solution: Redis cache for blocks

src/test/groovy/io/emeraldpay/dshackle/cache/BlocksRedisCacheSpec.groovy

@@ -0,0 +1,55 @@
+package io.emeraldpay.dshackle.cache
+
+import io.emeraldpay.dshackle.test.TestingCommons
+import io.emeraldpay.grpc.Chain
+import io.infinitape.etherjar.domain.BlockHash
+import io.infinitape.etherjar.rpc.json.BlockJson
+import io.infinitape.etherjar.rpc.json.TransactionRefJson
+import io.lettuce.core.RedisClient
+import io.lettuce.core.api.StatefulRedisConnection
+import spock.lang.IgnoreIf
+import spock.lang.Specification
+
+import java.time.Instant
+import java.time.temporal.ChronoUnit
+
+@IgnoreIf({
+    env["DSHACKLE_TEST_ENABLED"] == null || !env["DSHACKLE_TEST_ENABLED"].contains("redis")
+})
+class BlocksRedisCacheSpec extends Specification {
+
+    StatefulRedisConnection<String, String> redis
+
+    String hash1 = "0xd3f34def3c56ba4e701540d15edaff9acd2a1c968a7ff83b3300ab5dfd5f6aab"
+    String hash2 = "0x4aabdaff9acd2f30d15e00ab5dfd5f6c56ba4ea1c968a7ff8d3f34de70153b33"
+    String hash3 = "0x40d15edaff9acdabd2a1c96fd5f683b3300aad34e7015f34def3c56ba8a7ffb5"
+    String hash4 = "0xa4e7a75dfd5f6a83b3304dc56bfa0abfd3fef01540d15edafc9683f9acd2a13b"
+
+
+    def setup() {
+        RedisClient client = RedisClient.create("redis://localhost:6379");
+        StatefulRedisConnection<String, String> connection = client.connect();
+        connection.sync().flushdb()
+        redis = connection
+    }
+
+    def "Add and read"() {
+        setup:
+        def cache = new BlocksRedisCache(
+                redis.reactive(), Chain.ETHEREUM, TestingCommons.objectMapper()
+        )
+        def block = new BlockJson<TransactionRefJson>()
+        block.number = 100
+        block.timestamp = Instant.now().minusSeconds(100).truncatedTo(ChronoUnit.SECONDS)
+        block.hash = BlockHash.from(hash1)
+        block.transactions = []
+        block.uncles = []
+
+        when:
+        cache.add(block).subscribe()
+        def act = cache.read(BlockHash.from(hash1)).block()
+        then:
+        act == block
+    }
+
+}