jrmccluskey commented on a change in pull request #15483: URL: https://github.com/apache/beam/pull/15483#discussion_r706301334
########## File path: sdks/go/pkg/beam/core/runtime/harness/statecache/statecache.go ########## @@ -0,0 +1,172 @@ +// 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. + +// Package statecache implements the state caching feature described by the +// Beam Fn API +package statecache + +import ( + "sync" + + "github.com/apache/beam/sdks/v2/go/pkg/beam/core/runtime/exec" + "github.com/apache/beam/sdks/v2/go/pkg/beam/internal/errors" + fnpb "github.com/apache/beam/sdks/v2/go/pkg/beam/model/fnexecution_v1" +) + +// SideInputCache stores a cache of reusable inputs for the purposes of +// eliminating redundant calls to the runner during execution of ParDos +// using side inputs. +type SideInputCache struct { + cache map[string]*exec.ReusableInput + idsToTokens map[string]string + validTokens []string + mu sync.Mutex + capacity int +} + +// Init makes the cache map and the map of IDs to cache tokens for the +// SideInputCache. Should only be called once. +func (c *SideInputCache) Init(cap int) error { + if cap <= 0 { + return errors.Errorf("capacity must be a positive integer, got %v", cap) + } + c.mu.Lock() + defer c.mu.Unlock() + c.cache = make(map[string]*exec.ReusableInput, cap) + c.idsToTokens = make(map[string]string) + return nil +} + +// Completely clears the list of valid tokens. Should be called when +// starting to handle a new request. +func (c *SideInputCache) clearValidTokens() { + c.validTokens = nil +} + +// SetValidTokens clears the list of valid tokens then sets new ones, also updating the mapping of +// transform and side input IDs to cache tokens in the process. Should be called at the start of every +// new ProcessBundleRequest. If the runner does not support caching, the passed cache token values +// should be empty and all get/set requests will silently be no-ops. +func (c *SideInputCache) SetValidTokens(cacheTokens ...fnpb.ProcessBundleRequest_CacheToken) { + c.mu.Lock() + defer c.mu.Unlock() + c.clearValidTokens() + for _, tok := range cacheTokens { + // User State caching is currently not supported, so these tokens are ignored + if tok.GetUserState() != nil { + continue + } else { + s := tok.GetSideInput() + transformID := s.GetTransformId() + sideInputID := s.GetSideInputId() + token := string(tok.GetToken()) + c.setValidToken(transformID, sideInputID, token) + } + } +} + +// setValidToken adds a new valid token for a request into the SideInputCache struct +// and maps the transform ID and side input ID pairing to the cache token. +func (c *SideInputCache) setValidToken(transformID, sideInputID, token string) { + idKey := transformID + sideInputID + c.idsToTokens[idKey] = token + c.validTokens = append(c.validTokens, token) +} + +func (c *SideInputCache) makeAndValidateToken(transformID, sideInputID string) (string, bool) { + idKey := transformID + sideInputID + // Check if it's a known token + tok, ok := c.idsToTokens[idKey] + if !ok { + return "", false + } + // Check if the known token is valid for this request + for _, t := range c.validTokens { + if t == tok { + return tok, true + } + } + return "", false +} + +// QueryCache takes a transform ID and side input ID and checking if a corresponding side +// input has been cached. A query having a bad token (e.g. one that doesn't make a known +// token or one that makes a known but currently invalid token) is treated the same as a +// cache miss. +func (c *SideInputCache) QueryCache(transformID, sideInputID string) *exec.ReusableInput { + c.mu.Lock() + defer c.mu.Unlock() + tok, ok := c.makeAndValidateToken(transformID, sideInputID) + if !ok { + return nil + } + // Check to see if cached + input, ok := c.cache[tok] + if !ok { + return nil + } + return input +} + +// SetCache allows a user to place a ReusableInput materialized from the reader into the SideInputCache +// with its corresponding transform ID and side input ID. If the IDs do not pair with a known, valid token +// then we silently do not cache the input, as this is an indication that the runner is treating that input +// as uncacheable. +func (c *SideInputCache) SetCache(transformID, sideInputID string, input *exec.ReusableInput) error { + c.mu.Lock() + defer c.mu.Unlock() + tok, ok := c.makeAndValidateToken(transformID, sideInputID) + if !ok { + return nil + } + if len(c.cache) > c.capacity { + err := c.evictElement() + if err != nil { + return errors.Errorf("Cache at or above capacity, got %v", err) + } + } + c.cache[tok] = input + return nil +} + +func (c *SideInputCache) isValid(token string) bool { + for _, t := range c.validTokens { + if t == token { + return true + } + } + return false +} + +// evictElement randomly evicts a ReusableInput that is not currently valid from the cache. +// It should only be called by a goroutine that obtained the lock in SetCache. +func (c *SideInputCache) evictElement() error { + deleted := false + // Select a key from the cache at random + for k := range c.cache { + // Do not evict an element if it's currently valid + if !c.isValid(k) { + delete(c.cache, k) + deleted = true + break + } + } + // Nothing is deleted if every side input is still valid, meaning that the cache size + // is likely too small. + if !deleted { Review comment: Made a first run at it, hopefully it's what you have in mind. All of the operations that would add metrics (hit, miss, evict, failed evict) are already behind having the lock so that was pretty straightforward. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
