steveloughran commented on a change in pull request #2069:
URL: https://github.com/apache/hadoop/pull/2069#discussion_r474654134
##########
File path:
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FSInputStream.java
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@@ -134,4 +137,23 @@ public void readFully(long position, byte[] buffer)
throws IOException {
readFully(position, buffer, 0, buffer.length);
}
+
+ /**
+ * toString method returns the superclass toString, but if the subclass
+ * implements {@link IOStatisticsSource} then those statistics are
+ * extracted and included in the output.
+ * That is: statistics of subclasses are automatically reported.
+ * @return a string value.
+ */
+ @Override
+ public String toString() {
+ final StringBuilder sb = new StringBuilder(super.toString());
+ sb.append('{');
+ if (this instanceof IOStatisticsSource) {
+ sb.append(IOStatisticsLogging.ioStatisticsSourceToString(
+ (IOStatisticsSource) this));
+ }
+ sb.append('}');
+ return sb.toString();
+ }
Review comment:
the logging lets us see what IO downstream apps are doing even without
them picking up the API -the way S3A and ABFS streams do; The FSDataInputStream
wrapper class &c do toString passthrough to help here. The IOStreams API Does
exactly the same thing.
Result
1. code against this API, all the details, snapshots, java and JSON
serialization, aggregation etc
2. just log streams & fs & remoteiterable and anything else @ debug and you
get to see what is going on without having binaries which only link against
Hadoop releases with the API
Option #2 is the interim one which you can do for any app today -we just
have to make sure the hadoop wrapper/aggregate classes all have toString()
calls which forward/include stats from inner classes, and do it efficiently
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