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|
# frozen_string_literal: true
#
module Gitlab
module Diff
class HighlightCache
include Gitlab::Metrics::Methods
include Gitlab::Utils::StrongMemoize
EXPIRATION = 1.week
VERSION = 1
delegate :diffable, to: :@diff_collection
delegate :diff_options, to: :@diff_collection
define_histogram :gitlab_redis_diff_caching_memory_usage_bytes do
docstring 'Redis diff caching memory usage by key'
buckets [100, 1_000, 10_000, 100_000, 1_000_000, 10_000_000]
end
define_counter :gitlab_redis_diff_caching_hit do
docstring 'Redis diff caching hits'
end
define_counter :gitlab_redis_diff_caching_miss do
docstring 'Redis diff caching misses'
end
def initialize(diff_collection)
@diff_collection = diff_collection
end
# - Reads from cache
# - Assigns DiffFile#highlighted_diff_lines for cached files
#
def decorate(diff_file)
if content = read_file(diff_file)
diff_file.highlighted_diff_lines = content.map do |line|
Gitlab::Diff::Line.safe_init_from_hash(line)
end
end
end
# For every file that isn't already contained in the redis hash, store the
# result of #highlighted_diff_lines, then submit the uncached content
# to #write_to_redis_hash to submit a single write. This avoids excessive
# IO generated by N+1's (1 writing for each highlighted line or file).
#
def write_if_empty
return if cacheable_files.empty?
new_cache_content = {}
cacheable_files.each do |diff_file|
new_cache_content[diff_file.file_path] = diff_file.highlighted_diff_lines.map(&:to_hash)
end
write_to_redis_hash(new_cache_content)
end
def clear
Gitlab::Redis::Cache.with do |redis|
redis.del(key)
end
end
def key
strong_memoize(:redis_key) do
['highlighted-diff-files', diffable.cache_key, VERSION, diff_options].join(":")
end
end
private
def cacheable_files
strong_memoize(:cacheable_files) do
diff_files.select { |file| cacheable?(file) && read_file(file).nil? }
end
end
# Given a hash of:
# { "file/to/cache" =>
# [ { line_code: "a5cc2925ca8258af241be7e5b0381edf30266302_19_19",
# rich_text: " <span id=\"LC19\" class=\"line\" lang=\"plaintext\">config/initializers/secret_token.rb</span>\n",
# text: " config/initializers/secret_token.rb",
# type: nil,
# index: 3,
# old_pos: 19,
# new_pos: 19 }
# ] }
#
# ...it will write/update a Gitlab::Redis hash (HSET)
#
def write_to_redis_hash(hash)
Gitlab::Redis::Cache.with do |redis|
redis.pipelined do
hash.each do |diff_file_id, highlighted_diff_lines_hash|
redis.hset(
key,
diff_file_id,
compose_data(highlighted_diff_lines_hash.to_json)
)
end
# HSETs have to have their expiration date manually updated
#
redis.expire(key, EXPIRATION)
end
record_memory_usage(fetch_memory_usage(redis, key))
end
# Subsequent read_file calls would need the latest cache.
#
clear_memoization(:cached_content)
clear_memoization(:cacheable_files)
end
def record_memory_usage(memory_usage)
if memory_usage
self.class.gitlab_redis_diff_caching_memory_usage_bytes.observe({}, memory_usage)
end
end
def fetch_memory_usage(redis, key)
# Redis versions prior to 4.0.0 do not support memory usage reporting
# for a specific key. As of 11-March-2020 we support Redis 3.x, so
# need to account for this. We can remove this check once we
# officially cease supporting versions <4.0.0.
#
return if Gem::Version.new(redis.info["redis_version"]) < Gem::Version.new("4")
redis.memory("USAGE", key)
end
def file_paths
strong_memoize(:file_paths) do
diff_files.collect(&:file_path)
end
end
def read_file(diff_file)
cached_content[diff_file.file_path]
end
def cached_content
strong_memoize(:cached_content) { read_cache }
end
def read_cache
return {} unless file_paths.any?
results = []
Gitlab::Redis::Cache.with do |redis|
results = redis.hmget(key, file_paths)
end
results.map! do |result|
JSON.parse(extract_data(result), symbolize_names: true) unless result.nil?
end
file_paths.zip(results).to_h
end
def compose_data(json_data)
if ::Feature.enabled?(:gzip_diff_cache, default_enabled: true)
# #compress returns ASCII-8BIT, so we need to force the encoding to
# UTF-8 before caching it in redis, else we risk encoding mismatch
# errors.
#
ActiveSupport::Gzip.compress(json_data).force_encoding("UTF-8")
else
json_data
end
rescue Zlib::GzipFile::Error
json_data
end
def extract_data(data)
# Since when we deploy this code, we'll be dealing with an already
# populated cache full of data that isn't gzipped, we want to also
# check to see if the data is gzipped before we attempt to #decompress
# it, thus we check the first 2 bytes for "\x1F\x8B" to confirm it is
# a gzipped string. While a non-gzipped string will raise a
# Zlib::GzipFile::Error, which we're rescuing, we don't want to count
# on rescue for control flow. This check can be removed in the release
# after this change is released.
#
if ::Feature.enabled?(:gzip_diff_cache, default_enabled: true) && data[0..1] == "\x1F\x8B"
ActiveSupport::Gzip.decompress(data)
else
data
end
rescue Zlib::GzipFile::Error
data
end
def cacheable?(diff_file)
diffable.present? && diff_file.text? && diff_file.diffable?
end
def diff_files
# We access raw_diff_files here, as diff_files will attempt to apply the
# highlighting code found in this class, leading to a circular
# reference.
#
@diff_collection.raw_diff_files
end
end
end
end
|
