private static void execute(TikaServerConfig tikaServerConfig) throws Exception {

        if (tikaServerConfig.isNoFork()) {
            noFork(tikaServerConfig);
        } else {
            try {
                mainLoop(tikaServerConfig);
            } catch (InterruptedException e) {
                //swallow
                LOG.debug("interrupted", e);
            }
        }
    }
This value is set to the server's id in the forked process.
tika-server/tika-server-core/src/main/java/org/apache/tika/server/core/TikaServerCli.java