[HTTPCLIENT-1858] Alleviate GC pressure due to wire logging

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 4.5.2
• Fix Version/s: 5.0 Alpha3
• Component/s: HttpClient (classic)
• Labels: performance
• Assignee: Unassigned
• Reporter: Arya Ketan
• Created: 21/Jun/17 02:40
• Updated: 01/Aug/17 17:28
• Resolved: 16/Jul/17 19:02

Description

While running performance tests, I am seeing very high GC pressure due to the following code
in Wire.java

private void wire(final String header, final InputStream instream)
      throws IOException {
        final StringBuilder buffer = new StringBuilder();
        int ch;
        while ((ch = instream.read()) != -1) {
            if (ch == 13) {
                buffer.append("[\\r]");
            } else if (ch == 10) {
                    buffer.append("[\\n]\"");
                    buffer.insert(0, "\"");
                    buffer.insert(0, header);
                    log.debug(id + " " + buffer.toString());
                    buffer.setLength(0);
            } else if ((ch < 32) || (ch > 127)) {
                buffer.append("[0x");
                buffer.append(Integer.toHexString(ch));
                buffer.append("]");
            } else {
                buffer.append((char) ch);
            }
        }
        if (buffer.length() > 0) {
            buffer.append('\"');
            buffer.insert(0, '\"');
            buffer.insert(0, header);
            log.debug(id + " " + buffer.toString());
        }
    }

This is because, we are trying to expand Stringbuffer continously , thus leading to lot of char[] garbage.
2 suggestions for improvements
a) we look into whether logging level is enabled and only then construct the message
b) efficiently construct log message.