96 lines
2.3 KiB
Lua
96 lines
2.3 KiB
Lua
--[[
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Implements a simple in-memory cache. The cache has no upper size limit, and
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may cause out-of-memory errors. When this happens, the OS will kill the kore
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worker process, and the kore parent process will restart with a fresh, empty
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cache
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]]
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local sql = require("lsqlite3")
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local queries = require("queries")
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local util = require("util")
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local ret = {}
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local stmnt_cache, stmnt_insert_cache, stmnt_dirty_cache
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local oldconfigure = configure
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function configure(...)
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local cache = util.sqlassert(sql.open_memory())
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--A cache table to store rendered pages that do not need to be
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--rerendered. In theory this could OOM the program eventually and start
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--swapping to disk. TODO: fixme
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assert(cache:exec([[
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CREATE TABLE IF NOT EXISTS cache (
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path TEXT PRIMARY KEY,
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data BLOB,
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updated INTEGER,
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dirty INTEGER
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);
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]]))
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stmnt_cache = assert(cache:prepare([[
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SELECT data
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FROM cache
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WHERE
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path = :path AND
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((dirty = 0) OR (strftime('%s','now') - updated) < 20)
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;
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]]))
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stmnt_insert_cache = assert(cache:prepare([[
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INSERT OR REPLACE INTO cache (
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path, data, updated, dirty
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) VALUES (
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:path, :data, strftime('%s','now'), 0
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);
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]]))
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stmnt_dirty_cache = assert(cache:prepare([[
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UPDATE OR IGNORE cache
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SET dirty = 1
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WHERE path = :path;
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]]))
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return oldconfigure(...)
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end
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--Render a page, with cacheing. If you need to dirty a cache, call dirty_cache()
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function ret.render(pagename,callback)
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stmnt_cache:bind_names{path=pagename}
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local err = util.do_sql(stmnt_cache)
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if err == sql.DONE then
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stmnt_cache:reset()
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--page is not cached
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elseif err == sql.ROW then
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local data = stmnt_cache:get_values()
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stmnt_cache:reset()
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return data[1]
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else --sql.ERROR or sql.MISUSE
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error("Failed to check cache for page " .. pagename)
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end
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--We didn't have the paged cached, render it
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local text = callback()
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--And save the data back into the cache
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stmnt_insert_cache:bind_names{
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path=pagename,
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data=text,
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}
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err = util.do_sql(stmnt_insert_cache)
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if err == sql.ERROR or err == sql.MISUSE then
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error("Failed to update cache for page " .. pagename)
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end
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stmnt_insert_cache:reset()
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return text
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end
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function ret.dirty(url)
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stmnt_dirty_cache:bind_names{
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path = url
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}
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util.do_sql(stmnt_dirty_cache)
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stmnt_dirty_cache:reset()
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end
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function ret.close()
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end
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return ret
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