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Posted to github@beam.apache.org by GitBox <gi...@apache.org> on 2021/09/10 01:04:38 UTC
[GitHub] [beam] lostluck commented on a change in pull request #15483: [BEAM-11097] Add implementation of side input cache
lostluck commented on a change in pull request #15483:
URL: https://github.com/apache/beam/pull/15483#discussion_r705810136
##########
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()
Review comment:
Since the tokens are for Cross Bundle caching, wouldn't this prevent caching from happening across different bundles, if this is called for each ProcessBundleRequest?
##########
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
Review comment:
What' invalidates a side input token?
##########
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 {
Review comment:
Why not just have a valid token map, instead of iterating through a slice?
##########
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
Review comment:
Interfaces must never be refered to by pointer, as they're already reference types. In short, drop the *.
https://github.com/apache/beam/blob/410ad7699621e28433d81809f6b9c42fe7bd6a60/sdks/go/pkg/beam/core/runtime/exec/input.go#L36
Interfaces also are fine with being multiply duplicated, so if necessary we can define our own ReusableInput interface here that's identical to the exec.ReusableInput, and break that explicit dependency, which prevents the exec package from using this. (though not the harness package, which is certainly where it starts out. Hmmm More information required for a meaningful review).
##########
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.
Review comment:
Consider describing in prose how use of this maps to an SDK worker lifecyle. Not in great depth, but in particular:
initialization, a bundle request comes in, during bundle execution, bundle termination, if subsequent bundle requests come in, multiple happen simultaneously, sequentially, etc. If eviction needs to happen what's prioritized?
The goal is to allow someone to understand how it works, and possibly use it (maybe not in this case) without reading the raw code.
##########
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
Review comment:
If you have a link to a Doc, or even just an appropriate location of the proto on github, that might be useful to add here.
##########
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)
+ }
Review comment:
Style nit: idomatic go says to drop the "else" block wrapping if the if block is terminal. The rest of the loop is already getting skipped by the `continue` if the `if` clause is true, so there's no need for the else block and it's indentation.
##########
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:
While it's a good idea to try to avoid avoid evicting a small set of values from the cache, it would be incorrect to fail pipelines because the cache is too small. The cost of a too small a cache should be "more work" because of the additional read from the runner.
The Portable Beam model does allow for SDK side metrics that aren't attached to any bundle. SideInput cache hits, misses, and evictions, and "in use" evictions would be a great set of metrics to collect, and we can see how much this gets used for arbitrary pipelines. I recommend we collect those instead (int64s protected by the lock, possibly abstracted into an easy to copy/return by value struct for later access), and I'll work with you to get them into the monitoring responses in a later PR.
This also avoids returning errors around when things can't/shouldn't fail.
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