fix: use less RPC calls to listen on the blockchain

src/main/java/com/iexec/blockchain/chain/BlockchainListener.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2025 IEXEC BLOCKCHAIN TECH
+ *
+ * Licensed 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 com.iexec.blockchain.chain;
+
+import com.iexec.commons.poco.chain.SignerService;
+import io.micrometer.core.instrument.Metrics;
+import io.micrometer.core.instrument.Tag;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Service;
+import org.web3j.protocol.Web3j;
+import org.web3j.protocol.core.DefaultBlockParameterName;
+import org.web3j.protocol.core.methods.response.EthBlock;
+import org.web3j.protocol.http.HttpService;
+import org.web3j.utils.Async;
+import org.web3j.utils.Numeric;
+
+import java.math.BigInteger;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicLong;
+
+@Slf4j
+@Service
+public class BlockchainListener {
+
+    static final String LATEST_BLOCK_METRIC_NAME = "iexec.chain.block.latest";
+    static final String TX_COUNT_METRIC_NAME = "iexec.chain.wallet.tx-count";
+
+    private final String walletAddress;
+    private final Web3j web3Client;
+    private final AtomicLong lastSeenBlock;
+    private final AtomicLong latestTxGauge;
+    private final AtomicLong pendingTxGauge;
+
+    public BlockchainListener(final ChainConfig chainConfig, final SignerService signerService) {
+        this.walletAddress = signerService.getAddress();
+        this.web3Client = Web3j.build(new HttpService(chainConfig.getNodeAddress()),
+                chainConfig.getBlockTime().toMillis(), Async.defaultExecutorService());
+        lastSeenBlock = Metrics.gauge(LATEST_BLOCK_METRIC_NAME, new AtomicLong(0));
+        latestTxGauge = Metrics.gauge(TX_COUNT_METRIC_NAME, List.of(Tag.of("block", "latest")), new AtomicLong(0));
+        pendingTxGauge = Metrics.gauge(TX_COUNT_METRIC_NAME, List.of(Tag.of("block", "pending")), new AtomicLong(0));
+    }
+
+    @Scheduled(fixedRate = 5000)
+    private void run() {
+        try {
+            final EthBlock.Block latestBlock =
+                    web3Client.ethGetBlockByNumber(DefaultBlockParameterName.LATEST, true).send().getBlock();
+            final BigInteger blockNumber = Numeric.toBigInt(latestBlock.getNumberRaw());
+            lastSeenBlock.set(blockNumber.longValue());
+            final BigInteger pendingTxCount = web3Client.ethGetTransactionCount(walletAddress,
+                    DefaultBlockParameterName.PENDING).send().getTransactionCount();
+            if (pendingTxCount.longValue() > pendingTxGauge.get() || pendingTxGauge.get() != latestTxGauge.get()) {
+                final BigInteger latestTxCount = web3Client.ethGetTransactionCount(walletAddress,
+                        DefaultBlockParameterName.LATEST).send().getTransactionCount();
+                pendingTxGauge.set(pendingTxCount.longValue());
+                latestTxGauge.set(latestTxCount.longValue());
+            }
+            log.info("Transaction count [block:{}, pending:{}, latest:{}]",
+                    lastSeenBlock, pendingTxGauge.get(), latestTxGauge.get());
+        } catch (Exception e) {
+            log.error("An error happened while fetching data on-chain", e);
+        }
+    }
+
+}

src/test/java/com/iexec/blockchain/chain/WebSocketBlockchainListenerTests.java → src/test/java/com/iexec/blockchain/chain/BlockchainListenerTests.java

@@ -33,15 +33,15 @@
 import java.util.Objects;
 import java.util.concurrent.TimeUnit;
 
-import static com.iexec.blockchain.chain.WebSocketBlockchainListener.LATEST_BLOCK_METRIC_NAME;
-import static com.iexec.blockchain.chain.WebSocketBlockchainListener.TX_COUNT_METRIC_NAME;
+import static com.iexec.blockchain.chain.BlockchainListener.LATEST_BLOCK_METRIC_NAME;
+import static com.iexec.blockchain.chain.BlockchainListener.TX_COUNT_METRIC_NAME;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.awaitility.Awaitility.await;
 
 @Slf4j
 @Testcontainers
 @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
-class WebSocketBlockchainListenerTests {
+class BlockchainListenerTests {
 
     private static final String CHAIN_SVC_NAME = "ibaa-chain";
     private static final int CHAIN_SVC_PORT = 8545;