// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root. package com.yahoo.vespa.flags; import com.yahoo.component.Vtag; import com.yahoo.vespa.defaults.Defaults; import java.time.Instant; import java.time.LocalDate; import java.time.ZoneOffset; import java.time.format.DateTimeFormatter; import java.util.List; import java.util.Optional; import java.util.TreeMap; import static com.yahoo.vespa.flags.FetchVector.Dimension.APPLICATION_ID; import static com.yahoo.vespa.flags.FetchVector.Dimension.CONSOLE_USER_EMAIL; import static com.yahoo.vespa.flags.FetchVector.Dimension.HOSTNAME; import static com.yahoo.vespa.flags.FetchVector.Dimension.NODE_TYPE; import static com.yahoo.vespa.flags.FetchVector.Dimension.TENANT_ID; import static com.yahoo.vespa.flags.FetchVector.Dimension.VESPA_VERSION; import static com.yahoo.vespa.flags.FetchVector.Dimension.ZONE_ID; /** * Definitions of feature flags. * *

To use feature flags, define the flag in this class as an "unbound" flag, e.g. {@link UnboundBooleanFlag} * or {@link UnboundStringFlag}. At the location you want to get the value of the flag, you need the following:

* *
    *
  1. The unbound flag
    2. *
  2. A {@link FlagSource}. The flag source is typically available as an injectable component. Binding * an unbound flag to a flag source produces a (bound) flag, e.g. {@link BooleanFlag} and {@link StringFlag}.
    3. *
  3. If you would like your flag value to be dependent on e.g. the application ID, then 1. you should * declare this in the unbound flag definition in this file (referring to * {@link FetchVector.Dimension#APPLICATION_ID}), and 2. specify the application ID when retrieving the value, e.g. * {@link BooleanFlag#with(FetchVector.Dimension, String)}. See {@link FetchVector} for more info.
    4. *
* *

Once the code is in place, you can override the flag value. This depends on the flag source, but typically * there is a REST API for updating the flags in the config server, which is the root of all flag sources in the zone.

* * @author hakonhall */ public class Flags { private static volatile TreeMap flags = new TreeMap<>(); public static final UnboundDoubleFlag DEFAULT_TERM_WISE_LIMIT = defineDoubleFlag( "default-term-wise-limit", 1.0, List.of("baldersheim"), "2020-12-02", "2022-06-01", "Default limit for when to apply termwise query evaluation", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundStringFlag FEED_SEQUENCER_TYPE = defineStringFlag( "feed-sequencer-type", "THROUGHPUT", List.of("baldersheim"), "2020-12-02", "2022-06-01", "Selects type of sequenced executor used for feeding in proton, valid values are LATENCY, ADAPTIVE, THROUGHPUT", "Takes effect at redeployment (requires restart)", ZONE_ID, APPLICATION_ID); public static final UnboundIntFlag FEED_TASK_LIMIT = defineIntFlag( "feed-task-limit", 1000, List.of("geirst, baldersheim"), "2021-10-14", "2022-06-01", "The task limit used by the executors handling feed in proton", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundIntFlag FEED_MASTER_TASK_LIMIT = defineIntFlag( "feed-master-task-limit", 1000, List.of("geirst, baldersheim"), "2021-11-18", "2022-06-01", "The task limit used by the master thread in each document db in proton. Ignored when set to 0.", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundStringFlag SHARED_FIELD_WRITER_EXECUTOR = defineStringFlag( "shared-field-writer-executor", "NONE", List.of("geirst, baldersheim"), "2021-11-05", "2022-06-01", "Whether to use a shared field writer executor for the document database(s) in proton. " + "Valid values: NONE, INDEX, INDEX_AND_ATTRIBUTE, DOCUMENT_DB", "Takes effect at redeployment (requires restart)", ZONE_ID, APPLICATION_ID); public static final UnboundIntFlag MAX_UNCOMMITTED_MEMORY = defineIntFlag( "max-uncommitted-memory", 130000, List.of("geirst, baldersheim"), "2021-10-21", "2022-06-01", "Max amount of memory holding updates to an attribute before we