refactor tail invokation into logtail.sh

src/tasks.js

@@ -46,12 +46,11 @@ const assert = require('assert'),
     BoxError = require('./boxerror.js'),
     database = require('./database.js'),
     debug = require('debug')('box:tasks'),
-    LogStream = require('./log-stream.js'),
+    logs = require('./logs.js'),
     path = require('path'),
     paths = require('./paths.js'),
     safe = require('safetydance'),
     shell = require('./shell.js'),
-    spawn = require('child_process').spawn,
     _ = require('underscore');
 
 let gTasks = {}; // indexed by task id
@@ -269,19 +268,8 @@ function getLogs(taskId, options) {
 
     debug(`Getting logs for ${taskId}`);
 
-    const lines = options.lines === -1 ? '+1' : options.lines,
-        format = options.format || 'json',
-        follow = options.follow;
-
-    const cmd = '/usr/bin/tail';
-    let args = [ '--lines=' + lines ];
-
-    if (follow) args.push('--follow', '--retry', '--quiet'); // same as -F. to make it work if file doesn't exist, --quiet to not output file headers, which are no logs
-    args.push(`${paths.TASKS_LOG_DIR}/${taskId}.log`);
-
-    const cp = spawn(cmd, args);
-
-    const logStream = new LogStream({ format, source: taskId });
+    const cp = logs.tail([`${paths.TASKS_LOG_DIR}/${taskId}.log`], { lines: options.lines, follow: options.follow });
+    const logStream = new logs.LogStream({ format: options.format || 'json', source: taskId });
     logStream.close = cp.kill.bind(cp, 'SIGKILL'); // hook for caller. closing stream kills the child process
 
     cp.stdout.pipe(logStream);