apache/hadoop · warning · BadRequestException

tasktype must be either m or r

Error message

tasktype must be either m or r

What it means

Thrown by the JobHistoryServer REST endpoint GET /ws/v1/history/mapreduce/jobs/{jobid}/tasks?type=... when the type value is not exactly 'm' or 'r'. The handler calls MRApps.taskType(type), which only maps the single-character symbols 'm' (map) and 'r' (reduce) and throws YarnRuntimeException for anything else; HsWebServices converts that to a BadRequestException (HTTP 400).

Source

Thrown at hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/main/java/org/apache/hadoop/mapreduce/v2/hs/webapp/HsWebServices.java:350

  @GET
  @Path("/mapreduce/jobs/{jobid}/tasks")
  @Produces({ MediaType.APPLICATION_JSON + "; " + JettyUtils.UTF_8,
      MediaType.APPLICATION_XML + "; " + JettyUtils.UTF_8 })
  public TasksInfo getJobTasks(@Context HttpServletRequest hsr,
      @PathParam("jobid") String jid, @QueryParam("type") String type) {

    init();
    Job job = AMWebServices.getJobFromJobIdString(jid, ctx);
    checkAccess(job, hsr);
    TasksInfo allTasks = new TasksInfo();
    for (Task task : job.getTasks().values()) {
      TaskType ttype = null;
      if (type != null && !type.isEmpty()) {
        try {
          ttype = MRApps.taskType(type);
        } catch (YarnRuntimeException e) {
          throw new BadRequestException("tasktype must be either m or r");
        }
      }
      if (ttype != null && task.getType() != ttype) {
        continue;
      }
      allTasks.add(new TaskInfo(task));
    }
    return allTasks;
  }

  @GET
  @Path("/mapreduce/jobs/{jobid}/tasks/{taskid}")
  @Produces({ MediaType.APPLICATION_JSON + "; " + JettyUtils.UTF_8,
      MediaType.APPLICATION_XML + "; " + JettyUtils.UTF_8 })
  public TaskInfo getJobTask(@Context HttpServletRequest hsr,
      @PathParam("jobid") String jid, @PathParam("taskid") String tid) {

    init();

View on GitHub (pinned to 2add963021)

Solutions

1. Use exactly type=m or type=r (lowercase single character)
2. Omit the type parameter to list all tasks of both kinds
3. Map friendly names to symbols before building the URL

Example fix

# before
curl "http://jhs:19888/ws/v1/history/mapreduce/jobs/$JID/tasks?type=map"

# after
curl "http://jhs:19888/ws/v1/history/mapreduce/jobs/$JID/tasks?type=m"

static String taskTypeSymbol(String input) {
  if (input == null || input.isEmpty()) return null;      // no filter
  if (input.equalsIgnoreCase("m") || input.equalsIgnoreCase("map"))  return "m";
  if (input.equalsIgnoreCase("r") || input.equalsIgnoreCase("reduce")) return "r";
  throw new IllegalArgumentException("type must be m or r: " + input);
}

When it happens

Trigger: GET /ws/v1/history/mapreduce/jobs/{jobid}/tasks?type=map, type=MAP, type=reduce, type=mapper, or any string other than exactly 'm' or 'r'. An empty value is treated as 'no filter' and does not trigger this.

Common situations: Passing the full word because the same API family (AM web services) documents type as m|r but users assume words; Case mismatch: 'M'/'R' are rejected — the check is case-sensitive; Scripts templating type=${TASK_KIND} where TASK_KIND is 'map' from other tooling

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• startedTimeEnd must be greater than 0
• startedTimeEnd must be greater than startTimeBegin
• finishedTimeBegin must be greater than 0
• finishedTimeEnd must be greater than 0
• finishedTimeEnd must be greater than finishedTimeBegin

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/57a29073b314642e. Report an issue: GitHub.