do a commit.", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundStringFlag RESPONSE_SEQUENCER_TYPE = defineStringFlag( "response-sequencer-type", "ADAPTIVE", List.of("baldersheim"), "2020-12-02", "2022-06-01", "Selects type of sequenced executor used for mbus responses, valid values are LATENCY, ADAPTIVE, THROUGHPUT", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundIntFlag RESPONSE_NUM_THREADS = defineIntFlag( "response-num-threads", 2, List.of("baldersheim"), "2020-12-02", "2022-06-01", "Number of threads used for mbus responses, default is 2, negative number = numcores/4", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag SKIP_COMMUNICATIONMANAGER_THREAD = defineFeatureFlag( "skip-communicationmanager-thread", false, List.of("baldersheim"), "2020-12-02", "2022-06-01", "Should we skip the communicationmanager thread", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag SKIP_MBUS_REQUEST_THREAD = defineFeatureFlag( "skip-mbus-request-thread", false, List.of("baldersheim"), "2020-12-02", "2022-06-01", "Should we skip the mbus request thread", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag SKIP_MBUS_REPLY_THREAD = defineFeatureFlag( "skip-mbus-reply-thread", false, List.of("baldersheim"), "2020-12-02", "2022-06-01", "Should we skip the mbus reply thread", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag USE_THREE_PHASE_UPDATES = defineFeatureFlag( "use-three-phase-updates", false, List.of("vekterli"), "2020-12-02", "2022-05-01", "Whether to enable the use of three-phase updates when bucket replicas are out of sync.", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag USE_ASYNC_MESSAGE_HANDLING_ON_SCHEDULE = defineFeatureFlag( "async-message-handling-on-schedule", false, List.of("baldersheim"), "2020-12-02", "2022-06-01", "Optionally deliver async messages in own thread", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundDoubleFlag FEED_CONCURRENCY = defineDoubleFlag( "feed-concurrency", 0.5, List.of("baldersheim"), "2020-12-02", "2022-06-01", "How much concurrency should be allowed for feed", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag CONTAINER_DUMP_HEAP_ON_SHUTDOWN_TIMEOUT = defineFeatureFlag( "container-dump-heap-on-shutdown-timeout", false, List.of("baldersheim"), "2021-09-25", "2022-06-01", "Will trigger a heap dump during if container shutdown times out", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundDoubleFlag CONTAINER_SHUTDOWN_TIMEOUT = defineDoubleFlag( "container-shutdown-timeout", 50.0, List.of("baldersheim"), "2021-09-25", "2022-06-01", "Timeout for shutdown of a jdisc container", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundListFlag ALLOWED_ATHENZ_PROXY_IDENTITIES = defineListFlag( "allowed-athenz-proxy-identities", List.of(), String.class, List.of("bjorncs", "tokle"), "2021-02-10", "2022-06-01", "Allowed Athenz proxy identities", "takes effect at redeployment"); public static final UnboundIntFlag MAX_ACTIVATION_INHIBITED_OUT_OF_SYNC_GROUPS = defineIntFlag( "max-activation-inhibited-out-of-sync-groups", 0, List.of("vekterli"), "2021-02-19", "2022-05-01", "Allows replicas in up to N content groups to not be activated " + "for query visibility if they are out of sync with a majority of other replicas", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundIntFlag MAX_CONCURRENT_MERGES_PER_NODE = defineIntFlag( "max-concurrent-merges-per-node", 16, List.of("balder", "vekterli"), "2021-06-06", "2022-05-01", "Specifies max concurrent merges per content node.", "Takes effect at redeploy", ZONE_ID, APPLICATION_ID); public static final UnboundIntFlag MAX_MERGE_QUEUE_SIZE = defineIntFlag( "max-merge-queue-size", 100, List.of("balder", "vekterli"), "2021-06-06", "2022-05-01", "Specifies max size of merge queue.", "Takes effect at redeploy", ZONE_ID, APPLICATION_ID); public static final UnboundDoubleFlag MIN_NODE_RATIO_PER_GROUP = defineDoubleFlag( "min-node-ratio-per-group", 