adutra commented on code in PR #18754: URL: https://github.com/apache/iceberg/pull/18754#discussion_r4511432361
########## core/src/main/java/org/apache/iceberg/rest/auth/FileTokenSource.java: ########## @@ -0,0 +1,178 @@ +/* + * 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 org.apache.iceberg.rest.auth; + +import java.io.IOException; +import java.io.InputStream; +import java.io.UncheckedIOException; +import java.nio.charset.StandardCharsets; +import java.nio.file.Files; +import java.nio.file.Path; +import java.time.Duration; +import java.util.concurrent.atomic.AtomicReference; +import java.util.function.LongSupplier; +import org.apache.iceberg.relocated.com.google.common.base.MoreObjects; +import org.apache.iceberg.relocated.com.google.common.base.Preconditions; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * A {@link BearerTokenSource} that reads the token from a local file, and re-reads it once the + * token is older than the configured reload interval. + * + * <p>No background thread is used: reloads happen lazily, on the calling thread, when the token is + * requested. Only one thread reloads at a time; concurrent callers get the current token without + * waiting. + * + * <p>If a reload fails, the last valid token is kept, and the next reload is attempted after a full + * reload interval. As a consequence, deleting the token file does not revoke the token. + */ +final class FileTokenSource implements BearerTokenSource { + + private static final Logger LOG = LoggerFactory.getLogger(FileTokenSource.class); + + /** + * Maximum token file size. Large enough for JWTs signed with the largest post-quantum signature + * schemes. + */ + static final int MAX_FILE_SIZE = 256 * 1024; + + private final Path path; + private final Duration reloadInterval; + private final long reloadIntervalNanos; + private final LongSupplier nanoTime; + private final AtomicReference<State> state; + + /** + * An immutable snapshot of the source's mutable state, swapped atomically. + * + * @param token the last valid token + * @param readAtNanos when the token was last read, or when the last reload attempt failed + * @param reloading whether a thread has claimed the current reload + * @param failing whether the last reload attempt failed, used to log on transitions only + */ + private record State(String token, long readAtNanos, boolean reloading, boolean failing) {} + + FileTokenSource(Path path, Duration reloadInterval) { + this(path, reloadInterval, System::nanoTime); + } + + FileTokenSource(Path path, Duration reloadInterval, LongSupplier nanoTime) { + Preconditions.checkArgument(path != null, "Invalid token file: null"); + Preconditions.checkArgument(reloadInterval != null, "Invalid reload interval: null"); + this.path = path; + this.reloadInterval = reloadInterval; + this.reloadIntervalNanos = reloadInterval.toNanos(); + this.nanoTime = nanoTime; + // the initial read must succeed, otherwise the session fails to initialize + this.state = new AtomicReference<>(new State(readToken(), nanoTime.getAsLong(), false, false)); + } + + @Override + public String token() { + State current = state.get(); + if (current.reloading || isFresh(current)) { + return current.token; + } + + State claimed = new State(current.token, current.readAtNanos, true, current.failing); + if (!state.compareAndSet(current, claimed)) { + // another thread claimed the reload + return current.token; + } + + // only the thread holding the claim gets here, so a plain set() is enough to both publish the + // new state and release the claim; on unexpected errors, the unclaimed state is restored so + // that the next call retries again. + State next = current; + try { + next = reload(current); + } finally { + state.set(next); + } + + return next.token; + } + + private State reload(State current) { + String token; + try { + token = readToken(); + } catch (RuntimeException e) { + if (!current.failing) { + LOG.warn( + "Failed to reload bearer token from {}, will keep using the last valid token", path, e); + } + + // keep the last valid token and wait a full interval before the next attempt + return new State(current.token, nanoTime.getAsLong(), false, true); + } + + if (current.failing) { + LOG.info("Successfully reloaded bearer token from {}", path); + } Review Comment: I'm going to rename the field to `lastReloadFailed` -- This is an automated message from the Apache Git Service. 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