Add a PerformanceStringBuilder to build the performance string instead of a Map.

//AuditLogger.java
  public static class PerformanceStringBuilder {
    private final StringBuilder builder = new StringBuilder(1024).append('[');

    public void appendNanos(String name,long nanos){
      append(name, TimeUnit.NANOSECONDS.toMillis(nanos));
    }

    public void append(String name,long value){
      builder.append(name)
          .append('=')
          .append(value)
          .append(", ");
    }

    public String build() {
      final int length = builder.length();
      if (length < 2) {
        return "[]";
      }
      builder.setCharAt(length - 2, ']');
      builder.setLength(length - 1);
      return builder.toString();
    }
  }

This has been implemented

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Done.

Let's call it COPY_MULTIPART_KEY?

I'm referencing the AWS API name

CREATE_MULTIPART_KEY: AWS API name UploadPart
CREATE_MULTIPART_KEY_BY_COPY: AWS API name UploadPartCopy

I think it's a better match, what do you think?

Sure. Let's keep it then.

AUDIT may not log reads because of performance, but the perf does always build(). Should the performance data be passed as a lamba instead, so that a new string is not actually built when read audi logs are not enabled?

This is a problem that deserves attention
We currently generate AuditMessages via buildAuditMessageForSuccess, etc. In the AuditMessageForSuccess we perform the build of all relevant messages, regardless of whether or not the logs are logged.
This is probably not just a perf problem.

I agree that the problem also applies to the existing, "functional" part of the audit message.

Audit logging is enabled by default, and we need several changes to improve it, so I think we should do it separately.

Reopened HDDS-2638 for the improvement of audit message processsing/allocations.