0.0, List.of("geirst", "vekterli"), "2021-07-16", "2022-05-01", "Minimum ratio of nodes that have to be available (i.e. not Down) in any hierarchic content cluster group for the group to be Up", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundIntFlag METRICSPROXY_NUM_THREADS = defineIntFlag( "metricsproxy-num-threads", 2, List.of("balder"), "2021-09-01", "2022-06-01", "Number of threads for metrics proxy", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundIntFlag AVAILABLE_PROCESSORS = defineIntFlag( "available-processors", 2, List.of("balder"), "2022-01-18", "2022-04-01", "Number of processors the jvm sees in non-application clusters", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag ENABLED_HORIZON_DASHBOARD = defineFeatureFlag( "enabled-horizon-dashboard", false, List.of("olaa"), "2021-09-13", "2022-04-01", "Enable Horizon dashboard", "Takes effect immediately", TENANT_ID, CONSOLE_USER_EMAIL ); public static final UnboundBooleanFlag DELETE_UNMAINTAINED_CERTIFICATES = defineFeatureFlag( "delete-unmaintained-certificates", false, List.of("andreer"), "2021-09-23", "2022-03-14", "Whether to delete certificates that are known by provider but not by controller", "Takes effect on next run of EndpointCertificateMaintainer" ); public static final UnboundBooleanFlag UNORDERED_MERGE_CHAINING = defineFeatureFlag( "unordered-merge-chaining", true, List.of("vekterli", "geirst"), "2021-11-15", "2022-03-01", "Enables the use of unordered merge chains for data merge operations", "Takes effect at redeploy", ZONE_ID, APPLICATION_ID); public static final UnboundStringFlag JDK_VERSION = defineStringFlag( "jdk-version", "11", List.of("hmusum"), "2021-10-25", "2022-03-15", "JDK version to use on host and inside containers. Note application-id dimension only applies for container, " + "while hostname and node type applies for host.", "Takes effect on restart for Docker container and on next host-admin tick for host", APPLICATION_ID, TENANT_ID, HOSTNAME, NODE_TYPE); public static final UnboundBooleanFlag IGNORE_THREAD_STACK_SIZES = defineFeatureFlag( "ignore-thread-stack-sizes", false, List.of("arnej"), "2021-11-12", "2022-06-01", "Whether C++ thread creation should ignore any requested stack size", "Triggers restart, takes effect immediately", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag USE_V8_GEO_POSITIONS = defineFeatureFlag( "use-v8-geo-positions", false, List.of("arnej"), "2021-11-15", "2022-12-31", "Use Vespa 8 types and formats for geographical positions", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag USE_V8_DOC_MANAGER_CFG = defineFeatureFlag( "use-v8-doc-manager-cfg", false, List.of("arnej", "baldersheim"), "2021-12-09", "2022-12-31", "Use new (preparing for Vespa 8) section in documentmanager.def", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundIntFlag MAX_COMPACT_BUFFERS = defineIntFlag( "max-compact-buffers", 1, List.of("baldersheim", "geirst", "toregge"), "2021-12-15", "2022-03-31", "Upper limit of buffers to compact in a data store at the same time for each reason (memory usage, address space usage)", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag FAIL_DEPLOYMENT_WITH_INVALID_JVM_OPTIONS = defineFeatureFlag( "fail-deployment-with-invalid-jvm-options", false, List.of("hmusum"), "2021-12-20", "2022-03-01", "Whether to fail deployments with invalid JVM options in services.xml", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag ENABLE_SERVER_OCSP_STAPLING = defineFeatureFlag( "enable-server-ocsp-stapling", false, List.of("bjorncs"), "2021-12-17", "2022-06-01", "Enable server OCSP stapling for jdisc containers", "Takes effect on redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag ENABLE_DATA_HIGHWAY_IN_AWS = defineFeatureFlag( "enable-data-highway-in-aws", false, List.of("hmusum"), "2022-01-06", "2022-04-06", "Enable Data Highway in AWS", "Takes effect on restart of Docker