue;
+ }
+ consensus_cache_entry_unmap(ent);
+ } SMARTLIST_FOREACH_END(ent);
+}
+
+/**
+ * Delete every element of <b>cache</b> has been marked with
+ * consensus_cache_entry_mark_for_removal, and which is not in use except by
+ * the cache.
+ */
+void
+consensus_cache_delete_pending(consensus_cache_t *cache)
+{
+ SMARTLIST_FOREACH_BEGIN(cache->entries, consensus_cache_entry_t *, ent) {
+ tor_assert_nonfatal(ent->in_cache == cache);
+ if (ent->refcnt > 1 || BUG(ent->in_cache == NULL)) {
+ /* Somebody is using this entry right now */
+ continue;
+ }
+ if (ent->can_remove == 0) {
+ /* Don't want to delete this. */
+ continue;
+ }
+ if (BUG(ent->refcnt <= 0)) {
+ continue; // LCOV_EXCL_LINE
+ }
+
+ SMARTLIST_DEL_CURRENT(cache->entries, ent);
+ ent->in_cache = NULL;
+ char *fname = tor_strdup(ent->fname); /* save a copy */
+ consensus_cache_entry_decref(ent);
+ storage_dir_remove_file(cache->dir, fname);
+ tor_free(fname);
+ } SMARTLIST_FOREACH_END(ent);
+}
+
+/**
+ * Internal helper: rescan <b>cache</b> and rebuild its list of entries.
+ */
+static void
+consensus_cache_rescan(consensus_cache_t *cache)
+{
+ if (cache->entries) {
+ consensus_cache_clear(cache);
+ }
+
+ cache->entries = smartlist_new();
+ const smartlist_t *fnames = storage_dir_list(cache->dir);
+ SMARTLIST_FOREACH_BEGIN(fnames, const char *, fname) {
+ tor_mmap_t *map = NULL;
+ config_line_t *labels = NULL;
+ const uint8_t *body;
+ size_t bodylen;
+ map = storage_dir_map_labeled(cache->dir, fname,
+ &labels, &body, &bodylen);
+ if (! map) {
+ /* Can't load this; continue */
+ log_warn(LD_FS, "Unable to map file %s from consensus cache: %s",
+ escaped(fname), strerror(errno));
+ continue;
+ }
+ consensus_cache_entry_t *ent =
+ tor_malloc_zero(sizeof(consensus_cache_entry_t));
+ ent->magic = CCE_MAGIC;
+ ent->fname = tor_strdup(fname);
+ ent->labels = labels;
+ ent->refcnt = 1;
+ ent->in_cache = cache;
+ ent->unused_since = TIME_MAX;
+ smartlist_add(cache->entries, ent);
+ tor_munmap_file(map); /* don't actually need to keep this around */
+ } SMARTLIST_FOREACH_END(fname);
+}
+
+/**
+ * Make sure that <b>ent</b> is mapped into RAM.
+ */
+static void
+consensus_cache_entry_map(consensus_cache_t *cache,
+ consensus_cache_entry_t *ent)
+{
+ if (ent->map)
+ return;
+
+ ent->map = storage_dir_map_labeled(cache->dir, ent->fname,
+ NULL, &ent->body, &ent->bodylen);
+ ent->unused_since = TIME_MAX;
+}
+
+/**
+ * Unmap <b>ent</b> from RAM.
+ *
+ * Do not call this if something other than the cache is holding a reference
+ * to <b>ent</b>
+ */
+static void
+consensus_cache_entry_unmap(consensus_cache_entry_t *ent)
+{
+ ent->unused_since = TIME_MAX;
+ if (!ent->map)
+ return;
+
+ tor_munmap_file(ent->map);
+ ent->map = NULL;
+ ent->body = NULL;
+ ent->bodylen = 0;
+ ent->unused_since = TIME_MAX;
+}
+
diff --git a/src/or/conscache.h b/src/or/conscache.h
new file mode 100644
index 0000000..0a0fc61
--- /dev/null
+++ b/src/or/conscache.h
@@ -0,0 +1,48 @@
+/* Copyright (c) 2017, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_CONSCACHE_H
+#define TOR_CONSCACHE_H
+
+typedef struct consensus_cache_entry_t consensus_cache_entry_t;
+typedef struct consensus_cache_t consensus_cache_t;
+
+consensus_cache_t *consensus_cache_open(const char *subdir, int max_entries);
+void consensus_cache_free(consensus_cache_t *cache);
+void consensus_cache_unmap_lazy(consensus_cache_t *cache, time_t cutoff);
+void consensus_cache_delete_pending(consensus_cache_t *cache);
+consensus_cache_entry_t *consensus_cache_add(consensus_cache_t *cache,
+ const config_line_t *labels,
+ const uint8_t *data,
+ size_t datalen);
+
+consensus_cache_entry_t *consensus_cache_find_first(
+ consensus_cache_t *cache,
+ const char *key,
+ const char *value);
+
+void consensus_cache_find_all(smartlist_t *out,
+ consensus_cache_t *cache,
+ const char *key,
+ const char *value);
+void consensus_cache_filter_list(smartlist_t *lst,
+ const char *key,
+ const char *value);
+
+const char *consensus_cache_entry_get_value(const consensus_cache_entry_t *ent,
+ const char *key);
+const config_line_t *consensus_cache_entry_get_labels(
+ const consensus_cache_entry_t *ent);
+
+void consensus_cache_entry_incref(consensus_cache_entry_t *ent);
+void consensus_cache_entry_decref(consensus_cache_entry_t *ent);
+
+void consensus_cache_entry_mark_for_removal(consensus_cache_entry_t *ent);
+void consensus_cache_entry_mark_for_aggressive_release(
+ consensus_cache_entry_t *ent);
+int consensus_cache_entry_get_body(const consensus_cache_entry_t *ent,
+ const uint8_t **body_out,
+ size_t *sz_out);
+
+#endif
+
diff --git a/src/or/include.am b/src/or/include.am
index d65d0d3..688ac62 100644
--- a/src/or/include.am
+++ b/src/or/include.am
@@ -36,6 +36,7 @@ LIBTOR_A_SOURCES = \
src/or/connection.c \
src/or/connection_edge.c \
src/or/connection_or.c \
+ src/or/conscache.c \
src/or/consdiff.c \
src/or/control.c \
src/or/cpuworker.c \
@@ -152,6 +153,7 @@ ORHEADERS = \
src/or/connection.h \
src/or/connection_edge.h \
src/or/connection_or.h \
+ src/or/conscache.h \
src/or/consdiff.h \
src/or/control.h \
src/or/cpuworker.h \
More information about the tor-commits
mailing list