Say that an environment opt-out skips the server-wide file

README.md

@@ -136,7 +136,7 @@ generates, reads or writes an ID.
 | Property | Meaning |
 |---|---|
 | **Returns immediately** | The HTTP call runs on one daemon thread the client owns. A Spigot plugin can report from the server thread and no tick waits on the network. |
-| **Never throws** | A server that is down, slow, or rejecting the key is a dropped report, not an exception in your program. Drops are logged at `FINE` if you gave a logger, otherwise not at all. |
+| **Never throws** | A server that is down, slow, or rejecting the key is a dropped report, not an exception in your program. Such a failure is logged at `FINE` if you gave a logger, otherwise not at all. |
 | **Bounded** | At most 256 reports wait to be sent; past that, new ones are dropped without a log line, even at `FINE`. A trace server that is unreachable for a week costs a few kilobytes, not your heap. |
 | **Throttled** | Repeats of one event within a minute are counted, not sent: the first goes out at once, the rest as one event when the minute is up. See [below](#repeated-events-are-coalesced). |
 | **`close()` drains** | Reports already queued get up to the client timeout (5 s total) to be sent before the thread stops, so a CLI that reports and exits at once does not lose its event. Still bounded: an unreachable server delays exit by at most the timeout. |

src/main/java/software/stephenson/trace/TraceClient.java

@@ -504,7 +504,8 @@ ServerWideConfig readFromDisk(boolean created) {
 
     /**
      * Ensures {@code <pluginsDirectory>/trace/config.yml} exists and reads its
-     * {@code enabled:} line and {@code tags:} block. No YAML library: the file
+     * {@code enabled:} line, {@code tags:} block and {@code server-id:} line.
+     * Not called when the environment opts out. No YAML library: the file
      * is ours, shallow, and a line scan is enough. Anything going wrong on
      * disk is logged at FINE and counts as enabled with no tags -- a
      * read-only plugins directory must not silently switch reporting off,
@@ -1123,8 +1124,9 @@ public Builder enabled(boolean enabled) {
          * server-id: 0f8b6c1e-...
          * </pre>
          *
-         * <p>Both are read once, here. Optional; programs that are not
-         * plugins leave it unset.
+         * <p>All three are read once, here. When an environment variable has
+         * already turned reporting off, the file is neither read nor created.
+         * Optional; programs that are not plugins leave it unset.
          */
         public Builder serverWideConfig(File pluginsDirectory) {
             this.pluginsDirectory = pluginsDirectory;