container", ZONE_ID, APPLICATION_ID); public static final UnboundStringFlag ZOOKEEPER_SNAPSHOT_METHOD = defineStringFlag( "zookeeper-snapshot-method", "gz", List.of("hmusum"), "2022-01-11", "2022-03-01", "ZooKeeper snapshot method. Valid values are '', 'gz' and 'snappy'", "Takes effect on Docker container restart", ZONE_ID, APPLICATION_ID, NODE_TYPE); public static final UnboundStringFlag PERSISTENCE_ASYNC_THROTTLING = defineStringFlag( "persistence-async-throttling", "UNLIMITED", List.of("vekterli"), "2022-01-12", "2022-05-01", "Sets the throttling policy used for async persistence operations on the content nodes. " + "Valid values: UNLIMITED, DYNAMIC", "Triggers restart, takes effect immediately", ZONE_ID, APPLICATION_ID); public static final UnboundStringFlag MERGE_THROTTLING_POLICY = defineStringFlag( "merge-throttling-policy", "STATIC", List.of("vekterli"), "2022-01-25", "2022-05-01", "Sets the policy used for merge throttling on the content nodes. " + "Valid values: STATIC, DYNAMIC", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundDoubleFlag PERSISTENCE_THROTTLING_WS_DECREMENT_FACTOR = defineDoubleFlag( "persistence-throttling-ws-decrement-factor", 1.2, List.of("vekterli"), "2022-01-27", "2022-05-01", "Sets the dynamic throttle policy window size decrement factor for persistence " + "async throttling. Only applies if DYNAMIC policy is used.", "Takes effect on redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundDoubleFlag PERSISTENCE_THROTTLING_WS_BACKOFF = defineDoubleFlag( "persistence-throttling-ws-backoff", 0.95, List.of("vekterli"), "2022-01-27", "2022-05-01", "Sets the dynamic throttle policy window size backoff for persistence " + "async throttling. Only applies if DYNAMIC policy is used. Valid range [0, 1]", "Takes effect on redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundIntFlag PERSISTENCE_THROTTLING_WINDOW_SIZE = defineIntFlag( "persistence-throttling-window-size", -1, List.of("vekterli"), "2022-02-23", "2022-06-01", "If greater than zero, sets both min and max window size to the given number, effectively " + "turning dynamic throttling into a static throttling policy. " + "Only applies if DYNAMIC policy is used.", "Takes effect on redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundDoubleFlag PERSISTENCE_THROTTLING_WS_RESIZE_RATE = defineDoubleFlag( "persistence-throttling-ws-resize-rate", 3.0, List.of("vekterli"), "2022-02-23", "2022-06-01", "Sets the dynamic throttle policy resize rate. Only applies if DYNAMIC policy is used.", "Takes effect on redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag PERSISTENCE_THROTTLING_OF_MERGE_FEED_OPS = defineFeatureFlag( "persistence-throttling-of-merge-feed-ops", true, List.of("vekterli"), "2022-02-24", "2022-06-01", "If true, each put/remove contained within a merge is individually throttled as if it " + "were a put/remove from a client. If false, merges are throttled at a persistence thread " + "level, i.e. per ApplyBucketDiff message, regardless of how many document operations " + "are contained within. Only applies if DYNAMIC policy is used.", "Takes effect on redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag INHIBIT_DEFAULT_MERGES_WHEN_GLOBAL_MERGES_PENDING = defineFeatureFlag( "inhibit-default-merges-when-global-merges-pending", false, List.of("geirst", "vekterli"), "2022-02-11", "2022-06-01", "Inhibits all merges to buckets in the default bucket space if the current " + "cluster state bundle indicates that global merges are pending in the cluster", "Takes effect on redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag USE_QRSERVER_SERVICE_NAME = defineFeatureFlag( "use-qrserver-service-name", true, List.of("arnej"), "2022-01-18", "2022-12-31", "Use backwards-compatible 'qrserver' service name for containers with only 'search' API", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag ENABLE_JDISC_PRESHUTDOWN_COMMAND = defineFeatureFlag( "enable-jdisc-preshutdown-command", false, List.of("bjorncs", "baldersheim"), "2022-01-31", "2022-05-31", "Enable pre-shutdown command for jdisc", "Takes effect at redeployment", APPLICATION_ID, HOSTNAME, TENANT_ID); public static final UnboundBooleanFlag AVOID_RENAMING_SUMMARY_FEATURES = defineFeatureFlag( "avoid-renaming-summary-features", false, List.of("arnej"), "2022-01-15", "2023-12-31", "Tell backend about the original name of summary-features that were wrapped in a rankingExpression feature", "Takes effect at redeployment", ZONE_ID, APPLICATION_ID); public static final UnboundBooleanFlag REUSE_NODE_INDEXES = defineFeatureFlag( "reuse-node-indexes", false, List.of("bratseth"), "2022-02-25", "2022-04-25", "Whether we should reuse earlier indexes when allocating new nodes", "Takes effect immediately", ZONE_ID); /** WARNING: public for testing: All flags should be defined in {@link Flags}. */ public static UnboundBooleanFlag defineFeatureFlag(String flagId, boolean defaultValue, List owners, String createdAt, String expiresAt, String description, String modificationEffect, FetchVector.Dimension... dimensions) { return define(UnboundBooleanFlag::new, flagId, defaultValue, owners, createdAt, expiresAt, description, modificationEffect, dimensions); } /** WARNING: public for testing: All flags should be defined in {@link Flags}. */ public static UnboundStringFlag defineStringFlag(String flagId, String defaultValue, List owners, String createdAt, String expiresAt, String description, String modificationEffect, FetchVector.Dimension... dimensions) { return define(UnboundStringFlag::new, flagId, defaultValue, owners, createdAt, expiresAt, description, modificationEffect, dimensions); } /** WARNING: public for testing: All flags should be defined in {@link Flags}. */ public static UnboundIntFlag defineIntFlag(String flagId, int defaultValue, List owners, String createdAt, String expiresAt, String description, String modificationEffect, FetchVector.Dimension... dimensions) { return define(UnboundIntFlag::new, flagId, defaultValue, owners, createdAt, expiresAt, description, modificationEffect, dimensions); } /** WARNING: public for testing: All flags should be defined in {@link Flags}. */ public static UnboundLongFlag defineLongFlag(String flagId, long defaultValue, List owners, String createdAt, String expiresAt, String description, String modificationEffect, FetchVector.Dimension... dimensions) { return define(UnboundLongFlag::new, flagId, defaultValue, owners, createdAt, expiresAt, description, modificationEffect, dimensions); } /** WARNING: public for testing: All flags should be defined in {@link Flags}. */ public static UnboundDoubleFlag defineDoubleFlag(String flagId, double defaultValue, List owners, String createdAt, String expiresAt, String description, String modificationEffect, FetchVector.Dimension... dimensions) { return define(UnboundDoubleFlag::new, flagId, defaultValue, owners, createdAt, expiresAt, description, modificationEffect, dimensions); } /** WARNING: public for testing: All flags should be defined in {@link Flags}. */ public static UnboundJacksonFlag defineJacksonFlag(String flagId, T defaultValue, Class jacksonClass, List owners, String createdAt, String expiresAt, String description, String modificationEffect, FetchVector.Dimension... dimensions) { return define((id2, defaultValue2, vector2) -> new UnboundJacksonFlag<>(id2, defaultValue2, vector2, jacksonClass), flagId, defaultValue, owners, createdAt, expiresAt, description, modificationEffect, dimensions); } /** WARNING: public for testing: All flags should be defined in {@link Flags}. */ public static UnboundListFlag defineListFlag(String flagId, List defaultValue, Class elementClass, List owners, String createdAt, String expiresAt, String description, String modificationEffect, FetchVector.Dimension... dimensions) { return define((fid, dval, fvec) -> new