apache/hadoop · error · IOException

Cannot concat with a symlink target:

Error message

Cannot concat with a symlink target: 

What it means

Error "Cannot concat with a symlink target: " thrown in apache/hadoop.

Source

Thrown at hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java:992

    Path absF = fixRelativePart(trg);
    // Make all srcs absolute
    Path[] srcs = new Path[psrcs.length];
    for (int i=0; i<psrcs.length; i++) {
      srcs[i] = fixRelativePart(psrcs[i]);
    }
    // Try the concat without resolving any links
    String[] srcsStr = new String[psrcs.length];
    try {
      for (int i=0; i<psrcs.length; i++) {
        srcsStr[i] = getPathName(srcs[i]);
      }
      dfs.concat(getPathName(absF), srcsStr);
    } catch (UnresolvedLinkException e) {
      // Exception could be from trg or any src.
      // Fully resolve trg and srcs. Fail if any of them are a symlink.
      FileStatus stat = getFileLinkStatus(absF);
      if (stat.isSymlink()) {
        throw new IOException("Cannot concat with a symlink target: "
            + trg + " -> " + stat.getPath());
      }
      absF = fixRelativePart(stat.getPath());
      for (int i=0; i<psrcs.length; i++) {
        stat = getFileLinkStatus(srcs[i]);
        if (stat.isSymlink()) {
          throw new IOException("Cannot concat with a symlink src: "
              + psrcs[i] + " -> " + stat.getPath());
        }
        srcs[i] = fixRelativePart(stat.getPath());
      }
      // Try concat again. Can still race with another symlink.
      for (int i=0; i<psrcs.length; i++) {
        srcsStr[i] = getPathName(srcs[i]);
      }
      dfs.concat(getPathName(absF), srcsStr);
    }
  }

View on GitHub (pinned to 2add963021)

Solutions

1. Pass the concat target as a direct HDFS path, not a symlink.
2. Resolve symlinks before calling concat so the target is a real DFS file.

When it happens

Trigger: concat is called with a target path that is a symlink; concat requires real DFS paths for both target and sources.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/hadoop@2add963021 (2026-08-22). Data as JSON: /api/errors/68115243e069693e. Report an issue: GitHub.