Add limitation for the number of span logs, to avoid OOM (#773)

Author: hxd123456

CHANGES.md

@@ -14,6 +14,7 @@ Release Notes.
 * Bump up cli to the 0.15.0-dev.latest(77b4c49e89c9c000278f44e62729d534f2ec842e) in e2e.
 * Bump up apache parent pom to v35.
 * Update Maven to 3.6.3 in mvnw.
+* Fix OOM due to too many span logs.
 
 All issues and pull requests are [here](https://github.com/apache/skywalking/milestone/242?closed=1)
 

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/conf/Config.java

@@ -97,6 +97,11 @@ public static class Agent {
          */
         public static int TRACE_SEGMENT_REF_LIMIT_PER_SPAN = 500;
 
+        /**
+         * The max number of logs in a single span to keep memory cost estimatable.
+         */
+        public static int LOG_LIMIT_PER_SPAN = 300;
+
         /**
          * The max number of spans in a single segment. Through this config item, SkyWalking keep your application
          * memory cost estimated.

apm-sniffer/apm-agent-core/src/main/java/org/apache/skywalking/apm/agent/core/context/trace/AbstractTracingSpan.java

@@ -175,6 +175,9 @@ public AbstractTracingSpan log(Throwable t) {
         if (!errorOccurred && ServiceManager.INSTANCE.findService(StatusCheckService.class).isError(t)) {
             errorOccurred();
         }
+        if (logs.size() >= Config.Agent.LOG_LIMIT_PER_SPAN) {
+            return this;
+        }
         logs.add(new LogDataEntity.Builder().add(new KeyValuePair("event", "error"))
                                             .add(new KeyValuePair("error.kind", t.getClass().getName()))
                                             .add(new KeyValuePair("message", t.getMessage()))
@@ -196,6 +199,9 @@ public AbstractTracingSpan log(long timestampMicroseconds, Map<String, ?> fields
         if (logs == null) {
             logs = new LinkedList<>();
         }
+        if (logs.size() >= Config.Agent.LOG_LIMIT_PER_SPAN) {
+            return this;
+        }
         LogDataEntity.Builder builder = new LogDataEntity.Builder();
         for (Map.Entry<String, ?> entry : fields.entrySet()) {
             builder.add(new KeyValuePair(entry.getKey(), entry.getValue().toString()));

apm-sniffer/config/agent.config

@@ -36,6 +36,9 @@ agent.authentication=${SW_AGENT_AUTHENTICATION:}
 # The max number of TraceSegmentRef in a single span to keep memory cost estimatable.
 agent.trace_segment_ref_limit_per_span=${SW_TRACE_SEGMENT_LIMIT:500}
 
+# The max number of logs in a single span to keep memory cost estimatable.
+agent.log_limit_per_span=${SW_LOG_LIMIT_PER_SPAN:500}
+
 # The max amount of spans in a single segment.
 # Through this config item, SkyWalking keep your application memory cost estimated.
 agent.span_limit_per_segment=${SW_AGENT_SPAN_LIMIT:300}