UnboundListFlag<>(fid, dval, elementClass, fvec), flagId, defaultValue, owners, createdAt, expiresAt, description, modificationEffect, dimensions); } @FunctionalInterface private interface TypedUnboundFlagFactory> { U create(FlagId id, T defaultVale, FetchVector defaultFetchVector); } /** * Defines a Flag. * * @param factory Factory for creating unbound flag of type U * @param flagId The globally unique FlagId. * @param defaultValue The default value if none is present after resolution. * @param description Description of how the flag is used. * @param modificationEffect What is required for the flag to take effect? A restart of process? immediately? etc. * @param dimensions What dimensions will be set in the {@link FetchVector} when fetching * the flag value in * {@link FlagSource#fetch(FlagId, FetchVector) FlagSource::fetch}. * For instance, if APPLICATION is one of the dimensions here, you should make sure * APPLICATION is set to the ApplicationId in the fetch vector when fetching the RawFlag * from the FlagSource. * @param The boxed type of the flag value, e.g. Boolean for flags guarding features. * @param The type of the unbound flag, e.g. UnboundBooleanFlag. * @return An unbound flag with {@link FetchVector.Dimension#HOSTNAME HOSTNAME} and * {@link FetchVector.Dimension#VESPA_VERSION VESPA_VERSION} already set. The ZONE environment * is typically implicit. */ private static > U define(TypedUnboundFlagFactory factory, String flagId, T defaultValue, List owners, String createdAt, String expiresAt, String description, String modificationEffect, FetchVector.Dimension[] dimensions) { FlagId id = new FlagId(flagId); FetchVector vector = new FetchVector() .with(HOSTNAME, Defaults.getDefaults().vespaHostname()) // Warning: In unit tests and outside official Vespa releases, the currentVersion is e.g. 7.0.0 // (determined by the current major version). Consider not setting VESPA_VERSION if minor = micro = 0. .with(VESPA_VERSION, Vtag.currentVersion.toFullString()); U unboundFlag = factory.create(id, defaultValue, vector); FlagDefinition definition = new FlagDefinition( unboundFlag, owners, parseDate(createdAt), parseDate(expiresAt), description, modificationEffect, dimensions); flags.put(id, definition); return unboundFlag; } private static Instant parseDate(String rawDate) { return DateTimeFormatter.ISO_DATE.parse(rawDate, LocalDate::from).atStartOfDay().toInstant(ZoneOffset.UTC); } public static List getAllFlags() { return List.copyOf(flags.values()); } public static Optional getFlag(FlagId flagId) { return Optional.ofNullable(flags.get(flagId)); } /** * Allows the statically defined flags to be controlled in a test. * *

Returns a Replacer instance to be used with e.g. a try-with-resources block. Within the block, * the flags starts out as cleared. Flags can be defined, etc. When leaving the block, the flags from * before the block is reinserted. * *

NOT thread-safe. Tests using this cannot run in parallel. */ public static Replacer clearFlagsForTesting(FlagId... flagsToKeep) { return new Replacer(flagsToKeep); } public static class Replacer implements AutoCloseable { private static volatile boolean flagsCleared = false; private final TreeMap savedFlags; private Replacer(FlagId... flagsToKeep) { verifyAndSetFlagsCleared(true); this.savedFlags = Flags.flags; Flags.flags = new TreeMap<>(); List.of(flagsToKeep).forEach(id -> Flags.flags.put(id, savedFlags.get(id))); } @Override public void close() { verifyAndSetFlagsCleared(false); Flags.flags = savedFlags; } /** * Used to implement a simple verification that Replacer is not used by multiple threads. * For instance two different tests running in parallel cannot both use Replacer. */ private static void verifyAndSetFlagsCleared(boolean newValue) { if (flagsCleared == newValue) { throw new IllegalStateException("clearFlagsForTesting called while already cleared - running tests in parallell!?"); } flagsCleared = newValue; } } }